Hot tensile deformation behaviour and microstructure evolution of Al3La phase reinforced Mg-5Li-3Al-2Zn alloy formed in-situ by La2O3 particle

Abstract

In this study, LAZ532 alloy reinforced with Al 3 La phase in-situ precipitated by adding La 2 O 3 particle was fabricated by melting casting. The hot tensile deformation behaviour of the composite was investigated at deformation temperatures of 423 K ~ 573 K and strain rates of 8.3 × 10 −5 s −1 –1.7 × 10 −3 s −1 . The results indicated that the peak stress and elongation at fracture of the composite gradually decreased and increased respectively, with the deformation temperature increased or the strain rate decreased. In particular, the composite exhibited outstanding quasi-superplasticity with elongation to fracture up to 213% at 573 K and 8.3 × 10 −5 s −1 . Based on the results of theoretical calculation, the activation energy Q of the composite was 97.8 kJ/mol. In addition, by the observation and analysis of microstructure at different strains, the strain induced the precipitation of pearlite-like Al 3 La phase in the grains during hot tensile deformation. The deformation behaviour of the composite was a synergetic deformation mechanism dominated by GBS, supplemented by DDRX and intragranular slip, and the intragranular slip was dominated by prismatic and pyramidal I <c+a> slips. • The Mg Li composite exhibits excellent performance with tensile strength of 229 MPa at 423 K and 1.7 × 10 −3 s −1 . • The Mg Li composite exhibits excellent superplastic deformation ability with elongation of 213% at 573 K and 8.3 × 10 −5 s −1 . • Strain induced precipitation of pearlite-like Al 3 La particles in the grain during the thermal deformation. • The deformation behaviour is a synergetic mechanism dominated by GBS, supplemented by DDRX and intragranular slip.