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Cryogenic rolling experiments have been conducted on the AZ31 magnesium (Mg) alloy sheet with bimodal non-basal texture, which is fabricated via the newly developed equal channel angular rolling and continuous bending process with subsequent annealing (ECAR-CB-A) process. Results demonstrate that this sheet shows no edge cracks until the accumulated thickness reduction reaches about 18.5%, which is about 105.6% larger than that of the sheet with traditional basal texture. Characterization experiments including optical microstructure (OM), X-ray diffractometer (XRD), and electron backscatter diffraction (EBSD) measurements are then performed to explore the microstructure characteristics, texture evolution and deformation mechanisms during cryogenic rolling. Experimental observations confirm the occurrence of abundant {10–12} extension twins (ETs), twin-twin interactions among {10–12} ET variants and {10–12}-{10–12} double twins (DTs). The twinning behaviors as for {10–12} ETs are responsible for the concentration of c-axes of grains towards normal direction (ND) and the formation of transverse direction (TD)-component texture at the beginning of cryogenic rolling. The twinning behaviors with respect to {10–12}-{10–12} DTs are responsible for the disappearance of TD-component texture at the later stage of cryogenic rolling. The involved deformation mechanisms can be summarized as follows: Firstly {10–12} ETs dominate the plastic deformation. Subsequently, dislocation slip, especially basal slip, starts to sustain more plastic strain, while {10–12} ETs occur more frequently and enlarge continuously, resulting in the formation of twin-twin interaction among {10–12} ET variants. With the increasing rolling passes, {10–12}-{10–12} DTs incorporate in the plastic deformation and dislocation slip serves as the major one to sustain plastic strain. The activities of basal slip, {10–12} ETs and {10–12}-{10–12} DTs benefit in accommodating the plastic strain in sheet thickness, which contributes to the improved rolling formability in AZ31 Mg alloy sheet with bimodal non-basal texture during cryogenic rolling. [ABSTRACT FROM AUTHOR]

Heterostructure materials have attracted much attention owing to their excellent strength-ductility synchronization. In this work, a heterogeneous structure consisting of coarse grains and ultrafine grains was developed in 3003 aluminum alloy by cryogenic rolling and short-time annealing. The recrystallization behavior and texture evolution in cryogenic-rolled 3003 aluminum alloy were investigated by using X-ray diffraction and Electron Back-Scatter Diffraction. The results show that various annealing temperatures and time led to a significant difference in the microstructure and texture evolution. As annealing progressed, the recrystallized volume fraction raised with the increment of annealing time, and the β-fiber rolling texture gradually developed to recrystallization texture including R, Cube and R-Cube ND. Recrystallization kinetics were constructed based on the Johnson-Mehl-Avrami-Kolmogorov model. An excellent strength-ductility balance can be obtained for cryogenic-rolled samples annealed at 390°C/45 s owing to the formation of a heterogeneous structure comprising coarse grains and ultrafine grains. • A heterogeneous structure was produced by cryogenic rolling and short-time annealing. • The recrystallization kinetics of cryogenic-rolled 3003 aluminum alloy were constructed. • Microstructure and texture evolution during cryogenic rolling and annealing was investigated. [ABSTRACT FROM AUTHOR]

Shear deformation through severe plastic deformation (SPD) is an effective method for achieving material refinement and twinning. In this study, T2 copper was subjected to contnuous equal channel angular pressing (C-ECAP) and liquid nitrogen cooled cryogenic rolling (CR) processes. The microstructure and texture evolution of the material were detected by X-ray diffraction (XRD), electron back-scattered diffraction (EBSD) and transmission electron microscope (TEM). The study shows that utilizing C-ECAP continuous directional shear can enhance the continuous directional twinning of T2 copper structure. Additionally, cryogenic rolling can promote the material structure to be dominated by twinning segmentation. During the deformation, the texture experiences significant fluctuations, after C-ECAP the initial {111}〈110〉 texture is rapidly transformed into a strong {110}〈112〉 Brass texture. Among various combinatons of C-ECAP and cryogenic rolling, it was noted that, after 2 passes and cryogenic rolling at 75% total thickness reducton yields, the tensile strength, hardness and conductivity reached of 462 MPa, 120 HV and 95% IACS. • In this study, the C-ECAP method was used to quickly and consistently prepare bulk ultrafine grained materials of pure copper. • Five possible modes of lattice evolution under shear action are proposed. • C-ECAP Combined with cryogenic rolling can easily form nanocrystals and induce continuous directional twinning of materials. [ABSTRACT FROM AUTHOR]

