大应变条件下铝锶合金连续挤压组织演变

Microstructure evolution of aluminum–strontium alloy continuous extrusion under large strain

摘要:

摘要：本研究将连续挤压与等通道模具相结合，通过有限元模拟、金相显微镜、X射线衍射仪和透射电子显微镜分析大应变条件下铝锶中间合金微观组织的变化机理。结果表明：等通道模具中等效应变最大值可达16，出现在经过第一转角外角的a路径上，对Al4Sr相细化效果最好，各路径对Al4Sr相的细化作用为：内侧a路径>中间b路径>外侧c路径；采用这种一模双孔的挤压方式，可以使进料口中心粗大的Al4Sr相粒子经过等通道模具中应变最大的a路径，使其得到有效细化，最终使得产品中心和边缘的Al4Sr相均得到有效细化，尺寸约为4.5 μm。透射电镜观察表明，经过大塑性变形后，由于累积应变值增加，微观应变增大，Al4Sr相内部位错缠结交割，形成位错墙，与外部位错相互作用，使Al4Sr相粒子断裂碎化，对Al4Sr相粒子产生了显著的细化效果，同时由于界面能的增大，促使Al4Sr相出现少量回溶。

Abstract:

Abstract: In this study, the continuous extrusion is combined with an equal-channel die. The microstructure evolution of Al-Sr master alloy under large strain extrusion is analyzed by finite-element simulation, metallographic microscopy, X-ray diffraction, and transmission electron microscopy. Results show that the maximum effective strain in the equal-channel die can reach 16, which appears on the a-path passing through the outer corner of the first die angle, and the refinement effect of Al4Sr phase is the best. The refinement effect of each path on Al4Sr phase is as follows: inner a-path > middle b- path > outside c-path. Using the extrusion method with one die of double hole, the coarse Al4Sr phase particles in the center of cavity inlet can pass through the a-path with largest strain in the equal-channel die, so that they can be effectively refined. Finally the particles of Al4Sr phase in the center and edge of the product are effectively refined, with an average length of about 4.5 μm. Transmission electron microscopy observation shows that after large plastic deformation, due to the increased cumulative strain and increased microscopic strain, the internal dislocations of Al4Sr phase are entangled and delivered, forming a dislocation wall that interacts with the external dislocations to break Al4Sr phase particles. The fragmentation exerts a significant refining effect on Al4Sr phase particles. At the same time, due to the increased interfacial energy, a small amount of Al4Sr phase dissolves.