Microstructure and mechanical properties of large-size titanium alloy components fabricated by laser melting deposition

High-power laser melting deposition stands as a viable solution for the high-quality and efficient manufacturing of large-sized titanium alloy components. This article explores how laser influences the quality of deposited layers when operating within a laser power range of 3−8 kW, and a H-shaped TC4 component with half-meter high was successfully fabricated by the laser melting deposition technology with a power of 5 kW, exhibiting a well-formed surface. In addition, the microstructure and properties of deposited TC4 components are examined. The as-deposited component is mainly composed of coarse columnar crystals. However, the distribution and size of grains is particularly uneven with a range of 1−5 mm in length. The deposited TC4 is made up of lots of basketweave structure and a bit Widmanstatten structures at the grain boundaries. What’s more, lath-shaped α phase and a small amount of β phase can be found in the grain. There is no significant disparity in grain size along the height direction; however, the heat accumulation resulting from deposition leads to a reduced length-to-width ratio of α-laths in the bottom region. The tensile performance of samples from the top area marginally surpasses that of the bottom, and the tensile performance in the vertical direction is marginally better than that in the horizontal direction. According to the prevailing GB/T38915-2020 and HB5432-89 standards, the tensile properties of the fabricated components, sampled from various regions and directions, exceed those of forgings. The direction of sampling has weak influence on impact energy; however, fatigue crack propagation experiments indicate that cracks are more prevalent and propagate at a slightly faster rate in horizontally-oriented specimens, a phenomenon attributed to the combined effects of grain morphology and microstructure.