Cryorolling Research Articles

AA1050 metal matrix composites reinforced by high-entropy alloy particles via stir casting and subsequent rolling

AA1050 metal matrix composites (MMCs) reinforced by Al0.5CoCrFeNi high-entropy alloy particles (HEAp) were prepared by stir casting and subsequent rolling (room temperature rolling (RTR) and cryorolling (CR)). The mechanical properties and microstructures of the AA1050−HEAp MMCs were studied. By adding 3 wt% HEAp, the ultimate tensile strength of the stir-casted AA1050−HEAp MMCs increased by 74.3% compared with AA1050. After rolling, the mechanical properties of the CR AA1050−HEAp MMCs were better than those obtained by RTR. The differences of the mechanical properties of the AA1050−HEAp MMCs obtained by CR and RTR increased with a higher rolling deformation and a lower mass fraction of HEAp. After RTR, there were various voids in AA1050−HEAp MMCs, which were not observed in CR MMCs through both scanning electron microscopy and transmission electron microscopy. Finally, the effect of cryogenic temperature on microviods and mechanical properties of MMCs were discussed.

Microstructure and mechanical properties of ARB-processed AA1050/AA5052 multilayer laminate sheets during cryorolling

AA1050/AA5052 multilayer laminate sheets were fabricated by accumulative roll bonding (ARB) and cryorolling (CR). The ultimate tensile strength (UTS) of the laminate sheets produced by combining ARB and CR increased up to 18.4% compared to that by five ARB passes. Necking and fracture occurred in the hard layer after the fourth ARB pass. In contrast, the hard layer remained continuous and relatively straight during CR, which suggested that CR can delay the onset of necking and fracture. TEM results showed that CR can not only refine grain size but also significantly improve interfacial bonding quality. CR can accumulate higher dislocation density. Therefore, the laminate sheets prepared by the combination of ARB and CR obtained better mechanical properties than that by five ARB passes.

Exploring a hybrid manufacturing process to develop high performance age hardenable ultrafine grained AA6063/SiC nano-composite sheets

In the present work, a novel hybrid manufacturing process is established to develop high performance AA6063/SiC nano-composite sheets. The novel hybrid manufacturing process consists of cryorolling (CR) followed by warm rolling (WR). The resultant effect of the hybrid processing route on the mechanical properties, strain hardening ability, microstructural evolution and age hardening response was studied in detail. The outcomes of the hybrid processing route showed a significant enhancement in strength of CR + WR nano-composites. The improvement in strength of CR + WR is due to the combined effect of increased dislocation density, dynamic recovery, grain refinement, and aging treatment. Imparting of optimum age hardening (A) treatment (150 °C for 4 h) to CR + WR nano-composite resulted in significant enhancement of strength-ductility combination which is found to be highest among the published literature on AA6XXX/SiC composites. The mechanical properties of peak aged CR + WR composites are also found to be higher than that of CR (90% cryorolled +Peak aged)) nano composite. The scientific knowhow and governing mechanisms were established to understand the potential of hybrid manufacturing process on significant enhancement of mechanical properties and age hardening response on AA6063/SiC nano-composites.

Effect of Rolling Temperature and Subsequence Ageing on the Mechanical Properties and Microstructure Evolution of an Al-Cu-Li Alloy

The mechanical properties and microstructure evolution of an Al-Cu-Li alloy sheet processed via hot rolling (HR) (at 400 °C and 500 °C) or cryorolling (CR) (at −100 °C and −190 °C) and subsequence aging at 160 °C for 10 h were investigated. Before aging, the highest ultimate tensile strength of 502 MPa was achieved when the sheets were cryorolled at −190 °C, while the better ultimate tensile strength of 476 MPa and the best elongation rate of 11.1% was achieved simultaneously when the sheets were cryorolled at −100 °C. The refined grains and numerous uniform deformation-induced dislocations microstructures were responsible for the improved strength and enhanced ductility of the cryorolled sheets compared to that of the alloy processed by hot rolling with a low dislocation density zone (LDDZ) and high dislocation density zone (HDDZ). After aging at 160 °C for 10 h, the ultimate tensile strength further improved resulted from the greater precipitation strengthening, and the increased precipitates provided greater resistance to dislocations movement resulting in the increased ductility although the dislocation density decreased. The uniform dislocation microstructures in the cryorolled sheets provide numerous nucleation sites for the precipitates, leading to higher strength after aging.

