Mechanical properties of Al-Nb in situ metal-matrix composites fabricated by constrained high pressure torsion at 10 GPa and subsequent annealing

Abstract

Mechanical alloying of dissimilar metals by means of severe plastic deformation techniques is known to be a perspective method of obtaining in situ metal matrix composites with advanced properties. Recent investigations found out that besides severe mixing of elements, intensive formation of non-equilibrium intermetallic phases takes place. Presence of intermetallic particles in the composite affects both its physical and mechanical properties. In this work we have realized the fabrication of Al-Nb composites in one step by means of high-pressure torsion technique. A non-trivial phenomenon of growth of tensile strength with increasing number of revolutions during HPT was revealed. It was explained by more homogeneous mixing of components and precipitation of intermetallic phase in the vicinity of Al-Nb interphases. The microstructural observations and X-ray diffraction analysis allowed to reveal Al3Nb intermetallic phase in the as deformed composites, while the equilibrium temperature of formation of this phase is above 600°C. Varying the number of revolutions and post deformation annealing allows obtaining composites with different fractions of intermetallic particles. This approach can be considered as a way for the development of composites with a tailorable complex of physical and mechanical properties.