Fabrication and characterization of Al/TiNi shape memory composites

Metal matrix composites reinforced with shape memory alloys induce compressive residual stress in the matrices resulting in improved tensile properties in the composite. In the present study, Al/TiNi shape memory composites were fabricated by squeeze casting and powder metallurgy the so-called Plasma Activated Sintering (PAS). Fairly good matrix/reinforcement bonding was observed in the Al/TiNi composites. The effects of the residual stress caused by the shape recovery force were compared as a function of reinforcement volume fraction, prestrain, matrix strength and reinforcement shape. Strengthening effect due to TiNi reinforcement as well as the compressive residual stress were investigated. It was found that the yield strength of the composites increased the volume fraction of TiNi reinforcement increased and the amount of prestrain applied to the composite. Moreover, the percentage of strength increment of the pure continuous fiber Al/TiNi (Al/TiNicf) composite caused by prestrain was higher than that of the AC4A Al/TiNicf composite. The percentage of strength increment of the AlTiNicf composite was higher than that of the particulate Al/TiNi (Al/TiNiP) composite.