A front automobile fender with a negative angle was trial produced via rapid superplastic forming (SPF) technology. The tensile test of industrial AA5083 was carried out at elevated temperatures, and the results showed that the maximum elongation was 242% at 480 °C/0.001 s−1. A rigid-plastic constitutive model of the SPF process was established. Initial dies of preforming and final forming were designed. The finite element method (FEM) was used to simulate the forming process and predict the thickness distribution of different areas. Furthermore, the dies were optimized to make the thickness distribution uniform. In the final structure, the maximum thinning ratio decreased from 83.2% to 63% due to the optimized design of the forming dies. The front automobile fender was then successfully fabricated by the preforming process and final forming process at 480 °C. A thickness measurement was carried out, and the minimum thickness of the preforming structure was 2.17 mm at the transverse tank, while that of the final structure was 2.49 mm near the edge of the lamp orifice. The average grain size grew from 20 to 35 μm. The grain growth led to the reduction of mechanical properties. Compared with the mechanical properties of the initial material, the maximum decrease in tensile strength for the material after superplastic forming was 5.78%, and that of elongation was 18.5%.
28 March 2019 in Journal of Materials Engineering and Performance
TiAl alloy is a high temperature structural material with excellent comprehensive properties in the range of 750–900 °C. However, its engineering application is limited by its poor plasticity and hot working properties at room temperature. Based on the above background, a novel three-phase Ti-40Al-6V-1Cr-0.3Ni (at.%) alloy was designed and fabricated in the present study. The as-cast ingot was subjected to near-isothermal forging, and the thermoplastic deformation behavior, microstructure evolution and mechanical properties were systematically studied. Near-isothermal forging shows excellent forming capability, and the forging disk is flawless without cracking. The core of the forging disk shows the greatest degree of deformation, and the microstructure is composed of fine equiaxed grains and residual (α2/γ) lamellae. The hardness of the B2 phase and the hardness difference between the B2 phase and γ phase are reduced by the Cr and V elements added in the alloy. The wrought alloy exhibits excellent mechanical properties at room temperature and elevated temperature, respectively. The uniform fine microstructure, low nanohardness of the B2 and γ phase and the property matching of each phase can be accounted for the excellent mechanical properties.