Effects of extrusion temperature on the microstructure and tensile properties of Al–16 wt% Al4Sr metal matrix composite

This study was undertaken to investigate the effect of extrusion temperature on the microstructure and tensile properties of Al metal matrix composite (MMC) containing 16 wt% Al4Sr intermetallic. Microstructural examinations were assessed by the use of optical microscope, scanning electron microscope (SEM) and X-ray diffractometry (XRD). The results showed that hot extrusion with the ratio of 18:1 at 420 °C reduces the maximum length of Al4Sr particles from 222 μm to 35 μm. It was found that by applying extrusion parameters in optimum conditions, uniform distribution of fine Al4Sr intermetallic in Al matrix is obtained. Microstructural evolution also intensified the ultimate tensile strength (UTS) values of the MMC from 54 MPa to 145 MPa. Remarkable result of this study revealed that hot extrusion improves the ductility of the MMC significantly. Fractographic examinations of the composite in as-cast condition showed a complete cleavage fracture surface that changes to more homogenous dimples after hot extrusion process.

► Extrusion temperature on the microstructure of Al–Al4Sr composite.
► Extrusion in optimum condition changed Al4Sr size from 222 μm to 35 μm.
► Higher UTS and elongation values obtained by extruding at 420 °C.
► Fracture behavior has been changed from brittle to ductile by extrusion process.