H:2;5:,__:_,_:_E_,,_E_5.: so, . W H’- N4 .‘\ ‘3 .. a =. ’2" THES‘? This is to certifg that the thesis entitled TH”. EFFECT OF TEI‘TP’VRATUR“. “RADIVNT ON SOLIDIFICATION IN ALUMINUM-COPPER ALIDYS presented by Doarde G, Triponi has been accepted towards fulfillment of the requirements for Master's degree in Metallurgical Eng. 9/ r V Major professor natemnmJLflfi— 0-169 THE EFFECT OF TEEEERATURE GRADlEAT Oh bCLlDiFlUA‘lCN IL ALUKINUK-OCEBER ALLCYS By DLARDE 3. IRIECNI ”a A Tm“- *0 .uau‘lw submitted to the School of Graduate Studies of Eicnigan State University of Aericulture and Apnliei Science in partial fuifillment of the requirecents for the degree of p‘ _ MAbiai r vaEKUE Department of Metallur?ical Engineering 1956 Lb...) l. 1111‘.) I‘ A brief review of the net ode availfble for the study of the solidification of natal: is pzesentsd and discussed, alcn7 with a review of the nost recent published literature on the srlidificotion process. In: thernal analvsis technique was used to stuiy the corps: alloys containing fron l to #fl copper were melt2d in a nirh-irequencv induction furnace ;nd cast into horizontal bars, one inch in diareter and twelve inches long. Conti- C... nuous coolin: curves were recor’ed in the castinzs with a high-speed recorder. Studies of the necrostructure of the bars were 'correlated with the sclidificetiou infiey and pourinv temp- erature. The k-rey analvsis technique ves used to study the extent of macro-segreration in a number of selected test bars. It was shown that a larre solidification index favors tee formation of an equi-axsd structure and a small solid- iiicotion index favors the fornetion of the columnar structure. A-re; diffraction analysis did not reveal any arose macro-ssjrsqation in an} of the cast bars unier toe conditions used in tnis experiment. Ina EllELBUCG. of non- eouilitriun eutectic tee detected by inernel neasurensnt in all castin?e conteinin: were than 1.53% corner in tnis invest"ation. ACKhuaszGNENT The author wishes to express his sincere thanks to Professor Austen J. Smith for his technical advice andv guidance which made it possible to conduct the research reported in this thesis. The author also wishes to take this Opportunity to thank the other members of the faculty of the Metallurgical Engineering Department for their technical advice during the course of this invostiqstion and Mr. Ralph Bacon for the spectzozrenhic analysis reported in this experiment. TABLE OF Acknowledgement . Introduction . . History . . . Procedure. . . Discussion of Results Conclusions . . Recounandations . Appendix Data . . Cooling Curves. Dia7rnms . . Calculations . Bibliography . . COKEENES INTRODUCTION The practical importance of the phenomena of solid- ification must have been recognized for a very long time. Phe difference between ice and water, for example, has had a profound influence on the history of mantind and the evolution of society. The possibility of melting a metal and allewing it to freeze in a nold to a desired shape has been an essential incredient in our mastery of the art of shaping metals for thousands of years. The importance of melting and freezing as applied to metals and alloys has been so great, in fact,.that empirical solutions have been found for the multitude of practical problems that have arisen. Tnis approach has been so successful that relatively little attention has been directed to arriving at an understanding of the fundamentals of the process. In 1924 the British non-Ferrous Metals Research Association began a long-term study of the solid- fication of castings. the basic problem, to which this thesis is devoted, is this: A mass of metal of knomn Chemical composition, is melted, heated to a siven temperature, and allowed to solidify in a 7reen sand mold. What efiect will the resulting temperature gradient have on the distribution of the chemical elesents and the shape of the grains formed in the casting? U" HISTORY The effect of the structure assured by most alloy castinzs at the time of solidification persists throughout l it's life. The microstructure may be altered by heat- treatment, if the alloy is of a suitable constitution to respond to sucn treatment, but the nacrostructure of a casting is rarely affected by heat-treatment.(1) This feature plays an important part in the behavior of the cast article in service. Solidification is a process of nucleation and growth. The rate of solidification of a cast article is the result- ant of the rate of nucleation and the rate of growth. The rate of srowth at high temperature is very high and the rate of nucleation is low; at low tewperature the reverse is true. Therefore, at a high temperature few nuclei have a chance to form before tn \ D rapid rate growth has completed the freezing process. Imus the final structure is coarse-grained. At low teuperatures, many nuclei form before the freezing process is cocpleted and the resulting structure is fine- grained.