I N D U S T R I A L A N D ENGINEERING C H E X I X T R Y
838
The following figures showing results obtained by the distillation method with anode slimes are identical with those obtained by Skowronski3 using the Keller method: Selenium Per cent
8
7.01 7.09 7.10 J . A m Chem. Soc , 19, 771 (1897).
Vol. 16, No. 8
The results obtained by the distillation method with metallic copper are identical with those found by Skowronski using the Keller method.
Tellurium Per cent
Selenium Per cent
4.29 4.28 4.30
0.02 0.03
Tellurium Per cent
Less than 0.01
Properties and Structure of Some Alloys of AluminiumCopper-Tellurium'" By F. T. Sisco and M. R. Whitmore AIR SERVICE, WARDEPARTMENT, McCoox FIELD,DAYTON, OHIO
D
URING a research
The wort described here is the result of an exploratory inoestigatelluride of aluminium and tion on the alloys of aluminium containing 5 per cent copper to which rise to the top of the metal on the light alloys as It Was decided, tellurium has been added in amounts wrying from 0.25 to 5.00 per of aluminium, the MetallUrgiCal Branch, cent. Following a briefdescription of foundry practice, the physical however, to verify this SUSMaterial Section, of the Enproperties of these alloys and the eflect of tellurium on the microPicion and in addition, gineering Division, Air Serstructure of aluminium are discussed. A method of analysis for should tellurium be insoluble, to discover what deoxithe al/oys is giden. vice, decided to investigate the effects of some of the dizing or degasifying effect, rarer elements on the propif any, the metal might have erties of aluminium containing 5 per cent copper. on the molten aluminium. Consequently, the alloys of the Owing to the large amount of work necessary to investigate composition noted in Table I were mixed and melted. completely the physical properties and microstructure of the FOUNDRY PRACTICE alloys as cast and after a variety of heat treatments, it was The metals were r d t e d in a No. 20 Plumbago crucible in considered advisable to conduct a few experiments in the nature of an exploration and from the results of this explora- i'donarch oil-fired furnace. A total melt Of 10 to 12 Pounds tory investigation to decide whether the series of alloys would was made in each instance. The aluminium was used in the form of notched bars; the copper was added in the form of be worth an extensive research. a 50:50 hardener containing 50 per cent each of copper and MATERIAL aluminium and only traces of impurities. (A 50: 50 copperThe alloys used in the investigation are shown in Table I. aluminium hardener is made by melting copper and alum&m The compositions noted here are as mixed before melting. in separate furnaces and mixing the metals. Owing to the exothermic reaction when molten copper is added to molten TABLE I-PERCENTAGE COMPOSITION OF ALLOYS A S MIXED aluminium, about half the aluminium is melted, the reMelt Aluminium Copper Tellurium mainder being added in the form of bars to avoid an extreme 5.00 0.25 1 94.75 5.00 0.50 94.50 2 rise in temperature. After mixing, the metal is poured into 5.00 0.75 a 94.25 small ingots.) 5.00 1.00 94,OO 4 5.00 2.00 93.00 5 The aluminium and the copper-aluminium hardener were 5.00 3.00 92.00 6 5.00 4.00 91.00 charged into the crucible and melted as rapidly as possible. 5.00 5.00 90.00 A8 A Although a very accurate temperature control of melting was 5,OO None 95.00 5.00 None 95.00 8B not necessary, it was kept between 1350" and 1400" F. As None 0.07 XC 99.820 soon as the alloy was melted, the temperature was taken a This is the pure alumin~umused as the basis for all the alloys. (with a bare chromel-alumel thermocouple and a potentiomI n order to have conditions as nearly ideal as possible the eter) and the crucible removed from the furnace. purest commercial aluminium and copper were used. The The tellurium was now added, being poled well below the analysis of these materials is as follows: surface, and the melt stirred thoroughly. The melted alloy Si Cu Fe A1 was then brought to the pouring temperature, 1300" F., Aluminium 0 04 0 07 0 07 99 82 which temperature within a 10-degree range was maintained Copper .. 99 94 .. .. for all the melts. As soon as the metal was a t the desired The tellurium used was the pure metal purchased from temperature, the test bars were cast. Three sets of TB-1 the manufacturer. test bars were cast in green sand from each melt. Metals of high purity were used in order to prevent the The TB-1 test bar, which is the standard of the Air Serappreciable amounts of silicon and iron occurring in ordinary vice for sand-cast aluminium alloys, is shown in Fig. 1. The aluminium from influencing the physical results. By melting central bar of the three is designated B; either of the outside metals of a very high purity, any appreciable change in physi- bars is then designated A or C. cal properties would be due to the different amounts of tellura Private communication, S. Skowronski, research chemist, Raritan Copper Works, Perth Amboy, N. J., May 24, 1923. Skowronski stated, ium. It was suspected early in the work that tellurium would "in five meltings, the maximum amount of tellurium that could be found in aluminium was 0.32per cent.* * * Aluminium telluride decomposes with not dissglve in molten aluminium, but rather would form the the water, giving o f f hydrogen telluride, which is readily recognized owing to its
-
1 2
Received March 22, 1924. Published by permission of Chief of Air Service, War Department.
fetid odor, which you will promptly notice if you put any residue or slag from your alloy in water."
