Phase Field Modeling for Temperature- and Stress-induced Martensitic Phase Transformation

Speaker :
Mr Gangpeng WU
Department of Mechanical and Aerospace Engineering, HKUST
Date : 24 Jan 2019 (Thu)
Time : 3:00 pm
Venue : Room 2548, HKUST (2/F., Lift #27/28)


For a better understanding of martensitic transformation, a novel phase field model is built up to simulate the evolution of the microstructures in shape memory alloys. The model is set in the energy framework so that the kinetic equations and mechanical equilibrium equations are fully defined by specifying the free energy. The proposed free energy density involves the bulk and interfacial energy contributions. The latter one describes the energy of diffusive interfaces with a specific phase field ansatz. In order to reflect different interfacial energies of austenite-martensite interfaces and twin boundaries, the order parameters are introduced in a hierarchical manner. Considering the solution to crystallographic equations of martensite, we propose a kinematic model for transformation strain tensors. Besides, the bulk energy is given in a way to avoid the unphysical shift of equilibrium state of order parameters. To make the phase field model capable of simulating martensitic transformation under different temperature conditions, the proposed free energy function explicitly incorporates temperature and latent heat.

To perform numerical simulations with different boundary conditions, the model is implemented into the finite element solver COMSOL. Several simulations are performed. The numerical results are consistent with the experimental observations and the solution to crystallographic equations of martensite. Through a series of simulations, the effects of crystal orientation, boundary condition, temperature and loading rate on the evolution of microstructures and thermomechanical properties of shape memory alloys are discussed.

(Supervisor: Prof. Xian CHEN)