The current focus on low-cost and high strength materials for advanced engineering applications attracted the research on the development of metal matrix syntactic foams. It is due to its highly tailorable properties. They are lightweight, higher ductility, quasi-static and dynamic compressive strength, better damping and energy absorption behavior and plateau strength. Different hollow particles were tried in the development of metal-based closed-cell syntactic foams such as cenosphere, ceramic, hollow glass particles, and expanded clay particles. Many researchers studied the physical and mechanical properties of polymer matrix syntactic foam. Very few reports are available on metal matrix syntactic foams, which remain a challenge to explore the properties. This present study provides a comprehensive insight into metal matrix syntactic foams, fabrication techniques and its influence on the mechanical properties, future scope, and its applications.

The research on lightweight materials for advanced engineering applications attracted the development of metal matrix syntactic foams. The automobile sector has started using Al-based alloys in structural components such as crash-box, underride-guard, fenders, dampers, A, B, and C Pillars. The present study explores the energy absorption behavior; microstructural characterization such as SEM, EDS, and XRD analysis of hollow glass microsphere (HGM) filled aluminum matrix syntactic foam. A380 aluminum alloy reinforced with different volume fractions 10%, 20%, 30%, and 35% of hollow glass microspheres were used in the fabrication of syntactic foam using the stir casting technique. The quasi-static compression test conducted, evaluated the plateau strength, which improved from 284.14 to 341.69 MPa, and energy absorption capacity was observed in the range 139.25–187.92 MJ/m³. The plateau strength and energy absorption capacity were improved by 16.82% and 25.89% for the 35 vol.% HGM sample as compared with 10 vol.% HGM filled aluminum matrix syntactic foam. The addition of a calcium thickening agent in the casting process improved the bonding between aluminum and HGM particle and also the homogeneous distribution of HGM. The XRD analysis revealed the chemical reaction that occurred between aluminum and SiO₂ that produced the AlSiO₂ and Al₂SiO₅ interfacial compounds. This reaction tends to collapse the HGM cell wall and fills it with matrix material.

Metal matrix composites (MMCs) outperform typical metals in mechanical, thermal, and tribological qualities, acquiring interest across industries. The variability of MMCs, which affects both the process and the joint qualities, creates difficulties when it comes to combining MMCs. Welding, brazing, adhesive bonding, and mechanical attaching are all examples of conventional techniques of joining. The process of welding can result in heat stresses, porosity, and interfacial reactions, all of which can compromise the integrity of the joint. Brazing struggles with matrix-filler compatibility and interfacial reactivity. Adhesive bonding is restricted by its endurance to high temperatures and mechanical loads, while mechanical attaching requires additional machining and weakens composite integrity Recently developed MMC-specific joining methods include ultrasonic welding, laser welding, diffusion bonding and friction stir welding. These methods improve joint quality and mechanical qualities by reducing heat stresses, distortion, and microstructural control. Surface modification, interlayers, and advanced filler materials reduce interfacial reactions and promote matrix-reinforcement bonding. Despite these advances, optimum process variables, influencing interfacial consequences, maintaining uniform reinforcement distribution, and accomplishing high bonding strength without compromising composite characteristics require interdisciplinary materials science, mechanical engineering, and manufacturing research. <!----> <!----> <!----> <!---->