Isothermal superplastic solid-state welding of 40Cr and QCr0.5, ZQSn6-6-3

To investigate the feasibility of isothermal superplastic solid-state welding of 40Cr steel and QCr0.5, ZQSn6-6-3 copper alloys, the welded surface of 40Cr steel surface is ultra-fined through laser quenching, and then the welding process tests between different base metals of 40Cr and QCr0.5, ZQSn6-6-3 are made under vacuum-free condition. The experimental results show that, under the pre-pressed stress of 56.6–84.9 MPa, at the welding temperature of 750–800 °C and at initial strain rate of (2.5–7.5) × 10−4 s−1, the superplastic solid-state welding can be finished in 2–4 min. The strength of the joints is up to that of QCr0.5 base metal or close to that of ZQSn6-6-3 base metal and the expansion rate of the joints is below 6%. The plastic deformation of the joint is further analysed. The superplastic deformation of the copper alloys occurs in welding process and the deformation of 40Cr steel is limited.