Effect Of Rolling Reduction Research Articles

Obtaining Heterogeneous Microstructure and Enhanced Mechanical Properties in ECAP-Processed AZ61 Alloys via Single-Pass Rolling with Increased Rolling Reduction

Material design and preparation based on constructing heterogeneous microstructures can break the conventional performance limitations of fine-grained magnesium alloys. In this study, AZ61 alloys processed via multi-pass equal channel angular pressing (ECAP) were subjected to single-pass rolling (SPR) with increased rolling reductions. The effect of rolling reduction on the formation of heterogeneous microstructure and the mechanical properties of the alloy was investigated. Microstructural examinations revealed that a heterogeneous microstructure was formed in the alloy at varied rolling reductions, but the desired heterostructure with higher fine grain contents could only be achieved at increased rolling reduction. This was mainly due to the fact that the alloy underwent partial dynamic recrystallization (PDRX) under SPR, and PDRX more easily occurred with higher rolling reduction. The tensile test results showed that with increased rolling reduction, the strength of the alloy first increased and then decreased slightly, with the ductility steadily increasing. Improved mechanical properties were achieved in the alloy rolled at increased rolling reductions owing to the heterogeneous microstructure with a greater content of fine grains.

Effect of rolling reduction on microstructure and tension-compression yield asymmetry of rolled AZ31 magnesium sheet

Magnesium (Mg) alloys have been receiving significant applications in automotive and aerospace industries owing to its high strength-to-weight ratios. Approximately 30 % (by weight) of material used in automobiles are in the form of sheet metal. Therefore, in the present work AZ31 magnesium (Mg) alloy was hot rolled with different reduction ratios to produce Mg sheet. The results revealed that employing a 40 % reduction per pass led to a remarkable 92 % reduction in thickness, outperforming the 82 % reduction achieved with a 20 % reduction per pass, along with fine grain of 8 μm. Investigation has been conducted on the relationship between grain size and its impact on the tension-compression yield asymmetry in Mg sheet. This investigation unveiled that the suppression of {101‾2} extension twinning mode of deformation due to the back stress imposed by the simultaneous action of grain boundaries and twin overlap, effectively minimizing the asymmetry from 2.11 (as received AZ31 alloy) to 1.13 (5th pass rolling sheet). The study extensively explored the underlying mechanisms governing the yield asymmetry behavior of AZ31 Mg sheets. These mechanisms included strain hardening tendencies, Schmid Factor, and KAM (Kernel Average Misorientation) assessment, all of which were interconnected with microstructural attributes.

Effect of rolling reduction on the microstructure and mechanical properties of hot-rolled Mg-Li-Al-Ca alloys

To improve the strength of magnesium (Mg)-lithium (Li) alloy without sacrificing plasticity, Mg-7.3Li-4Al-3Ca alloy is designed and subsequently rolled at 350 °C. The microstructure evolution and mechanical properties of the alloy under different rolling reductions are studied. The results show that the as-cast and hot rolled alloy is composed of α-Mg, β-Li matrix phases as well as Al2Ca and (Mg, Al)2Ca precipitated phases. After hot rolling, the agglomerated Al2Ca precipitates are broken and dispersed in the matrix. A large amount of continuous filamentous (Mg, Al)2Ca phase becomes discontinuous and the phase content decreases monotonously with increasing rolling reduction due to the decomposition of (Mg, Al)2Ca phase and the corresponding constituent elements dissolve in the matrix. During the hot-rolling process, some fine equiaxed grains appear in the alloy matrix due to dynamic recrystallization. Both the strength and elongation of Mg-7.3Li-4Al-3Ca alloy increases monotonously with increasing rolling reduction. For the alloy with rolling reduction of 60%, the ultimate tensile strength and elongation are 218Mpa and 24.8%, respectively, which are 52.4% and 153% higher than those for the as-cast alloy. The strengthening mechanism is attributed to fine grain strengthening, precipitation strengthening and solid solution strengthening. Grain refinement and the appropriate distribution of Al2Ca and (Mg, Al)2Ca phases causes the obvious increase of the plasticity.

