Study of microstructure evolution and preference growth direction in a fully laminated directional micro-columnar TiAl fabricated using laser additive manufacturing technique

In this study, a fully laminated Ti-48Al-2Nb-2Cr alloy plate with no cracks and aluminum loss is successfully fabricated using laser additive manufacturing technique. A well-aligned micro-columnar microstructure is expected to grow along the deposition direction. Attributed to the rapid cooling, micro-segregation between interdendritic and dendrite areas is observed in the fabricated alloy. Meanwhile, rapid cooling results in existence of B2 phases in the center of dendrites, which will then decompose with the gradual coarsening of α ₂ /γ lamella under subsequent thermal cycling. Additionally, dominant growth of 〈1 1 0〉 _β during solidification of molten pool is predicted, which is the preference growth direction of primary β phase.