Influence of atomized powder size on microstructures and mechanical properties of rapidly solidified Al-Cr-Y-Zr aluminum alloys

摘要

Rapidly solidified powders of Al-5.0Cr-4.0Y-1.5Zr (wt%) were prepared by using a multi-stage atomization-rapid solidification powder-making device. The atomized powders were sieved into four shares with various nominal diameter level and were fabricated into hot-extruded bars after cold-isostatically pressing and vaccum degassing process. Influence of atomized powder size on microstructures and mechanical properties of the hot-extruded bars was investigated by optical microscopy, X-ray diffraction, transmission electronic microscopy with EPSX and scanning electron microscopy. The results show that the fine atomized powders of rapidly solidified Al-5.0Cr-4.0Y-1.5Zr aluminum alloy attains supersaturated solid solution state under the exist condition of multi-stage rapid solidification. With the powder size increasing, there are Al20Cr2Y (cubic, a = 1.437 nm) and Ll2 Al 3Zr (FCC, a = 0.407 nm) phase forming in the powders, and even lumpish particles of Al20Cr2Y appearing in the coarse atomized powders, as can be found in the as-cast master alloy. Typical microstructures of the extruded bars of rapidly solidified Al-5.0Cr-4.0Y-1.5Zr aluminum alloy can be characterized by fine grain FCC α-Al matrix with ultra-fine spherical particles of Al20Cr2Y and Al 3Zr. But a small quantity of Al20Cr2Y coarse lumpish particles with micro-twin structures can be found, originating from lumpish particles of the coarse powders. The extruded bars of rapidly solidified Al-5.0Cr-4.0Y-1.5Zr aluminum alloy by using the fine powders eliminated out too coarse powders have good tensile properties of σ0.2 = 403 MPa, σb = 442 MPa and δ = 9.4% at room temperature, and σ0.2 = 153 MPa, σb = 164 MPa and δ = 8.1% at high temperature of 350 °C.