Shape memory alloy-reinforced self-healing aluminum composites with in situ low melting point healing phase

Abstract

Shape memory alloy (SMA)-reinforced self-healing metal matrix composites (SHMMCs) are an emerging class of materials capable of semi-autonomously repairing cracks—a process termed assisted self-healing, offering significant potential for enhancing structural longevity. This study investigated the effects of varying SMA volume fractions (1.5 and 4.2 vol%) and in situ low melting point phases (15 and 40 wt% tin) on the self-healing performance of the aluminum matrix composites. Additionally, the study investigates the influence of a clamping mechanism and the use of etchants and a phosphoric acid-based flux on enhancing load transfer and improving healing efficiency in NiTi SMA-reinforced SHMMCs. Flexural testing confirmed the restoration of mechanical properties after healing, while microstructural characterization using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy Analysis (EDS) revealed interfacial bonding between the Al–Sn matrix and NiTi reinforcement. Among the tested compositions, the Al–40 wt% Sn–1.5 vol% NiTi composite without a clamping mechanism exhibits the highest flexural property recovery, attributed to the synergistic effect of shape restoration by the NiTi SMA and effective sealing of the healing agent at the crack site. These findings highlight the potential of SMA-reinforced SHMMCs for enhancing material durability and sustainability.