Morphology and crystallography of β precipitate phase in Mg-Gd-Y-Nd-Zr alloy

Mg-Gd-Y-Nd-Zr合金中β相的形貌和晶体学特征(英文)

Morphology and crystal structure of β precipitate phase in Mg-7Gd-5Y-1Nd-0.5Zr (mass fraction, %) alloy were characterized by optical microscopy, scanning electron microscopy and transmission electron microscopy. Compositions were determined for β phase using thin foil energy dispersive spectroscopy. Precipitation at 400 ℃ involves formation of platelet and block-shaped β phase. The orientation relationship is and between β precipitate phase and α-Mg matrix with habit planes parallel to , and a composition of Mg5(Y0.4Gd0.4Nd0.2) is suggested for the β phase in Mg-7Gd-5Y-1Nd-0.5Zr alloy.

通过OM、SEM、TEM及EDS分析,研究MgGdYNdZr镁合金中β相的形貌、成分和晶体学特征,分析连续冷却与等温时效两种方式对β相析出行为的影响规律。结果表明,合金在400°C过时效阶段的沉淀相为(1100)面上的板状和块状β相。β相以(1100)为惯习面,与基体的取向关系为(211)//(0110),[011]//[0001]。根据EDS统计分析确定β相的成分为Mg5(Y0.4Gd0.4Nd0.2),与Mg5Gd同型。在连续冷却方式中,相变驱动力较小,晶界等缺陷处结构紊乱,易于松弛、应变,因而优先在晶界附近形核。