Phase transformation in shape memory alloys

Dear all,

As part of my MSc thesis I am using molecular dynamics simulation to study the pseudoelastic effect of Cu-Zr shape memory alloy during a tensile and shear tests. My question is related to the stress induced phase transformations during both tests.

During the tensile test I can clearly see a stress-induced phase transformation (B2 to B19') which agrees well with the literature but for some reason, I can't see any phase transformations during the shear test. In few words, during the shear test I can see an elastic region and a plastic deformation region with no phase transformations. Unfortunately there is no information on phase transformations in Cu-Zr during shear tests in the literature. My question is, why can we see a phase transformation during a tensile test but not during a shear test?

My interpretation is the following but I do wish anyone can help in case I am wrong. I am assuming that in the shear test the energy required for dislocation nucleation is lower than the energy required for phase transformation hence the alloy deforms plastically with no prior phase transition. The opposite happens during a tensile test, where the energy required for dislocation nucleation is higher than the energy required for phase transformation, hence we can see the pseudoelastic effect before the alloy deforms plastically.
If my interpretation was the correct one it would mean that the energy required for dislocation nucleation changes depending on the crystal orientation where the load is being applied but I am not fully sure if this is the case.

If any one can help explain why there is no phase transformation during a shear test but there is during a tensile test I would greatly appreciate it!

Many thanks,
Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.

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