On the effect of superimposed external stresses on the nucleation and growth of Ni4Ti3 particles: A parametric phase field study
W. Guo, I. Steinbach, C. Somsen, G. Eggeler.
Acta Materialia, 59, 3287-3296, (2011)
The effect of a superimposed stress on the coarsening of interacting Ni4Ti3 particles is studied using the multi-phase field method. It is found that the thickness/diameter ratio of a Ni4Ti3 particle in a (1 1 1)B2 plane increases with an increasing [1 1 1]B2 stress component. The particle shape can change from a disk to a sphere with increasing applied stress. It is also found that diffusional and mechanical interactions between two Ni4Ti3 particles can promote the nucleation of new particles. This provides an explanation for the autocatalytic nature of nucleation reported previously. Compressive stresses along [1 1 1]B2 increase the volume fraction and growth velocity of the Ni4Ti3 particles of the (1 1 1)B2 plane. Misoriented particles disappear during particle growth. The simulation results are discussed in the light of previous experimental results.
Keyword(s): Multi-phase field; Shape memory alloy; Ni4Ti3; precipitation; Applied stress; Diffusion