THERMAL-METALLURGY OF 
 
 ZING ALLOYS 
 
 BY 
 
 AMBROSE ALLEN ARNOLD 
 
 THESIS 
 
 FOR THE 
 
 DEGREE OF BACHELOR OF SCIENCE 
 
 IN 
 
 CHEMICAL ENGINEERING 
 
 COLLEGE OF LIBERAL ARTS AND SCIENCES 
 UNIVERSITY OF ILLINOIS 
 
 1921 
 

 Digitized by the Internet Archive 
 in 2015 
 
 https://archive.org/details/thermalmetallurgOOarno 
 
/ 92 / 
 Ar 6 
 
 UNIVERSITY OF ILLINOIS 
 
 i92_^__ 
 
 THIS IS TO CERTIFY THAT THE THESIS PREPARED UNDER MY SUPERVISION BY 
 AMBR 0 SE_ ALLBML A M OLD. 
 
 ENTITLED I lijiIEiiu. TALL.U RG- Y- -Q£ - - ALL-Q Y-S 
 
 IS APPROVED BY ME AS FULFILLING THIS PART OF THE REQUIREMENTS FOR THE 
 DEGREE OF J3ac h P..1 or — Qf— Sc-i^nc e _ All A iaer t . ia £t X_ tie. ing 
 
 [OiAA/l 
 
 Instructor in Charge 
 
 Approved : (A 
 
 
 
 HEAD OF DEPARTMENT OF 0- HEm TS ARY 
 
 *J'<s 
 
 S0189 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

C-Q-JS-T-E-N-T-S 
 
 Introduction 
 
 
 Pages 
 
 Zinc - Tin Alloys 
 
 
 Page 
 
 Graphs 
 
 11 umbers 
 
 1-12. 
 
 Zinc - Lead - Tin Alloys 
 
 Pages 
 
 Graphs 
 
 numbers 
 
 13-24. 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 - 
 
 - 
 
 
 
 
 
 
 
 
 
 
THERMAL METALLURGY OP ZIUC ALLOYS 
 
 Zinc is practically in its infancy as far as its possible 
 exploitation of uses is concerned. In order to discover new appli- 
 cations it is necessary to understand zinc and its varying condi- 
 tions. That has been the objeot of this investigation — How does 
 Zinc behave when alloyed with certain other metals? 
 
 In order the better to understand metals, a comparatively 
 new branch of scientific endeavor has recently been given more 
 attention — that of Physical Metallurgy. The scope of Physical 
 Metallurgy is exceedingly wide and makes generous use of chemistry, 
 physics, mechanics (strength of materials) .crystallography, and 
 Thermal analysis. 
 
 It is in part to the latter division — thermal analysis — 
 that this study directs itself in so far as certain Zinc alloys are 
 concerned — Zn— Sn, and Zn - Pb - Sn - although thermal relations 
 of metallic alloys have been given some attention, it is a compara- 
 tively new consideration and much work remains to be done. A survey 
 of the literature gave no evidence of any work along the lines of 
 this particular investigation, alloys of zinc and tin, and of zinc 
 lead, and tin. Excellent work had "been carried on with some of the 
 more common alloys used in everyday metallurgical practice, notably 
 that of iron, carbon, and copper, and also a few zinc combinations. 
 
 A study of the changes which occur when metals are heated and cooled 
 has thrown much light on the constitution of those metals and their 
 alloys. The following have done work along these lines :- 
 
 Metallic Alloys William T. Brannt. 
 
 Introduction to Physical Metallurgy 
 
 Walter Bosenhain 
 
 Metallurgy of the Common Metals 
 

 
 
 
 
 
 
 
 
 
 . 
 
 
 
 • 
 
 
 — 
 
 
 
 
 
 
 
 
 '• 
 
 ' . 
 
 
 
 
 
 . • j 
 
 » 
 
 * 
 
 
 
 
 
 . 
 
 
 
- 2 - 
 
 The Physical Chemistry of the Metals 
 
 Rudolph Schenck. 
 
 Translated by Reginald Scott Dean. 
 
 Traite de Metallographic Felix Robin 
 
 The Elements of Metallography Rudolph Ruer. 
 