For ultralight Mg–Li alloys, the improvement of strength is the most concerned issue. In this work, we successfully realize the incredible enhancement of strength in the Mg-8.5Li-7.5Zn-1.5Y alloy via a series of preparation processes, and the excellent tensile properties containing high yield strength of 312.4 MPa and good elongation of 14.2 % are obtained. Yield strength increment is as high as 213 MPa through deformation processing, which is rarely reported in Mg–Li alloys. Qualitative and quantitative studies reveal that the dislocation cutting of semi-coherent MgLi 2 Zn nano-precipitates is mainly responsible for such a high yield strength. The new finding for strengthening way is expected to contribute to the design of high-performance Mg–Li alloys. [ABSTRACT FROM AUTHOR]

A Cu-0.4Cr-0.39Zn-0.1Mg-0.07Zr (wt%) alloy was prepared using cryogenic rolling process and multistage thermo-mechanical treatment to achieve excellent comprehensive properties with tensile strength of 635 MPa, yield strength of 620 MPa and electrical conductivity of 75.3% IACS. A large number of nano deformation twins appeared in the alloy after cryogenic rolling, and the width of the nano twins decreased with the deformation, and the average width of nano twins decreased by 8.4% and 11.8% after the second and the third cryogenic rolling, respectively. The high density of dislocations introduced by cryogenic rolling provided more nucleation sites for Cr phase precipitation, which promoted the diffusive precipitation of Cr phase. With the synergy of microalloying of Mg and Zn elements, cryogenic rolling and multistage thermo-mechanical treatment, the copper alloy with high density of nano deformed twins, fine and diffuse precipitation phases and excellent performance was prepared, which can be used as high-performance copper alloys for lead frames of large-scale integrated circuits. • Designed alloy achieved excellent properties by cryogenic rolling and heat treatment. • Cryogenic rolling introduced nanotwins. [ABSTRACT FROM AUTHOR]

In this study, CoCrFeMnNi (Cantor alloy) high-entropy alloy (HEA) with ultra-fine grained (UFG) structure were prepared using cryogenic (liquid nitrogen, 77 K) rolling followed by short time annealing. The deformation behavior and strain rate sensitivity (SRS) of processed material were investigated by tensile test at temperatures ranging from 77 K to 573 K. It was found that the critical twinning stress of the UFG alloy decreased at 77 K, which was attributed to the decrease of stacking fault energy with the temperature. In addition, the UFG alloy exhibited plastic instability and was prominently strengthened with increasing testing temperature from 293 K to 473 K, which was related to obviously grain boundaries relaxation in HEAs. The strain rate jump test revealed that the SRS change of UFG specimen with the decrease of grain size was inversely proportional to the associated strength enhancement, and exhibited a stronger temperature dependence than that of CG specimens especially from 293 K to 473 K. The stronger temperature dependence of SRS of UFG Cantor alloys was due to the increased grain boundary relaxation, which was a thermal activation process and depended on strain rate and temperature. • UFG Cantor alloy was prepared using cryo-rolling and short time annealing. • Tensile and strain rate jump tensile test were conducted from 77 K to 573 K. • UFG alloy exhibited a prominent strengthening from 293 K to 473 K. • Change of SRS in UFG alloy displayed a strong temperature dependence. [ABSTRACT FROM AUTHOR]

In this paper, the microstructural characteristics and deformation behaviors of a CoCrFeNiMo 0.15 high-entropy alloy (HEA) with a low volume fraction of σ precipitates during rolling deformation at cryogenic temperature and room temperature were investigated. The stacking fault energy of the HEA was experimentally estimated via measuring the widths of the dissociated dislocations. Deformations at two temperature conditions were both characterized by dislocation activities and extensive nano-twinning, while the rate of these microstructural evolution was accelerated with the aid of the cryogenic temperature. Abundant microbands, nanotwins and stacking faults were detected during deformation under both temperature conditions. Moreover, the hexagonal close-packed structure can only be observed in the cryogenic rolled sample, which was produced via the glide of Shockley partials on every other {111} FCC plane. At the late deformation stage of cryogenic rolling, the nanotwins were markedly distorted or even fractured, and shear bands were also formed. The contributions of different strengthening mechanisms of cryogenic rolling were discussed. [ABSTRACT FROM AUTHOR]

