High-temperature Pseudoelasticity of Co49Ni21Ga30 Shape Memory Alloy Single Crystals under Compression
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Pseudoelasticity as a function of temperature and crystallographic orientation in Co49Ni21Ga30 single crystals was studied under compression. The pseudoelastic (PE) temperature window and its dependency on the Clausius-Clapeyron (CC) slope and the resolved shear stress factor (RSSF) for the phase transformation were revealed for as-grown 100, 123 and 235 orientations. A high RSSF value results in a low CC-slope, which in turn brought about a large PE window of 400C for the 100 orientation. Thus, the effect of homogenization on crystals with this orientation was also investigated. Homogenization restored the single phase B2 austenite () from the dual phase ( + ) as-grown crystals changing the chemical composition of the -matrix, which lead to increase in the CC-slope. This in turn depressed the PE temperature window to 350C. The results suggested that the pseudoelasticity of CoNiGa alloys can be tailored for specific elevated temperature applications by the selection of crystallographic orientation and heat treatment. Copyright 2008 ASM International All rights reserved.
