Influence of Hot Rolling on Mechanical Behavior and Strengthening Mechanism in Boron Carbide Reinforced Aluminum Matrix Composites

Boron carbide reinforced aluminum matrix composites are widely used as neutron absorption materials. Here we report that mechanical alloying has been successfully employed to synthesize metal matrix composite powders with Al as the matrix and B₄C, Al₄Gd and Al₄Sm as the reinforcement. The effects of hot rolling on the morphology, mechanical properties as well as the strengthening mechanisms are investigated. Hot rolling results in improving particle distribution and less agglomeration, improving the bonding between particles and matrix and decreasing voids. Thermomechanical processing can increase the density and remove the defects. As increasing rolling deformation to 50%, both YS and UTS of composites are enhanced significantly, showing 25.8 and 27.0% improvement in comparison with composites after sintered, but the elongation changes little. The increase in the yield strength after hot rolling can be attributed to two primary strengthening mechanisms in this work: The coefficient of thermal expansion (CTE) mismatch between B₄C, Al₄Gd and Al₄Sm reinforced particles and Al matrix and the existence of load transfer from Al matrix to the hard reinforced particles.