Abstract In this work, microstructural evolution of a solutionized Al-Cu-Mg alloy during rolling at liquid-nitrogen temperature was studied and concomitant strengthening effect was elucidated. It was found that a prior solid-solution treatment as well as a lowering of deformation temperature to the cryogenic range essentially suppressed dislocation mobility. This promoted an abrupt increase of dislocation density but considerably retarded microstructural processes, particularly texture evolution and development of deformation-induced boundaries, thus suppressing grain refinement. Hence, the strengthening effect of the cryogenic rolling was mainly contributed by the work hardening mechanism. [ABSTRACT FROM AUTHOR]

Abstract Cu–Cr alloys have been widely used in industrial applications owing to their good combination of mechanical properties and electrical conductivity. However, the comprehensive performance of the alloy needs to be further improved to meet the harsh working environment. Hence, in this study, a new type of Cu–Cr alloy with Co and Si additions together with cryogenic rolling (CR) was designed and investigated. Microstructure analysis confirms that the Cr 15 Co 9 Si 6 and Co 2 Si phases are formed with Co and Si additions into the Cu–Cr alloy. For the more, partial Cr 15 Co 9 Si 6 phase decomposes during heat treatment process, and the Co 2 Si and Cr precipitates are precipitated from matrix during aging process. The improvement of tensile properties of the Cu–1Cr–1Co–0.6Si alloy is mainly attributed to the precipitation strengthening and grain boundary strengthening, and is also benefited from dislocation density strengthening, twin boundary strengthening, and solid solution strengthening. The electrical conductivity of the Cu–1Cr–1Co–0.6Si alloy decreases dramatically mainly due to the increase of impurity scattering caused by surplus Si atoms. CR deformation is helpful for more solute atoms precipitated from the supersaturated solid solution during aging process, and thus the electrical conductivity of the Cu–1Cr–1Co–0.6Si alloy increases with increasing deformation amount. After homogenizing treatment at 900 °C for 2 h, hot rolling by 60% at 900 °C, solution treating at 990 °C for 4 h, cold rolling by 90%, and aging at 440 °C for 1 h, the hardness, yield strength (YS), ultimate tensile strength (UTS), and electrical conductivity of the Cu–1Cr–1Co–0.6Si alloy are 214.6 HV, 663.7 MPa, 745.9 MPa and 41.6%IACS, respectively, which exhibit good mechanical properties with a proper electrical conductivity. These results provide a feasible route for developing high performance Cu–Cr alloys. [ABSTRACT FROM AUTHOR]

• Strain localizations (SLs) were observed preferentially in Copper-type grains in the CR Cu-Fe-P specimens. • Self-annealing at room temperature was observed at the deformed GBs and at SLs in the CR specimens. • TEM and TKD confirms that DSRX and CSRX were responsible for the self-annealing phenomena in the CR specimens. • CPFEM simulation was showing the nearby predictions for average grain size (GS avg) and texture fraction. • Activation of single-slip system in the Copper and S oriented grains was the primary cause of SLs formations. Deformation of Cu-Fe-P alloys at cryogenic temperature (CT) leads to the evolution of a complex microstructure, which includes deformed and recrystallized grains, strain localizations (SLs), and heterogeneous deformation. In this study, specimens of Cu-Fe-P alloy were subjected to cryogenic rolling (CR) at reduction ratios (RR) of 20, 40, 60, and 80%. The microstructural evolution of the CR specimens was characterized using electron back-scattered diffraction (EBSD) and high-resolution transmission electron microscopy (HR-TEM). Severely deformed CR specimens showed SLs, which formed predominantly in the Copper and S oriented grains. After deformation, the CR specimens exhibited self-annealing behavior, which is also referred to as static recrystallization (SRX). Self-annealing at room temperature (RT) caused grain nucleation at the deformed grain boundaries (GBs) and at the SLs. The nucleation of new grains was attributed to both discontinuous SRX (DSRX) and continuous SRX (CSRX) phenomena. The characteristics of DSRX and CSRX grains were analyzed based on transmission Kikuchi diffraction (TKD) and HR-TEM investigations. DSRX grains were surrounded by high-angle GBs, whereas CSRX grains showed sub-boundaries with no dislocations inside. The as-received Cu-Fe-P specimen showed a weak plane-strain texture that intensity increased with an increase in the RR. The CR-80 specimen showed the highest-intensity for plane-strain texture components. SRX at the SLs showed preferential formations of Copper, Brass and S-nucleated grains in the CR-80 specimen. In this study, crystal plasticity finite element method (CPFEM) was used to calculate the stored energy, relative slip activity and texture fractions for the CR specimens. Copper and S oriented grains showed the occurrence of predominant single-slip systems near the severely deformed regions which was the primary cause of SLs formation. [Display omitted] [ABSTRACT FROM AUTHOR]

