Solid solutions of rhodium with copper and nickel

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Technical Report No. 2, Contract Nonr 551 (42). Univ. of Pennsylvania, Philadelphia, 1962. 4 J. D. ESHELBY, W. T. READ AND W. SHOCKLEY. Acta Met. I (1953) 251~-259. 3 A. E. H. LOVE, A Treatise on the Mathematical Theory of Elasticity, Fourth Edition, Dover Publications, New York, 1944. 6 SyrnPosium on the .Detevvnination of Elastic Constads, ASTM, STP No. 129, June 25, 1952. 7 D. I. BOLEF, J. A$@. Phys., 32 (1961) roe-log. 8 J. F. ?;YE, The ~hys~~a~ ~~o~ert~es of Crystats, Clarendon Press, Oxford, 1957.

Received September 3rd,

1963

J.

Less-CommonMetals, 6 (1964) 245-248

Solid solutions of rhodium with copper and nickel The tentative phase diagram for rhodium-copper alloys proposed in ref. I (see also ref. 2) consists of two terminal solid solutions separated by a miscibility gap. Since Rh and Cu satisfy the generally accepted conditions for complete miscibility in the solid state, it was anticipated that rapid quenching from the melt could lead to metastable solid solutions at all concentrations. Complete miscibility in similar cases has been previously reported for Ag-Cu3 and Ag-Pt4 binary alloys. No phase diagram for rhodium-nickel alloys could be found in the literature. In Ref. 5, however, a statement is made that Rh-Ni form a continuous series of solid solutions but no experimental evidence is presented. The present study confirms this statement. The alloy constituents, of purity greater than 99.9%, were melted by induction heating in an alumina crucible in a hydrogen atmosphere. After melting, the small ingots weighing about three grams were checked for weight losses, and since these losses were smaller than o.r%, the actual composition of the ingots was assumed to be within f 0.2 at.% of the nominal composition. Because of possible segregation in the ingots, however, the uncertainty in the actual compositions of the X-rayed specimens is probably greater than -&o.z at.?;. Judging from the scatter in lattice parameters obtained for several specimens supposedly having the same composition, the uncertainties in concentrations were estimated to be Ifr 1.0 at.% for Rh-Cu alloys and fo.5 at.% for Rh-Ni alloys. All alloys were quenched from the liquid state using a technique previously reported”,4,67?. A small amount (- 30 mg) of alloy was melted in an alumina ceramic insert under an argon flow prior to quenching. The quenched specimens were in the form of flakes about I mm2 in area and about IO microns thick. Diffraction patterns, were obtained with a 114.6 mm diameter Debye-Scherrer camera using nickel-filtered CU Ka radiation. High angle lines were always resolved and spacings were computed using il Koll= 1.54050 A. Lattice parameter and associated uncertainties were estimated from extrapolation against the Nelson-Riley function. The variation of lattice parameter with composition of the quenched alloys is shown in Fig. I. Each point on the graph represents at least two independent measurements. Both systems show a positive deviation from Vegard’s law. The stability of the solid solutions was checked by various heat treatments. The as-quenched Rh-Cu alloys containing 50 and 75 at.% Cu were annealed in evacuated quartz capsules at 600” and at 800°C for seven to ten days. These alloys decomposed J. Less-Common

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6 (1964) 248-249

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into two face-centered cubic solid solutions and since the X-ray diffraction back reflection doublets were resolved, it can be assumed that the alloys were in equiIibrium after heat treatment. The lattice parameters of the two face-centered cubic solid solutions corresponded to copper concentrations of 9.2 and 81.5 at.76. These concentration limits for the terminal solid solutions in the equilibrium diagram at 600’ and

3.50' RH

' IO

8 I 1 20

! 30

ATOMIC

40 PERCENT

SOLUTE

Fig. I. Lattice parameter vs. concentration of Rh---Cu and Rh-Ni solid solutions. Except for the alloy containing go at.:/, Cu. the Rh-Cu solid solutions were obtained by fast quenching from the melt only and are mrtastablc (see text).

800°C are very close to those shown in the tentative diagram of ref. I, namely about IO and 80 at.% copper. The quenched specimens of Rh-Ni alloys containing 33, 45, hz and 80 at.“/; Ni were annealed at 3o0°, LOO’, 5o0°, 600’ and 800°C for at least seven days. No decomposition nor ordering was observed, and the lattice parameters of the alloys were essentially unchanged after heat treatment. It can be concluded that Rh and Ni form a complete series of solid solutions. This work was sponsored assisted in the experiments. W. M. Keck

by the U.S. Atomic

Laboratory of Engineering of Tedmology,

Energy

Commission.

Mate~ids,

WUEY-LIN

Lvo

P. DUWEZ

California Institute

Pasadena, Calif.

J. II. McCoy

(U.S.A.)

1 0. E. SVYAGINTSEV AND B. K. RRUNOVSKIY, Izv.Sektora Ratiwy, IZ (Ig3j) 37-66. 2 RI. HANSEN AND II.ANDERKO,C~~S~~~~~~~~ ofRinca7~ABoys, McGraw-Hill, New York, 1958. 3 I’. DUWEZ, R.H. WILLEN~ AND W. KLEMENT,J. A#% Phys..31 (1960) 1136 and rsoo. 1 W. KLEMENT AND H. 1,. Luo, Trans. Met. Sot. AIME, 227 (1963) 1253. 3 l?. RAUB, J, Less-Common Metals, I (1959) 3. 6 IV. KLEMENT, Ph. 13. Thesis, California Institute of Technology, 1962. 7 W. KLEMENT, J. Inst. Metals, 90 (1961) 27.

Received

September

6th, 1963 j.

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6

(1964) 2+X-qg