PROPERTIES OF Al-BASED ALLOYS PREPARED BY CENTRIFUGAL ATOMISATION AND HOT EXTRUSION

Aluminium alloys are prospective materials that can be used in wide range of applications requiring good weight-to-strength ratio, convenient corrosion resistance and others. However, low thermal stability is a problem that limits their use in applications with temperatures typically exceeding 300 degrees C. Solution to this problem can be found in addition of appropriate amounts of transition elements (Fe, Ni) that are characterized by low diffusion coefficients in solid aluminium. However, their solubility in solid aluminium is limited only to a few percents. Centrifugal atomisation, as one of many rapid solidification techniques, can solve this problem. In this work, two PM alloys with nominal composition of Al-12Fe and Al-7Fe-5Ni (in wt.%) were prepared by a centrifugal atomisation. Prepared powders were compacted via hot extrusion at an extrusion ratio of 10:1 and a deformation rate of 2.5 mm/min into rods of 6 mm in diameter. Microstructure of tested materials was examined by light microscopy and by electron scanning microscopy. Chemical composition as well as phase composition was confirmed by XRF and XRD analysis. An Al-12Si-1Cu-1Mg-1Ni alloy that is commonly considered as thermally stable was used as a reference material. Thermal stability of tested materials was determined on the basis of Vickers hardness change during long-term annealing at 300 degrees C and 400 degrees C. To complete the thermal stability investigations, creep test were performed at a compressive stress of 120 MPa and temperature of 300 degrees C. All of prepared PM alloys exhibited better thermal stability compared to the reference material.