Insight to the evolution of nano precipitates by cryo rolling plus warm rolling and their effect on mechanical properties in Al 6061 alloy

Evolution of nano-precipitates after Cryorolling (CR) followed by warm rolling (WR) at rolling temperatures of 100 °C, 145 °C and 175 °C on the microstructure and strengthening of Al-6061 alloy has been investigated. The enhanced yield (401 MPa) and tensile strength (415 MPa) with 6% ductility was achieved after CR plus 80% WR. The evolution of various precipitates such as G.P. zones, Cluster/co-cluster, β’ and β” after CR plus WR was investigated, by studying the thermal behavior using Differential scanning calorimetry studies (DSC). Time of the optimized artificial ageing temperature (125 °C for 45 Hrs) was obtained using hardness testing and DSC study. Significant improvement in ductility (9%) of CR plus 80% WR Al 6061 alloy after peak ageing showing 450 MPa tensile strength was obtained, due to the evolution of highly dense coherent nano-precipitates (β”) responsible for uniform flow localization. A graphical model is proposed explaining the effect of solution treatment, deformation temperature, dislocations and peak ageing on evolution of precipitates.

Improvement of mechanical properties of cryorolled LM6 alloy

Mechanical properties and fracture behavior of bulk UFG LM6 alloy processed through cryorolling (CR) is investigated in the current work. LM6 Al alloy is reduced through CR upto thickness reduction of 50%, 75% and 90% at liquid nitrogen temperature. Mechanical properties of bulk and deformed alloys were investigated through tensile and three-point bend test. These properties are correlated with microstructural features by the help of optical microscopy and scanning electron microscopy. The significant improvement in strength (UTS: 64.18% and YS: 125.16%) of CR upto 90% deformed sample were recorded. This enhancement is attributed due to the formation of ultrafine grained (UFG) structure resulting grain boundary strengthening. However, the fracture mode of tensile tested samples is transformed from ductile to brittle nature with the increment in thickness reduction from ST to 90% CR sample substantiating the lack of strain hardening ability of the UFG LM6 alloy.

Effect of cryorolling on microstructure and property of high strength and high conductivity Cu−0.5wt.%Cr alloy

Abstract Cu−0.5wt.%Cr alloy with high strength and high conductivity was processed by cryorolling (CR) and room temperature rolling (RTR), respectively. The microstructure, mechanical property and electrical conductivity of Cu−0.5Cr alloy after CR/RTR and aging treatment were investigated. The results indicate that obvious dislocation entanglement can be observed in matrix of CR alloy. The Cr particles in the alloy after CR and aging treatment possess finer particle size and exhibit dispersive distribution. The peak hardness of CR alloy is HV 167.4, significantly higher than that of RTR alloy. The optimum mechanical property of CR alloy is obtained after aging at 450 °C for 120 min. The conductivity of CR Cu−0.5Cr alloy reaches 92.5% IACS after aging at 450 °C for 120 min, which is slightly higher than that of RTR alloy.

Sandwich‐Like Cu/Al/Cu Composites Fabricated by Cryorolling

Herein, sandwich‐like Cu/Al/Cu composites are fabricated by hot rolling (300 °C), cold rolling (25 °C), cryorolling (−100 and −190 °C), respectively. Tensile tests are conducted and the fracture surfaces of both the Al and Cu sides are examined using scanning electron microscopy (SEM) for fractography and SEM‐based energy‐dispersive analysis. The microstructure of the composites is evaluated by optical microscopy and SEM. Results reveal that the highest ultimate tensile strength and the best ductility of the composites have been achieved using cryorolling of the rolling temperature −100 °C. Finally, discussion on grain size, bonding quality, and the thickness of the intermetallic layer between Cu and Al layers on the mechanical properties of the sandwich‐like Cu/Al/Cu composites is focused.

