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Highlights: [•] 55vol.% TiB2/2024Al composites are fabricated by pressure infiltration method. [•] Effect of surface roughness on tribological properties are investigated. [•] Optimal roughness is determined by combining microstructure and wear mechanism. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, 55vol.% TiB2/2024Al composites were obtained by pressure infiltration method. Compressive properties of 55vol.% TiB2/2024Al composite under the strain rates of 10−3 and 1S−1 at different temperature were measured and microstructure of post-compressed TiB2/2024Al composite was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). No trace of Al3Ti compound flake was found. TiB2–Al interface was smooth without significant reaction products, and orientation relationships ( and ) were revealed by HRTEM. Compressive strength of TiB2/2024Al composites decreased with temperature regardless of strain rates. The strain-rate-sensitivity of TiB2/2024Al composites increased with the increasing temperature. Fracture surface of specimens compressed at 25 and 250°C under 10−3 S−1 were characterized by furrow. Under 10−3 S−1, high density dislocations were formed in Al matrix when compressed at 25°C and dynamic recrystallization occurred at 250°C. Segregation of Mg and Cu on the subgrain boundary was also revealed at 550°C. Dislocations, whose density increased with temperature, were formed in TiB2 particles under 1S−1. Deformation of composites is affected by matrix, reinforcement and strain rate. [Copyright &y& Elsevier]

In this research, the ballistic behavior and microstructure evolution of 45vol% B 4 C/AA2024 composites produced by pressure infiltration method were studied. The ballistic behavior of composites was carried out using 7.62 mm armor-piercing incendiary (API). The results demonstrate that the 45vol% B 4 C/AA2024 composites has excellent ballistic performance and the protection coefficient reaches 3.6. The residual microstructure of composites after impact was mainly investigated by the transmission electron microscope (TEM). The results show that the residual microstructure of B 4 C particles mainly include dislocations, stacking faults, twins and poly-crystallization. For Al matrix, the residual microstructure is mainly the existence of large numbers of dislocations especially in the area near the sharp corner of B 4 C particles. In addition, inhomogeneous precipitates of AA2024 matrix were observed after impact. [ABSTRACT FROM AUTHOR]

Abstract: The resistance of Al2O3 +TiB2/2024Al composite to hypervelocity impact was tested by a two-stage light gas gun. The impact damage behaviors of the Al2O3 +TiB2/2024Al composite by different-sized Al projectiles with a velocity of 2.49km/s and the residual microstructures associated with the crater impacted by a 1.2mm aluminum projectile were investigated by transmission electron microscopy and high-resolution transmission electron microscopy. Both the diameters of craters at front face and spalling areas at back face increased with the aluminum projectile diameter. The diameter of perforation on the 2mm thick Al2O3 +TiB2/Al composite target was zero when impacted by 1.2mm aluminum projectile and it increased to 2.4mm when the projectile diameter was 1.5mm, indicating that the critical perforation diameter of the aluminum projectile was between 1.2mm and 1.5mm when the 2mm thick Al2O3 +TiB2/Al composite target was impacted by 2.49km/s aluminum projectiles. The diameter of perforation increases with the diameter of Al projectile. In addition, under each impact condition, the diameters of craters at front face were smaller than that of spalling areas at back face. Microstructure observations by transmission electron microscopy demonstrated four characteristics: stacking faults around TiB2 particle and dislocations within the TiB2 particle; twins in the Al2O3 particle; recrystal grains in 2024 Al matrix; and mixture of amorphous microstructure and nanograins in the matrix. [Copyright &y& Elsevier]

Abstract: Interfacial structure in 55%TiB2/Al composite before and after high speed impact was investigated in detail. It is found that there is no stacking fault in original TiB2 particle before fabrication or in TiB2 particle in composite. However, after the composite is impacted by 1.2mm projectile with the velocity of 2.5km/s, stacking fault forms along the (0001) plane around the edge of TiB2 particle and grows with a step-like epitaxial way, resulting from the high pressure of shock wave. At the bottom of crater in the target, Al matrix around the TiB2 particle was molten and then oxidated, which results in the formation of Al x O1−x (x <1) phase between TiB2 particle and Al matrix. It is found that TiB2 particle and Al x O1−x phase combine well and have no reacted layer at the interface and there exists an orientation between two phases: , . [Copyright &y& Elsevier]