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Due to excellent chemical stability, high rigidity, superior corrosion and wear resistance, aluminum oxynitride (AlON) has been considered as one of most promising candidate ceramic materials in high-performance structural, advanced abrasives and refractory fields. However, it usually exhibited relatively low flexural strength and poor fracture toughness. The study is aimed to develop silicon carbide (SiC) and zirconium nitride (ZrN) nano-particulate reinforced AlON composites with improved mechanical properties and fracture resistance via a hot-press sintering process. It was found that the addition of ZrO 2 nanoparticles would be transformed into ZrN during sintering. Due to the pinning effect of SiC and ZrN nano-particles positioned at grain boundaries of micro-sized AlON particles, the presence of SiC and ZrN nano-particles resulted in the reduction of both porosity and grain size, and a change of fracture mode from intergranular cracking in AlON to intragranular cracking in composites. With presence of 8 wt% SiC and 5.2 wt% ZrN nano-particles, the relative density, microhardness, Young’s modulus, flexural strength and fracture toughness increased. Different toughening mechanisms including crack bridging, crack branching and crack deflection were observed, thus effectively increasing the crack propagation resistance and leading to a considerable improvement in flexural strength and fracture toughness. [ABSTRACT FROM AUTHOR]

The in-situ laminated Nb/Nb 5 Si 3 composite was prepared by spark plasma sintering. The microstructures and mechanical properties of the laminated Nb/Nb 5 Si 3 composite were investigated in present work. It could be found that, alternant distribution microstructures of Nb ss and Nb 5 Si 3 layers were observed after sintering. The Nb/Nb 5 Si 3 composite exhibited fracture toughness of 11.2 MPa·m 1/2 , and the predicted fracture toughness was estimated by the Ashby model. Moreover, the deviation of the experimental value from the predicted value was discussed. In addition, the compressive strength of the in-situ laminated Nb/Nb 5 Si 3 composite was measured at 1400 °C and compared with that of the unidirectionally solidified Nb-17.5Si alloy. [ABSTRACT FROM AUTHOR]

Abstract: Aluminium oxynitride (Alon) exhibits excellent stability, high rigidity and good thermal shock resistance, but it has relatively low strength and poor fracture toughness. The aim of this investigation was to develop a new type of zirconium nitride (ZrN) nano-particulate reinforced Alon composites via a change of ZrO2 nano-particles during sintering. A reduction of porosity and grain size was observed in the composite. With increasing amount of ZrN nano-particles up to 2.7%, the relative density, hardness, Young''s modulus, flexural strength, and fracture toughness all increased. When the ZrN nano-particles exceeded 2.7%, while the flexural strength and fracture toughness decreased slightly, the density, hardness and Young''s modulus continued to increase. Different toughening mechanisms including crack bridging, crack branching and crack deflection were observed, thus effectively increasing the crack propagation resistance and leading to a considerable improvement in the flexural strength and fracture toughness of the composites. [Copyright &y& Elsevier]

• The influence of thermal-cold cycling on dimensional stability of composite. • The microstructure, dimensional change, magnetic property, hardness were analyzed. • The underlying dimensional stabilizing mechanisms of the composite were revealed. • An optimal improvement of dimensional stability of the composite was achieved. Thermal-cold cycling (TCC) treatment was applied to improve the dimensional stability of TiC reinforced steel matrix composite materials in this study. Also, the microstructure, related properties and potential stability mechanisms were investigated. When the TCC cycles were 3, Vickers hardness reached the peak value of 1051.7 HV and relative dimensional change was only 0.012% in a natural service for 30 days. Besides, the retained austenite disappeared and residual stress dramatically decreased from −740 MPa to −357 MPa. It demonstrated that the TiC reinforced steel matrix composite possessed the best dimensional stability after 3 TCC cycles. A variety of stabilizing mechanisms, including martensitic refinement, retained austenite-martensite transformation, carbides precipitation, and residual stress release were observed, hence resulting in a significantly improvement of the dimensional stability of the composite. [ABSTRACT FROM AUTHOR]

• The influence of tempering on dimensional stability of TiC-reinforced composite. • The microstructure, hardness, thermal strain and magnetic property were analyzed. • The underlying dimensional stabilizing mechanisms of the composite were revealed. • An optimal improvement of dimensional stability of the composite was achieved. To improve the service reliability of components prepared by TiC-reinforced steel matrix composite material, tempering treatment was carried out to tailor the microstructure and properties of the composite. The aim of this study was to investigate the microstructure, properties, and dimensional stability of a TiC-reinforced steel matrix composite during tempering and to identify the underlying stabilizing mechanisms. We observed that the metastable retained austenite transformed into martensite and that residual stress released during tempering. The microstructure and properties of the composite reached an optimal state for a tempering time of 10 h. Furthermore, the relative dimensional change, Vickers hardness, thermal strain, and saturation magnetization of the composite were 0.0219%, 960.8 HV, 3.16 × 10−4, and 109.7 emu/g, respectively. Various stabilizing mechanisms, including retained austenite-martensite transformation and residual stress release, were observed during tempering, effectively improving the dimensional stability of TiC-reinforced steel matrix composites. [ABSTRACT FROM AUTHOR]

[Display omitted] • The influence of vibration aging on residual stress relief of composite. • The residual stress, hardness and magnetic property were analyzed. • The underlying mechanisms of the composite were revealed. • An optimal improvement of the composite was achieved. To further improve the long-term service reliability of high-precision inertial instruments prepared with TiC reinforced steel matrix composite materials, vibration aging treatment was carried out to improve the comprehensive properties of the instrument-grade composite. The effects of vibration aging on microstructure, stress relief, hardness, and magnetic properties of the stabilized composite were investigated, and the underlying mechanisms were also elucidated. The results showed that the vibration aging treatment significantly released the residual stress and improved the Vickers hardness of the composite, while also promoting the precipitation of fine carbides in the matrix and the microstructure transformation of metastable retained austenite to relatively stable martensite. When the vibration aging was conducted at 80 °C for 30–60 min, the composite possessed excellent comprehensive properties. During the vibration aging process, various mechanisms, such as residual stress relief, retained austenite–martensite transformation, and carbides precipitation acted on the composite, resulting in a significant improvement in the performance of TiC reinforced steel matrix composite. [ABSTRACT FROM AUTHOR]