Mechanical properties optimization of AZX612-Mg alloy joint by double-sided friction stir welding

[Display omitted] •The joint’s mechanical properties firstly increase and then decrease with the evolution of 0001 texture strength at the SZ.•Beat phenomenon of pitch behavior was observed which indicated the complication of metal flow caused by asymmetric DFSW.•Asymmetric DFSW was proven to be a preferable joining method for flame-resistant magnesium alloy than the conventional FSW. AZX612 (Mg-6% Al-1% Zn-2% Ca) non-combustive magnesium alloy joints formed by asymmetric double-sided friction stir welding with different lower tool rotation rates were investigated. Compared with the conventional one-sided friction stir welding, joints fabricated by the asymmetric double-sided friction stir welding showed better tensile strength and elongation values. EBSD observations of the stir zone indicate that the stir zone formed at the upper and lower tool rotation rates of 600rpm and 500rpm exhibits the lowest 〈0001〉 texture intensity thereby showing the best balance of tensile strength and ductility. With defect-free joining parameters, the complexity of the material flow caused by the asymmetric layout of the double tools needs both a small difference between the upper and lower tool rotation rates and a proper heat input.