Mechanical properties and thermal stability of Al-Fe-Ni alloys prepared by centrifugal atomisation and hot extrusion

In this work, Al-12Fe and Al-7Fe-5Ni (wt%) alloys prepared by a novel technique including centrifugal atomisation and hot extrusion were studied. The microstructures were investigated using light microscopy, electron scanning microscopy, transmission electron microscopy and X-ray diffraction. The mechanical properties were determined by Vickers hardness measurements and compressive stress-strain tests. To study the thermal stability, the mechanical properties were also measured after 100 h of annealing at 300 degrees C and 400 degrees C. In addition, creep tests at a stress of 120 MPa and a temperature of 300 degrees C were performed. The investigated materials were composed of fine-grained alpha-Al and intermetallic phases identified as Al13Fe4 and Al9FeNi. The Vickers hardness and compressive yield strength were 68 HV5 and 183 MPa, respectively, for the Al-12Fe alloy and 73 HV5 and 226 MPa, respectively, for the Al-7Fe-5Ni alloy. After long-term annealing, the change in the mechanical properties was negligible, indicating the excellent thermal stability of both materials. The creep tests confirmed the highest thermal stability of the Al-7Fe-5Ni alloy with a total compressive creep strain of 15%. The thermally stable casting Al-12Si-1Cu-1Mg-1Ni alloy treated by the T6 regime was used as a reference material. The casting alloy exhibited sufficient mechanical properties (hardness and compressive yield strength) at room temperature. However, annealing remarkably softened and reduced its compressive yield strength to almost 50% of the initial values. Additionally, the total creep strain of the casting reference material was almost three times higher than that of the Al-7Fe-5Ni alloy. It has been proven that centrifugally atomised materials quickly compacted via hot extrusion can compete or even exceed the properties of common casting aluminium alloys that are used in automotive industry. (C) 2014 Elsevier B.V. All rights reserved.