EFFECTS OF HOT EXTRUSION ON MICROSTRUCTURE OF Al – 16 WT.% Al4Sr IN-SITU METAL MATRIX COMPOSITE CONTAINING DIFFERENT WEIGHT PERCENTAGES OF Cu

The effects of hot extrusion on the microstructure of cast aluminum metal matrix composite (MMC) containing 16 wt.% long and bulky Al4Sr intermetallics with different weight percentages (0.3 wt.% - 5 wt.%) of Cu were studied. Microstructural examinations were assessed by the use of optical microscope (OM), scanning electron microscope (SEM) and X-ray diffractometry (XRD). The results showed that hot extrusion with the ratio of 12:1 at 500 ˚C reduces the size ofAl4Sr particles tremendously. The maximum length of Al4Sr particles changes from 222 μm to 95 μm.Due to the presence of coarse particles and intrinsic brittleness of Cu-rich intermetallics before hot extrusion, reaching to suitable mechanical properties is not optimistic. After hot extrusion with optimum parameters, CuAl2 particles alter from coarse to fine; moreover, the distribution mode of precipitates (Al4Sr particles and Cu-rich intermetallics mainly CuAl2) becomes uniform

Keywords:

Metal matrix composite (MMC) , Al4Sr intermetallics , Cu-rich intermetallics , Microstructure , Hot extrusion