Structure and Mechanical Properties of Al–Fe–Si–V Powder Alloys Doped with Cr, Ti, and Zr

Abstract

The structure and mechanical properties of rods produced from alloys in the Al–Fe–Si–V system, additionally doped with Cr, Ti, and Zr, were studied. In contrast to the creep-resistant Al–Fe–Si–V alloys, commonly known as FVS alloys and characterized by an optimal Fe/V ratio of ~5–11, the Fe content in the test alloys was reduced by adding Cr, ensuring that the (Fe + Cr)/V ratio remained within the ~5–11 range. Rods with a 9 mm diameter were produced from the test alloys by extruding degassed capsules filled with compressed water-atomized powders in the (–63+40) μm size fraction. The powder was consolidated through severe plastic deformation without sintering. The structure was examined using X-ray diffraction, transmission electron microscopy, and scanning electron microscopy with electron probe microanalysis. The phase composition and distribution of the doping elements were determined as a function of the alloy chemical composition. Mechanical properties were evaluated at 20, 190, and 300°C through tensile tests. Fracture of the test alloy rods followed a ‘cone–cup’ pattern at room temperature and 300°C. The fracture mechanism was dimple-like. The replacement of some iron by chromium in the base alloy resulted in a shift in the phase composition of the strengthening particles. Specifically, instead of the Al₁₃(FeV)₃Si intermetallics typical of Al–Fe–Si–V alloys, particles of the icosahedral quasicrystalline phase and Al₁₃Cr₂ intermetallics were observed. All studied alloys exhibited high strength at temperatures up to 300°C, surpassing the strength of established creep-resistant alloys such as FVS 0812. This enhanced strength was attributed to precipitation hardening effects induced by two distinct types of nanosized particles within the aluminum matrix, having a crystalline and icosahedral quasicrystalline structure. The Al₉₃Fe₂Cr₂V_0.5Si_1.5Ti_0.5Zr_0.5 alloy showed the highest mechanical properties at both elevated and room temperatures.