Effect of rolling temperatures on mechanical and fracture behavior of AA 3003 alloy and pure Cu

Ultrafine-grained materials have an enormous scope of structural and functional applications owing to their higher mechanical properties compared to that of coarse-grained materials. The influence of room temperature and cryogenic temperature rolling of AA 3003 alloy and pure Cu on its mechanical properties and fracture behavior has been investigated in the present study. Both the materials are rolled to a thickness of 2 mm and 1 mm with a true plastic strain of 0.40 and 1.09, respectively. The deformed samples are characterized by tensile test, hardness test, and X-ray diffraction analysis. It has been observed that tensile strength and hardness of cryorolled (CYR) samples are higher than cold rolled (CR) samples and it is due to the fact that rolling at an extremely low temperature (− 196 °C) suppresses the dynamic recovery and hence mobility of dislocations becomes difficult as a result dislocation density increases. In CYR, low stacking fault energy material (Cu) has higher tendency to increase strength and work hardened compared to higher stacking fault energy materials (AA 3003) without much loss of ductility. SEM pictorial view of fractography revealed that CYR samples have mix mode of failure compared to CR samples. The dimple size is gradually decreased with increasing plastic strain and that is due to severe strain hardening and grain refinement.

Microstructure, mechanical and corrosion properties of cryorolled-AA5052 at various solution treatment temperatures

Initial solution treatment (ST) of aluminium alloys prior cryorolling (CR) enhances the ultrafine grain structure formation hence, improving their mechanical and corrosion properties. However, determining the appropriate ST temperature is crucial to obtain the optimum properties. In this work, ST followed by cryorolling of AA 5052 alloy was performed at varying temperatures; 480 °C, 510 °C and 540 °C. Mechanical and microstructural characterization of the cryorolled samples with and without ST and the base metal were performed using Vickers hardness tester, universal tensile testing machine, FESEM, EBSD and HRTEM. All the ST cryorolled samples showed the finer structure and better mechanical and corrosion performances than those without ST and the base metal. The smallest crystallite size and lattice strain achieved were 24.88 nm and 3.86 × 10−3 respectively at 540 °C. The hardness, yield and tensile strength increased with increasing the ST temperature with the highest values of 85.2 Hv, 254.82 MPa and 303.35 MPa, respectively, at 540 °C. Cryorolled sample solution treated at 540 °C also showed the highest corrosion resistance based on low corrosion current and high corrosion potential. The work gives the appropriate ST temperature at which improved microstructure, mechanical and corrosion properties of the cryorolled AA5052 can be obtained.

Mechanical Behavior and Deformation Kinetics of Aluminum Alloys Processed through Cryorolling and Subsequent Annealing

The influence of cryorolling (CYR) on the microstructure, mechanical properties, and formability of heat-treatable (AA 6061) and non heat-treatable (AA 5083) aluminum alloys was investigated. Solutionized (SL) AA 5083 and AA 6061 alloy plates are cryorolled to reduce the thickness from 6.5 to 1 mm (the total true strain of 1.87). Short annealing treatment is performed on cryorolled samples at different temperatures with a fixed annealing time to improve ductility. The effect of annealing temperature on microstructure, mechanical properties, and formability was systemically studied. The results showed grain refinement after CYR with higher dislocation density when compared to the SL condition, and their effect is reflected in the mechanical properties. The limiting dome height test is used in the present work to compare the formability of cryorolled and annealed samples. The formability characteristics correlated well with the strain hardening behavior, which is modeled using the Kocks–Mecking–Estrin (KME) dislocation density model. The dislocation density evolution in the original KME model was modified to consider the contributions of grain size, solutes, and precipitates. The tensile curves predicted from the KME model correlated well with the experimental curves in all the conditions investigated. In addition to that, the predicted dislocation density using the modified KME model agreed well with the dislocation density determined experimentally.

