Interdiffusion in β (BCC) Phase of the Ti-Al-Mn System at 1100 °C

Abstract

Interdiffusion was studied on the titanium-rich side of ternary β (BCC) Ti-Al-Mn system at 1100 °C by the solid-solid diffusion couple technique. Ternary interdiffusion coefficients were evaluated at 13 different compositions using the Kirkaldy’s approach. It was observed that the main coefficients, $\tilde{D}_{\text{TiTi}}^{{ {\text{Al }}}}$ and $\tilde{D}_{\text{MnMn}}^{{ {\text{Al }}}}$, are positive while the cross terms, $\tilde{D}_{\text{TiMn}}^{{ {\text{Al }}}}$ and $\tilde{D}_{\text{MnTi}}^{{ {\text{Al }}}}$, are mostly negative and smaller in magnitude as compared to respective main coefficients. Based on the main interdiffusion coefficients, aluminum was found to be the slowest interdiffusing species in this system. Strong diffusional interactions were present in two iso-concentration couples, which were manifested in the form of uphill diffusion regions. Tracer diffusion coefficients were evaluated by the generalized Hall’s method, and binary interdiffusion coefficients ($\tilde{D}$) were estimated by the method of interpolation in three terminal binary alloys. Binary $\tilde{D}$ were found to be consistent with the literature data.