Effect of Zr Addition on Dynamic Recrystallization during Hot Extrusion in Al Alloys
Effect of Zr Addition on Dynamic Recrystallization during Hot Extrusion in Al Alloys
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DOI：
10.2320/matertrans.46.211
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发表时间：
2005-02
影响因子：
1.2
通讯作者：
H. Adachi;K. Osamura;K. Kikuchi;J. Kusui
中科院分区：
文献类型：
--
作者：
H. Adachi;K. Osamura;K. Kikuchi;J. Kusui
Al 3 Zr析出相的存在促进了Al-Zn-Mg合金在热挤压过程中的连续动态再结晶，形成细晶组织。利用高分辨率EBSP技术观察了热挤压过程中组织的变化，并对这一现象的机理进行了研究。在挤压模口后部，由于流动应力较低，晶界迁移受到Al 3 Zr颗粒的抑制，晶界迁移率较低。因此，为了降低变形引起的高位错密度，发生连续动态再结晶，其不涉及长程晶界迁移，从而导致更细晶粒的结构。流动应力，因此，晶界的流动性增加附近的模具口。这促进了长程晶界迁移，从而降低了位错密度。在这些条件下没有观察到连续动态再结晶。由于Al 3 Zr析出物抑制了晶界的长程迁移，因此，随着Al 3 Zr析出物含量的增加，连续动态再结晶发生的区域向模口方向扩展，从而导致组织的细化。
The presence of Al 3 Zr precipitates promotes continuous dynamic recrystallization in Al-Zn-Mg alloys during hot extrusion, resulting in a fine-grained structure. The mechanism for this phenomenon was investigated by observing the change in microstructure under hot extrusion using high resolution EBSP. In the rear of the extrusion die mouth, grain boundary mobility is low since the flow stress is comparatively low and grain boundary migration is inhibited by Al 3 Zr particles. Thus, in order to reduce the deformation-induced high dislocation density, continuous dynamic recrystallization occurs, which does not involve long-range grain boundary migration, resulting in a finer-grained structure. The flow stress, and hence, the mobility of the grain boundary increase near the die mouth. This promotes long-range grain boundary migration, which reduces the dislocation density. Continuous dynamic recrystallization is not observed under these conditions. Since Al 3 Zr precipitates inhibit long-range grain boundary migration, increase of the Al 3 Zr precipitate content expands the region where continuous dynamic recrystallization occurs towards the die mouth, resulting in a finer-grained structure.