Microstructure and mechanical properties of cryorolled Al–6Zn–3Mg–2Cu–0.5Sc alloy

Abstract Al–6Zn–3Mg–2Cu–0.5Sc alloy with 85% rolling reduction from the original thickness at room and cryogenic temperatures leads to high tensile strength and higher dislocation density for the cryorolled (CR) (−80 °C) sample. Microstructural investigation and their properties on mechanical behaviour of Al–6Zn–3Mg–2Cu–0.5Sc alloy were noted in detail during rolling as-cast, room temperature rolling (RTR) and cryorolling (−80 °C) conditions. The CR (−80 °C) sample revealed greater work hardening value than the as-cast alloy, due to the effect of CR and the presence of Al3CuMg precipitates. The Hierarchical Grain Size Distribution (HGSD) reported in cryorolled samples via Electron Back Scattered Diffraction (EBSD) studies, and it leads to a high strength of 537 MPa and 17% ductility in CR (−80 °C) samples. Transmission electron microscope (TEM) studies revealed that the high dense dislocations and nano sized intermetallic compounds are equally distributed alongside the matrix in the CR (−80 °C) among the rolled samples. Al–6Zn–3Mg–2Cu–0.5Sc alloy showed improved mechanical properties during various rolling conditions.

Forming of AA2xxx and AA7xxx Sheet Alloys and their Studies on Microstructural and Mechanical Properties of Cold and Cryo Rolled Aluminum Alloys

High strength aluminum alloys will enhancing mechanical properties always plays a major role in controlling microstructure of cast and processed alloy. The desire for more efficient aircraft materials has fueled research of aluminum AA-2xxx and AA7xxx alloys. In these alloys were rolled at cold rolling and at cryorolling to 80 % thickness reductions and an attempt was made to evaluate the optical-microstructural variation and the variation in tensile properties of these aluminum alloys. Cryorolled alloy also exhibited better hardness and strength compared to cold alloy due to suppressed thermal recovery. Coldrolled alloy showed more necking percentage compared to cryorolled for rolling reductions of 80% and more formability was observed.

Evaluating tensile properties and fracture toughness of Al 2014 alloy processed by different rolling methods

Influence of different rolling methods on the mechanical properties and microstructure were studied in current investigation. The solution-treated (ST) Al 2014 alloy were deformed through room temperature rolling (RTR), cryorolling (CR) and cryo grove rolling (CGR) at different thickness reduction values such as 50%, 75% and 90%. The mechanical properties of ST and deformed samples were investigated through tensile/3-point bend test and correlated with microstructural features by electron backscattered diffraction (EBSD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Study revealed the formation of ultrafine grains (UFG) for all rolling methods (RTR/CR/CGR) after 50, 75 and 90% thickness reduction of ST Al 2014 alloy. The remarkable improvement in the tensile properties and fracture toughness of CGR sample were observed for all thickness reductions as compared to all processing methods such as RTR and CR. The enhancement in the mechanical properties of CGR samples can be attributed to the dislocation strengthening, grain boundary strengthening and formation of much finer UFG grains with respect to the other rolling methods as observed from EBSD, TEM and SEM micrographs.

