Microstructures and Mechanical Properties of Al–20Si–xFe (x=3, 5, 7) Alloys Manufactured by Rapid Solidification Processing

Abstract

Rapidly solidified Al–20Si–xFe (x=3, 5 and 7 mass%) powders were prepared by gas atomization. The microstructure consisted of needle shaped δ-Al₄FeSi₂ particles and primary Si embedded in Al–Si–Fe eutectic. With increasing Fe content, the size and volume fraction of primary Si decreased. After extrusion, the microstructures of the extruded bars showed a homogeneous distribution of two different sizes β-Al₅FeSi and Si particles embedded in the α-Al matrix. By increasing the Fe content from Al–20Si to Al–20Si–7Fe, the ultimate tensile strength (UTS) increased from 215 to 404 MPa at 300 K and from 122 MPa to 240 MPa at 473 K. Of these alloys, Al–20Si–5Fe alloy showed the best wear resistance. The UTS varied significantly with the initial powder size but wear resistance was independent of powder size. The effect of the particles distributed in the Al matrix upon the UTS was considered in terms of the cooling rate and particle distribution.