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Magnesium alloys have low density, high specific strength and stiffness, good machining performance, etc., in recent years, automotive, electronics and other industries preferred metal structural materials. However, in the development and application strength, heat-resistant magnesium alloy often occur during the performance and cost of the many contradictions and obstacles. Therefore, reducing costs and improving the heat resistance of magnesium alloy research in the field has become critical. In this paper, Mg-Al-based alloy AM80 as the matrix, inexpensive alkaline earth elements Ca and Sr as alloying additives, the use of optical microscopy, X-ray diffraction, scanning electron microscopy, differential thermal analysis and mechanical testing machine and other electronic universal studied AM80-Ca-Sr alloy casting process parameters of the best, and focuses on the xCa and y1 ~ y4Sr right AM80 alloy microstructure, properties and aging behavior. Study found that in the current experimental conditions, the pouring temperature and mold preheating temperature was 740 ℃ and 250 ℃, the use of bottom gating means casting AM80-Ca-Sr alloy, can reduce shrinkage, shrinkage and oxidation the degree of physical defects such as inclusions, get finer grain structure, improve the mechanical properties. Add xCa can refine AM80 alloy, the grain size fell by a 109.6μm 64.8μm; continue adding y1 ~ y4Sr, y1Sr will alloy grain coarsening, when Sr increased by the y2 y4, the alloy grain size and gradually reduced to 65.8μm. xCa conjunction with the AM80 alloy Al grain boundary precipitation similar bone-like Al2Ca melting phase, inhibition of β-Mg17Al12 melting phase precipitation; continue adding y1 ~ y3Sr, Al2Ca phase gradually turned into small pieces or strips, diffusion distributed at grain boundaries, y4Sr the alloy secondary phase at the grain boundaries and reticular distribution, y1 ~ y4Sr Al will gradually increase the solubility of the substrate, to further suppress the precipitation of β-Mg17Al12 phase. Room temperature (25 ℃ and 175 ℃) conditions, will reduce the AM80 alloy added xCa overall tensile properties; continue adding y1 ~ y4Sr, overall tensile properties of the alloy rose after the first drop lower and lower, which, AM80-xCa- y2Sr Alloy better performance, and its rooms, high tensile strength were 173MPa and 160MPa, elongation were 5.2% and 8.2%. 200 ℃ / 56MPa conditions, add xCa AM80 alloy can significantly improve the creep resistance; continue adding y1-y4Sr, the creep resistance of the alloy generally continued to rise, which, AM80-xCa-y4Sr the creep performance The optimal experimental alloy system, the steady-state creep rate and creep 100h were reduced 1.7 × 10-9S-1 and 0.8%. However, AM80-xCa-y3Sr alloy creep resistance suddenly deteriorated sharply, this phenomenon may be related to the secondary phase alloy elongated strip distributed, leading to lower grain boundary strength and excessive stress concentration related. xCa and y2Sr hindered AM80 Alloy initial β-phase discontinuous precipitation, inhibiting the aging process of the alloy, the alloy can be enhanced aging is reduced, but it can improve the thermal stability of the alloy.
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