(2!3!4) If the rate of cooling is high, as in a metal mold, freezing will occur at a low tefiperature, and a fine-grained structure is formed. If the rate of cooling is low, as in a sand mold, freezin; occurs a: a hi:h temperature and a coarse-grain structure is formed. Considerable proeress has been made in recent years 0\ toward an understanding of the solidification of metals. Cralners, flineiard and their co-worxers(5’€) have done considerable research reeardine supercoolinz, dendritic freezing and the solid-liquid interface in alloy systems. R.u. Huddle and his co-worcers in England have conducted exper ments relating to the solidification of castines. in 1950 R.n.Ruddle(7} made a survey of the literature relating to the solidification of castinzs and to methods of controlling solidification. Ruddle's review is divided into two sections. The first covers the general work which has been done towards the application of scientific prin- ciples to the production of castings and ineots. The second part is concerned with a more fundamental study of the solidification rates of castines and the nethois available for the investization of solidification rates. The fundamental principles of solidification of metals in molds can be investigated in four ways: 1. by mathe- matical analysis; 2. by electrical analogue; 3. by "pour- oufl'methods; 4. through temperature neasuremente taKen in the solidifyine casting and in the mold. The mathematical approach to the problem becomes exceedingly difficult and often insoluble if all the factors affecting the solidification phenowena are considered. Even if simplifying assumptions are made, the equations are only solvable with :reat difficulty. In addition, the matjenatical method requires muce data concerning thermal prOperties at hiss temperature and especially in the liquid state. The data are very meager and much of the information which is available is of doubtful reliability at the present time. The electrical-analogue method is the newest method of solving heat-flow oroblens. lhis method is not as restric- ted in its application as the mathematical method. however, it also requires knowledge of much unknown data. The main difficulty with both methods is that they are unable to provide information concerning the behavior of an alloy between the liquidus and the solidus temperature. This information is essential for a complete understanding of the factors involved in the solidification of metals. This is especially true of non-ferrous alloys, where the freezing ranges are large and the pouring temperatures are low. A good deal of practical work on the solidification of steel and cast iron has been carried out in recent years using the "pour-out" technique. This method is of limited value because it enables one quantity, the rate of skin formation, to be measured. Its application to non-ferrous alloys having long freezing ran:ee would yield little information, since the formation of a solid skin takes place at some unknown point between the liquidus and the solidus. The results of such investigations throw no light on the beginning or end of solidification. Bochvar and Kuzina (E) have shown experimentally that the solid shin left in the mold will contain considerable liquid in aluminum-cepper alloys. A further objection to this method, is that in nany alloys it may not work at all. hunsicaer (9) examined a number of aluminum alloys, but use unable to octain satis- factory 53114 shells. Ins "pour-out" EELLOd is a crude ‘ Ln method of investigation ani it may yield misleading rasult . The nea;ura"ent of Le parature in the natal and in the mold is a such more versatile method and offers a number of advantaves over the retnois i scrioed above. This method requires a nininum of high—temperature data, and enables the prorress of both the beginning and LB! and of solidification to be followed. it rlso shows the behavior in the zone where solidification is taking place. reapsrature at various pzifits in the casting and the mold can be measured at the same tine, thus, permitting the calculation of the temperature gradient existing in both the casting and the mold. fhe temperature measurexent method is the best technique for the investigation of solidification in non—ferrous alloys. This nethor had not been used extensively prior to 1950. Some results have , i a "it 1 been publisned by orivds 3nd 192511U5,( )Baher,( l) \12) Chvorinov, and others. ‘ 'wc (13) ‘I ‘ 1n 13,0 Ruddle made a prelininury study of the solidification of superepure aluminum and aluiinum alloys c ntaining 4, 8 and 30% conoer usinv the temperature measure- ment technique. he reported that super-purity aluminum solidified by skin formation and 4% cooper alloy solidified in a ”pasty" manner. he was unable to determine the method of solidification of tne 30% cocoer alloy. Huddle calcul- leted the solidification times for aluoinum alloys using Unver- »- ' ‘; , L' ,,,_l .4 ‘ _ : ~ , . inov s fornule and ieunj that they Compared favorably with the experimental data. Cnvorinov's formula is expressed as. T = (V/sA)3/i2 P = freezing time, hours; V = volume; LA = surface area; sand M = constant. A correlation of tensile properties of aluminum alloy ;plate castinss with temperature gradients during solidificat- .ion was also pUblishsd by Huddle in 1950.(:;) He reported ‘that plates havinq the steepest temperature gradient had (considerably superior tensile properties. This was the case <3btained in his é inch plate. He also concluded that plates ‘thicker than % inch could not be soundly cast when rapidly ;poured, revardless of the size of the feeder employed. liuddle did not discuss the affect that miznt be due to variation of grain size. Cibuls and Huddle (4) made a study of the effect of grain size on the tensile properties of cast aluminum alloys. ’Ths grain size was varied in a 4k% aluminum-copper alloy by ‘varying the pouring temperature of the casting. Ins tensile properties of this alloy were found to increase markely with (decrease in grain-size. hondic and Shutt<14) investigated the macrostructure of super-pure and commercially pure aluminum using the temper- ature zeasursment method. They found that with super-pure aluninum, the number of wrains in the cast structure was independent of the d gree of superheatin?. With commercially (O .Dure aluminum, a qreater number of crystals of different Btmpms in the same casting were obtained over a narrow range of superheatins temperature. Iney also showed that on superheatin: