COMPRESSION OF CuAlNi CRYSTALS.

Abstract

Single crystals of beta Cu-14. 1Al-3. 0Ni in (100) orientation were reversibly strained in compression to 18%, and 200,000 psi. Above the martensite finish temperature ( minus 11 degree C), the initial luders band deformation produced a single crystal of (010) oriented gamma prime martensite, the stress level linearly dependent upon temperature. Below minus 11 degree C, the martensite itself was reoriented to a single crystal. Beyond 8 to 10% strain, martensite twinning produced an almost linear reversible strain with a temperature independent slope of 1. 5 to 2 million psi. No plastic strain was detectable, the crystals being completely brittle, but the total strain was recoverable. Although the measured austenite finish temperature was 20 degree C, crystals compressed below 50 degree C remained martensitic upon unloading with a residual 7. 8% unrecovered strain. Upon warming to 50 degree C, the sample instantaneously and completely converted to the beta phase in a burst.