Mg - Sr - Zinc - Y And Mg - Sr - Al - Y Alloy Microstructure And High Temperature Compression Performance Research

As the lightest metal structure material, magnesium alloy has been extensively applied moreand more in the automobile and electronic communications industry. For Mg alloy, it issignificant to the national economy. Mg and its alloys have a broad prospect of application. But,high temperature heat resistant performance of Mg alloy is poor and limits its application fields.Based on Mg-Sr binary alloy, Mg-Sr-Zn-Y and Mg-Sr-Al-Y alloys were successfullyfabricated by melting-leaching technique. The thermal extrusion test was conducted to eliminatethe casting defects. By means of X-ray diffraction, the phases of the alloys were identified, andthe microstructures were analyzed by optical microscope and scanning electron microscope（SEM） and transimission electron microscope. The elevated compression properties weremeasured by tensile test machine attached to a heating furance. The relationship between thestress and the strain of the different compression temperatures and different strain rates wereeatablished. The strain rate sensitive index and apparent activate energy in the differentdeformation stages were calculated, the high-temperature compression deformation mechanismwere investigated.The results show that, Mg-Sr-Zn-Y and Mg-Sr-Al-Y alloys are composed of whitedendrite α-Mg and discontinous sticky and particulated second phases distributed at theboundaries. Compared to Mg-Sr-Y and Mg-Sr-Zn and Mg-Sr-Al alloys, the microstructures andgrains of the Mg-Sr-Zn-Yå'ŒMg-Sr-Al-Y alloys fine, and little impurities can be found. ForMg-Sr-Zn-Y alloy, α-Mg and Mg₁₇Sr₂and Mg₁₂YZn are main phases, and particulatedMg₁₂YZn is located in the dendrites and interdendrites, which will stop the immirgration ofdislocations and grain boundaries and strengthens the alloys. For Mg-Sr-Al-Y alloy, α-Mg andMg₁₇Sr₂and Al₂Y are main phases, particulated Al₂Y distributes in the dendrites.The results further prove that, the compressive strengths of the alloys increases withincreasing Al and Zn and Y contents. The sliding of dislocations and twinning is characterstic ofthe main the deformation mechanisms for Mg-Sr-Zn-Y alloy within the test temperature limitsand for Mg-Sr-Al-Y alloy ranged from300K to425K. The deformation mechanism ischaracteristed by boundary creeping for Mg-Sr-Al-Y alloy ranged from425K to525K.