초 미세조직 Al81Si19 합금분말 압출재의 미세조직과 기계적 성질에 미치는 압출온도의 영향

Abstract

The effect of extrusion temperature on the microstructure and mechanical properties was studied in gas atomized Al81Si19 alloy powders and their extruded bars using SEM, tensile testing and wear testing. The Si particle size of He-gas atomized powder was about 200 - 800 nm. Each microstructure of the extruded bars with extrusion temperature (400, 450 and 500℃) showed a homogeneous distribution of primary Si and eutectic Si particles embedded in the Al matrix and the particle size varied from 0.1 to 5.5 ㎛. With increasing extrusion temperature from 400℃ to 500℃, the ultimate tensile strength (UTS) decreased from 282 to 236 MPa at 300 K and the specific wear increased at all sliding speeds due to the coarse microstructure. The fracture behavior of failure in tension testing and wear testing was also studied. The UTS of extrudate at 400℃ higher than that of 500℃ because more fine Si particles in Al matrix of extrudate at 400℃ prevented crack to propagate.