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Nanoindentation-derived mechanical properties and strain rate sensitivity assessment of a set of stir-cast metallic reinforced Aluminium-based composites, with an antecedence of anomalous stress oscillations and strain rate insensitivity during hot compression, was investigated in this study. For the evaluation, Al6063-based composites reinforced with 6 wt% CuZnAl, steel, nickel, and SiC particles were subjected to nanoindentation, and their strain rate sensitivity was assessed using a strain rate jump test. The results show that the AMCs reinforced with metallic particles presented better mechanical properties than those reinforced with SiC. The CuZnAl reinforced AMC had the best hardness (1.25 ± 0.25 GPa) and elastic modulus (∼83 GPa), which is opined to be on account of thermoelastic contributions to the basic strengthening mechanisms. The large scatter observed in the mechanical response of the AMCs is largely due to the inhomogeneous particle distribution. The higher indentation resistance with an increase in strain rate, coupled with the absence of displacement bursts, indicated that the composites largely exhibit positive strain rate sensitivity. [ABSTRACT FROM AUTHOR]

The present investigation aimed at evaluating the mechanical and corrosion performance of stir-cast ZA-27 based composites reinforced with stainless steel machining chips (SSMC), which is presumed offer to improve ductility and toughness to the composite but it is unclear how it can affect the strength and the corrosion resistance. The results indicate that the ZA-27 composites produced were technically not defective, judging from the very low porosity levels observed in them. The hardness and ultimate tensile strength of the composites improved with increase in wt. % SSMC, and no significant difference in values noticed when compared to the ZA-27 based composite reinforced with alumina. The ductility and fracture toughness of the SSMC containing ZA-27 based composites increased with the increase in the reinforcement wt. % and were significantly better than the alumina reinforced composition. The corrosion resistance of the composites in H2SO4 solution also improved with increase in the wt. % of SSMC, and the resistance to corrosion for all the composites were higher than the unreinforced ZA-27 alloy. [ABSTRACT FROM AUTHOR]

This study investigates the wear behaviour of aluminium metal matrix composites reinforced with 10 wt.% Si-based refractory compounds (SBRC) derived from rice husk (RHs). The wear test was conducted using a pin-on-disk tribometer under varying loads with a fixed sliding distance. Scanning electron microscope was used to characterize the worn-out surface and the wear debris. From the results obtained, as the applied load increases, the coefficient of friction (CoF) value reduces to a significant extent. This reduction might be associated with the presence of graphite phase in all the composites developed. The results showed that for samples subjected to 5 N load, T1650 had the optimum value of wear volume amounting to 25–93% increase in wear volume against other samples. Additionally, for 8 N load, K1650 showed a higher response in wear volume having 26–74% improvement in wear volume. The specific wear rate of the composites developed at 5 N load application can be ranked in the following order: T1600 > K1250 > T1650 > K1650 > T1250. A severe agglomeration, possibly caused by fragmentation of the clustered debris, dominated the morphology of the worn-out surface. From the EDS spectra, the iron content appears to be low while the oxygen content very high, this is an indication that the tribolayer island was oxidized. An optical photograph showing the wear profile was also taken. It is inferred that the initial wear mechanism of the composites is adhesive, this later converted to abrasive. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of Zn–27Al based composites reinforced with rice husk ash (RHA), silicon carbide (SiC), and graphite (C g ) particles have been investigated. The Zn–27Al composites consisting of varied weight ratios of the reinforcing materials were produced using the stir casting process. Hardness test, tensile properties evaluation, fracture toughness determination, and microstructural examination, were used to characterize the composites produced. Results show that the microstructures of the composites are similar, consisting of the dendritic structure of the Zn–27Al alloy matrix with fine dispersion of the reinforcing particles. The hardness of the composites decreased with increase in the weight percent of RHA (and corresponding decrease in SiC weight percent) in the reinforcement. The tensile strength and yield strength decreased slightly with increase in the weight ratio of RHA in the composites with a maximum of 8.5% and 9.6% reductions respectively observed for as much as 40% RHA (corresponding to 40% reduction in SiC) in the hybrid reinforcement. Although some of the composite compositions containing RHA had slightly higher % elongation values compared with those without RHA, it was generally observed that the % elongation was invariant to the composite RHA content. The fracture toughness of the composites increases with increase in the weight percent of RHA with as much as a 20% increase obtained for as much as 40% RHA (corresponding to 40% reduction in SiC) in the hybrid reinforcement. [ABSTRACT FROM AUTHOR]

The influence of cobalt based and zirconia mixed binder additives on the mechanical properties and tribological characteristics of WC based spark plasma sintered cermet composites was investigated. Varied weight proportions of zirconia stabilized with yttria along with constant weights of 9Co/WC–4.5CO–2Cr–5Ni metallic binder were blended with WC, consolidated and sintered using spark plasma sintering process. The composites produced were characterized using SEM and XRD analyses, density measurements, mechanical properties and wear test evaluations. The results show that the use of the mixed binder additives did not significantly affect the densification process as relative densities above 92% (7.5% less than that achieved using only the Co based metallic binders) were achieved using SPS processing. However, the grain size was observed to increase with increase in zirconia content in the mixed bond composites, and the hardness values decreased with increase in zirconia content. The toughness and fracture toughness showed significant improvement with the addition of zirconia. Also the coefficient of friction for the mixed binder sintered composites were on the average lower than that of the cermet composites without zirconia. Pseudoplastic properties characterized by the presence of delaminations were the primary wear mechanism observed for the zirconia containing cermets; while pits and wear groove formations were observed in the cermets without zirconia. [ABSTRACT FROM AUTHOR]

The mechanical behaviour of cold deformed and solution heat-treated aluminium alloy (6063)- alumina particulate composites was investigated. AA 6063-Al2O3 particulate composites having 6, 9, and 12 volume percent of Al2O3 were produced using two-step stir casting process. The composites were cold rolled to 20 and 35% deformation before solution heat-treating at 550°C for 1 hour cooling rapidly in water. Density measurements were used as a basis of evaluating the percent porosity of the composites; while tensile properties and fracture toughness were utilised to study the mechanical behaviour. It was discovered that the cold rolling and solution heat-treating processes resulted in remarkable reduction in porosity levels in the AA 6063/Al2O3p composites (≤ 2.8 % porosity). A good uniform distribution of the alumina particulates in the matrix of the AA 6063 was also produced. The tensile strength and yield strength increased with increase in alumina volume percent and degree of cold rolling. The strain to fracture and fracture toughness decreased with increasing volume percent alumina but improved with increase in the degree of cold deformation. [ABSTRACT FROM AUTHOR]