Effect of Ca and Sm Combined Addition on the Microstructure and Elevated-Temperature Mechanical Properties of Mg-6Al All
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JMEPEG https://doi.org/10.1007/s11665-019-04044-9
Effect of Ca and Sm Combined Addition on the Microstructure and Elevated-Temperature Mechanical Properties of Mg-6Al Alloys Yanhong Chen, Liping Wang, Yicheng Feng, Erjun Guo, Sicong Zhao, and Lei Wang (Submitted September 14, 2018; in revised form February 10, 2019) In the present study, the microstructure and elevated-temperature mechanical properties of Mg-6Al, Mg6Al-4Ca, Mg-6Al-4Sm and Mg-6Al-2Ca-2Sm alloys were investigated. The experimental results showed that the microstructure and elevated-temperature mechanical property of Mg-6Al alloy changed obviously with the different elements addition. By analyzing the results of optical microscope, x-ray diffraction analysis, scanning electron microscope, and transmission electron microscope, it could be determined that there was only Mg17Al12 phase in Mg-6Al alloy, there were Al2Ca and (Mg, Al)2Ca phases in Mg-6Al-4Ca alloy, there were Al2Sm and Mg17Al12 phases in Mg-6Al-4Sm alloy, and there were (Mg, Al)2Ca, Al2Ca and Al2Sm phases in Mg-6Al-2Ca-2Sm alloy. In addition, the addition of alloying elements including Ca and Sm, especially the composite addition, could significantly improve the tensile properties of Mg-6Al alloy. Compared to Mg-6Al alloy, the tensile strengths of Mg-6Al-2Ca-2Sm alloy at 448, 473 and 498 K were enhanced by 50.32, 87.92, and 94.99%, respectively. Furthermore, when the stretching temperatures were 448 and 473 K, the fracture pattern of Mg-6Al-2Ca-2Sm alloy was the mixture of intergranular fracture and trans-crystalline fracture. However, when the stretching temperature was 498 K, the fracture pattern of Mg-6Al-2Ca-2Sm alloy was the intergranular fracture. Keywords
fracture morphology, mechanical property, Mg alloy, microstructure
1. Introduction Nowadays, Mg-Al alloys have wide prospects in automotive, electronics, and military industry products because of their advantages of lower density, excellent thermal conductivity, and recyclability (Ref 1-7). However, the heat-resistant performance of Mg-Al alloys is poor and their working temperatures are limited at 393 K; therefore, the wide application of Mg-Al alloys has been greatly restricted (Ref 8, 9). Hence, improving the heat resistance of Mg-Al alloys has become one of the focuses in the current research. Wu et al. (Ref 10, 11) found that the main reason for the poor heat resistance of Mg-Al alloys is the b-Mg17Al12 phase, which was precipitated in the grain boundary. The b-Mg17Al12 phase softened at elevated temperature and lost the effect of inhibiting grain boundary slip. Hence, it made the Mg-Al alloys more prone to grain boundary sliding at elevated temperatures. Adding such elements as rare earth (RE) or alkaline earth to the alloy can improve its heat resistance (Ref 12-17). Zhang et al. (Ref 18) studied the effect of Nd elements on the microstructure of the as-cast Mg-4Al alloy. The research results showed that the Al elements in Mg-4Al alloy could combine preferentially Yanhong Chen, Liping Wang, Yicheng Feng, Erjun Guo, Sicong Z
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