 Translated by C. H. Mathews on. 
 
 Chemische Technologic Der Legierungen 
 
 Dr. P. Runglass 
 
 A Treatise on Brasses, Bronzes, and other Alloys 
 
 Robert H. Thurston. 
 
 Metallogrphy Cecil H. Desoh. 
 
 Alloys and their Industrial Applications, 
 
 Edward F, Law. 
 
 There are various methods of making cooling curves, de- 
 pending upon methods of heating and methods of plotting. For heat- 
 ing purposes, furnaces of the gas or electical resistance types are 
 commonly employed. In this investigation a gas furnace was used. 
 There are three distinct methods of plotting data: first, "time - 
 temperature,” which is simplest and gives behavoir of metal in most 
 direct way; second, "inverse rate,” for which the observer notes 
 the time intervals occupied by the metallic solution in rising or 
 falling through successive equal differences of temperature and plots 
 a curve whose ordinates are T (temperature) and whose abscissae 
 are ^ where t is time and T is temperature; third, the "differ- 
 ential" and "derived differential" in which the rate of heating or 
 cooling of the metal under investigation is compared with a stand- 
 ard piece of metal placed in the same furnace and treated under the 
 same conditions at the same time. In this investigation the first, 
 or "time-temperature" method of plotting cooling curves was followed. 
 It is easily the simplest and for this purpose seemed sufficiently 
 adequate. 
 

 
 
 
 
 
 
 
 . 
 
 
 ■ 
 
 
 
 — 
 
 * / - ■ 
 
 ' i i» yta 
 
 [. ■ ■ ' ' ", . ; , 
 
 
 
 
 
 
 
 
 
 
 
 
 . 
 
 
 r.; 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 . 
 
 
 
 
 
 
-3- 
 
 The procedure was simply to get a melt of the alloy, in- 
 sert a thermo oouple and read temperature as it cooled, at one 
 minute intervals, and plot the data on graph paper. Wherever a 
 flattening of the curve is evident, at that temperature a solidi- 
 fication took place. 
 
 An ordinary pot furnace was used into which air and gas 
 in proper proportions .admitted under the usual laboratory pressures, 
 were burned. This furnaoe was thoroughly saturated with heat to a 
 temperature several hundred degrees higher than that required for 
 the melt in order that the radiation of heat might be slower and 
 more uniform. This is an important precaution as was learned by 
 experience. A mixture of the metallic constituents in granulated 
 form, chemically pure, 200 grams in weight, was placed in a fire 
 clay crucible and covered with about one quarter inch of pulver- 
 ized bone charcoal. The crucible and its contents were then placed 
 in the furnace until a good melt was assured. The heavy covering 
 of bone charcoal prevented oxidation. The melted solution was then 
 thoroughly stirred with a steel spatula, a thermo couple inserted 
 into the melt, the gas and air turned off, all openings carefully 
 covered with heavy asbestos sheets, and the regular readings were 
 then taken. The graphs show that all readings were begun at 525 C. 
 As a matter of fact the cooling usually started at 600 C, By the 
 time the thermo couple indicated 525 C the rate of heat radiation 
 was quite uniform. While the diagrams indicate only fifty minutes 
 for each "run", some of the melts were continued for longer periods 
 with the same evidence — namely, that the cooling continued to drop 
 regularly. 
 
 A portable Hoskins, type (PA), pyrometer, frequently 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
-4 
 
 calibrated, was constantly used throughout. 
 
 The melting points of the metals concerned are as follows:- 
 
 Zinc 
 
 419 
 
 C 
 
 Lead 
 
 327 
 
 C 
 
 Tin 
 
 232 
 
 C 
 
oo/ 
 

 


 
 . 
 
 
 
 p 
 
 
 
 
 c- 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ■( 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ' ; , 
 
 
 
 
 
 
 ■ 
 
 . 
 
 
 . 
 
