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研究砂型铸造过程中浇注温度(680~780°C)对Mg-10Gd-3Y-0.4Zr合金凝固行为、组织与性能的影响。结果表明:随着浇注温度从680°C先提高至750°C再提高至780°C,α-Mg的形核过冷度从2.3°C提高到6.3°C后不再提高;α-Mg的平均晶粒尺寸先由44μm增加至71μm而后减小到46μm;共晶组织先由网格状转变为不连续的块状继而转变为大块的岛状;β-Mg24RE5相的体积分数增加,由颗粒状转变为短棒状;溶质富集的现象变得更加明显;合金的屈服强度由138 MPa提高至151 MPa,抗拉强度由186 MPa提高至197 MPa。750°C浇注的合金具有最佳的强度与延展性。断口形貌特征由准解理断裂转变为穿晶韧性断裂,并伴随着不同程度的缩松与氧化夹杂等铸造缺陷。相对于铸造缺陷、共晶组织以及溶质富集,α-Mg的晶粒尺寸是砂型铸造Mg-10Gd-3Y-0.4Zr合金屈服强度最主要的影响因素。
The effects of pouring temperature (680 ~ 780 ° C) on the solidification behavior, microstructure and properties of Mg-10Gd-3Y-0.4Zr alloy during sand casting process were studied. The results show that as the pouring temperature increases from 680 ° C to 750 ° C and then increases to 780 ° C, the nucleation supercooling degree of α-Mg increases from 2.3 ° C to 6.3 ° C. Α-Mg The average grain size increases from 44μm to 71μm and then decreases to 46μm. The eutectic structure changes from a grid to a discontinuous block and then transforms into a massive island. The volume fraction of β-Mg24RE5 phase increases, The transition from granular to short rod-shaped; solute enrichment phenomenon becomes more obvious; the yield strength of the alloy increased from 138 MPa to 151 MPa, tensile strength increased from 186 MPa to 197 MPa. 750 ° C cast alloy with the best strength and ductility. The fracture topography changed from quasi-cleavage fracture to transgranular ductile fracture accompanied by various casting defects such as shrinkage and oxidation inclusions. Compared with the casting defects, the eutectic structure and the solute enrichment, the grain size of α-Mg is the most important factor affecting the yield strength of sand cast Mg-10Gd-3Y-0.4Zr alloy.