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An addition of Ti or Ti/B is an accepted technique to produce cast aluminum alloys having fine grain size and superior mechanical properties. Present investigation focuses on the role of grain refinement treatment on the SiC particle distribution in Al-7 wt.% Si-10 vol.% SiCp cast composites and also on the degree of refinement of matrix microstructure. Composites manufactured by vortex method were treated with three different commercial grain refiners namely; K2TiF6 salt, Al–6Ti and Al–5Ti–1B master alloys. Microstructural characteristics including nature of distribution of SiCp in the matrix, grain size and dendritic arm spacing have been studied. It was found that complete dewetting of the SiCp and consequently their rejection from the melt takes place when the composite was treated with K2TiF6 salt. Improved distribution of SiCp in the matrix of composites was observed when the melt was treated with either Al–6Ti or Al–5Ti–1B master alloy. Composite melt treated with Al–5Ti–1B master alloy show excellent combination of matrix grain refinement and uniform SiCp distribution.

The effect of additions of Sr (in the range 0.05–0.5%) on the microstructural characteristics of Al–7 wt.% Si–10 vol.% SiCp composites have been studied. Optical microscopy (OM), SEM, EDS, WDS microanalysis techniques and X-ray diffraction powder techniques have been used for the characterization of the composites. It was found that Sr concentrations between 0.05 and 0.20 facilitates incorporation of higher volume fraction of SiC particles and also does not contribute to the overall modification of the matrix. However, at higher wt.% of Sr, Sr-rich compounds were found. These Strontium rich compounds were located at the matrix–ceramic interface.

This paper studies potential explanations of the declining wage inequality in Brazil such as changes in demographic/skill composition, wage structure, occupations/sectors and minimum wage. I perform a wage inequality decomposition to quantify composition and price effects and use a CES production function to estimate the effects of the skill supply on relative wages. I find that the fall in upper-tail inequality is driven by changes in the returns to education and experience, while that in lower-tail inequality is also given by those to minimum wage and female workers. These patterns are consistent with the decline in relative wages between skill groups which are given by the increase in both the supply of skills and the real minimum wage.