Modification of Al-Si eutectic alloy structure by alloying with Nb atoms under compression plasma flows impact

Abstract

Aluminium alloy matrix composites attract considerable attention due to their low density and low cost. Transition metals, such as Ti, Zr, Hf, V, Nb and Ta constitute a group of alloying additions to Al that show particular promise for developing creep-resistant, thermally stable Al-based alloys due to formation of Al3M (M=Ti, Zr, Hf etc.) intermetallides /1/. Such trialuminides possess high melting temperature, low density, high elastic modulus, high thermal and oxidation resistance /1/. A large number of investigations were carried out in the field of synthesis of bulk aluminium matrix composites reinforced by metals trialuminides. At the same time many applications require good exploitation properties only of the materials surface layer. In this case techniques providing synthesis of composites in the surface layer are of interest /2/. Treatment of a coating/substrate system by high energy particles (≥106 W/cm2) is one of such techniques that allows alloying the surface layer of a substrate with coating elements /2, 3/. Such treatment provides enough energy for melting the coating and the surface layer of a substrate. Convection in the melt leads to mixing and homogenization of elemental composition in the melted layer. A high cooling rate results in the formation of a disperse structure having submicron or nanocrystalline grains and phases. This approach was used to form the surface composite layer reinforced by intermetallic particles on the basis of Al3Nb in the Al-Si piston eutectic alloy and was realized by subjecting Nb coated alloy samples to compression plasma flows (CPF) treatment.