V.V. Stolyarov

Enhanced low-temperature impact toughness of nanostructured Ti

Impact toughness is one of the major mechanical properties for structural materials. It is generally observed that in coarse-grained materials the impact toughness decreases with decreasing testing temperature. Here, we report that the impact toughness of nanostructured Ti processed by severe plastic deformation is enhanced at low temperatures of −70°C and −196°C, a unique phenomenon that contradicts the observations in coarse-grained materials. The enhanced impact toughness is attributed to the increased strength and ductility of nanostructured Ti as well as smaller fracture dimples at lower temperatures. This result demonstrates the advantage of using nanostructured Ti in low-temperature applications.

Structure evolution and changes in magnetic properties of severe plastic deformed Nd(Pr)–Fe–B alloys during annealing

Abstract Structural changes and hysteresis properties of Nd(Pr)–Fe–B alloys of various compositions were studied after severe torsion straining under high pressure and following annealing. It was shown that in all the alloys studied, severe plastic deformation leads to formation of ultrafine-grained non-equilibrium structure and, at extremely large strains, even to formation of an amorphous structure. Annealing resulted in crystallization of alloys, formation of stable magnetic and non-magnetic phases and in marked improvements in hard magnetic properties. Homogenization of alloys is responsible for an increase in coercivity of the deformed samples.

Metastable States in R2Fe14B-Based Alloys Processed by Severe Plastic Deformation

Abstract The influence of severe plastic torsion straining (SPTS) under high pressure on microstructure, phase composition and coercivity of cast sub-, super- and stoichiometric R2Fe14B (R = Nd, Pr)-based alloys was investigated. Deformation results in the formation of a metastable state characterised by ultrafine-grained (UFG) structure and non-equilibrium phase composition. Annealing at 600°C leads to complete or partial restoration of the initial phase composition depending on the alloy composition. Due to SPTS and subsequent annealing of the Pr20Fe73.5B5Cu1.5 alloy, the formation of high coercivity UFG state with jHc up to 2240 kA/m is observed.