Abstract

The microstructure evolution and dynamic precipitation behavior of Mg–10Gd–4Y–1Sm–0.5Zr alloy during backward hot extrusion are studied. The results show that the equiaxed grains become polygonal grains and fine DRX grains are generated which form a “necklace structure” along the initial deformed grain boundaries. With further increase of deformation, DRX grains volume fraction significantly increases and finally almost fully DRX extruded microstructure is obtained in the completely hot-extruded sample. The extrusion deformation results in increase of dislocation density and formation of dislocation cells. The subgrain boundaries continue to absorb dislocations and finally change from the low angle grain boundaries to the high angle grain boundaries. Hot extrusion deformation results in formation of dynamic precipitated phase, β phase particle, i.e., Mg₅(Gd,Y) phase, with diameter of 45–145 nm, which is incoherent relationship with the matrix. In process of increasing deformation, the shape of β phase changes from spindle shape to disc shape and the distribution of β phase transforms from strip distribution along grain boundary to discrete distribution.

Graphic Abstract

摘要

研究了Mg-10Gd-4Y-1Sm-0.5Zr合金在逆向热挤压过程中的组织演变和动态沉淀行为。结果表明，等轴晶粒变成了多边形晶粒，并生成了细的DRX晶粒，沿着初始变形的晶界形成了“项链结构”。随着变形的进一步增加，DRX晶粒体积分数显着增加，最终在完全热挤压的样品中获得了几乎完全被DRX挤压的显微组织。挤压变形导致位错密度的增加和位错单元的形成。亚晶界继续吸收位错，并最终从低角度晶界变为高角度晶界。热挤压变形导致形成动态沉淀相β相颗粒，即。₅（Gd，Y）相，直径为45–145 nm，与基质不相干。在变形增加的过程中，β相的形状从纺锤形变为盘形，β相的分布从沿晶界的带状分布转变为离散分布。

图形摘要