Effects of temperature gradient on the interface microstructure and diffusion of diffusion couples: phase-field simulation

The temporal interface microstructure and diffusion in the diffusion couples with the mutual interactions of temperature gradient, concentration difference and initial aging time of the alloys were studied by phase-field simulation, the diffusion couples are produced by the initial aged spinodal alloys with different compositions. Temporal composition evolution and volume fraction of the separated phase indicates the element diffusion direction through the interface under the temperature gradient. The increased temperature gradient induces a wide single-phase region at two sides of the interface. The uphill diffusion proceeds through the interface, no matter the diffusion directions are up or down to the temperature gradient. For an alloy with short initial aging time, phase transformation accompanying the interdiffusion results in the straight interface with the single-phase regions at both sides. Comparing with the temperature gradient, composition difference of diffusion couple and initial aging time of the alloy show greater effect on the diffusion and interface microstructure.