Unraveling the effect of deformation-induced phase transformation on microstructure and micro-texture evolution of a multi-axially forged Mg-Gd-Y-Zn-Zr alloy containing the LPSO phase

Abstract

The effect of blocky to lamellar phase transformation on the microstructure and micro-texture of a Magnesium-Rare earth alloy containing long-period stacking order (LPSO) phases were examined comprehensively at the isothermal temperature of 400 °C via multiaxial forging. A very fine-grained microstructure with an average grain size of 1 μm was achieved after applying three multi-axial forging (MAF) passes. Particle stimulated nucleation (PSN) along with continuous dynamic recrystallizations (CDRX) due to the blocky LPSO phases were realized to be the main reasons for the achievement of such fine microstructure. The deformation-induced blocky to lamellar phase transformation began at 1/3 pass and expanded through the whole microstructure after the third pass. Such phase transformation was found to be initiated by the fragmentation of blocky phases. As a result of PSN and CDRX mechanisms, two new rare earth (RE) texture components of and || Transverse Direction (TD) were formed at the second MAF pass that led to a highly randomized deformation texture. Nevertheless, the continuous breakdown of blocky phases and their subsequent phase transformation to lamellar LPSO suppressed PSN at the third deformation pass. Hence, the formed RE texture components were disappeared which in turn increased the texture intensity at this deformation pass.

Keywords

• Magnesium alloys
• Rare earth elements
• Phase transformations
• Microstructure
• Texture evolution
• Multi-axial forging