Effect of Heating Temperature on Grain Size and Properties of CuAlMnNi Memory Alloy
In this paper,the effect of heating temperature on the microstructure and properties of Cu Al Mn Ni memory alloy sheet in the low-temperature cyclic heat treatment process is studied.The results show that with the increase of the heating temperature,the volume fraction and the maximum size of the precipitated phase α in the annealing at 550℃ for 30 min are increased and then decreased,and the average size is increasing.The grain size after the subsequent high-temperature annealing is increased and then decreased,and thus the superelasticity of the alloy specimen is increased and then decreased.On the contrary,the residual strain is decreased and then increased.The larger the grain size is,the smaller the critical strength for initiating the phase transformation.The reason for this is that the heating temperature affects the grain boundary activity B and the precipitation of α phase,which in turn changes the grain size during subsequent high-temperature annealing.The increase in grain size reduces the obstruction of the martensitic phase transformation by the grain boundaries and improves the deformability of the alloy,which results in the increasememt of superelasticity and decrement of residual strain.
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