the commercially pure aluminuu to 9503 C, and holding the nelted metal at a tenperature close to the liquidus teeperature, caused a fine-grain structure to appear in the Casting. They concluded that an increased rate of cooling refines the columnar structure of pure metals and modifies the equi-axed structuie of impure natal, first, into a partly columnar and partly equi-axed structure, and secondly, at still HlTheT rates of cooling, into a wholly columnar structure. Measurements of undercooling snowed that any grain refinement of a pure metal with increased rates of coolin? is accompanied by an increased de7ree of undercoolini. The formation of equieaxed struct- ure was found to be primarily due to tne present of alloy- ing elements. Bishop, Brandt, and Pellini<15) investigated the solidification of steel ingots using thermal analysis. They were able to determine that solidification in a steel ingot proceeds in a wave-lite fashion at rates which were deter- mined by tne carbon level, superheat, and mold thickness. They showed that inc easin: superheat produces a general coarsening of the nacrostructure. They concluded that the classic relationship, thickness : a constant times the m w m C? ( 'H C Q (0 square root of the time, applies only to the fir= of solidification. hineward and Ghalne:s(13} discussed the meccanisn of super-cooling and dendritic freezing in alloy systeus in a ll publication in 19E}. They were able to show that super- coolicg nay result from the enrichment in the solute of the liquid immediately ahead of the advancin? solid-liquid interface. They preposed that dendrites in ingot structure are produced as a result of constitutional supercooling and that dendritic equi-axed zone in the center of inqots is a result of nucleation in a larag constitutionally super- cooled region. I Morris, Tiller, Rutter, and nineeard‘ 5) investigated the conditions for dendritic growth in alloys of lead containing from 0.25% to 5% tin, using the thermal analysis technique. It was shown that dendrite fornation is favored by a rapid rate of solidification and a low temperature gradient. The results indicated that the factor controlling he beginning of dendritic growth is the ratio of the rate of solidification to the tecperature gradient. Wren an alloy solidifies differences in chemical composition may occur on either a small or large scale. If within the individual crystals or crains, it is called eicro-segrezation. Seareqation nay be observed on quite a large scale within the mass of solid metal, the composition on the outside, for instance, beinc qtite different from the center of the mass. In this ease, the difierence in comp- osition is referred to as macro-seareaation. Segregation can occur only in cast alloys that solidify vaer a ranze of tenperature, with a difference in the nf‘irn.ed his mathematical analysis using radioactive antimony. he showed that there was a snarp decrease in concentration at eac; reeelt boundary and an increase in concentration in the last regidn to freeze. Killably, Taylor, and winesardcx)) investiqated segregation during casting of lead-antirony alloys, using radioactive antimony. Thay were able to show that gravity soareration is minimized by fast coolinv rates. W (‘52 l) . winecar investirated sevregation in bronze usin: radioactive tochnioue and found that the outside of small castinzs were high in tin when made to solidify fron outside inward. 14 PRCCiDUfib The Aluminum—COpner Alloys usei in this experiment were ride fros hiWh-purity alurinun of 99.999-C % urity, and D electrolytic conner of 99.99% purity. The alloys were pre- pared from a 67:33 aluminum-COerr hardener made from the above materials. Spectrographic analysis showed a very slight trace of mansanese, a trace of silicon, a trace of iron, and more than a trace of magnesium. spectrographic analysis on two of the cast bars showed that the amount of the above elements did not increase in the alloys under the Casting conditions used in this experiment. A 20 K.d. Ajax hixh-frequency induction furnace was used to melt all of the heats poured in this investization. ’Ihe alloys were melted in'a 12 p und magnesia crucible and (cast into horizontal bars, 1 inch in diameter and 12 inches Ilene. Risers 1 inch in diameter were placed at each end of tLhe bar. The castinre were poured directly into one of these I‘isers. The ?reen sand molds were made from Tennessee bank Band blended with 1:13.- Ctta-.-:a silica sand. The curves Shown appendix was construCLed by measuring the physical FDIfogerties of various percentazes of lennessse sand and ‘33~lica sand. The 59:41 mixture was selected because it seve tlfie maximum strenvth with relatively hiTh perneability. The 331 378 analysis of the iennsssee sand and the blended sand is Sifcswn in Table l. A moisture determination was made prior L2 to the preparation of each mold and maintained between 5 and 6% The thermocouples were placed with the hot-junctions in the center of the mold cavity at the parting line, as shown in fiqure 1. These thermocouples were constructed from 22 Figure l. Mold and thermocouple Grace chromel-alucel wire and were calibrated with pure zinc, t.1n, high-purity aluminun, and electrolytic c0pper. The I‘eeults are shown in Table 2. A test bar of hiqh-ptrity Ellmmdnum cast in a green sand mold showed the tenperature I"eadinv to be 5° F. hi: . All thermocouples were used with— Crut protection except heats T-lEEA, T-lEYB, and T-lZSB. heats 1“-125A was coated vith a rash of aluhdum and heats T-lETB and I"-12€B had a thin silica ttbe covering all the couple, except atDout 1/16 of an inch at the hot junction. These heats show- €W1.tlat the couples cave readings with unprotected thermocou- ples. The