铸态Mg96Zn3Y1合金高温热处理显微结构的电子显微研究

本文应用扫描背散射电子(SEM-BSE)像和透射电子显微(TEM)像观察的方法,研究了铸态Mg96Zn3Y1(at.％)合金经过500℃高温热处理后显微组织结构的变化.结果表明铸态Mg96Zn3Y1(at.％)合金中的初生相为网格状形貌,其中多数为面心立方W(Mg3Zn3Y2)相,少数为二十面体准晶Ⅰ(Mg3Zn6Y)...

Electron microscopy study of microstructural variations for the as-cast Mg96 Zn3 Y1 alloy subjected to high-temperature heat treatment

SEM-BSE,TEM and HREM observations have been carried out to characterize the microstructural variations for the as-cast Mg96Zn3Y1（at.%） alloys subjected to high-temperature heat treatment at 500℃.The results show that the characteristic network structure formed in the as-cast Mg96Zn3Y1 alloy is constructed with most primary W-phase（fcc,Mg3Y2Zn3 type） and a small amount of coexisting icosahedral quasicrystal phase（I-phase）.After heat treated at 500℃ for 4 h,the network structure retained without apparent morphological variation even through the I-phase melted down and disappeared.In addition,a large number of platelet-shaped fcc W＇-phases were observed to precipitate in the matrix due to the heat treatment,and relative increase of Zn-concentration in the Mg matrix was also detected.These variations are responsible for the significant hardness enhancement of the heat-treated alloy.HREM observations indicate a ledge growth mechanism for the platelet-shaped W＇-phase whose interface exhibits a semi-coherent relationship with the Mg-matrix.The orientational relationships between the W＇ precipitate phase and the Mg-matrix have been determined to be as follows： W＇∥Mg,（311）W＇∥（110）Mg,（022）W＇∥（001）Mg.