Rapidly Solidified Microstructure and Failure Analysis of Powder Metallurgy Al-Si Alloys

Abstract The microstructure of the extruded bars showed a homogeneous distribution of eutectic Si and primary Si particles embedded in the Al matrix. The grain size of α-Al varied from 150 to 600 nm and the size of the eutectic Si and primary Si in the extruded bars was about 100–200 nm. The room temperature tensile strength of the alloy with a powder size < 26 μm was 322 MPa, while for the coarser powder (45–106 μm) it was 230 MPa. With decreasing powder size from 45–106 μm to < 26 μm, the specific wear of all the alloys decreased significantly at all sliding speeds due to the higher strength achieved by ultra-fine grained constituent phases. The thickness of the deformed layer of the alloy from the coarse powder (10 μm at 3.5 m/s) was larger on the worn surface in comparison to the bars from the fine powders (5 μm at 3.5 m/s) due to the lower strength of the bars with coarse powders. The fracture mechanism of failure in tension testing and wear testing was also studied.