unprotected couples qsve a more rapid reading :nd .. (21) were tsed for this reason. A.B. Lichael has also shown this to be true in aluminum-conper alloys of the composition used in the esperiment. Continous coolin: curves were recorded in the cost t st m bars with a Brown Hivh Speed Electronik Recorder. The cast- in; tenperature was measured in the crucible just prior to pouring mitn a chromel-alumel thermocouple and a portable potentiometer. Samples 1 inch long were taken from each bar, adjacent to the therm;couple and the beginnin; and end of freezing temperatures measured for comparison hitfi the measurements U) taken in the casting. The 3 measurements were made with the previous described recorder, and a_g K.fi. Lepel high-freq? uency furnace usina sl zed porcelain crucibles. These results are shown in Table 4. Samples 5 inch lone were taken from the casting adjacent to the thermocouple for macro-examination, and X ray diffraction analysis. Each sample was then marked on the top side so that its position in the mold could be identified. Turninss were tanen_from the face of the bar adjscent to this sasple for chemical analysis. Ihe samples were ground on a belt sander and 1/0 ‘oaoer, then polished with levieeted alumina powder. A mixture of it ml. of HCl, 5 ml. of nb., and SE ml. of ziistilled water was used to etch all samp es for macro- examination, and Keller's etch was used for macro-examina- tjgon. Photonacrographs were taken of selected samples amjdtate shown in the discussion. Fine drillinss were taken with a 1/16 inch drill perpendicular to the face of selected speciaens at the fcallowin: positions: 1/16 inch from the mold-metal interface Eat. the bottom, tsp, side, and at the center of the tee seguecinens. A few samples were taken from the half-radius pnosition between the tsp and center of the samples. The (ilnillinvs were placed in a 5 mt. pyrex tube, evacuated and ssealed. All X-ray samples were given a 2 hour solution t reatnent at lOOOOF, and quenched in a beaker of water upon r‘euoving from the furnace. The drillinss were remcved from t.hn pyrex tube, and dried in an erlenneyer- flask, usin? \Iacuum and heat, being careful not to heat the flask above fiend-touChinI tenperature. X-Ray diffraction patterns were obtained of the filings Lising a Van Arkel Camera and unfiltered c0pper radiation. '1 he position of the diffraction li es for the 422, Ell-333 I‘sflecting planes were measured with a Phillips Comparator fRor K¢Jand K«zradiation. The lattice constants were czalculated for each plane and corrected by extrapolation. 11:) exaeple of the extrapolation curves is shown in the Evprmndix. The c0pper content of the sanple was determined fromthe curve shown in the appendix. This curve was cOnstructed from lattice parameter neesur a: cents as described above for Lien-purity aluminum, test bar T-llE containing (3-90; COpper, test bar f-l212 containin? 1.53% COpper, test bar T-ljfi containinr 2.50% c0prer, test bar T-AE cont- aininv 3.01% cepper; and a high—purity aluminum copper alloy containing 95.09% aluminum and 4.89% c0pper supplied by the Aluminum Cowpany of America. Chemical analysis was performed using the following A 2 to E rrram sample was dissolved in tCl, e lectrolytic method . it udxture of 200 0.0. of iistilled water, 10 0.0. of 220 0.0. of BRO}. Aperoxiuately 2 0.0. of H2 504 per gram c>f sanple was added, and the solution evaporated to fumes of £5<33. The residue was then dissolved in distilled water with 3% HNO} and 3% HQ 5C4, and electrolyzed. The method was (:tieCAed with an aluminum-COpper alloy supplied b3 the U.S. ESLxreau of Standards and found to be within 2% error. DIECUSSION High-purity aluminum and electrolytic copper was used in this axperinent to trinimize the affect of residual elements. (14)have demonstrated that minor impurities Kondic and Shutt [Lazy conpletely outweight the thermal factors in controlling r7LJC13aLlOD durinc solidification. The possibility of rszoducing fins-grained aluminun alloy castings, by additions C>f? small quantities of certain slenents to the melt has long been Known. Fne results of the spactrosraphic analysis show t.rxat there was no pick-up of undesirable elensnts under the casting. conditions used in this investifzation. The test bars used in this work were designed so that a zmorie in the C‘HLEF of the casting would represent a "semi- lnfinite" casting. in the "semi-infinite" zone, all of tn?2 ' rietat is lost in the direction of the side surfaces. Fellinig) hMiss shown this to be the case in siuilar bars cast in stool. All thermal meastrensnts, macro-specimens, X-ray samp as, and <3Y3endcal analyses were taken from this zone. fable J zivss the conpositions of the cast bars and the t'itres of sslidification. The cooling curves are shown in the a-‘*H‘endix. A cl se observation of the cooling curves reveal ‘ttlad.tre recorded liquidus and solidus temperatures are 1I3CTOnsiet€OL and in some cases hizhsr than the solidification trkflperaturs of pure aluminum. Prior calibzation of the t':11'!runocmgpla wire and recorder, indicated that the maximum t”9-H-‘perature deviation should not be more than 50 F. lhe rueccmfier fine a continuous balancina instrument and was tmalanced nanually prior to each operation. The interpretation of the data was based on the solid- igfication index to eliminate the above mentioned variation 1.!) temperature measureaenta in all tne alloys, except the 1% crc>pper alloys. The solidification index is defined as the cflnlfference between the observed liquidus and solidus temp- craturee, divided by the total time of solidification. I‘hie '1.ndex has the dimensions of a cooling rate, but also reflects éizny isothermal part of the solidification process. Many of t.he other variables in the casting process will exert an i nfluence on the eolidification index. An increase in §>0uring temperature will cause a decrease in the solidification 1.ndox due to an increase in the solidification time. Any crhanaee in the mold material that affect its thermal prop- lIrties will be reflected in the solidification index. An i.ncreane in the therval conductivity of the sand will cause iln increase in the eulidification index. The structure of t;eet bar T-137 is an exaaple of the influence of some un- Ltnown variable on the solidification index. This bar crontaine equi-uxed and colunnar ?rains, whereas bar T-133 {soured from 13009-F. contains all columnar :rains. 