Microstructure Evaluation on Friction Stir Welding of Cryorolled 2219 Aluminum Alloy

Abstract This article presents a study of friction stir welding (FSW) on cryorolled (CR) AA2219 alloy using a hexagonal pin tool with different set of process parameters. Normally, AA2219 alloy is difficult to weld, but it is possible to get a defect-free, sound weldment with a solid-state welding technique (FSW) compared to traditional welding methods. Here, among the 9 weld joints, the weld made on CR AA2219 by the hexagonal pin tool with 1,000 r/min tool rotational speed at 25 mm/min welding speed and 3° axis inclination exhibited better tensile strength, impact toughness, hardness, and corrosion resistance. It was confirmed by microscopy analysis that the ultrafine grains structure and dissolution of Al2Cu were present at the weld zone. The fine dimple morphology was found at the fracture surface area of weldment. Also, the X-ray Diffraction (XRD) and energy-dispersive X-ray results showed that the intensity of Al2Cu was decreased at the weld portion for the CR AA2219. Dissolution of precipitates resisted the flow of electrons and delivered good resistance against corrosion. Corroded portion surface topography was analyzed, and pit details were measured.

Effect of Annealing on Mechanical Properties and Metallurgical Factors of Ultrafine-Grained 6082 Al Alloy

In the present work, cryorolling (CR) (rolling temperature is − 196 °C) followed by annealing (AN) (100–400 °C for 1 h) of 6082 Al alloy has been performed. The main objective of this study was to investigate the thermal stability of the ultrafine-grained 6082 Al alloy, for higher temperature applications. The mechanical properties of the CR and the CR + AN 6082 Al alloy were investigated and correlated with the microstructure with the help of a transmission electron microscope (TEM). The hardness and the tensile strength of the CR + AN (150 °C) 6082 Al alloy were significantly improved up to 95% and 40%, respectively, when compared to the solution-treated (ST) 6082 Al alloy. The main reason behind the mechanical strength improvement was dislocation strengthening and precipitation strengthening. Thermal stability of the CR 6082 Al alloy was found up to a high annealing temperature of 300 °C due to the pinning of grain boundaries by precipitates evaluation during annealing by Zener drag effect. The formation of β″-phase, β′-phase and stable β-phase occurred at the annealing temperatures of 175 °C for 1 h, 200 °C for 1 h and 250 °C for 1 h, respectively.

Development of combined groove pressing and rolling to produce ultra-fine grained Al alloys and comparison with cryorolling

In the present work, aluminium alloys were subjected to two different severe plastic deformation (SPD) routes namely, cryorolling (CYR) and constrained groove pressing (CGP), to investigate their effect on microstructure and mechanical properties. Solutionized AA 5083 alloy and AA 6061 alloy sheets were cryorolled to a final thickness of 1 mm with a total logarithmic strain of 1.87. Samples of these alloys with 3 mm thickness were subjected to CGP with an equivalent plastic strain of 1.16. The CGP samples have been subsequently cold rolled (CR) to reduce the thickness to 1 mm (67% reduction). The microstructure of the deformed samples was characterized by electron backscatter diffraction (EBSD) coupled with kernel average misorientation (KAM) and X-ray diffraction (XRD). The techniques were employed to investigate the degree of grain refinement and local misorientation due to deformation. It has been found that the yield strength (YS) of 6061 alloy after CGP + CR is 19% higher than that of CYR sample while, in contrast, the YS of CGP + CR 5083 alloy is 18% less than that of CYR condition. A dislocation density-based model has been used to estimate the sub-structural changes during processing. The theoretical dislocation density estimated using the model agreed well with the experimental values of both the alloys with a difference of about 2.5% in the case of 5083 and 6.5% in the case of 6061. It is inferred from the analysis that the dislocation bow out is the predominant mechanism in both the materials.