Effect of rolling reduction on the microstructure, texture, and mechanical behavior of AZ91 alloy

In this study, the effect of rolling reduction on the microstructure, crystallographic texture, and mechanical properties of the AZ91 alloy is studied. Optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and tensile and hardness tests were used. The homogenization process significantly increased the grain size of the as-cast sample. The results showed that {101¯2}⟨101¯1⟩ extension twinning during rolling leads to rotation of {0001}∥RD initial orientation toward {0001}‖ND basal texture. During asymmetric hot rolling up to 15%, the intensity of {0002} basal texture increased to 10 multiples of random distribution. After 15% deformation, the average grain size decreased due to the occurrence of dynamic recrystallization. It was found that by increasing the rolling reduction up to 15%, the hardness and tensile strength greatly increased owing to an increase in the fraction of twins and the intensity of basal texture. The occurrence of the CDRX mechanism and the formation of strong basal texture resulted in an excellent combination of strength and ductility for the 15% rolled sample. The as-homogenized and 8% rolled samples had the maximum and minimum inhomogeneity factor (IF), respectively. The fracture surfaces indicated that the mixture of ductile and brittle fracture is the main failure mode.

Investigations on Microstructure and Mechanical Properties of AZ91 Alloy Processed by Single Pass Rolling with Varied Rolling Reductions

In this study, single pass rolling (SPR) with varied rolling reductions was conducted on pre-homogenized AZ91 alloys (H alloys) and ECAP-processed AZ91 alloys (HE alloys). The effects of rolling reduction on the microstructures and mechanical properties of HR alloys (pre-homogenized and rolled) and HER alloys (ECAP-processed and rolled) were investigated. The results showed that the HER alloys possessed much finer microstructures and superior mechanical properties than the HR alloys, which were significantly influenced by the rolling reduction. The microstructures of the HER alloys became bimodal, and the strength and elongation markedly improved with the increase in the rolling reduction. When the rolling reduction reached 70%, the HER alloys acquired a typical bimodal structure, contributing to their excellent comprehensive mechanical properties.

Microstructure, mechanical and thermo-physical properties of hot-rolled Mo-50Cu composite

Mo-50Cu composite plates were prepared by ball milling, hot isostatic pressing, and hot rolling. The microstructure and properties of Mo-50Cu composites with different rolling reductions were studied. When the rolling reduction is lower than 38%, the plastic deformation of the composite mainly occurs in the Cu phase. With the increase of rolling reduction, the texture of the Cu phase changes from Goss texture to Brass and S texture, and the plastic deformation of the Cu phase and Mo phase occurs simultaneously. During hot rolling deformation, the elongation of the composite decreases with the increase of the deformation degree. When the rolling reduction is 56%, the yield strength and tensile strength of the composite reach the maximum values of 522.3 MPa and 588.8 MPa, respectively. The composite with 56% rolling reduction also has the lowest coefficient of thermal expansion of 9.81 × 10−6·K−1. In addition, the composite has the highest thermal conductivity of 262.1 W·m−1·K−1 after hot 38% hot rolling reduction and 950 ℃ annealing. The effects of rolling reduction on the density, grain size, residual stress, dislocation density, Mo morphology, and the properties of the composite were analyzed.

Effect of rolling reduction on the microstructure of the copper/aluminum composite strip produced by micro flexible rolling

Copper/aluminum (Cu/Al) laminated composite has been extensively applied in the fields of batteries, electronics and electrochemistry owing to its cost reduction, light weight, good conductivity and resistance to corrosion. The Cu/Al composite strips produced by micro flexible rolling consist of three regions based on different thickness, i.e. the thicker, the transition and the thinner zones, and have a broad application prospect, especially in micro-electromechanical systems (MEMS). In this study, the effect of rolling reduction on the coordinated deformation of the Cu/Al interface and the microstructure of Cu/Al matrixes at three regions were investigated. The microstructure of the specimens was characterized using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and the thickness of thin strips with varying thickness (TSVT) were measured by laser scanning microscope to explore the mechanism of microstructural evolution. The results show that the increase of rolling reduction gives a rise to the proportion of deformation occurred in the Al matrix, and the fracture of the intermetallic compounds (IMCs) is observed at the interface, which plays a significant role of transmitting and releasing stress during plastic deformation.