1f the aatructurse are interpreted on the baeie of solidification tindex instead of pouring temperature, the duplexed structure \Mould be predicted for tnie bar. Cooling curves were determined from a renelted sample cf’each bar to see if the temperature measurements would be 21 aware consistent under different conditions. oanples of nigh- ptirity aluninun were run at various intervals, so that c<3rrections could be made to the recorded values. lhe cwsrwected values and the measurenents recorded in the mold ELI“? shown in Table IV. Cooling curve determinations for atlguninum indicated that the characteristics of the therm- C) crouple did not change in any way that could explain the fi‘ bove conditions. The inconsistent teuperature usasureuenta W 9 r} reared to be due to instrumental difficulties, but could riot be verifiéd. The horizontal portion of the cooling curve at the 1.1quidue, was observed in the alloys cast under the cond- i tions used in this experiment. Michael and bevsr(l7)also Cbtbserved this hori ontal in their investigation of aluninum- <2c>nper alloy. They suvqested the observation nivht be due ‘tcz a transient balance at the thernocouple head between the evolution of the heat of solidification and heat losses to ‘Ltue surroundinzs. Ruddle investirated the solidification C>f'aluninum alloys containinc 4% cepper and concluded that 53()% of the metal solidifies in the first lOOC.of the lreez- 1-rio ranve in a 5 inch cylinder. The cooling curves for all alloys containing more than 1..Eji c0pper, have an arrest at aroroximately lOlOCF, which 1-8 the tenperature of the euteCLic reaction. the eutectic l"ialt increased with cooper content. lhe photonicroqraph 1:) Figure 2 shows eutectic in the grain boundries of the 33.52% cooper alloy. Michael and Bever,(17)reoorted c>bservinq the eutectic halt in 2% conner alloys under . (2‘s) aihuler'coolinq rates. hondolfo ’ reports that the maximum ilmount of cooper that can be held in solution in sand cast alluninum-copper alloys is 2.5% at the eutectic temperature. 'Itmse data suggest that even less copper nivnt be held in solution 1 n casting. ”1?UP= 2 Test Bar 137 2.52% cooper soox The presence of the eutectic due to noneequilbrium conditions during subsequence heat treatment, may cause partial melting in the boundries of an alloy, whicn accord- (I in; to the phase diavram, should b a solid solution having a hisher solidus temperature. In the case of the homogen- ization for ace-hardening, the time required for solution treatment would be zuch longer and at a lower temperature. the presence of the eutectic in the grain boundries, 23 misyht possibly have some subtle affects on the physical prwsrsrties, and the fesdin: of casting during solidification. A. rion-equilibriun dieyran is constructed from these data ELCMj shown in the appendix. The influence exerted by COpCer on the nucleation rate sir: be observed from the photonacroarept in Figure 3- 13r‘e 1% and 2% cotper bars show s trace of columnar structure slrid the 3% and A? c0pper bars are all squi—axed wnen cast i’xocn lQECVF. It is evident that a scallsr solidification i.rijex is required to produce s colucnar Structure with zltncreasing c0ppsr content. Table V s CPS the relation tasetween copusr content, the solidification index, tsnpersture, :- nd the moi-(structure. the effect ttst cctling rats exerts on the structure of m 0 {D (-9- p 1') ‘Q 0 ’0 3 also be can frow the photonacrozraph as sho n i-ri Figure 3. Test bars that contain equi-sxed and columnar ;?1781n8 always have the equi-axed structure in the COpe side ‘~orbed hest DJ 0| m 9'! ( V" (f) C*f' the casting. Phis part of the rol fI‘om the first metal entering us cold and h* lower Q\ '0 SD C3c.olin: rats. ihis lowsr c cling rate in tts top of the r’CLJd, accounts for the observed duplex structure in these Table V sunnarizss tne solidification index measurements. L.s results indicate that a large solidification index favors ‘~t] squi-axsd structure and a snail solidification index f'Csvors the columnar structure. there appears to be a tLIV—.ehsition solidification index, Which sust be exceeded to prwyducs the equi-axed Structure. This relation is snown in tJucz curve in the appendix. This is in svrssment with the . . 14 ‘ ccoriclusions of bondic and ohuttf )that an increased rate of ccac>ling modifies the equi-axed structure of inpure metals partly columnar and partly equi-axsd structure, and 1:31;o a sit. still nizner rates of cooling into a wholly columnar a tructure. 1%CL1. “ficti. 1300°F 13250F i35o°F 12500F 1275°F Figure 3. 3/4 actual size, cOpe on the left side. The determination of the compositions of sarplss by 1~3¢¢ics constants is a precise method. Phe method offers an Eldditional advantave in that it requires a very small sample, ’ The method of elimination 9nd effective .4- order of a fan milligrsns. C>n Lns <>f systenatic errors by extrapolation is simple h) UT in back-reflectin: cameras, such as used in tnis investivation. The values of 6 obtained in this experiment, were betueen 50 and 90 devrees. This is the rance where extrapolations are best. The results of la tice measurements on high-purity aluminum compared favorably with the values presented by “A Barrett.