Abstract

Based on the modified KM (Kock–Mecking) model, a cutting constitutive model of AA7050-T7451 considering anisotropy is established in this article. With the aid of high-speed cutting FEM simulation and experiment, the micro-influence mechanism of anisotropy on high-speed cutting hardening of AA7050-T7451 was studied from three aspects: micro-morphology, residual strain, and plastic deformation. By analyzing the macro-micro correlation mechanism of dislocation density, work hardening, and cutting temperature, a “Three-Stage” model of work hardening is put forward. The results show that the work-hardening behavior of high-speed cutting AA7050-T7451 shows obvious anisotropic characteristics. And the work hardening degree is less than 0° and 90° at the material forming angle of 45°. At the 45° forming angle, the material dislocation density is the highest, and the grains are most prone to the dislocation slip. The macroscopic properties show that the microhardness of the material is small. The “Three-stage” model reveals the micro-evolution mechanism of work-hardening behavior. It is found that the dislocation density dominates the work-hardening behavior in stages I and II, and cutting temperature dominates the work-hardening behavior in stage III. The microhardness of the material increases sharply at first and then tends to be flat.

摘要

本文基于修正的KM（Kock-Mecking）模型，建立了考虑各向异性的AA7050-T7451切割本构模型。借助高速切削有限元模拟和实验，从微观形貌、残余应变和塑性变形三个方面研究了各向异性对AA7050-T7451高速切削硬化的微观影响机制。通过分析位错密度、加工硬化和切削温度的宏观-微观关联机制，提出加工硬化“三阶段”模型。结果表明，高速切削AA7050-T7451的加工硬化行为表现出明显的各向异性特征。材料成型角为45°时加工硬化度小于0°和90°。45°成型角时，材料位错密度最高，晶粒最容易发生位错滑移。宏观性质表明材料的显微硬度较小。“三阶段”模型揭示了加工硬化行为的微观演化机制。发现位错密度主导阶段 I 和 II 的加工硬化行为，而切削温度主导阶段 III 的加工硬化行为。材料的显微硬度先急剧增加，然后趋于平坦。发现位错密度主导阶段 I 和 II 的加工硬化行为，而切削温度主导阶段 III 的加工硬化行为。材料的显微硬度先急剧增加，然后趋于平坦。发现位错密度主导阶段 I 和 II 的加工硬化行为，而切削温度主导阶段 III 的加工硬化行为。材料的显微硬度先急剧增加，然后趋于平坦。