Processing of TiPd shape memory alloy reinforced Ti-matrix composites and their mechanical properties

Ti and Ti-2Cu matrix composites reinforced by TiPd-based shape memory alloys (SMAs) were fabricated by sheath rolling of Ti or Ti-2Cu plates with TiPd fiber. Fibers of three TiPd SMAs were used as reinforcements. The Youngʹs modulus of TiPd fiber increased with increasing temperature above austenite start temperature, As. Good bonding between the fiber and matrix was obtained by heat treatment at 1123 K for 3.6 ks following sheath rolling at the same temperature. A multi-layered reaction region was formed in the vicinity of the interface between Ti or Ti-2Cu matrix and TiPd-based SMA fiber. Tensile tests were performed at various temperatures for Ti-2Cu matrix composites containing Ti–22Pd–27Ni–1W and Ti/Ti–25Pd–24Ni–1W fiber. It was found that the 0.5% offset stress of these composites increased with increasing temperature. This stress increase is mainly caused by residual compressive stresses generated in association with shape memory effects of the TiPd-based SMAs. Surface observations of fractured specimens showed that interfacial layers were fractured in a ductile fracture mode.