The bulk material of the hyper-eutectic Al-30Si alloy was prepared via selective laser melt-ing(SLM)technique,aiming to solve the problem of high brittleness,easy cracking,and difficulty in pre-cise forming caused by the coarsening of primary Si in the alloy due to the coarsening of primary Si parti-cles in the alloy during ordinary making process.Then the microstructure,mechanical properties,and thermal properties of the SLM alloy after stress-relief annealing were studied.The results showed that the room temperature tensile strength of the SLM Al-30Si alloy after annealing was 254±3 MPa,which was 53.5％higher than that of the cast alloy.The hardness was 176.89±8.5 HV and the specific stiffness was 35.18 m2/s2.In terms of thermal properties,the thermal expansion coefficient of the SLM Al-30Si alloy is 13.8 to 16.3 x 10-6/℃ in the temperature range of-100～200℃,and the average thermal conductivity is 70.52 W·m-1·K-1.The study found that the rapid cooling characteristic of SLM could refine the primary Si particles,making the formed Al-30Si alloy have good comprehensive properties.The high specific stiff-ness and low thermal expansion coefficient are expected to maintain high dimensional stability for optical components.
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