(c ) ‘I Table VI summarizes the results of the A-ray diffract- ion analysis taken for studies of macro-segrevation. Ex.mination of the data shows evidences of RC segreration, btt does not reveal any particular pattern in relation to alloy content, pouring tejperature, position, or the structure. The maximum variation was 0.40% c0pper in the l and 2% c0pper alloys cast from lBOOOF. and 1350 F. respectively. Test bar T-l40 poured from 154003. and having a columnar structure showed 0.31% maximum variation, whereas test bar T-143 cast from 13000F had 0.25% maximum variation. The photomicroqraph shown in Fiiure 2, reveals that .1arze amounts of seqrevation did take place on a micro-scale not susceptible to X-ray analysis. The dark area adjacent to the srain boundries and the existence of the eutectic in the boundries, are evidence that the liquid near the advanc- in:_interface is enriched in solute, in this case copper. The last metal to solidify lies in a region between the solidifying dendrites and has the composition of the aluminum4c0pner eutectic. The existence of the eutectic in all regions of the cast bar, explains the small amount of macro-seeresation detected by X-ray analysis. The drillings taken for X-ray analysis contain both high and low concentrations of copper and the lattice determination is the average hf bath the nigh and ice concentration. The X-ray samples were homogenized at lOOOOF for 2 hours to eliminate segregation within the individual saeple. Calculations of the solidification constant“ used in Chvorinov's .... .. . . . -... . .. .. 1 . . . . .. .. . . ...- .. . - .... .... 1... . .. .... .. .. . . .. -.-. ..44 ....4 _- . . .. . .... . .. - . . .. . . .. .... ...44... .... 4.4. 4... .... .... . .. ..- . .... ..Y 4.1- .41- ..- .. . . . . . . ... . .. . .... . . . . .. ... ......... 4... ... .... ...- .... .... ... . .. .. .. . . .‘xvnt14 ..-. .... -. .. . . - ... .1 . . .... -. .... .. 1 .... .. . .... -T-... . .... .4.. ...11.... .... ... . . .. ...uv-y’t. .-.. » .... -. . . . . . . . . . . . e. .1. .-. .-.. .... .... ..4. .... . .. .... .... .-.4 ... .. - .. .... .-...4...1.v.4. ... .. . .. .. _. .-.. ... .... .... .. 1 ...o ...1 .... .4. . -. . .. .. 1 . .. ... . I 4 .- ...- .. . . . . . . . . .... .. . .... .. . ... .. v .... .... .. . _. . . . .. .... . -. .. . .-v.' .. o. . . . .... . ... - .. ... .. .... ..1. .... ... . .. _ . . .... .. . ...- .4.. .. .. . . . . . . . . . . .. . ... .... .... .... .... .... .... .. 1.. .. . . . .. -.. .... 1 .. .. .... .. V .. . . . . .. . .. . . .... I .. ...4 ... .... .... .... 4. . .... .. e.-. ... ... .... .... .-. v .. . .. ..v .. . . . . . ... .. ... .... .... ... ... .... .... .1 . .. . . .. . . . .... .... - .. .. ..4. ,. . . . . . ... .... ... .... .. ...v . .. 4.-. .4..- . -. 4... .... .. . . . ..- .. . . . .1.- ..4-1.... .... .... ... . . . a . .. ... .... o... .... .... .... o .. o... ...v. .... .... .... .... . . . .. ... ... .... .-.. - 1. I... ...4 ... . .a . . ... .. 4 1. .... . 1. .. 4...v4vl44 4..4 .... ...4 .1. . ... . .... .441 .411 . e .14.1.1-| .. . . . . . . . ... . . .. 4 .... ... .... .... -.-£. .... . .- . . 4. . . .. . .... .4.. . .. .... ......1.. 1... .... .. . . . . . . . ... . .. ...4 4..4 .... .... 0-041.4.V .... .... ..- 1-..... . ... ... .--. .. . .... .... .... .-.. '1 . .. . .... . . .. . .. . . 1 .. .. . .... ... 4... ..4. . .. .... ..-.. 44.Y- .11. ..-. .... . .- ... .... .. .... - .. .... .. . ..-. t 4 . .. . . . 1 - v. . ... . . . .. .... .... ... ... ... .... 40.. .. 11.14. .44. .... .4.. .. .. 1 . I . .. . . . .. . ... ... ...- . .. .. .... .... .... ... .... ...-1 1... -... ...-1. V .. . ...- y 1. 1 . .. . .- 4 ... . 1 .. . ..o. .-.. .-.. ... .... .... .-. .... .... - . .... .... . . 1 - .. . ...! . . . .. . . . , ... .... .. .. v . ... ... ... .. . ... ... ._ .... .... ...- e . . . . . ... .- .1 . .. ... .... ...- .... ... .... .. ... ...- . -. . . . . . . .. -.. ...- ... ... ... .... .41. ... .... . .. ... ... 1.14.9 . .. .. . . . . . . . . .. . .... 1... ... .... . . .... .4.. . .. .... 4 . .... . . ... .19. . . .. .. . . . . _ .. . . . .... . ... .... .4. . . . ... .... .. . ... .. . . .... ..-. . .... . . . . . ... .... . . .... .4 . .. .... ... ..-. .. . 1.. .. ..-. 1... . . . .. . .. . . . .... . .. ... .... .-.. .... .... . . . .1 . .1 , . . . .... .... .. . .. . ... ... .... ... ..-. .... .. . . . .. ...- . .... - . . . . .. .... .... .. . . . _. v .. .... .... ... . . . .... ... .. . ... - . I .. . . . .... .. . . ... . . . 1.. . . . . . . . . .... .... .. . ... . . .... .. ... . - .... ..-. .. . .. . .. . .. . .. .1 . . . .... ..- .1. . .. . .. _ .... -. . . . . . . , . .. . . . .. . . .. .-. ..- . . . . .. U. . .. . . .... . ... . . ..4 . . . .. .. . . .. . .... . .. . .. -. ..- .. .... - . 1 . .... .... . .. .4 1 . .... .... ... ... .. .... ... .. . .... . .. .. . .... . . . ... . . . . .. .... . .. .. - . . . .. .. . . .. .. .... 1... - - .. ... ... . . . . -- .... .... .... .... .... ... .. .... . - .. . . . .. .. . ... .. . ..1 .... .... . -. . . .... . 1 .. .... ..1 .... .. . . . . . . .. ... ... .. .. . . .1. . . .. . . ... . .. . ... .... .. . .. . .. . . . .. . . . .. .. .... .... ... ... 1. . 1 .. ..-. ... ... . .. .... .1-. -... . .. . .... . . 1... .- . . .... .... o... ... ..- . -. .. - . .1. ....4 .... . . .. ... . ....146 . . . . - . . .1 . .. . . . .. ..-. ... . . . . . . . . - .... ..1- ... .... . . .. 1.. . . . .. . . .. . ... ... .... ... .. . .. . . . ... .1. . .. ... . . ..1. . .. ...v . . . . . ... ... .... .... .... .... . .. . . ... o .. .. . . --.. 