Comparative analysis of the effect of mechanical activation in an attritor on the structure and behavior of β-RuAl and β-NiAl alloy powder mixtures during reactive sintering

Abstract

The structure of Ni + Al (two ductile fcc metals) and Al + Ru (ductile aluminum and hard-to-deform hcp ruthenium) powder mixtures subjected to short-term (≤16 h) mechanical activation (MA) is studied. During MA of a 50Ni + 50Al mixture, the powder particles undergo multiple compressive and shear deformation, and large layered granules form due to contact welding and flattening of the layers of both metals. The related increase in the internal stresses, the increase in the dislocation density in particles of both metals, and the decrease in the coherent domain size (CDS) lead to the fracture and fragmentation of the powder particles. In a 49Ru + 48Al + 3Re mixture, aluminum particles are deformed and “spread” over “rigid” ruthenium particles. The formed granules consist of disperse undeformable ruthenium particles connected by an Al binder. The work hardening of ruthenium occurs due to a decrease in CDS. An increase in the contact area between metal particles and a decrease in the diffusion path lengths (aluminum in nickel and ruthenium) cause a decrease in the temperature of the onset of interaction with the participation of liquid aluminum, the activation of solid-phase interaction, and the formation of aluminum-rich nickel (ruthenium) aluminide NiAl (RuAl). Nevertheless, unreacted nickel (ruthenium) particles are retained. A microhomogeneous distribution of the basic and alloying elements and phases in a compacted material is achieved Annealing at temperatures ≥0.8T m is required to complete reactive alloy formation.