 
 
 
 J - 
 
 
 
 
 
 
 
 
 
 
 
 
 ' 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 


 



5r\ 
 
 
5- 
 
 A study of the graphs for the binary system, Zn - Sn, 
 readily shows that as the percentage of Zinc decreased and that of 
 Tin increased the melting points decreased in value. This is to be 
 expected when a substance of a low melting point, Sn at 327 C, is 
 added to one of a higher melting point, Zn at 419 C and, since a 
 flattening of the curve took place but once in each instance, it 
 follows that Zn and Sn are soluble in each other in all proportions 
 considered. 
 
 The 
 
 points of the 
 
 following summary will briefly indicate the melting 
 different alloys 
 
 Zinc 
 
 Tin 
 
 MP 
 
 * 
 
 $ 
 
 C 
 
 100 
 
 — 
 
 419 
 
 95 
 
 5 
 
 410 
 
 90 
 
 10 
 
 400 
 
 85 
 
 15 
 
 397 
 
 80 
 
 20 
 
 395 
 
 75 
 
 25 
 
 393 
 
 70 
 
 30 
 
 390 
 
 65 
 
 35 
 
 385 
 
 60 
 
 40 
 
 380 
 
 55 
 
 45 
 
 373 
 
 50 
 
 50 
 
 365 
 
 These results have also been plotted — temperature 
 against percentage composition, on the Zn - Sn equilibrium curve, 
 which will give a visualized representation of the same data (See 
 graph Ho, 12.) 
 


 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ■ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 - 
 
 
 
 


 o 
 
 o 
 
 Y? 
 
 $ 
 
 <V 
 
 O 
 
 **> 
 
 <N 
 
 
 
 

^ ^ i- 
 
 3 - ^ 
 
 rr± 
 

-6 
 
 The binary system is comparatively simple* When the 
 ternary system however is considered, a number of irregularities are 
 at once evident. Zn - Pb - Sn are not, soluble in each other in 
 all proportions. This is borne out by the fact that in some in- 
 stances the curve has flattened out in as many as three distinct 
 places. 
 
 A composition of 90$ Zn - 5$ Pb - 5$ Sn was uniformily 
 soluble. The next graph (number 14) shows a remarkable change. 
 
 Some of this solution seems to have solidified at 419 C, the melt- 
 ing point of Zinc, a second solidification at 405 C, and a third 
 at 325 C, close to the melting point of Lead. From these facts, 
 as verified in other alloys, are shown that some of the Zinc went 
 out of solution in its pure state and solidified at 419 C; that 
 a solution of some mixture, presumably Zn, Pb, and Sn, solidified 
 at 4o5 C; and finally that some of the uncombined Lead went out of 
 solution very close to its usual melting point, 327 C. From such 
 data we must gather that a mixture of that composition upon complete 
 solidification is anything but uniform in texture. Strangely enough 
 graph 15 shows that the constituents are completely soluble in one 
 another. The very next composition, graph 16, shows another radical 
 change. In the latter instance another three fold solidification 
 took place - no separation of a pure element this time, but rather 
 three distinct combinations solidifying at 397 C, 380 C, and 295 C 
 respectively. A natural inference would be that all the Zinc had 
 fallen out in the first two separations and that in the latter case 
 lead and tin alone had combined. 
 
 A comparison of #16 and #17 shows that although the lead 
 control of the latter was more than that of the former, yet the 
 
-Y- 
 
 initial melting point of the former was higher than that of the 
 latter; while the final solidification of the latter is higher than 
 that of the former. The most logical explanation of this phenomena 
 seems to he that in #17 a larger part of the lead, in an uncomhined 
 state, fell out at 325 C - near its ordinary melting point. 
 
 lumber 18 in which 70 $ Zn was also employed, shows that 
 no lead fell out. This is not unusual since the lead content of 
 the alloy was only 10$, There was a double solidification, at 390 C 
 and at 380 C. This held true over a very small range of temperature 
 only 10 . In #17 there was a marked tendency toward a close double 
 
 solidification, which probably took place in a small degree, the 
 heat radiation of the furnace being too rapid for the thermocouple 
 to make the proper registration, 
 
 60$ Zinc was contained in the alloys indicated on graphs 
 # 19, #20, and #21. It is of interest to note the similarity of 
 graphs #16 and #19, the former containing 70$ Zinc and the latter 
 60$ Zinc. In both cases the first two solidifications took place at 
 the same temperatures 395 C and 380 C and practically during the 
 same time intervals. Why this should be true is difficult to de- 
 termine, The latter alloy had 10$ lead and that may be one of the 
 contributing factors. Of the three alloys containing 60$ Zinc only 
 one of them, #20, shows any evidence of a third solidification, at 
 320 C which was very likely caused by a freezing out of some lead 
 and tin. 
 
