Effect of aging time on multiphase microstructure and high-temperature creep properties of weldable Ni3Al-based alloy with ultrafine β phase

Laser remelting provides a novel approach to refine multiphase strengthening structure in weldable Ni₃Al-based alloy (particularly for β phase), significantly improving the creep property. However, the ultrafine multiphase strengthening structure evolution and creep performance in laser remelted alloy were still uncertain during heat treatment. In this paper, the evolution of ultrafine multiphase strengthening structure at 980 °C for 200–1100 h and high-temperature creep properties at 1000 °C/120 MPa in weldable Ni₃Al-based alloy with ultrafine β were investigated. Meantime, the relationship between evolution of ultrafine multiphase strengthening structure and creep properties was revealed. The findings show that rapid transformation of near-spherical γ′ phase (laser remelted) into cubic γ′ phase (200 h), growth (500 h), R-type γ′ rafting structure (800 h) and coarsened (1100 h) in ultrafine γ′+γ dendrite of the alloy were promoted by 980 °C for 200–1100 h high-temperature aging treatment, which significantly reducing steady-state creep rate in different aged alloys. Meanwhile, the dissolution and growth of ultrafine β phase lead to size from 0.81 μm to 1.64–2.28 μm and volume fraction from 13.61 % to 5.03 %–4.07 %. This is accompanied by the improvement of morphology distribution, from long strip discontinuous network bad distribution to the near-spherical dispersion uniform distribution, which significantly improves accelerated creep stage life of alloy. Among them, the 1100 h aged alloy had the highest creep life of 137 h and lowest steady-state creep rate of 0.01086 %/h at 1000 °C/120 MPa.