New Al-alloys with dispersed stable quasicrystal approximant phases: Overcoming the barrier of conventional casting processing and microstructure design

Multi-stage manufacturing processes, high production costs and narrow two-phase field of Al-alloys containing Al-FCC and quasicrystals or approximants phases have been barriers to the widespread use of these alloys in technological applications. In the present work, we demonstrated that new Al-alloys with dispersed stable quasicrystal approximant phases can be produced by conventional metallurgical fabrication methods. Six alloys containing different volume fractions (5% up to 40%) of the approximant alpha-phase were designed and produced by conventional solidification in a graphite mold. The hardness and tribological properties of Al-FCC matrix with different volume fractions of the quasicrystal approximant phase were evaluated. A wide range of wear rates, from 2.1 x 10-3 mm3/Nm to 6.3 x 10-4 mm3/Nm, could be achieved by tuning the volume fraction of the alpha-phase ranging from 5% up to 40%, respectively. Low coefficient of friction values around 0.3 were observed after the running-in periods, regardless of the alpha-phase content, indicating that the quasicrystal approximant phase played a critical role. The alloy containing 25% of alpha-phase was chosen to be processed by different manufacturing processes to show that the morphology of the stable approximant alpha-phase can also be controlled. This finding opens new perspectives for the commercial application of products derived from such light-and wear-resistant materials.