Development of Al-5Cu/B4C composites with low coefficient of thermal expansion for automotive application

Abstract

The purpose of this research is to provide a competitive alternative to aluminum silicon alloys used in automotive applications. This alternate was created by developing composites of Al-5%Cu alloy reinforced with B4C particulates with a low coefficient of thermal expansion. Stir casting was used to produce Al-5%Cu alloys containing 2%, 5%, and 7%wt. B4C particulates were subsequently added using the squeeze casting process. The squeeze casting technique decreased the porosity of the final composites. The composites exhibited a fairly uniform particle distribution throughout the alloy matrix. The microstructure and the XRD results of the composites indicated that a significant reaction had occurred at the interface between the particles and the matrix. Increasing the aging temperature from 200 to 250°C decreased the hardness values of the matrix and the composites and decreased the time required to reach the peak. The coefficient of thermal expansion (CTE) for both the stir and squeezed cast samples decreased as the percentage of reinforcements increased and increased as the temperature range increased. Increasing the concentration of B4C increased YS and decreased the plasticity during compression test at both room and elevated temperatures. The Al-5%Cu-7%B4C composite has a significant higher tensile properties than A336 (AlSi12CuMgNi) at 260°C. Special mould made of 20Cr13 steel was constructed to evaluate castability. The Al-5%Cu-7%В4С composite completely repeats shape of the mould during squeeze casting process without hot cracking.