Microstructure Characteristic of Adiabatic Shear Band in 55vol% TiB₂ Particles Reinforced Aluminum Matrix Composite at High Strain Rates

In order to research the new-found phase transformation band with the main characteristic of melting in aluminum matrix composite, microstructure characteristics of adiabatic shear band in 55vol% TiB₂ particles reiforced aluminum matrix composite at varied strain rates (7×10^-4-2×10³s^-1) were researched by using split Hopkinson pressure bar (SHPB), optical microscope (OM) and scanning electron microscope (SEM). The results show that molten aluminum bands or accumulation area of molten aluminum cells at approximate 45° to the compression axis, which was called phase transformation band, were found on the shear plane at high strain rates of (1-2)×10³s^-1. The formation of phase transformation band was related with adiabatic temperature-rise, which caused the aluminum alloy matrix melting, after quick cooling, the phase transformation formed. Adiabatic shear failure for the experimental aluminum matrix composite was controlled by thermal softening effect.