August, 1924
I.VDCSTRI$L A N D EXGIVEERING CHEMISTRY
The bars as cast are 0.505 inch in diameter and of a sufficient length hetween the shoulders to allow for a determination of elongation on a 2-inch original gage length. When cold, the test hars were sawed from the gate and riser and stamped with the melt number and their designating letter.
839
500-kg.load with the former and a 3.2-mm. ('/%-in.) ball with the latter. CHEMICAL AN.4LYsIS
Tellurium presents no theoretical difficulties of determination in aluminium alloys, being easily separated from the bulk of the aluminium by a sodium hydroxide separation and from the other elements present hy precipit.ation with reducing agents. The method nsed for tellurium was recommended by Skowroiiski,3 modified by the use of hydrazine hydrochloride according to I , e h m ~ ,and ~ is as follows: Transfer a 10-pram sample of the alloy to a 1000-cc. beaker
hot water and boil 5 minutes nlorc. Allow to cool and Ict the insduhle matter settle. Filtcr and wash with a 1 per cent solutioii of sodium hydroxide. Add dilute nitric acid (1: 1) in small portions to the insoluble 011 the papcr. allowing the solution to run into a clean 250-cc. beaker. When the residue has dissolved, wash the paper thoroughly with hot water. Add 10 cc. o f concentrated sulfuric acid to the solution and evaporate to heavy fumes of sulfur trioxide. Cool, add 50 cc. of water. and heat to Fru I-STANIMKU T 11-1 Tnsi UIHS FOB Sauo-Cas? A L U M ~ N WAI.LOYS I~ dissolve the salts. Filter off the insoluble and wash with a small amount of 1 per cent sulfuric acid. Adjust the acidity of the The t,est bars stamped In, IB, and IC were tested as cast, filtrate to I per cent suliuric acid by neutralization with ammathose stamped 2A, ZB,and 2C, arid 3.4,38, and 3Cmere heat- nium hydroxide and heat to boiling. Add 100 cc. of a saturated solution of sulfuric dioxide, 10 cc. of a 15 per cent solution of treated as noted below. hydrazine hydrochloride, and pass sulfur dioxide gas through the gently boiling solution for 30 minutes. Let thc solution stand EEAT TRZATMEW in a warm place over night, filter on a tared Gooch crucible, washing first with hot water and finally with alcohol. Dry at The heat treatment operation was carried on in an electric 105" C . to constant weight. The increase in weight is metallic mufflefuriiacccontr,rlled to within *6"C. (IO'F.) hyarecord- tellurium.
ing potentiometer and automatic current, regulator. The KO.2 series of ham was heated slowly to 510' C. (950" F.j, held at this temperature for 96 hours, aiid quenched in boiling water. The No. 3 series was heated slowly to 510" C. (950' I?.), held at this temperature for SF hours, and cooled slowly in the furnace. The rate of cooliiie was 12' C. (20" F.j an hour and was completed in 18 hours.
For copper a %gram sample ivvas dissolved in a mixture of sulfuric, nitric, and hydrochloric acids, evaporated to fumes of sulfuric trioxide, diluted, and filtered. The filtrate was electrolyzed in the usual manner. As tellurium and copper were the oiily elements that would be present in appreciable amounts, the percentage of alumiiiiuin could be determined by difference.
PHYSICAL TESTS >fET.4LI.OCRAPHY
The ultimate strength and yield point in pounds per square inch were determined on an Olsen 20,000-pound standard tensile machine. As the bars were cast to size, no machining was necessary. The bars were held in wedge grips and the yield point taken when the first permanent set was indicated hy a pair of dividers. The Rriuell and Rnekwell values were obtained under standard conditions, using a 1~1-uini.ball and
Fro 2-100
x.
A s CAST. U N I I T C H I ~
Fm. 8-500
x.
For nn examination of the structure, a 0.5-ineh section was cut from Bars IB, 2B, and 3B of Melts KO.2, 8, and SA. A specinren from Bar 1B of Melt 8B and a small section from the pure aluininiurn Melt 8C were also taken for comparative purposes.
As Cas=
??on.*. A m . Inil. .$fin. M a I . Eng,. 69, 11336 (1928).
UNBTCZZBD
Fm. 4-100
X.
As Qonrcneo. U~.L?ICB$D
Bra. 8-500
X.
AsQurNcnno.
UNErCnEn
F ' ~ .9-500
x.
The specimens were ground flat and vere rough-polishod on French emery paper Nos. 0, 00, and 000. The final rough polishing was accomplished by levigakd alumina on B disk covered wit,h broadcloth. The finish polishing was magnesia 011 broadcloth, followcd by a final treatment on broadc1ot.h drenched with divtilled water. Tho preparation of metallographic specimens of aluminiuiii and its alloys presents many difficulties and must he carried out very carefully to prevent the flow of the soft metal and to eliminate all scrat.chos.j There was no appreciable difference in structure betmeen Melts 2 and 8 to which 0.50 and 5.00 per cent tellurium had been added; hence the photomicrographs of Melt 2 are not, reproduoed here. RESULTS ~ o ~ l ~ o s ~ ~ l o x - T1a1bgives k the ana.lytiea1 results on Melts 4, 8, and SA. Only traces of tclluriuni were found, and from the discrepancy in the results on the same sainple i t is evident that what litdle remained in the alloy was segrcgated. This assumption was proved by a visual examination of the borings. Black psrticlcs containing tellurium were found scat.tered t.hrougli the sample. (This was decidedly noticeable in a sample containing 0.32 per cent tellurium 5
nix,
