Investigation on fabricating Ni/Ni3Al/NiAl thin-walled cup-shaped component by combining superplastic forming of Ni/Ni2Al3 composite sheet with subsequent in-situ reaction

Abstract

In the present study, a novel approach is proposed to fabricating Ni/Ni₃Al/NiAl thin-walled cup-shape component based on superplastic forming of Ni/Ni₂Al₃ composite sheet with heterogeneous bimodal grains. Firstly, Ni/Ni₂Al₃ composite sheet with heterogeneous bimodal grains is prepared by means of hot pressing reaction synthesis from Ni and Al for 2 h at 630 ℃ under the pressure of 20 MPa and it is characterized by superplasticity at 750℃ at the strain rate of 1 $\times {10}^{-3}$ to 1$\times {10}^{-2}$ s⁻¹. Subsequently, Ni/Ni₂Al₃ composite sheet can be readily used to be made into the thin-walled cup-shaped components by gas forming. The Ni/Ni₂Al₃ thin-walled cup-shape component is subjected to second-order in-situ reaction for 4 h at 1000℃ under the pressure of 20 MPa, and consequently the involved Ni/Ni₃Al/NiAl thin-walled cup-shaped component is fabricated, where Ni₃Al and NiAl phases are dominant. In particular, Ni₃Al phase contributes to enhancing high-temperature strength and NiAl phase is responsible for bolstering high-temperature plasticity. The present work provides a novel approach for fabricating Ni/Ni₃Al/NiAl thin-walled cup-shaped component.