1.1. . .. . . .. . . . -. . .... .. . .. - o-.. 4... ... . . .. . . . .. ..- . - 1.. b .. ... ... .4....4.-. . . . .. . . .... .... .... ... .-.. ... . . . . . .. . ... 3 - . ..11-.144 . . .. . ...- .... - .. . . .. - .. .. 1 . . . . . .... . ...- . . . . .... .... ... ... .. . ...: .. . . . - . . . . . . Y! 4 .. . v . .. .. . .. ... . .... .... . .. ...r. . .. ... ....a . . .. . . . . . . ... . .- . .. .. .... . . .v . . . .. .. ..- .. ...- . . .. . .. . 4. . . -.. . . . I. . .. - .... . . .1 . . . 1 . . . . . . . _. ... .... ...4 . .. .. .. . . . . 1. 1.... . .1 . . -... .-.4 . . .. . . . . . . . . .. . . ... ... . . . .1. 1... 1.. .- . . . l- . . . . . . . . .. , .. 11.. 4 .. ... .. . . . . O. ...- .... . .. . .... 1... . . .. . . . ... .-. -... .1.1111¢..1 .1. . . .-. . . . . ..14 -4.. - . -. . .4.- ..-. . . . .. _ v .-.. - .. ... Y4... .....1-a-1 .... -. 1,. . . .... ..41 -§.- . . . .T... .t . . .. . . ... ... ..... . ..11 -..o ...- . - 1. . - ..- .. .... 0.41.. ... .4.1- 1.14 . . . - .-. . .. .... ... ...4 ..114 ..41-1....o. 1. 1. .1. o. . .-..4 1. - . .- ..-. .61 1. . . . . . .. ... .1... .-.. ...!1. ....i .1. . .. - .4...-.4.1 4... .1 . 4-11..-1.41 . . . . .... .. .-...... 14.. .-.; . , .. . . 1.-. 11. ...... .01. ..- .- 11..-1 . . . . . . .. .. -. x ... ... l. ..711‘41 .1.01.. . ...1 (1.11. ..-. 1... .-.1 ....1 1119. . .. . . . .. -.-.. .... ., .....K .1. .. v .1 .1 . . O1. 1 . .6. .1- H....11--4-A-.111 11‘ . . . .. . . .... ...- .-. ... 1414.....1.-..17|11 . -1 19.. .- ... -.-4 .1-.‘r.v.4 --....-I-1 90-1-11.-- .. . 1 . . . 1 . .. ..4 4.1411 01.041 ...1 14.1 7 ..- I||0 fl 1. 11. . .41.. 41141101 -1411 41' 11011134144 ‘1': . . . . . . ..-. ..-. ..-. . .. ..- o--. ... . 1.1.1. . .. 1-..- 1-111.114.1L414T ..1. 1111-. 11.1.- .111 IGOO I300 EL umapqmmasfi» 450 350 250 l50 50 (SEC) TIME . .11... I. ,ffilb',.1.r..., ‘33.“. 35 COOLING CURVES TIME - TEMPERATURE 0 O 3 I200 EL um3h0 0 1010001. 0.101111 11.0.0 0 1 1 01.10 110 11¢..0I00 111100.?0 0 1.1 1 To 0|01 0 1 0 1 1 1 . 04 I 1 1 1 1 . . 0 .0011 0100 1100 100011401. 001.1 7.110 10.0.. 1w11011 01001900110 0|000#100.10 70VI0|0| 010 001.0011 01410.0 <01Y0¢0010 010.0w11I00 00.11.0100 110010 ..000 . . . 101. . .1. T1111 11.- .111.0000 101110101 0|0.0.01 1011410101 0001401011v000041011g0001§ 141110 1.11.9101. 0.0.9.0 0010 v1.0 .1010. 1 II .01. .1011H119 . .... ..1. 1.0. .1 . 10 0 . , A 4 0 00.11 1 1-. .111 01... 0000 .01 1 101. .1 .1. 0111 I190? 10.001.110I00 .110.0+To0.11 0.0. 1.01001 1001’ 060 r0101 10101 10.0.01fl0 011.. 11100 1.001 11. . .11... 1.01 0 10. 1 1111 101 . 01.11. 1001. . .00 .1... 1.10. 0.110 70000 111111 11.11 . 01|4$0000 011001 1.0 000151 00.’ 01.19.4194 01111511000 10.1111 1. 10 I 0. 0.10 .. .0 .1 1 1 0.11 . .. 011 01.....0F0101 ..10 .011 .000. 110.0 111110013000 .I111AT00110410100 .00001fl10. w1.1101 10010141100111.110 ..11v00. . 0...1111..1 0... . .. 1..1 .11... ‘ l 0 1 1 l 0 V 0 I 9 A O 0 . Q l v‘.'. 0 I C 0 1 A O CIT '10 D O 1. A O I Q C Q C I.‘ ‘ 0 ‘ 1‘ ’IY v ' ‘ Q 0‘ ‘ O ‘14 7 - O 1'11. 0 CH1 I 5 C '10 TQIHII‘ -1’1‘111]. ’1 "‘LI C U O b 0 1 1 1 V I 1 0 l 1 O 1 - 1 v V I O 0 0 I 0 , r . _ . 1 4 , 4 01.. .... .1111 1.01 101. 010. 1000 .00. 1000 .010 .0001 1000 fi1.0? -10 .011v010. 11.10 010.0%0101001wI000 110.1 00. V . . . 01 1111 10.1 . . . 00. . . . .. 10.1 101. 0011 .00 J 11. 1. .. 11.1 0.01. 1.014 .000 00... 010110 001 . 1010fl1011a01004000.0 10140 0111. '10. . . . .1 .I.10 ...1 . .11 . . 1. . . . . . ... 1.0 . . . .1 . .. 1 . .11 .. . . .. . . . .0. .11. .. .11 . 1.. . 1.011 1.4 . . . . .01. .. . .. . .0.1.000..11 11100 .11. .. . . . . . . . . . . .1 1... ... 10.. .11. 11.1 10.. .-.. .... 1.1. ....0..1. 1. . ..1.. .0.110.... .11... .. 11110 .1.1 1.1.0 .10.1. .. . . .. . . . .... ... N.. . . . . . . . . 1 .... .... . .. .. 11.. 1.. . 11.1 1 . 11 . . . . ...1 . . . 11.. .1. . 0011 1... . . . . . . . . . . . .. . . . . ..1 . . . . .1. ...1 . .1 . .. . .. . . . - . 10.1 . ..1 . . .. . . .1 .. .. . 11 1110 . . .. .. . . .. . . . .. . . 1 . . . . . 1 .1. . . . . 1. . . . . .. ... . 0.1. .... . . . .. .. . . . 0 .. .. 1 ..0. 1 1. . . . .. . .. . . 1. 1 . 1. .. . . . .. .1 ... . . .. . . .. . .. . . . .. . .... ...1 .1 .. 1. .. .. .. . .1 1... 1. .. 1110 . .. . .. 1 1.. . . . . . . ... . . 1 .1. 11.1 1. . . . .1 . ... .10. . . . . .. . . ..1. 0 . . . . ... 00.. 010. .... . 0. 1.1. .1. .1. 1 . . .0 11.1 010 .. 11 1... . 1. 1 .. 10. . . . . . ... . .1 . . .. ... . . .. . . 1 . .1 . 10.0 v.1. .001 .1 . . 11.. .. .0 ..-. 1.0. .110 ...... .011 100. . . . . .1. I10. 1. . .. .. .. .1 . . . .... . . .4 . . 1. .. ... . 1... .... ... . 1... .... .... . . . . ...- .... .... .1. . .. . 11.. . . . . .. .11.. 1-... . ,. ...w...-... .....-.. ... .... .... -...1... .... ... .... ....1... .... .... ....111. 1 ... . . . . ... . . .. 1 . . . . .. . . ... . .. ...0 .... . . ... 1... .+.. ..1. ..1 . .1.. .... .... . . . . . . .1 . . . . .111 . .. .. . . . . .. . . . . . . . . .... .... ... . . . . . . .. .... ... . .. 11.. . . . .1 . . . . . .. ... . .... . .. . . . . .. . . . . . .. .. . . .... ... . .... ... . . .I .. . . . . . . .1 . . . . .. . . . ...0 ... . ... . 1 . . . . . . .. _. . .... .. . . ... . .1. ..1 ... . .... . ... . .a . . .1. 1. .1 .... . ..1 . . . . .... . . .. _ . . . . . ... . .. . .1 . 11 .. .... .1.1 . . . . ...1 . . . . .11. . . .. .. . .. 1 1 . . . . . . . . ..1 1. .4 .. . . .. . . . . . . . .. . . . . . . . .. . . ... ... . ... . .... 1. .1 .... 1 . . . .... . . .. ...1 . . . .. . . 1 .1. . 1. .. . .. .. .... 1.11 . . .. .:...-... ... .: :. ..::.:.::.:.::.:..:.::.:.:1 .....2 .:.::.:.f&::. a . . . . . . . .. . . . . .. . . . . . . . .. . .. . .. . . .. .... ..11 1. .. . .. 1... .... .... .... . 1 ... . . . . . 1. .