Abstract

The effect of extrusion temperature on the microstructure and mechanical properties were studied in He-gas atomized Al_81-(x＋y)Si_19Ni_xCe_y alloy powders and their extruded bars using SEM, tensile testing and thermal expansion testing. The extruded bar of Al_73Si_19Ni_7Ce_1 alloy consists of a mixed structure in which fine Si particles with a particle size below 20∼500nm and very fine Al_3Ni,;Al_3Ce compounds with a particle size below 200nm are homogeneously dispersed in Al martix with a grain size below 500nm. With increasing extrusion temperature, the microstructural scale was decreased. The ultimate tensile strength of the alloy bars has incresed with decreasing extrusion temperature from 500 to 350°C and Al_73Si_19Ni_7Ce_1 alloy extreded at 350°C shows a highest tensile strength of 810 MPa due to the fine namostructure. The addition of Ni and Ce decreased the coefficients of thermal expansion and the effects of extression temperature on the thermal expansion were not significant.

• Keywords: Al-Si alloy;Nono structure;High strength;Gas atomization;