超高压凝固Mg_(82.13)Zn_(13.85)Y_(4.02)合金的组织及室温压缩性能

MICROSTRUCTURE AND ROOM TEMPERATURE COMPRESSION PROPERTIES OF Mg_(82.13)Zn_(13.85)Y_(4.02) ALLOY SOLIDIFIED UNDER SUPER-HIGH PRESSURE

研究不同压力凝固条件下Mg82.13Zn13.85Y4.02(质量分数,%)合金微观组织和力学性能,发现合金的凝固组织是由a-Mg基体,W-Mg3Y2Zn3和I-Mg3YZn6相组成.其中,常压下凝固组织中的a-Mg枝晶间分布着由共晶组织形态和杆状第二相组成的网状结构.随着凝固压力的增大,共晶网逐渐断开,其数量逐渐减少,a-Mg基体中Zn的溶解度逐渐增大.常压凝固合金的室温压缩强度为344 MPa,屈服强度为331 MPa,相对压缩率为16%.6 GPa,1250℃凝固合金的室温压缩强度可达455 MPa,屈服强度426 MPa,相对压缩率为25%.常压凝固合金的压缩断裂模式为典型的解理断裂,且解理面大而光滑平整,高压凝固合金的压缩断口解理面较小,并出现撕裂岭和类似"撕裂韧窝"的形貌特征,解理断裂的程度有所降低.

ABSTRACT By the investigation of the microstructures of Mg82.13Zn13.85Y4.02 （mass fraction, %） alloy solidified under different pressure, it is found that the solidification microstructure of the alloy is consisted of a-Mg matrix, W-Mg3Y2Zn3 phase and I-Mg3YZn6 phase. In the microstructure of the aIloy solidified under ambient pressure, the networks of the secondary phases of eutectic-like and rod-like shape are distributed in the a-Mg interdendritic space. As the solidification pressure increases, eutectic network is disconnected gradually and the amount of eutec- tic is diminished and the solubility of Zn in a-Mg rises gradually. The results of the measurement of the mechani- cal properties show that the compression strength, the yield strength and the compressibility of the alloy sample so- lidified under ambient pressure is 344 MPa, 331 MPa and 16% respectively. However, the compression strength,the yield strength and the compressibility of the alloy sample solidified from 1250 ℃ under 6 GPa is 455 MPa, 426 MPa and 25%, respectively. The observation of fracture surfaces shows that, in the alloy solidified under high pressure, the cleavage surface of the compressed fracture is decreased, and the tear ridge and tearing dimple can be found. The degree of cleavage fracture is decreased.