Microstructure-Processing-Property-Relationship of Rapidly Solidified Al-Fe-(V, Si) Alloys

Gas-atomised powders of Al-Fe-(V, Si) alloys exhibited microstructures consisting of several forms of icosahedral phase distributed in either supersaturated solid solution of α-Al matrix, or in intercellular/ dendritic regions depending on powder particle size. During processing of the powders by hot extrusion, the icosahedral phase particles transformed to more stable phase particles. Microstructures of extrudates produced from fine Al-Fe-V powder particles showed homogeneous precipitation of ultrafine needle-like particles in grains and at grain boundaries. This type of microstructure yielded high compressive strengths at room and elevated temperatures. In microstructures of extrudates produced from coarse Al-Fe-V powder particles, ultrafine needle-like particles were observed to coexist with globular particles. Because of large-size globular particles, low compressive strengths at room and elevated temperatures of the extrudates produced from coarse Al-Fe-V powder particles were obtained. The extrudates produced from fine Al-Fe-V-Si powder particles showed microstructures with homogeneous precipitation of spherical-like particles. In contrast, the extrudates produced from coarse Al-Fe-V-Si powder particles resulted in inhomogeneous microstructures, which were attributed to banded structures or donut-shaped aggregates of spherical-like particles. Because of inhomogeneous microstructures, low compressive strengths of the extrudates at room and elevated temperatures were obtained.