Influence of aging heat treatment on microstructure and mechanical properties of a novel polycrystalline Ni3Al-based intermetallic alloy

A novel polycrystalline Ni 3 Al-based intermetallic alloy was prepared using the vacuum induction melting process. Subsequently, the alloy was subjected to the solution-treatment underwent two different aging processes: 870 °C for 24 h in air cooling, referred to as AT 1, and 1060 °C for 4 h in air cooling followed by 870 °C for 24 h in air cooling, referred to as AT 2. The effects of different aging processes on the microstructure and mechanical properties of the polycrystalline Ni 3 Al-based intermetallic alloys were analyzed. Results indicated the cubicity of the primary γ′ phase within the dendritic γ+γ′ structure of the AT 2 sample was significantly enhanced, yielding the best overall mechanical properties for the alloy. The percentage elongation increased from less than 3 % for the AT 1 sample to about 4.5 %, highlighting a notable enhancement in room temperature tensile plasticity. The creep rupture time at 1100 °C/30 MPa reached 113 h. The α-Cr particles in the As-cast and solid solution alloy gradually transformed into Cr 23 C 6 during the aging process, exhibiting the orientation relationships of (020) Cr23C6 ||(010) γ' and [103] Cr23C6 ||[103] γ' . High-temperature aging treatments resulted in Cr 23 C 6 particles that provided enhanced precipitation strengthening effects , thereby improving the creep rupture performance of the Ni 3 Al-based intermetallic alloys. Following high-temperature aging, a four-layer interface structure formed around the blocky γ′ matrix phase , which altered the alloy's fracture mechanism from a brittle intergranular fracture to a ductile transgranular fracture . • The orientation relationship of (020) Cr23C6 .||(010) γ' and [103] Cr23C6 ||[103] γ' between the precipitates Cr 23 C 6 and γ′-matrix • A four-layer interface structure formed around the blocky matrix γ′ phase after high-temperature aging process. • The unique interface structure causes the fracture mechanism of the alloy to transition from brittle transgranular fracture to ductile intergranular fracture .