Annealing treatment on the microstructure evaluation and tensile properties of TC4 alloy fabricated by laser oscillation melting deposition

Laser oscillation possesses a stimulating impact on the melt pool, causing the disruption of columnar crystals and enhancing the creation of newly nucleated masses. As a consequence, an enhanced microstructure and a more refined grain size are achieved. The study compares the microstructure, phase composition, and mechanical properties of as-deposited and as-annealed TC4 alloys via various oscillation paths. The results show that the microstructure of the deposited TC4 alloys under the four oscillation paths is primarily acicular and cluster martensitic. Additionally, the plasticity of the specimens in the annealed state displays an overall improvement, except for linear oscillation, which experiences a decrease in overall yield strength and ultimate tensile strength. This can be attributed to the sub-stable alpha' phase undergoing coarsening during annealing and eventually decomposing into (alpha + beta) phase tissue. The beta phase, with a BCC structure and more slip systems, has a lower tensile strength but greater plasticity.