Microstructure and mechanical properties of rapidly quenched L1 1 alloys in Ni-Al-X systems
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I.
INTRODUCTION
IN recent years, melt-quenching technique has attracted an increasing interest from scientific and engineering points of view. The main reasons appear to be due to the following two factors: (1) It is possible to produce the materials in the form of wire, sheet, or powder directly from the liquid state, resulting in a remarkable simplification of the fabricating process. (2) From the structural point of view, it is possible to obtain the as-quenched phase having various features such as the refinement of grain size, the extension of solid solubility limit of solute elements, the formation of an amorphous phase or a nonequilibrium crystalline phase, the suppression of segregation, and the introduction of a high density of internal faults. It is well known that the ordered structure in Ni3AI (y') intermetallic compound with an fcc L 12 structure remains up to the melting point, as similar to CsCl-type compounds such as FeAI, NiAI, and CoAl. Therefore, it is impossible to achieve a disordered state of the 7' compound even by any heat treatments in solid. However, if these compounds are rapidly solidified from the liquid state, there is a high possibility that they may change into a disordered state and/or a low degree of ordered state containing a high density of anti-phase boundaries (APB). As a result, it is expected that the melt-quenched 3~' compound exhibits good ductility as well as high mechanical strength by the combination effect of the suppressions of ordering and grain boundary segregation and the grain size refinement, etc., even though the compound prepared by a conventional process is extremely brittle and undergoes an intergranular fracture without plastic elongation. This paper deals with the A. INOUE, with The Research Institute for Iron, Steel and Other Metals, Tohoku University, Sendai 980, Japan, is now Visiting Consultant, Bell Laboratories, 600 Mountain Avenue, Murray Hill, NJ 07974. H. TOMIOKA is with Research Staff, Unitika Research and Development Center, Unitika Ltd., Uji 611, Japan. T. MASUMOTO is Professor, The Research Institute for Iron, Steel and Other Metals, Tohoku University, Sendai 980, Japan. Manuscript submitted July 14, 1982. METALLURGICALTRANSACTIONS A
microstructures and mechanical properties in melt-quenched and annealed states of Ni-A1-X (X = IV -VIII A group transition metals, Cu or Si) ternary alloys which show the Llrtype y' single phase in an equilibrium state. II.
EXPERIMENTAL METHODS
The specimens used in the present work are Ni-A1-X (X = Ti, Zr, V, Nb, Cr, Mo, Mn, Fe, Co, Cu, or Si) ternary alloys. All the compositions of these alloys are located in the formation region of only Ni3Al-type compounds. The equilibrium phase diagrams ~indicate that a chemical formula of the resultant compounds is Ni3(A1-X) for X = Ti, Zr, V, Nb, Mn, Cu, or Si; (Ni-X)3(A1-X) for X = Cr, Mo, or Fe; and (Ni-X)3A1 for X = Co. Mixtures of these pure elements (Ni, A1, and X) were melted under argon atmosphere in an induction furnace to prepare the test alloys. The melts were
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