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This study reports the densification behavior and novel design of core-rim microstructure for different ZrB 2 –MoSi 2 -SiC w (ZMS w) composites. Four ZrB 2 –MoSi 2 composites containing various amounts of SiC w (0, 5, 10, and 20 vol%) were densified by multistage spark plasma sintering. Optimal combinations of sintering schedule, temperature, and composition are recognized for producing dense ZrB 2 -based ceramic-matrix composite with core-rim grain structure in the boride matrix, where ZrB 2 core is surrounded by a solid solution of (Mo,W)Si 2. Fragmentation, rearrangement, plastic deformation, and grain boundary diffusion mechanisms are responsible for densification of composites sintered by multistage SPS conditions at 1700 °C. Addition of SiC w significantly improves the density and mechanical properties of ZrB 2 –MoSi 2 –SiC w composites due to the formation of a core-rim structure. [ABSTRACT FROM AUTHOR]

The effect of SiC w addition on abrasive wear performance of ZrB 2 -MoSi 2 composites were examined. Coefficient of friction, specific wear rate, and surface roughness decrease with the addition of SiC w. The formation of the self-lubricating tribo-oxide layer caused by tribochemical reaction during frictional heating enhances wear resistance of the composites. Tribological performances of the composites are strongly influenced by parametric variation of different experimental conditions which are primarily sliding speed and applied load. The operational wear regime maps reveal that the workable damage tolerance limits for the applied load are 20−25 N for ZMS w -5 composite, whereas that for ZMS w -20 composite is ∼40 N. The wear mechanisms vary from delamination, cracking, and grain pull out at medium applied loads to grain boundary fracture at higher applied loads. [ABSTRACT FROM AUTHOR]

Abstract A comparative evaluation has been carried out off the physical and mechanical properties of ZrB 2 –20 vol% MoSi 2 composites reinforced with 5, 10 and 20 vol% SiC whiskers (SiC w). The abovementioned hybrid composites have been densified by spark plasma sintering (SPS) at 1600 °C for 10 min. The present study focuses on the effect of the quantity of SiC w on the densification, electrical conductivity, hardness, and fracture toughness ZrB 2 –MoSi 2 –SiC w composites in detail. Microstructural characterization suggests that SiC w restricts the grain growth of ZrB 2 during densification. The electrical conductivities of the ZrB 2 –MoSi 2 –SiC w composites have been found to vary in the range ~2.4–3.5 × 106 S/m, and it reduce with increasing SiC w content. Results exhibit that the indentation fracture toughness of ZrB 2 –20 vol% MoSi 2 improves ~70%, ~112% and ~130% with an addition of 5, 10 and 20 vol% SiC w , respectively. An increase in SiC w content leads to more amount of crack deflection and crack arrest that successively improves the fracture toughness of the composites. Highlights • Spark plasma sintering successfully densified the ZrB 2 –MoSi 2 –SiC w composites with varying amount of SiC w • With the increase in SiC w resulted in enhancement in fracture toughness of ZrB 2 –MoSi 2 –SiC w composites. • The fracture toughness of ZrB 2 –20 vol% MoSi 2 improves by about ~130% with the addition of 20 vol% SiC w. • Microstructure suggests toughening mechanism mainly controlled by crack deflection and interfacial debonding. [ABSTRACT FROM AUTHOR]

[Display omitted] • Compressive strength and internal fracture of Al-Mg 2 Si composites. • Actual microstructure-based RVE models. • Micromechanics and compressive failure of Al-Mg 2 Si composites. • Energy dissipation of Al-Mg 2 Si composites subjected to compression. Al-Mg 2 Si composites have been developed through gravity die-casting techniques. The influence of Mg 2 Si reinforcement concentration on strength, micromechanics and failure initiation of Al-Mg 2 Si composites subjected to compression has been studied. The compressive strength and brittle fracture of the Al-Mg 2 Si composite increase and strain decrease with an increase in Mg 2 Si concentration. The eutectic and primary Mg 2 Si phase sharp corners and narrow sections of Mg 2 Si are fracture initiation sites, and the Al phase nearby the eutectic and Mg 2 Si phase sharp corners and narrow Al phase regions between two Mg 2 Si islands are void initiation sites in the composites subjected to compression. [ABSTRACT FROM AUTHOR]