Simultaneously improving the mechanical and electrical conductivity of copper alloys has become an important challenge. In this paper, columnar crystal Cu-Ni-Si alloy materials were prepared using continuous unidirectional solidification method, and the effects of room temperature rolling (RTR), cryogenic rolling (CR) and subsequent aging treatment on the microstructure, mechanical and electrical properties of C70250 copper alloy were investigated. The results show that the material has good tensile strength (886 MPa), elongation after break (5.2%) and electrical conductivity (42.4% IACS) when the columnar crystal C70250 copper alloy is cryogenic rolled with 95% depression rate and aged at 450 °C for 1 h. After severe rolling deformation, both RTR and CR C70250 copper alloy produce uniform fibrous structure. Large deformation CR can exhibit higher dislocation density compared with RTR C70250 copper alloy, high lattice distortion results in the transformation of the matrix into an amorphous structure, which has a very strong promotion effect on solute atom diffusion and recrystallization. The precipitation of the fine Ni 2 Si cluster phase with average size of ∼3.2 nm can be accelerated in a shorter aging time compared to RTR, while the uniform fibrous structure after CR can rapidly recrystallize to produce uniform ultra-fine grains with diameter of ∼550 nm. The strength of the cryogenic rolling alloy can significantly increase through precipitation strengthening, fine grain strengthening and dislocation strengthening. This provides a feasible strategy to improve the overall performance of Cu-Ni-Si alloys. • A new process is developed to prepare C70250 copper alloys with high strength and electrical conductivity. • Ultra-fine grains and uniform Ni 2 Si phases are produced by cryogenic rolling with large deformation and peak aging. • Synergies of ultra-fine grains and Ni 2 Si are exploited to achieve a high comprehensive property. [ABSTRACT FROM AUTHOR]

In the present study, commercial Cu-35Zn α-brass sheets were subjected to cryogenic rolling (CR) to obtain samples with different amounts of deformation in the thickness direction. A self-designed liquid nitrogen cooling system that can simultaneously cool the work rollers and samples was used to ensure an ultra-low temperature condition during the rolling process. The grains, deformation twins, and dislocation density of the samples were studied by optical microscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). Uniaxial tensile tests and Vickers hardness measurements were conducted to measure the mechanical properties of the samples. The microstructures and mechanical properties of CR samples were apparently improved compared to the room temperature rolling (RTR) samples with increasing deformation amount. As a typical example, when the deformation amount is 90%, the CR sample possesses ultrafine microstructures and demonstrates extraordinary mechanical properties. The average tensile and yield strengths of a 90% deformation CR sample can be improved to 835.3 MPa and 711.5 MPa, while those of a 90% deformation RTR sample are 718.6 MPa and 481.2 MPa. The average elongation of the CR sample is 2.9%, which is acceptable compared with the RTR sample whose average elongation is 3.1%. The ultrafine microstructures containing ultrafine grains, high density dislocation, and nanometer scale deformation twins in the 90% deformation CR sample may be the main reason for its extraordinary mechanical properties. Therefore, samples with a good combination of strength and ductility were obtained in the present study. This may be a valuable exploration to fabricate Cu-35Zn alloy sheets with excellent microstructures and mechanical properties. [ABSTRACT FROM AUTHOR]

