Dispersion hardening of high-manganese iron alloys alloyed with niobium and vanadium

This work concerns the effect of temperature and rate of strain on the mechanical properties of terbium, erbium, and holmium (98.89%, 98.8%, and 97.8% pure) with hcp lattices. Samples for tensile tests 2mm in diameter, gauge length 10mm (total length of the sample 40mm), were annealed in vacuum at T=0.5Tsub(m)0K. Samples for compression tests were 3mm in diameter and 4.5mm high. To avoid oxidation of the surface at high temperatures, the mechanical tests (in tension and compression) were made in argon. The temperature dependences of the true stress for terbium, holmium, and erbium are nonmonotonic in character, probably due to strain aging. With increasing strain rates the anomalies of the strain-aging type shift to higher temperatures, and with increasing strain to lower temperatures. The point of intersection of the less-sloping section (B2) and the steeper superrecrystallization section (B1) is the recrystallization temperature T1, i.e., the temperature of the transition from cold to hot deformation; T1=(0.4-0.5)Tsub(m)0K. With increasing strain rates the value of sigma generally increases; the anomalous sections of the curves are exceptions. At standard temperature the metals investigated are considerably more difficult to subject to plastic deformation than fcc metals; on heating, the ductility increases sharply. The variation of the strength and ductile characteristics with temperature is nonmonotonic in character, with dips (anomalies) in strength and ductility. At negative temperatures the ductility of terbium, holmium, and erbium is low (low values of delta and psi), predisposing them to brittle fracture. Most metals with a hcp lattice can be subjected to plastic deformation in a wide range of temperature by compression without danger of cracking or fracture, i.e., with mild deformation (compression, pressing)