Microstructure and properties of low voltage electron beam wire deposition layer of TC4 titanium alloy

The low voltage electron beam wire deposition tests on TC4 titanium alloy were carried out to explore the feasibility of the method, and the influence of the number of deposited layers on the microstructure and properties was analyzed. The results show that the multi-layer wire deposition of TC4 titanium alloy can also be completed on the accelerated voltage of 10 kV. The average microhardness of the deposited parts after multi-layer deposition is about 260 HV, and only the microhardness of the banded texture at the bottom of the deposited parts is close to 288 HV of the annealed TC4 substrate. Banded texture produced in multi-layer deposition process, β phase grain transformed to α + α′ + β by the influence of thermal cycle, the banded texture which composited with basket-like α′ phase and lamellar α phase have high microhardness, the other feature of banded texture is that more basket-like phase gradually integrated into the lamellar structure as the increase of the distance with substrate. The tensile fracture of the deposited part is also ductile fracture with the maximum tensile strength of 862 MPa, which is slightly lower than the national standard. It because the columnar crystals will become huge in the deposited parts with multiple layers, and equiaxed crystals will also appear. The huge size of the grains will decrease the tensile properties of the deposited parts.