 Alloys #22, #23, and #24 contained 50$ Zinc. #22, with 
 
 35$ lead, shows a deposition of that metal alloyed with tin at 300 C. 
 The initial freezing point was at 400 C which is higher than for 
 the other two alloys. #23 and #24, on the other hand, show a 
 

 
 
 
 
 
 
 
 
 
 
 
 
 . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 _ 
 
 
 
 
 
 
 
 
 
 
 . 
 
 
 
 
 
 • 
 
 
 
 
 
 
 . 
 
 
 
 
 
 
 
 . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ■ 
 
 
 
 . 
 
 
 . 
 
 
 
 
 
 
 
 . 
 
 
 
 
 . 
 
 . 
 
 
 
 
 
 
 
 
 
 . 
 
 
 
 
 
 
- 8 - 
 
 triplicate solidification in each instance. This is undoubtedly due 
 to the increase of the tin content with which the Zinc and some lead 
 readily alloyed themselves. In #23 some lead fell out in an isolat- 
 ed way. That this did not hold true for #24 is evident from the fact 
 that the freezing temperature there was 340 C which is 13 higher 
 than the melting point of pure lead. This shows that some zinc must 
 have had an influence in the rise of temperature. 
 
 The following summary will briefly indicate the melting 
 points of the different alloys:- 
 
 1o 
 
 * 
 
 i 
 
 Soli 
 
 d 
 
 i f 
 
 ications. 
 
 Zn 
 
 Fb 
 
 Sn 
 
 1 
 
 
 2 
 
 3 
 
 90 
 
 5 
 
 5 
 
 415 
 
 
 — 
 
 — 
 
 80 
 
 10 
 
 10 
 
 420 
 
 
 405 
 
 325 
 
 70 
 
 25 
 
 5 
 
 400 
 
 
 — 
 
 — 
 
 70 
 
 20 
 
 10 
 
 397 
 
 
 380 
 
 295 
 
 70 
 
 15 
 
 15 
 
 405 
 
 
 395 
 
 325 
 
 70 
 
 10 
 
 20 
 
 390 
 
 
 380 
 
 — 
 
 60 
 
 30 
 
 10 
 
 397 
 
 
 380 
 
 ... 
 
 60 
 
 20 
 
 20 
 
 400 
 
 
 380 
 
 320 
 
 60 
 
 10 
 
 30 
 
 380 
 
 
 360 
 
 
 50 
 
 35 
 
 15 
 
 400 
 
 
 — 
 
 297 
 
 50 
 
 25 
 
 25 
 
 395 
 
 
 370 
 
 325 
 
 50 
 
 15 
 
 35 
 
 380 
 
 
 360 
 
 340 
 
 
 That Zn - Pb 
 
 - Sn will not combine 
 
 in 
 
 all 
 
 proportions is 
 
 amply borne out by the 
 
 evidence of 
 
 the above 
 
 experiments. This, 
 
 likewise , 
 
 indicates that there must 
 
 be a wide 
 
 range 
 
 in the texture 
 

 
 
 
 
 
 
 
 
 
 
 
 
 . 
 
 
 
 
 
 
 
 
 
 • 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
- 9 - 
 
 of the alloys — some will have higher tensile strengths, some will 
 withstand more compression, than others. Their molecular struct- 
 ures must greatly vary as a microscopic study would undoubtedly 
 reveal. This much given as a clue as to what might he expected, 
 further investigations are necessary to determine certain other 
 qualities more definitely. 
 
 / 
 

 - - 
 
 V, T ■ ‘ 
 
 - 
 
 
 
 
 
 ' 
 
 

 
 
 
 
 
 
 
 
 /