304 austenitic stainless steel plates have been deformed (10 to 40%) by multi-pass cold rolling incorporating soaking at 0 °C and − 196 °C after each pass with an aim to correlate the microstructure and mechanical properties under cold/cryogenically deformed conditions. Characterisation of phase constituents, microstructure and mechanical properties of such steel specimens has been conducted after processing under different schedules. Rolling of the investigated steel at near cryogenic temperature results into the formation of extended stacking faults, ε-martensite and α′-martensite in contrast to the formation of homogeneous dislocation structure along with α′-martensite in the samples rolled at 0 °C, which can be correlated with temperature dependent stacking fault energy. EBSD phase analysis reveals 46.3% and 69.2% α′-martensite in the austenitic matrix for 10% and 20% deformation at − 196 °C, respectively. Deformation twins are evident in all the samples rolled at 0 °C as well as − 196 °C. 40% cold deformation at 0 °C leads to high strength (1225 MPa) and 13% total elongation, whereas comparatively lower 10–20% deformation at − 196 °C leads to higher level of strength (1306–1589 MPa) with 15–9% elongation due to the formation of the higher volume fraction of strain induced martensite (ε/α′). [ABSTRACT FROM AUTHOR]

The microstructure/mechanical properties, annealing behavior, and post-annealed microstructure/property relationship of 5052 Al alloy processed by cryogenic rolling (CR) and room-temperature rolling (RTR) have been investigated. It was observed that the CR-processed 5052 Al alloy exhibits a refined crystallite size along with higher-density dislocations than that of the RTR-processed sample. As a result, the tensile strength of the CR-processed alloy increased significantly to 345 MPa because of the enhanced dislocation strengthening and grain-boundary strengthening. The effective suppression of dynamic recovery and accumulation of high-density dislocations caused by CR help accelerate recrystallization kinetics and refine the grain size, gaining higher yield strength for the post-annealed CR 5052 Al alloy compared to that of other commercial 5052-O Al alloys. [ABSTRACT FROM AUTHOR]

In order to improve the strength and electrical conductivity of Cu-Ni-Si alloy, the columnar crystalline C70250 copper alloy strip suffer from two deep cryogenic rolling-aging treatments with large deformation, and the relationship between the cryogenic rolling-aging process and microscopic structure, mechanical, conductive properties is studied, and the precipitation behavior is analyzed. The research findings show that the columnar crystalline C70250 copper alloy produced by continuous directional solidification can be directly processed by two cryogenic rolling-aging treatment with large deformation, eliminating the traditional solution treatment process and obtaining a fibrous tissue structures containing high-density dislocations and multi-scale precipitates, the yield strength, tensile strength and electrical conductivity of the alloy reached 879 MPa, 923 MPa and 38.7 % IACS respectively, combination of strength and electrical conductivity is excellent. Two deep cryogenic rolling with large deformation can force the matrix to change to amorphous, favorable to atomic diffusion. Solute atoms are continuously transformed into Ni 2 Si phase and Cu atoms are continuously expelled, forming large-sized pure Ni 2 Si precipitated phase and small-sized NiSi cluster phase containing Cu atoms, which together impede dislocation movement and reinforce alloy. With the uniform precipitation of multi-scale nano-precipitation phases and reduction of grain boundary density, the electrical conductivity along the rolling direction is significantly reduced. • A new process is developed to prepare C70250 copper alloys with high strength and electrical conductivity. • The high diffusion rate channel of elements is driven by two deep cryogenic rolling with large deformation. • Synergies of NiSi and Ni 2 Si are exploited to achieve a high comprehensive property. [ABSTRACT FROM AUTHOR]

In this work, abundant types of deformation twins were introduced in CP-Ti by cryogenic rolling. The stability of the twins under the annealing process and their contribution to texture were investigated. The EBSD results revealed that {11 2 ¯ 2} compression twins as the primary twin result in the texture with c-axis near ND and RD, while {10 1 ¯ 2}and {11 2 ¯ 1} tension twins as the primary twin induce the texture with c-axis nearly parallel to TD. Besides, the asymmetric texture intensity of the as-received sheet will be improved by the reorientation induced by deformation twins during the annealing process. Most twins show good thermal stability during the annealing process at 550 °C, however, all twins rapidly disappeared at 650 °C. The {10 1 ¯ 2} twins are the most thermally stable during annealing treatment at 600 °C. After full recrystallization, the texture induced by matrix reorientation maintains, while the texture associated with primary twins recovers. • Abundant deformation twins are activated in cryogenic rolled CP-Ti. Different twin interactions are investigated. • All twins show good thermal stability at 550℃ while they rapidly disappear at 650℃. {10 1 ¯ 2 } twins show the best thermal stability at 600℃. • The texture components induced by primary twins recover while those by secondary twins maintain after annealing. [ABSTRACT FROM AUTHOR]