Role of deformation induced martensite on mechanical properties of cryorolled 304 stainless steel

The transformation of γ—austenite to complete α′—martensite (strain-induced martensite) through ε—martensite with no traces of deformation nanotwins was reported on rolling austenitic stainless steel (SS 304) with two different rolling strains (50% and 75%) at room and cryogenic temperatures. Transformation of complete α′—martensite was evaluated through the electron backscattered diffraction phase analysis and x-ray diffraction techniques. A proportional increment in hardness with an increase in volume fraction of α′—martensite was noted. The SS 304 rolled up to 75% reduction at cryogenic temperature (Cryo 75) that showed 99% α′—martensite in its x-ray diffraction pattern had exhibited a maximum hardness value of 491 HV. The effect of rolling strain and suppression of dynamic recovery resulted in reduced crystallite size, enhanced lattice strain and dislocation density values in cryorolled SS 304. The strength of cryorolled SS 304 improved due to increased dislocation density and finer lath shaped α′—martensite. Though the total elongation was lower in the cryorolled (CR) SS 304 compared to the as-received sample and there was no severe degradation of total elongation in comparison to room temperature rolled (RTR) SS304. The strength of RTR with 75% reduction was nearly equivalent to CR with 50% reduction. However, the Cryo 75 showed the maximum tensile strength of 2054 MPa among the rolled samples of SS 304. The enthalpy change was higher for the cryorolled sample with 75% reduction (290 J g−1–from DSC curve) due to the accumulation defect density, low stacking fault energy and rolling strain. The contribution of the strengthening mechanism to yield strength was evaluated and to substantiate, the tensile test was conducted on the rolled samples. The contribution of dislocation strength evaluated from the strengthening mechanisms was predominant for the CR 75 sample.

Correlation of Tensile Properties and Fracture Toughness with Microstructural Features for Al–Li 8090 Alloy Processed by Cryorolling and Post-rolled Annealing

The influence of cryorolling and post-deformation annealing on the tensile and fracture behaviour of aluminium–lithium (Al 8090) alloy is reported in the present investigation. The solution-treated (ST) alloy was cryorolled (CR) up to the true strain of 2.3 to achieve ultrafine-grained (UFG) microstructure and then annealed at different temperature ranging from 100 to 350 °C. CR samples showed a significant increase in tensile strength (~ 373 MPa), hardness (~ 120 HV), and fracture toughness [KQ (21.9 MPa $$ \surd m $$ ), Kee [27.9 MPa $$ \surd m $$ ), J integral (21.8 kJ/m2)], while huge drop in ductility of CR alloy is observed as compared to coarser grain ST alloy. After annealing in the temperature ranging from 100 to 350 °C, the significant changes in the tensile and fracture behaviour of bulk UFG Al 8090 alloy were noticed. The tensile strength and fracture toughness were gradually improved up to the temperature 150 °C and observed to be maximum (~ 561 MPa) at 150 °C, while beyond this temperature, a significant drop in these properties was observed. The improved tensile and fracture properties of cryorolled followed by annealed alloy at 150 °C could be attributed to the precipitation of S′ (Al2CuMg) and $$ \delta $$ (Al3Li) phase as observed from XRD and TEM studies.

Experimental and numerical investigations of low cycle fatigue behavior of cryorolled AA 5754

The objective of the present work is to study the influence of cryogenic forming on low cycle fatigue (LCF) properties of Al-Mg (AA 5754) alloy. AA 5754 is rolled at liquid nitrogen temperature (cryorolling) for maximum of 40% thickness reduction. Post-annealing heat treatment (PAHT) at 250oC for 2 hours is adopted to enhance the mechanical and fatigue properties of the cryorolled alloy. A series of uniaxial strain controlled LCF tests are executed at three different strain amplitudes from 0.4% to 0.6% for cryorolled (CR) and annealed cryorolled (ACR) AA 5754 alloy. PAHT significantly improves the tensile strength as well as ductility of CR alloys. LCF tests reveal that cryorolled alloys show mild hardening in the initial cycles followed by noticeable cyclic softening at all strain amplitudes. In contrast, only cyclic hardening behavior is depicted by ACR specimens at all strain amplitudes. The extended finite element method (XFEM) has been utilized to simulate the tensile behavior of the specimen. Finite Element Method (FEM) coupled with Chaboche kinematic hardening cyclic plasticity model is used for simulating hysteresis loop obtained during LCF test. The present study exhibits good match between simulations and experimental results.