EFFECT OF PREAGING ON THE TRANSFORMATION BEHAVIOR OF THERMOMECHANICALLY TREATED SPINODAL CU-NI-CR ALLOY

Transformations occurring in a spinodal Cu-44Ni-5Cr alloy were investi gated under three different heat treatment conditions: quench, age; qu ench, work, age; and quench, age, work, age. While prior aging was car ried out at 550-degrees-C for various durations of time, prior deforma tion was 80 percent reduction in thickness by cold rolling. Final agin g was done at 550 and 600-degrees-C. The transformation behaviour was characterized through hardness measurements and X-ray diffraction stud ies, the latter for measurement of wavelength and amplitude of composi tion modulation. It was observed that at the lower aging temperature t here was an increase in hardness with increasing pre-aging time. The k inetics of spinodal decomposition was also found to simultaneously inc rease. Long pre-aging durations, or higher aging temperatures lead to early loss of coherency, which could be interpreted in terms of migrat ion of matrix dislocations to the particle interfaces under coherency strain.