Deformation and Defects in Laves-Phase Intermetallic Compounds: Final Report, April 1, 1987-September 29, 1989.

摘要

Most studies of deformation in intermetallic compounds have been on compounds such as Ni(sub 3)Al, NiAl, and Ti(sub 3)Al whose crystal structures are ordered forms of the basic fcc, bcc, and hcp structures. Most intermetallics have more complex structures, and we have chosen to study the largest class of such compounds, the Laves phases, on which information on deformation and mechanical properties is very limited. The approach was to couple basic mechanical property measurements on representative binary and ternary Laves phase with TEM studies of deformation-induced defects. Effects of temperature and strain rate on flow stress in compression were determined for the prototype cubic (C15) Laves phase MgCu(sub 2). More limited but related data were gathered for hexagonal (C14) MgZn(sub 2), dihexagonal (C36) MgNi(sub 2), and two higher-temperature Laves phase, ZrFe(sub 2) (C15) and TiFe(sub 2)(C14). Effects of stoichiometry were studied in ZrFe(sub 2+x) and TiFe(sub 2+x). Extensive studies by TEM showed the dominant slip systems in C15 and C14 phases, and the deformation-induced dislocation structures, are analogous to those in fcc and hcp metals. Significant solution hardening was demonstrated in C15 Mg(Cu, M)(sub 2), where M = Al,Ni,Si, and Zn. The compositional dependence of solution hardening was characterized in MgCu(sub 2(minus)x)Zn(sub x), and limited data indicated solution hardening in both C15 and C14 (Zr, Ti)Fe(sub 2) compounds. Room-temperature deformation of a HfV(sub 2)-based C15 phase in two-phase V-Hf-Nb and V-Hf-Nb-Ti alloys was shown to be produced by mechanical twinning and bands of concentrated shear. 64 refs., 52 figs.