Microstructural evolution of martensite during deformation in Zr50Cu50 shape memory alloy

The microstructural evolution of deformed martensite in the Zr50Cu50 shape memory alloy was studied by transmission electron microscopy (TEM) and the deformation mechanism was finally clarified. Before deformation, the intervariants in the Zr50Cu50 alloy showed a (021) type I twinrelationship, and the dominant substructures inside the martensite variant were (001) compound twins. Distinct deformation mechanisms were observed at different deformation stages. Detwinning of the (001) compound twins was the dominant mechanism during the primary stage. As the compressive strain increased, the detwinning zone expanded, but did not result in complete detwinning. At higher strain levels, stress induced the formation of many (021) and (20 (1) over bar) nanoscale deformation twins, originating from 1/10[012] partial dislocations; this was considered to be the dominant deformation mechanism. The irrecoverable strain was closely associated with crossed (021) and (20 (1) over bar) deformation twins that limited the mobility of martensite during heating. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.