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A Cu-1.79Ti-0.39Cr-0.1Mg (wt.%) alloy was prepared by a vacuum induction melting furnace in a high-purity argon atmosphere. The effects of room temperature rolling and cryogenic rolling on the microstructure, textures, and mechanical properties of the alloy were investigated by means of electron backscatter diffraction, transmission electron microscopy, and X-ray diffraction. The results show that the hardness of the cryogenically rolled alloy is 18–30 HV higher than that of the room temperature rolled alloy at any tested rolling reduction. The yield strength and tensile strength of the alloy cryogenically rolled by 90% reduction are 723 MPa and 796 MPa, respectively. With the increase of rolling reduction, the orientation density of the Cube texture decreases, while the Brass texture increases. The Brass texture is preferred especially during the cryogenic rolling, suggesting that the cross-slip is inhibited at the cryogenic temperature. The dislocation densities of Cu-Ti-Cr-Mg alloy increase significantly during the deformation, finally reaching 23.03 × 10−14 m−2 and 29.98 × 10−14 m−2 after a 90% reduction for the room temperature rolled and cryogenically rolled alloys, respectively. This difference could be attributed to the impediment effect of cryogenic temperature on dynamic recovery and dynamic recrystallization. The cryogenic temperature promotes the formation of the dislocation and the nano-twins, leading to the improvement of the mechanical properties of the alloy.

This study systematically investigated the performance and microstructure characterization of cryogenic rolling (CR) and room-temperature rolling (RTR) Al–Mg–Si alloys. The result showed that the hardness of the CR alloys decreased at the early aging stage, but that the hardness of the RTR alloys increased at the early aging stage. Retrogression phenomena were apparent in the CR alloys at the early aging stage. Despite undergoing the same solid solution treatment, a few substructures were still observed in the CR alloys, and the degree of recrystallization in the CR alloys was significantly inferior to that in the RTR alloys. After aging for 50 h, the strength and precipitates’ density in the CR 75 alloy were higher than that in the other alloys; this indicated that the substructures were beneficial to precipitation and precipitate growth. A precipitation strength model was employed to illustrate the precipitation contribution at different aging stages. The results showed that the CR 75 alloy obtained the strongest precipitation strengthening.

Twinning and shear bands are two main deformation structures in magnesium alloys at low temperatures, however, the relationship between these two deformation structures is still under debate. To clarify their relationship and behaviours at low temperatures, rolling tests to various thickness reductions at room temperature (RT) and liquid nitrogen temperature (LNT) were conducted for AZ31 magnesium alloys. The evolutions of shear bands and twinning, and their interactions with geometrically necessary dislocation (GND), were observed during the RT- and LNT-rolling process. Abundant shear bands, evolving from {101}-{102} double twins (DTWs), were observed in the RT-rolled samples, while a high quantity of twins, including {102} tension twins (TTWs), twin-twin interactions and twinning sequence, were observed in the LNT-rolled samples. More importantly, a rarely observed twinning sequence behaviour, namely primary TTW-TTW interactions→ secondary TTW-TTW interactions, creating a 45° misorientation peak, was studied. Abundant GNDs accumulated around these twin-twin interactions, twinning sequence, DTWs and shear bands, while the GND density was low around TTWs. This research delivers a systematic investigation into the deformation structures in Mg alloys during the rolling process from RT to cryogenic temperature and provides insights into the newly discovered twinning sequence and twin-twin interactions. President's PhD Scholarship, Imperial College London; EPSRC under the Grant Agreement EP/R001715/1 on “LightForm: Embedding Materials Engineering in Manufacturing with Light Alloys”.

Recently, advanced oxide dispersion strengthened (ODS) copper alloys have been developed using mechanical alloying process as a fusion material. In this study, to develop a superior ODS copper alloy containing 0.5wt% Y2O3, the effect of cryogenic rolling on microstructure development and tensile properties was studied using high resolution EBSD, TEM and tensile tests. During cryogenic deformation of ODS copper, grain structure remains in submicron size scale as a combinatorial result of geometrically effects, nanotwin bundle deformation, interaction of dislocations with fine oxide particles and some diffusional processes including static recovery and recrystallization. Clear microstructural characterizations confirmed nucleation of fine new oriented recrystallized grains mainly on the HABs of 80%cryogenic rolled ODS copper. Quantitative analyses indicated grain boundary migration at room temperature following cryogenic deformation originated from high driving force induced by grain boundary bulging and high mobility induced by vacancies. The tensile properties of cryogenic deformed samples showed superior tensile strength than room temperature deformation leading to UTS: 624 MPa, elt: 5.5%, while saturation of strength between 60%-80% reduction, approved occurrence of softening by diffusional processes.

Because of high strength to weight ratio and good resistance to corrosion, 2024Al alloy has attracted a high attention in the aerospace and shipbuilding industries. Most of the research activities to grain refinement lead to decrease in ductility. In this article, the researchers have developed a novel approach in achieving both high strength and good ductility in 2024 Al alloy. The approach involves Solid solution-treating, rolling at cryogenic temperature (containing a high density of dislocations) and artificial aging treatment to generate bimodal structure and nanosized S’ precipitates (Al 2 CuMg). Under optimal processing conditions, tensile strength (653 MPa), ductility (11% tensile elongation) and hardness (170 HV) were obtained.