Metal matrix composites made by a powder metallurgy route often exhibit clustering of the reinforcements due to geometrical reasons. The clustering tendency was studied in 2124 Al/30 v/o SiCp composites as a function of relative particle size ratio between the matrix and reinforcement particles. Dry blended composite powders, with different RPS ratios, were vacuum hot-pressed and microstructures were examined to assess the uniformity of the microstructure by measuring the local area fraction of the constituents. It was found that a decrease in RPS ratio resulted in an increase in strength as well as ductility, as a result of improved distribution of the SiCp. The improved response to the homogenisation treatment, observed in the composite with lower RPS ratio, is attributed to the smaller diffusion path length for the alloying element.

Structure–property correlation in discontinuously reinforced aluminium matrix composites as a function of relative particle size ratio

Hot deformation and processing maps of extruded ZE41A magnesium alloy

The hot working characteristics of 6061 Al/15%SiCp produced by stir casting are studied using processing maps. The maps, based on the dynamic materials model, were generated from the flow stress data obtained through hot compression tests conducted at strain rates and temperatures ranging from 0.0857 to 2.7 s−1 and 300 to 500 °C, respectively. From the experimental data the strain rate sensitivity (m), power dissipation efficiency (η) and instability parameter (ξ( e )) were computed and are plotted in the temperature-strain rate plane to obtain power dissipation and instability maps. The domains of dynamic recrystallization and wedge cracking are observed in the processing maps. Shear band formation and particle fracture were noticed at higher strain rates and lower temperature, thereby defining the flow instability domain.

Development of processing maps for 6061 Al/15% SiCp composite material

The aim of this study was to investigate the effects of matrix particle size, reinforcement particle size, volume fraction, and their interactions on the wear characteristics of Al–SiC p composites. Central composite design method was used to perform a series of experiments. The statistical analysis of experimental results showed that both main effect and interaction effect of factors investigated were effective on the wear behavior of Al–SiC p composites. Wear loss decreased as volume fraction increased; however, beyond volume fraction of 17.5%, it increased due to reinforcement particle clustering depending on volume fraction and matrix particle size to reinforcement particle size ratio. With decreasing of matrix particle size and increasing of reinforcement particle size, wear loss also decreased. However, after a certain volume fraction, large sized reinforcement particles had a negative effect on the wear resistance.

Main and interaction effects of matrix particle size, reinforcement particle size and volume fraction on wear characteristics of Al–SiCp composites using central composite design

Effect of high energy ball milling on the morphology, microstructure and properties of nano-sized TiC particle-reinforced 6005A aluminium alloy matrix composite

The hot working characteristics of 2124 Al alloy matrix composites reinforced with 0, 5, 10, 15, and 20 vol pct of SiC particulate, produced by the powder metallurgy route, were studied using processing maps. The maps based on the dynamic materials model were generated from the flow stress data obtained from hot compression tests, carried out at strain rates ranging from 0.001 to 10 s−1 and temperatures ranging from 300°C to 525°C. All the compositions studied exhibited domains of dynamic recrystallization (DRX) and superplasticity. Flow instabilities were found at higher strain rates and lower temperatures. The composite with 10 vol pct SiC showed a tendency for abnormal grain growth at lower strains, which manifested itself as a shift in the DRX domain to lower strain rates and the disappearance of the superplasticity domain.

Y. R. Mahajan

Papers

Effect of volume fraction of SiC p reinforcement on the processing maps for 2124 Al matrix composites

Clustering probability maps for private metal matrix composites