The Hot Tensile Properties, Fracture Features, and Microstructure Evolution of As-Cast 7005 Aluminum Alloy

Abstract

In order to explore the hot deformation behaviors of the as-cast 7005 aluminum alloy, a number of hot tensile tests with four temperatures (100, 200, 300, and 400 °C) and three strain rates (0.001, 0.01, and 0.1 s−1) were performed. The Johnson–Cook model was used to express the relationship between stress, strain, strain rate, and temperature. Scanning electron microscopy (SEM), optical microscopy (OM), and transmission electron microscopy (TEM) were selected to reveal fracture features and microstructure evolution of the studied alloy. The results indicate that the flow stress level of the alloy reduces with increases in the deformation temperature and decreases in the strain rate. The established Johnson–Cook model can be employed to characterize the thermal flow behavior of the experimental alloy. The grains near the fracture surface were elongated, and a certain number of holes were found after deformation at 400 °C. The alloy exhibits obvious ductile fracture features. The dimple is deep with high quantity. Due to the plastic deformation, a high-density dislocation structure is found in the material. High-temperature conditions promote the annihilation of dislocation, and, as a result, the dislocation density decreases gradually with the increase in temperature. In addition, a certain number of precipitates were found in the alloy after high-temperature tension.