Experimental Diffusion Research on BCC Ti-Mn Binary and Ti-Al‐Mn Ternary Alloys

Abstract

Interdiffusion in the BCC phase of the Ti-Mn binary and Ti-Al-Mn ternary systems was investigated between 1273 and 1473 K by applying the diffusion-couple technique. The local chemical compositions within the interdiffusion zone of the diffusion couples were acquired by electron probe microanalysis (EPMA). The raw composition profiles were then analytically represented by the error function expansion, which allow the ternary inter- and impurity diffusivities to be appropriately extracted by the Whittle–Green and generalized Hall methods, respectively. It was demonstrated that, all four diffusion coefficients $\mathop {\tilde{D}}\nolimits_{ij}^{k}$ (i, j = Al, Mn), both main and cross ones, increase with increasing the composition of diffusing specie at 1473 K, whereas at 1273 K $\mathop {\tilde{D}}\nolimits_{\text{MnMn}}^{\text{Ti}}$ and $\mathop {\tilde{D}}\nolimits_{\text{MnAl}}^{\text{Ti}}$ are enhanced by the addition of diffusing specie Mn but $\mathop {\tilde{D}}\nolimits_{\text{AlAl}}^{\text{Ti}}$ and $\mathop {\tilde{D}}\nolimits_{\text{AlMn}}^{\text{Ti}}$ are in weak dependence with the Al content. A complete comparison among seven Ti-Al-X (Ni, Co, Fe, Mn, Cr, V and Mo) ternary systems reveals that the order of the average main interdiffusion coefficients $\overline{{\mathop {\tilde{D}}\nolimits_{\text{XX}}^{\text{Ti}} }}$ (X = Ni, Co, Fe, Mn, Cr, V and Mo) exhibits D_Ni > D_Co > D_Fe > D_Mn > D_Cr > D_V > D_Mo.