(1. 燕山大學 機械工程學院，秦皇島 066004；
2. 中南大學 高性能復雜制造國家重點實驗室，長沙 410083)
摘 要: 通過等溫熱壓縮試驗，研究7A85鋁合金在應變速率為0.001~0.5 s-1、變形溫度為250~450 ℃條件下的流變行為。結(jié)果表明，7A85鋁合金在塑性變形過程中，流變應力達到峰值前后的軟化機制不同。在流變應力達到峰值應力前，加工硬化作用占主導地位，軟化機制主要是材料內(nèi)部位錯的交滑移，動態(tài)回復不明顯。當流變應力達到峰值后，材料內(nèi)部發(fā)生明顯的動態(tài)回復和再結(jié)晶現(xiàn)象。基于流變應力達到峰值前后的軟化機制不同，建立了“兩階段”式Kocks-Mecking(K-M)位錯密度模型來描述7A85鋁合金塑性變形過程的位錯密度演變規(guī)律，并驗證了模型的準確性。
關(guān)鍵字: 7A85鋁合金；塑性變形；位錯密度模型；位錯演變
（1. College of Mechanical Engineering, Yanshan University, Qinhuangdao 066004, China;
2. State Key Laboratory of High Performance Complex Manufacturing, Central South University, Changsha 410083, China）
Abstract:The flow behavior of 7A85 aluminum alloy was studied by isothermal compression test at the strain rate range of 0.001-0.5 s-1 and temperature range of 250-450 ℃. The results show that, during the plastic deformation process, the softening mechanism of the flow stress is different before and after the peak flow stress of the 7A85 aluminum alloy. Before the flow stress reaches the peak, the work hardening is dominant and the main softening mechanism is the cross-slip of the dislocation inside the material, whereas, the dynamic recovery is not obvious. After the flow stress reaches the peak, the obvious dynamic recovery and recrystallization occur inside the material. Based on the difference of the softening mechanism before and after the peak stress, a “Two-stage” Kocks-Mecking (K-M) dislocation density model was established to describe the dislocation evolution during the plastic deformation process of 7A85 aluminum alloy, and the accuracy of the model was verified.
Key words: 7A85 aluminum alloy; plastic deformation; dislocation density model; dislocation evolution
