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Step rolling can be used to mass-produce ultrafine-grained (UFG) Ti-6Al-4V sheets. This study clarified the effect of subsequent annealing on the tensile properties of step-rolled Ti-6Al-4V at room temperature (RT) and elevated temperature. The step-rolled alloy retained its UFG structure after subsequent annealing at 500–600 °C. The RT ductility of the step-rolled alloy increased regardless of annealing temperature, but strengthening was only attained by annealing at 500 °C. In contrast, subsequent annealing rarely improved the elevated-temperature tensile properties. The step-rolled Ti-6Al-4V alloy without the annealing showed the highest elongation to failure of 960% at 700 °C and a strain rate of 10−3 s−1. The ambivalent effect of annealing on RT and elevated-temperature tensile properties is a result of microstructural features, such as dislocation tangles, subgrains, phases, and continuous dynamic recrystallization.

The Fe–Mn–Al–C duplex lightweight steels have received considerable attention from the automotive industry because of their low density and good mechanical performance. However, their poor cold-rollability limits their applications. This study proposes a thermomechanical treatment that enhances the cold-rollability of duplex lightweight steels via deformation-induced ferritic transformation (DIFT). DIFT activated by warm rolling destroys the initial band structure and causes a partial grain refinement, thereby causing mechanical strengthening without the loss of ductility. Subsequent annealing enabled cold rolling, while the microstructure formed by DIFT was observed to remain. The steels fabricated using the proposed method exhibited more cold-rollability compared with that exhibited by the conventionally hot-rolled samples. Such an improvement can be attributed to the increased austenitic stability and the resultant inhibition of strain-induced martensitic transformation via DIFT.

The effect of grain size on tensile and cyclic deformation behaviors of carbon-containing CoCrFeMnNi high-entropy alloys (Cantor) were investigated. Heat treatment of warm-rolled and cold-rolled specimens yielded various microstructures with average grain sizes 4 ≤ d ≤ 66 μm. The fine-grained specimens (d ≤ 15 μm) showed very similar tensile deformation behaviors. However, the prosperity of mechanical twins in the coarse-grained specimen (d ~ 66 μm) led to a strain-hardening behavior different from those of the fine-grained ones. Refining d to 10 μm by decreasing the heat-treatment temperature after warm rolling increased the strength and extended low-cycle fatigue life. However, no significant change in fatigue cycles occurred in that they could survive at similar imposed plastic strain amplitudes. Meanwhile, the cold-rolled and annealed (at 800 °C) specimen presented the finest d of ~ 4 μm with the best yield strength, but also revealed coarse carbides in the microstructure. High stress concentrations developed at the boundaries of these coarse particles severely reduced fatigue life. Thus, to increase the fatigue life in carbon-containing Cantor, thermomechanical treatment should be controlled in such a way that results in fine-grained microstructures without precipitation of coarse carbides.

In this study, the low-cycle fatigue behavior of a cryogenic-rolled commercially pure titanium alloy was investigated, and compared with those of undeformed and room-temperature rolled ones. The amounts of deformation twins increased to >69.8% after cryogenic temperature rolling, and to 27.5% after room temperature rolling. Strain-controlled low-cycle fatigue tests were performed at total strain amplitudes 0.4 % ≤ Δ e t 2 ≤ 1.2%. The Coffin-Manson and hysteresis energy-based models confirmed that low-cycle fatigue resistance was remarkably improved with increasing the volume fraction of deformation twins by pre-deformation. As the proportion of deformation twins in the microstructure increased, the hysteresis loop area decreased, the striation spacing decreased, and the severity of crack-deflection behavior increased. At low Δ e t 2 = 0.4%, dislocation recovery was suppressed in the pre-deformed microstructure, so cyclic behavior was stable. However, at Δet/2 ≥ 0.8%, the recovery became the predominant mechanism, so well-defined cell structures formed and cyclic softening occurred. The smaller dislocation cells formed in RTR and CTR were considered to cause more severe crack arrest than in AR.