Microstructure, mechanical properties and deformation mechanism of powder metallurgy AZ31 magnesium alloy during rolling

To improve the microstructure compactness and mechanical properties of powder metallurgy (P/M) AZ31 magnesium alloy, hot rolling deformation was carried out in this work. The effect of rolling reduction on the microstructure and mechanical properties of P/M AZ31 magnesium alloy was investigated systematically. The results show that the equiaxed-shape prior particles gradually elongated along the rolling direction and evolved into banded-shape with the increase of rolling reduction. The grains with random orientation distribution gradually evolved into preferred orientation distribution, and the grain size gradually decreased. When the rolling reduction increases from 0 to 80%, the relative density, ultimate tensile strength and Vickers hardness increase from 98.03%, 244.37 MPa and 55.95HV to 98.5%, 296.56 MPa and 66.89HV, respectively, while the elongation decreases from 22.97% to 12.22%. A strong basal texture with (0001) basal plane parallel to the rolling surface was mainly formed in the alloy after hot-rolling. The improvement of mechanical properties of the alloy after hot-rolling was mainly due to the increase of microstructure compactness and fine grain strengthening. When the rolling reduction was small, the deformation was mainly dominated by slip and twinning; while when the rolling reduction was large, the deformation was mainly dominated by slip and dynamic recrystallization.

Pitting Corrosion Behavior and Surface Microstructure of Copper Strips When Rolled with Oil-in-Water Emulsions.

Copper strips experience severe corrosion when rolled with an oil-in-water (O/W) emulsions lubricant. The effects of rolling reduction on the pitting corrosion behavior and surface microstructure of Cu strips were studied in detail using electrochemical measurements and electron back scattered diffraction (EBSD) analysis. It was found that the corrosion current densities of the rolled Cu strips increased with accumulated reduction, which also lowered the pitting potentials and weakened their corrosion resistances. Therefore, the corrosive tendency of Cu strips under different rolling reductions (ε) followed the order of ε0% < ε20.7% < ε50.6% < ε77.3%. The Cu surface easily reacted with chlorine, sulfur, and carbon components from O/W emulsions to generate pitting corrosion. Under the interactive effect of pitting corrosion and stress corrosion, pits expanded along the rolling direction. The aggregation of anions in surface defects, such as dislocations, metastable pits, and microcracks, further accelerated the pitting corrosion of the surface.

Effect of rolling reduction on microstructure, texture and magnetic properties of twin-roll casting non-oriented 6.5 wt% Si electrical steel

In this study, an as-cast strip of non-oriented 6.5 wt% Si electrical steel with an equiaxed structure was fabricated by twin-roll strip casting and then treated by hot and warm rolling with different reductions, and annealing. The results showed that the as-cast microstructure was gradually pancaked and then underwent dynamic and static recrystallization as the hot rolling reduction exceeded 52%. The subsequent warm rolling brought about shear bands in part of the deformed grains. The texture evolution in the multiple rolling routes basically conformed to the classical gain-orientation rotating paths. The {001}∼{118} 〈110〉, {223} 〈110〉 and {111} 〈110〉 texture components were intensified after warm rolling. A decreased hot rolling reduction accompanied by an increased warm rolling reduction raised the number of shear bands in the warm rolled sheets and decreased the annealing grain size. An improper combination of hot and warm rolling reductions tended to make the γ nuclei gain the superiority in number through grain-boundary or shear-band nucleation, leading to the prevalence of the γ annealing texture. By comparison, an alternative rolling regime adopting moderate hot (∼50%) and warm rolling (∼70%) reductions promoted the oriented nucleation of λ, {114} 〈48¯1〉 and many other non-γ nuclei in shear bands of the {223} 〈110〉 deformed grains which had already acquired a high volume fraction in the warm rolled sheet. Consequently, mixed λ, α* and γ annealing textures were formed, giving rise to enhanced magnetic properties. The combined oriented nucleation and oriented growth mechanism was responsible for the overall evolutions of the annealing textures.

Effect of rolling reduction and heat treatment on the microstructure and mechanical properties of Al1060/Al6061-0.5SiC/Al1060 laminates

Sandwich type Al1060/Al6061-0.5SiC/Al1060 laminates were fabricated by hot roll bonding and then subjected to heat treatment. The microstructure, texture and mechanical properties of the laminates were investigated. The inhomogeneity of microstructure throughout the thickness of 1060 Al layer was present in the as-rolled laminates. After heat treatment, the Al6061-0.5SiC composite layer was in a partially recrystallized condition. Some grains were subdivided by low-angle grain boundaries (LAGBs), and the fraction of LAGBs increased with increasing rolling reduction. The amount of Mg2Si precipitates increased with increasing rolling reduction. The Al6061-0.5SiC composite was characterized by the α fiber and β fiber after hot rolling. After heat treatment, the texture in Al6061-0.5SiC composite was dominated by Goss and R component. The tensile strength of the as-rolled laminates increased with increasing rolling reduction, while the elongation first increased and then decreased. The heat treatment could effectively improve the tensile properties of the Al1060/Al6061-0.5SiC/Al1060 laminates.

