Directed Energy Deposition‐Arc Repair Al6.5Cu2Ni0.3Ti0.5Zr0.25V Alloy: Microstructure Evolution and Strengthening Mechanism

Abstract

Casting Al6.5Cu2Ni0.3Ti0.5Zr0.25V alloy is applied to aircraft engine components, but the casting defects are difficult to avoid. In this research, the local defects of casting heat‐resistant Al6.5Cu2Ni0.3Ti0.5Zr0.25V alloy parts are repaired by the arc‐directed energy deposition method. To examine the mechanism of the microstructure in the repaired zone of the heat treatment condition on the high‐temperature characteristics, the microstructure evolution of the repaired zone before and after heat treatment is analyzed. The results indicate that stratification exists in the sedimentary layer, however, the overall grain distribution is relatively uniform. After heat treatment, the microstructure of the repaired zone is changed, Cu element distribution becomes uniform and dendrite segregation disappears; simultaneously, the grain in the repaired zone mainly exists as high angle grain boundaries, which improves the fracture resistance ability of the material. At 350 °C, the average tensile strength, yield strength and elongation are 120.0 MPa, 98.6 MPa and 12.9%, respectively, the tensile strength reaches 94.1% of the matrix. Dimples abound on the fracture's exterior, and the fracture form of the repaired zone is microporous aggregate fracture. δ‐Al3CuNi and γ‐Al7Cu4Ni enhance the grain boundary strength, and θ′‐Al2Cu diffuses from the α‐Al matrix during aging, which is the main reason for the excellent high‐temperature performance of the repaired zone.