MICROSTRUCTURE AND ROOM TEMPERATURE COMPRESSION PROPERTIES OF Mg82.13Zn13.85Y4.02ALLOY SOLIDIFIED UNDER SUPER-HIGHPRESSURE

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-Mg3Y2Zn3phase and I-Mg3YZn6phase. In the microstructure of the alloy 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 eutectic is diminished and the solubility of Zn in a-Mg rises gradually. The results of the measurement of the mechanical properties show that the compression strength, the yield strength and the compressibility of the alloy sample solidified 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.