Comparison of Hardness and Thermal Conductivities of Mg-9%Al-1%Zn Alloy Subjected to T6 Heat Treatment and Continuous Cooling after Solution Treatment

T6 열처리 및 용체화처리 후 연속 냉각한 Mg-9%Al-1%Zn 합금의 경도 및 열전도도 비교

This work was intended to comparatively investigate the hardness and thermal conductivities of Mg-9%Al-1%Zn (wt%) alloy having fully discontinuous precipitates microstructure obtained by continuous cooling after solution treatment(designated as "DPs-CC") and T6 heat-treated microstructure, respectively. The T6 microstructure was distinctively characterized by two regions of (i) discontinuous precipitates showing (α + β) lamellar morphology and (ii) finely distributed continuous precipitate particles. The DPs-CC microstructure had various (α + β) lamellar spacings due to different transformation temperatures during continuous cooling. The T6 microstructure exhibited slightly higher hardness than the DPs-CC one, resulting from the lower (α + β) interlamellar spacing of the discontinuous precipitates and the fine distribution of continuous precipitates. It is noticeable that the DPs-CC microstructure possessed 98.2% level of thermal conductivity between RT and 200℃ compared to the T6 microstructure. The XRD analyses suggest that similar level of Al concentration in α-(Mg) matrix may well be responsible for the almost identical thermal conductivities for the T6 and DPs-CC microstructures.