Compressive response and microstructural evolution of in-situ TiB2 particle-reinforced 7075 aluminum matrix composite
(School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China)
Abstract: The hot forming behavior, failure mechanism, and microstructure evolution of in-situ TiB2 particle-reinforced 7075 aluminum matrix composite were investigated by isothermal compression test under different deformation conditions of deformation temperatures of 300-450 °C and strain rates of 0.001-1 s-1. The results demonstrate that the failure behavior of the composite exhibits both particle fracture and interface debonding at low temperature and high strain rate, and dimple rupture of the matrix at high temperature and low strain rate. Full dynamic recrystallization, which improves the composite formability, occurs under conditions of high temperature (450 °C) and low strain rate (0.001 s-1); the grain size of the matrix after hot compression was significantly smaller than that of traditional 7075Al and ex-situ particle reinforced 7075Al matrix composite. Based on the flow stress curves, a constitutive model describing the relationship of the flow stress, true strain, strain rate and temperature was proposed. Furthermore, the processing maps based on both the dynamic material modeling (DMM) and modified DMM (MDMM) were established to analyze flow instability domain of the composite and optimize hot forming processing parameters. The optimum processing domain was determined at temperatures of 425-450 °C and strain rates of 0.001-0.01 s-1, in which the fine grain microstructure can be gained and particle crack and interface debonding can be avoided.
Key words: in-situ TiB2 particles; aluminum matrix composite; hot compression deformation; particle fracture; interface debonding; dynamic recrystallization