• Microstructural and crystallographic texture evolution in the RTR and CR ETP copper were investigated systematically. • CR-processed specimens showed higher hardening and softening rate than RTR-processed specimens. • SRX at room temperature was the main softening phenomena observed in the severely deformed specimens. • DSRX and CSRX were responsible for the nucleation of small grains at room temperature in the severely deformed RTR and CR-processed specimens. • Time-dependent decay in the hardness values for the RTR and CR specimens, attributed to the SRV and SRX. The present study addresses the evolution of microstructural and crystallographic texture in room-temperature-rolled (RTR) and cryogenic-rolled (CR) electrolytic tough-pitch (ETP) copper. Copper specimens were subjected to 20, 40, 60, and 80% reductions via RTR and CR processing. The microstructure evolution of the severely deformed RTR and CR specimens revealed deformed and recrystallized grains. Static recrystallization (SRX) at room temperature (RT) was observed in the severely deformed RTR and CR specimens. Both discontinuous SRX (DSRX) and continuous SRX (CSRX) were responsible for the nucleation of small grains at RT. Particle-stimulated nucleation (PSN) was also responsible for small-grain formations around the Cu 2 O particles. The initial ETP copper specimen showed a weak texture whose intensity increased after the RTR and CR deformation. The texture intensity of the severely deformed specimens was affected by both deformation and the SRX phenomena. The CR specimens showed texture that was stronger than that of the RTR specimens up to the point of an intermediate reduction (60%), whereas at higher deformation (80%), the RTR specimens showed stronger texture intensity compared with that of the CR specimens. The texture weakening in the CR80 specimen was due to the formation of strain localizations (SLs) and to the nucleation at SLs. Large amounts of stored energy and SL formation in severely deformed CR specimens led to a different recrystallization texture compared with that of RTR specimens. A Cube component was dominant in the RTR80, whereas Goss, Copper and S components were observed in the CR80 specimen for SRX grains. The CR specimen showed a relatively high hardness value compared with the RTR specimen. Time-dependent decay in the hardness values for both the RTR and the CR specimens were attributed to room-temperature recovery (SRV) and recrystallization (SRX). [ABSTRACT FROM AUTHOR]

Nowadays, due to their potential for superior mechanical properties, a considerable interest in bulk ultrafine grained metals exists. One of the possible formation methods for this ultrafine grained material is cryogenic rolling. In this work, the influence of cryogenic rolling on the texture and the microstructure of pure copper is investigated by electron backscatter diffraction (EBSD), both in the deformed and the annealed state. This is done by comparing cryogenically rolled copper with room temperature rolled copper, rolled to the same thickness reductions. A texture difference between the room temperature rolled and cryogenically rolled copper is seen in the deformed state, although the largest texture difference is observed after annealing. These texture differences are mainly attributed to the presence of shear bands in the microstructure of the cryogenically rolled copper. In order to obtain a better understanding of the influence of shear bands on the texture evolution, the grain orientations inside the shear bands are analyzed both experimentally and numerically by applying the visco plastic self-consistent (VPSC) model. A number of shear band specific orientations, which are not observed in the conventional rolling texture of fcc materials, could be identified both in the experimental observations and in the simulations. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: The effect of cryogenic rolling on the natural aging behavior of a commercial AA7050 aluminum alloy was investigated. Solutionized 10mm-thick sheets were cryo-rolled to true strains of 0.5, 0.9, 1.1 and 1.4 followed by natural aging (T4 temper) at times ranging from 10 to 1000h. Light optical microscopy (LOM), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were used to follow the microstructural changes upon processing. Mechanical properties were assessed by Vickers hardness measurements and tensile tests. During natural aging the hardness values increased from 100 HV to approximately 145 HV after 100h. The strength of the undeformed specimen, naturally aged for 100h, was much higher than that in the as-quenched state. The yield strength (YS) increased from 130 to 375MPa (188% increase) and the increment of ultimate tensile strength (UTS) was almost 47% (321–470MPa). A superior combination of mechanical properties was achieved for the specimen cryo-rolled to a true strain of 0.5 followed by natural aging for 1000h (YS=611MPa and 15% total elongation). These results suggest that a combination of cryogenic rolling with natural aging is a useful method for achieving optimized mechanical properties for the AA7050 alloy. [Copyright &y& Elsevier]

