Search

The poor mechanical and tribological properties limit the higher requirements of aluminum alloys in engineering and industrial applications, which leads to the rapid development of aluminum matrix composites (AMCs). Particulate reinforced AMCs have attracted extensive attention in automobile, electronics and military industries due to their low density, high strength, and excellent wear resistance. However, the interfacial reaction between reinforcements and the Al matrix tends to occur in conventional preparation processes owing to the higher reaction temperatures. The spark plasma sintering (SPS) technique is considered to be an efficient method for the fabrication of metal matrix composites, which can achieve rapid sintering, lower sintering temperatures, and higher densities than conventional fabrication processes. In addition, SPS can produce AMCs with excellent non-porous microstructure, fine grain size, and a strong bonding interface between reinforcement and Al matrix. Therefore, the interfacial reaction is effectively controlled and the structural integrity is maintained, resulting in enhanced strength and ductility. Based on the advantages of particulate reinforced AMCs and the SPS technique, the particulate reinforced AMCs fabricated by SPS have been extensively studied in recent decades, but have not been systematically evaluated. Therefore, this paper reviews the state-of-the-art particulate reinforced AMCs fabricated by SPS, focusing on the microstructure characterization, strengthening mechanisms, and mechanical and physical properties. Furthermore, the future research priorities and challenges of the high-performance particulate reinforced AMCs fabricated by SPS are also prospected. [ABSTRACT FROM AUTHOR]

The comparative assessments and an overview of mechanical, chemical, and physical properties of rail axles are presented. This review focused on the effects of compositions and microstructure on fatigue, fretting and corrosion fatigue of rail axles. The two main steel grades: low carbon steels for commuter trains and high strength low alloy steels for high-speed trains have ferrite-pearlite microstructures with 20–40 µm ferrite grain sizes. Minimum allowable yield and ultimate tensile strengths are 330 MPa and 600 MPa, and the minimum longitudinal and transverse toughnesses are 35 J and 22 J. Most axle failures are associated with surface and sub-surface defects with micro-cracks nucleating from ballast (small-sized pebbles in rail tracks), minute oscillatory movement leading to fretting, microstructural inclusions, and corrosion pits. The implications for structural integrity are highlighted and areas for future research directions are highlighted. [ABSTRACT FROM AUTHOR]