Microstructure and Phase Transformation of Super-High Pressure Mg-Li Alloy

Abstract:

Super-high pressure (SHP) changes crystal structure and electronic distribution of metallic materials, which plays an important role in properties. Herein, a duplex Mg-7%wt.Li alloy was heat-treated under SHP (2 GPa) by cubic-anvil large-volume press with six rams for 2 h in the temperature range of 450~1350 °C. Microstructure, phase transformation behavior and mechanical properties were examined. Compared with the as-cast sample, the SHP samples after heat-treating from 450 °C to 750 °C under 2 GPa were composed of twinning in addition to duplex structure. Comparatively, the samples treated between 1050 °C and 1350 °C exhibit typical dendritic morphology. Phase transformation from Li₃Mg₇ phase or Li_0.92Mg_4.08 phase to Li₃Mg₁₇ phase occurred during the whole investigated temperature range, in which only the Li₃Mg₁₇ phase maintained when the temperature exceeds 1050 °C. The microhardness of the sample prepared at 750 °C under 2 GPa was 73.15HV, which is 1.5 times higher than that of the as-cast one. The improved microhardness is mainly attributed to the formation of nanosized twins during SHP treatment. These fine twins effectively prohibit the dislocation movement during deformation. It reveals the SHP is an effective approach to prepare high performation Mg alloys.

• Periodical: Materials Science Forum (Volume 816)
• Pages: 375-380
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.816.375
• Online since: April 2015
• Authors: Qiu Ming Peng*, Hui Fu, Yan An Wang, Hui Li
• Keywords: High Pressure, Mg-Li Alloys, Microhardness, Microstructure, Phase Transformation

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