The effects of microstructure, texture evolution and strengthening mechanisms on mechanical properties of 3003 aluminum alloy during cryogenic rolling (CR) and room temperature rolling (RTR) processing were investigated by electron backscatter diffraction, transmission electron microscopy and X-ray diffraction. The results show that the CR processing can significantly decrease the size of sub-grains and second-phase particles, and increase the dislocation density of the 3003 aluminum alloy. During the CR and RTR processing, the initial Cube and R-Cube textures are gradually rotated into the β -fiber texture. The CR processing can obviously delay the texture evolution from initial Cube texture to β -fiber texture during rolling. A significant enhancement in the yield strength, ultimate tensile strength and elongation of the 3003 aluminum alloy after the CR processing is obtained comparing with the RTR processing. This can be explained by the contribution of dislocation strengthening and grain refinement strengthening. • Microstructure, texture evolution and strengthening mechanisms in 3003 aluminum alloy during CR and RTR were investigated. • CR processing can refine the size of sub-grains grains and increase the dislocation density. • CR processing can delay the texture evolution from initial cube texture to β-fiber texture. • CR processing can enhanced the YS, UTS and EL of CR samples compared with the RTR samples. [ABSTRACT FROM AUTHOR]

Cryogenic deformation had been proved to promote the strength and toughness in several kinds of alloys. The microstructure responses and mechanical properties of cryogenic rolling 2195 Al–Cu–Li alloy after heat treatment were investigated systematically in this study. The annealed 2195 Al–Cu–Li alloy plates were subjected to cryogenic rolling to a reduction of 80% at −190 °C, followed by the solid solution at 540 °C for 2 h and aging treatment at 175 °C for different durations. Both the tensile strength and ductility of heat-treated specimen increased compared with the as-rolled sample, while the yield strength of the cryogenic rolling sample was higher anomaly. In addition, the tensile strength, yield strength, and elongation of the heat-treated samples increased firstly and then decreased with the increase of aging time. The number of T 1 phases was initially increased with the aging time extended to 12 h and decreased after the aging duration was increased to 16 h. While the number of θ' gradually decreases with aging time increased. Based on the precipitation kinetics, aging kinetics, and dislocation theory, a physically based model considering the variation of dislocation density and volume fraction of the T 1 phase and aging duration was established in this paper, which is in good agreement with the experimental data. Meanwhile, a strong connection between the dislocation density and fraction of the T 1 phase and aging duration is established. [ABSTRACT FROM AUTHOR]

Investigating recrystallization is essential to optimize the microstructure including texture weakening and grain refinement in the rolling of magnesium alloys, thus to improve the mechanical properties of magnesium sheets for industrial applications. This research has gained an in-depth understanding of the effects of deformation bands and twin-twin interactions on recrystallization, which will potentially lead to improved manufacturing processes and mechanical properties of magnesium alloys. To study their individual effects, the recrystallization mechanisms of the room-temperature (RT)-rolled and liquid-nitrogen-temperature (LNT)-rolled samples during the annealing process were analysed with the quasi-in-situ electron backscatter diffraction method, respectively. It is found that recrystallization mainly occurred in deformation bands in the RT-rolled sample, which enhanced the initially formed texture, due to oriented and inhomogeneous grain growth. However, it is of great interest to see that the recrystallized sites were mainly located around the (10 1 ¯ 2)-(01 1 ¯ 2) twin-twin interactions with high kernel average misorientation (KAM) values in the LNT-rolled samples, resulting in rather weaker texture, finer grain size and more homogeneous microstructure, because of the randomized orientations of recrystallized grains and uniform grain growth, while almost no recrystallization was observed around the single tension twin variant. Unlabelled Image • Recrystallization around twin-twin interactions results in weakening texture in annealed cryogenically-rolled samples. • Twin-twin interactions are prone to recrystallization due to high kernel average misorientation values. • Recrystallization around deformation bands results in strengthening texture in annealed room-temperature-rolled samples. [ABSTRACT FROM AUTHOR]

