5xxx铝合金热轧厚板退火过程中表层与心部再结晶行为差异研究

Differences in Recrystallization Behavior between the Surface and Center Layers of Hot-Rolled Thick Plate of 5xxx Aluminum Alloy

摘要:

以终轧温度为300℃的5xxx铝合金热轧厚板为研究对象，系统研究了不同退火工艺（300~500℃，0.5~8 h）对其微观组织、力学性能与电导率的影响。结果表明，提高退火温度显著促进了表层的再结晶过程，而心部再结晶进程相对滞后。表层因高位错密度和充分的动态回复，退火时主要发生以亚晶合并长大为主的连续再结晶；而心部因储能较低、形核位置少，主要以不连续再结晶为主。450℃保温2h后，表层再结晶分数达66.6%，心部仅为18.9%。随着退火温度升高，硬度、强度下降，伸长率与电导率上升。保温时间对力学性能影响较小，2h为较优选择。本研究揭示了热轧厚板在退火过程中表层与心部再结晶行为差异的机制，为优化退火工艺提供理论依据。

Abstract:

A 5xxx series aluminum alloy hot-rolled thick plate with a final rolling temperature of 300?°C was used to systematically investigate the effects of different annealing processes (300–500?°C, 0.5–8?h) on its microstructure, mechanical properties, and electrical conductivity. The results show that increasing the annealing temperature significantly promotes recrystallization in the surface layer, while recrystallization in the center proceeds more slowly. Due to the high dislocation density and sufficient dynamic recovery introduced during hot rolling, continuous recrystallization via subgrain coalescence and growth dominates in the surface layer during annealing. In contrast, discontinuous recrystallization prevails in the center owing to its lower stored energy and fewer nucleation sites. After annealing at 450?°C for 2?h, the recrystallization fraction reaches 66.6?% at the surface but only 18.9?% in the center. With increasing annealing temperature, hardness and strength decrease, while elongation and electrical conductivity increase. Holding time has a relatively minor influence on mechanical properties, and 2?h is identified as the optimal duration. This study clarifies the mechanism underlying the difference in recrystallization behavior between the surface and center of hot-rolled thick plates during annealing, providing a theoretical basis for optimizing annealing processes.