CRYSTALLOGRAPHY OF MARTENSITE IN A Cu-10Al-5Ni-5Fe ALLOY

Abstract
The morphology and crystallography of quench-induced martensite in a Cu-10Al-5Ni-5Fe alloy has been studied using transmission electron microscopy. On quenching from 1000°C, the high temperature β-phase transformed to martensite based on the 3R-type structure. Numerous small iron-rich particles ~0.l µm diameter, were observed within martensite plates. The parallel-sided martensite plates were twin-related. When the alloy was quenched from the α+β phase field, the β-phase, which now had a higher aluminium content, transformed to martensite based on either the ordered 3R or 2H type structure. On tempering, the martensite phase rejected Ni, Al and Fe as precipitates based on NiAl and the matrix transformed to a f.c.c. copper-rich solid solution.