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 {10 1 ¯ 1}-{10 1 ¯ 2} double twins (DTWs), were observed in the RT-rolled samples, while a high quantity of twins, including {10 1 ¯ 2} 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° <20 2 ¯ 1 ¯ > 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. Unlabelled Image • A new twinning sequence, namely primary twin-twin interactions → secondary twin-twin interactions, was discovered. • The rolling at cryogenic temperature was accommodated by tension twins → twin-twin interactions → twinning sequence. • Regarding rolling at room temperature, the deformation was governed by double twins → shear bands. • The geometrically necessary dislocation density was high in twin-twin interactions, twinning sequence and shear bands. [ABSTRACT FROM AUTHOR]

Microstructure and mechanical properties of cryogenic-rolled LA141-xYb (x = 0, 0.1) alloys were investigated. With the addition of Yb, the grains of the alloy are refined, and some fine Al 3 Yb phases are formed. The submicron scale dynamic recrystallized grains can be observed in the cryogenic rolled specimen. The addition of Yb inhibits the dynamic recrystallization and refines the grains during cryogenic rolling. As a result, the work softening is greatly reduced, and the strength is significantly increased. The results show that, due to the addition of Yb, the ultimate tensile strength of as-cast and CR-processed alloys is increased by 14.5% and 40.1%, respectively, reaching 197 MPa and 241 MPa. It is mainly caused by the combined effects of refinement, dispersive fine Al 3 Yb particles, high density dislocation and stack faults (SFs). • The excellent mechanical properties of LA141 alloy were obtained by combination effects of Yb addition and cryogenic-rolling. • With the addition of Yb, the grains of the alloy are refined, and some fine Al 3 Yb phases are formed. • The mechanism of microstructure evolution of the CR-processed specimen was discussed. [ABSTRACT FROM AUTHOR]

The pure copper sheets were rolled with a small strain in one pass at cryogenic and room temperature, respectively. The total thickness was reduced by 55% through three rolling passes. The microstructural evolution and mechanical properties of Cu sheets were investigated by metallographic characterizations, tensile tests and fracture analysis. It is found that several nanoscale mechanical twins are generated in the cryogenically rolled Cu sample. The restricted atomic motion at ultralow temperature inhibits the dislocation slip and then induces the occurrence of grain kinking and mechanical twining. The yield strength and ultimate tensile strength of cryo-rolled Cu sample are enhanced by the remarkable accumulation of dislocations and mechanical twins. During annealing treatment, the recrystallization behavior is accelerated by the dramatic strain energy and microstructural defects in cryogenically rolled Cu samples. Compared with the recrystallization concentrated on the surface of room temperature rolled Cu sample, a few of recrystallized grains are formed in the central position of cryogenically rolled Cu sample at 180 °C annealing. The rapid progress of thermal recovery during annealing treatment improves the tensile ductility and strain-hardening capacity of cryo-rolled Cu sample. Several pores are formed on the tensile fracture due to the incompatible deformation between the inhomogeneous grains. The results demonstrate that combining the cryogenic rolling and 200 °C annealing is able to improve the mechanical properties of pure copper sheet. [ABSTRACT FROM AUTHOR]

Mg-14Li-1Al (LA141) alloy was processed by cryogenic rolling (CR) and room temperature rolling (RTR) with large deformation. The microstructure evolution in the CR and RTR-processed samples was investigated. The dynamic recrystallization grains with sub-micron size were observed in both rolled samples. A large number of nano-twins appeared in the CR-processed sample. Compared with the as-homogenized specimen, the mechanical properties of both rolled specimens were significantly improved. The ultimate tensile strength (UTS) of the RTR and CR-processed specimens increased by 36% and 46% respectively, reaching 208 MPa and 223 MPa due to the grain boundary strengthening and dislocation strengthening. The elongation of the RTR-processed specimen increased by nearly three times, 18.5%, mainly due to the formation of dynamic recrystallization grains. And that of the CR-processed specimen increased by more than four times, 25.8%, because of the coordinated deformation of dynamic recrystallization and nano-twins. • The excellent mechanical properties of LA141 alloy were obtained by cryogenic rolling and room-temperature rolling processes. • A large munber of nano-twins were prepared by the cryogenic rolling process. • The mechanism of microstructure evolution of the cryogenic rolling and room-temperature rolling processes was discussed. [ABSTRACT FROM AUTHOR]