- . . . . . . . . . . . ... . . . 1... .... 11.. .0.1 . . . .. . . . 1.. . .. 1 . ...1 . . 1 . . . . . . .. . . . .. . .. . . . . . . . . .. .. .1... 0.1111 0... .. . .1.. 1 .. . .... 1 . ..11 . .. . . . . .. .. .. . ... . .. .... .. .. . .... . . . . 1. .. .. .. . ..1 1.... ..11 . . .. .... 1 .. .... .. . . . ... . . . . . . 1 .. . 1.. . 1. 1 . . . . .. . . . 00. .... 011. 00111 ... 11. . .. .1 1. . . . . . 1. .. ... .. . . . . . . .. .. . . 1. .. .1. ... . . .. . .1.. 1. .. .. ._ .1. . . . . .. . . . . ... .. . . . .. . .111 .. . . . .. .. 1..- . ... . .. . .01. .1..- ... ...1 .0. . ... . . . .. . .. . . .. . . . . . . . . . . . . . .-.. . . 1... ...1 .11. .. . 0.1. . . . . . . . . .. . . . . . . . . . .. . . ... .. . ... . . .. . , .... . .11 0110 . . . . . . .. . . . . . .. .. . . ...1 .. . . 1... ... . . .1. ...1 11 ... . . . . . ...1 .... .11. . ... ... . . ... .. .... 1 .. ..... .... I... .... .... ..... ... ...1. .... .... .1...1.1 . . . .. . .. . ...- .-. ...... .... .-.. ...., . .... ...... .. .... .01- . . .. . . . . . . .. . . . . . . . . . . . «... a. .. .. 0 1.0. ..1. .0.. 11 ..1. .1 fl... . . . ... . . . . . . . . .. ... . . . 1. . . .1. . .... .... .... . . .0 111 . 1.. .1 . . . . . . . . . .. . .. . .. . . . . . .. . . ... ... . 1,... . .. . 0110. w .11. 1...: 1. . 1.1 _ b 1 .. 1. . .. . . . . . , . .. . . . . ... . .. . ... . . ... ..1. 1 . . . . ... . . .. . . , . . . . . . . . .. . .. . .1. . ... . . . ... . .. 1. . . . . . . . . . . .. . . ... . . . . . .. . .... 1.. . . . . . . , . . . .11. .0. . . . .. . .. . . . . . . . ..... . . . . .. . .... . . . .. . . . 0. . .1. . . . . . . . . . . 1.. . . . .. . .1 . . .. 1. .. . . .. . . . . ... . . . . . . .. . . . . .. . . . . . . . . . . .. . . .... ... . . . . . .. . . . . .11. .1. .. .... . . . . . . . . . . . . .. . . . . . . . .1. . . . .. . .. .... .10 . . . . . .1.. 1.. . ... . . . .. . .. .. . . . . . . .- . . . . . 1 .. .. .. 1 .11. 0 , . 1.1 .... .0. . . ... .. . . . .. . . . . . . . . . .. . . . .. . . . . .. . . ... . . . . .. ... .... . ... . . . . . . .. .1 .... ..1 .... 1... 11 .. .11 . . . . . .. . . . . . . . ... . ... . . . . . . . . . .. .. . . .111 . .... . . .1. 1 1.. . 1 1 . .. . .. . 1 . . ..11 . . . . . .11. . . .. . . .. . . . . . . 1 ..1 . .. . .... 1 0. .111 ..1. 1. . . ... . . .. 11.. 1101 ... 1.... .. . .1. . .. . . o . . . . . . . 1 1. .. . . ... . .. .... . .. . . . . ... . .... .. 011 .... r. 1 .1 .1 1. . .. . . 1..1 .1 1 . . 11. . 1. . .1 . .111 . . . . . . . . . . .. . . . . . . .. .. , . . .. . .. .. v.1. . . . .. .. .... . . . .... ... . . . . . l 0.1 .. .1 .11 11.1 . . .11 . . . . . . . . . .. . . . . . . . . 1 .... . .. 0... 11 . ..11 . .. . . . . . . 1. .. . 1 . 1.1 1-. . ... . .. .4 . . .... . . . . . .. . . . . . . . . . .1. .. . . ...11 .. 1 o. .. . .1.. . . . .. . ..1 . . . ..1. . . . 1 . . ..- . . . . . . c . . . . . . .. ....0 . . . . .. . . .. . . . 0.. 11 0 1 . 1 1 0 .11.. 1-.I . .1. . . . 11 . .. . 1 .1 0. .. .11 1... 1. . .1 1.. 011. 4 . . . . . .. . . . . .. . ... . .. ... . . . .... ... . ... 1 .... 1. . 1. .. . 1. . . . .1 . ..... 1 .. 1... . ..1 . . . . . . . . .. . .. . . .. . .. .. ... .11 1 ... .... . ... . . 1 .. . 1... . . . . . ... . . . . . . . . . . .. ... .. . 0. ... . . ..- . 1 . .. .. . ...1 1. .. . .. . . . . . . . . . . . . . . . ... . . . . . . . .. . ... .. 1 . .. ..1. . .. . . . .1 . .11... ... . . . . . . . . . . . . . . . . . . . . . . . . .. .... . . .... . . . . . . . 1. ..I1.1 . . . . . .. . . . .. . . . . . . ... . . . . 01 1.. .1. .1. . . . .1 . ..11 .. . . .. . .. . . . . . .. . . . . . ..1 . . . . . . . . . . . . . . . .. ...1. .1..- . . . . . . . .H .l . . . . . . . 1 .. . .. 11.1 . . .. . . . .. . . . .... 1 .1. .. . . .. . . .. 1 . . . . .. . . .. . . . .... .. . .. . . . .. ..1 . .. ...... . .1. 11. 1..- .1 . . . . .. . .. . . . . . . ....1 .. . ... T .. . ... .. .1 . . 11.1 ... . 1 . 1. . . .1. . . . . . .. . - . .. .. . .. 1.0. 1 . . 1 . 111.1 1 .. . . . . .11.. 11. . . . . . . 1 1.1 . . . . . . . . . . . . . . 1. . 1 . 4 .1111 11101.... . .4 11 1 .. . . . . 1.11 I-111| 11.. . . ..-I . . 1 1.. . . 1. . .. _ . .. . . . . . .. .1 11 1 .. .111 .111 . ..A111 . . . .1 . ... 110-11 0...; . 11 I . . 1. . . . . . . . . .... . . .. .. 1 1.01 1.101. .. ... 111 . 1.1. 1].. ..19 0111 .111 1 . .1 1 .. . . . . . .. . 1 . . . .. ,. . . . 1.1.- . ..10 1... 1. .1 1.1. .11. .1. . . . . .. .1 1. .10-.. .1... . I. 1 1.1. . . . . . . . . ., . .. . . . .. . . .1 . . ... C-.. ..01 . 1 .. .1 01-- . ...111 .1 11.11 1 1.. 1.10 .. ..11 . . . . .. . . . . . . .. . . .. . 1. . . .1. -11.. -.- . 1... .. . 1 1- .. I- . . I- 1. .1 .1I1 1 1 1 . . ... . . . . . . . .. . . . . ... . . .. . . . 0.. 1, .0. 11.. . . . . . 1. . . . 1. . 1.1.. I111 11.11 .11 ... ...11 v. .1. . . . . .. . . . .. . ... . 1. . . 1 ... 1... .11. . .. . 1.. .1 .1 1 ..IIJ.0II. 1.I11 1... ..1.. 101.01 _ . . . . .. . . .. . .... .... .... 1 . ..1 .1... 0.1. .... 1 1. ...1 . .. . v 111 101.1 1l.11 1.1. ..II 11101 . . . . . .. . . . . . . . . . .. .1 .1 .11.. .111 . 1 1.110 . 1 1 . . . 1 . . .1 . 011 1 1.11I1 0| .1 0111.4 0-1000. 1017011101 . . v . . . 1 . 1. . .1 . . . .0 . . . 1.1 ... . .II A . 1. 1 . . 1. . I . .1 11 1 1101 11.1; 1 10 1141 Y1011I1 .. . . . ...- . . . . ... ...- 11 . - . . . . . . 1 1 .. -1 ..1 11.111..III .-11 111..r11|1.. I500 I400 I300 IZOO IIOO IOOO 90 an L mmahdm waim... (SEC) 250 TIME I50 50 42 COOLING CURVES TIME — TEMPERATURE I500 O O 2 who. mmahdmmaEMP 450 350 250 |50 50 TIME (SEC) 43 COO LING CURVES TTME -TEMPERATURE 450 350 ISOO 250 50 IQOO '300 Auov mmDh.VL olfiuo Ola... ‘004A4-3? 40140 Tclvlolc IO'OLTOQIO‘T. ‘Tbao 'r‘)‘ l 4 .... a T. Oat‘rn¢70 vu-TQ o'Tv TvO.9T 0.7.- 06T‘0 VIII. 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