Effects of rolling reduction on microstructural evolution and mechanical properties of W-0.5wt%ZrC alloys

The effects of hot rolling reduction on microstructures and mechanical properties of W-0.5 wt%ZrC (WZC) materials were investigated. Four WZC specimens with rolling reductions of 46%, 69%, 77%, and 96% were prepared by multi-step rolling processes. Metallographic observation, SEM, EBSD, and TEM characterization were conducted to obtain information on the microstructures of the materials. The metallography and EBSD results indicate that W grains were refined to 0.4–0.5 μm in the 96%-rolled WZC01 specimen. In addition, Vickers microhardness measurements at room temperature (RT) and tensile tests at various temperatures from RT to 500 °C were conducted. The results indicate that hardness and strength increase with the increase in rolling reduction. The 96%-rolled 1-mm thick WZC plate exhibits an ultra-high tensile strength of 1450 MPa at 100 °C. The 77%-rolled 6-mm thick WZC bulk material demonstrates both high tensile strength with an ultimate tensile strength of 620 MPa and good ductility with a tensile elongation of 21% at 400 °C, which are superior to those of most reported bulk W materials. The relationships between microstructure, mechanical properties, and rolling reduction were investigated and discussed systematically.

Investigation of austenite decomposition behavior and relationship to mechanical properties in continuously cooled medium-Mn steel

The austenite decomposition behavior in medium-Mn steel was investigated here by combining thermo-mechanical controlled processing (TMCP) and continuous cooling processes. Microstructures were characterized by means of optical microscopy, electron probe micro analyzer, scanning electron microscopy, electron backscattered diffraction, and transmission electron microscopy. Furthermore, the effect of rolling reduction and cooling path on microstructural evolution and mechanical properties were studied. The results indicated that the austenite region was expanded by manganese, and the ferrite, pearlite, and bainite were not nucleated before martensite transformation even when the cooling rate was decreased to 0.07 °C/min. The approach to tailor yield ratio without compromising tensile strength depends on the control of martensite lath morphology and internal dislocation density. The resistance of lattice to shear transformation increases with the increasing strain hardening of prior austenite, which leads to decrease martensite-start (Ms) temperature. The martensite formed at lower transformation temperatures exhibited relatively high dislocation density and refined laths, resulting in high work-hardening capacity during the early stage of plastic deformation. The crack propagation can be effectively deviated or even terminated by high angle grain boundaries (HAGBs) and the nonparallel structures of martensite packets. These studies on the kinetics and thermodynamics of martensitic transformation confirmed the viability of processing continuously cooled medium-Mn steel in the hot rolling production line.

Effects of rolling reduction on Burgers orientation relationship and slip behavior of a Ti–5.5Mo–7.2Al–4.5Zr–2.6Sn–2.1Cr alloy

The important but highly complex α/β Burgers orientation relationship and slip behavior of a Ti–5.5Mo–7.2Al–4.5Zr–2.6Sn–2.1Cr titanium alloy plate were obtained and elaborated, which was subjected to hot rolling with 20%, 40%, and 60% reductions in thickness. The electron backscatter diffraction statistical results showed that the Burgers orientation relationship was strictly maintained in the initial microstructure and exhibited a slight deviation of ∼10° at 20% reduction. With the thickness reduction increasing to 40% and 60%, this classical relation between α- and β-Ti will be gradually broken. Furthermore, the low-angle grain boundaries fractions of the β phase were 94.95% and 92.77% at 20% and 40% reductions, respectively, indicating that the β phase had a significant contribution to the overall plastic deformation. For the α phase, the relative frequencies of the <112¯0>{0001}α and <112¯0>{101¯0}α slip systems were 32.81% and 44.43% at 20% reduction, respectively. Noticeably, under the applied loading of normal direction, the <112¯0>{0001}α slip system became more pronounced at 60% reduction (i.e., 59.01%) and, hence promoted a considerable strain partitioning in the α phase. In terms of typical α grains, an obvious intragranular misorientation diversity at 60% reduction was further traced, thereby reasonably leading to the Schmid factor gradient within grain interior and the breakdown of Burgers orientation relationship.

Effect of rolling reduction and annealing process on microstructure and corrosion behavior of LZ91 alloy sheet

Abstract The effect of rolling reduction and annealing process on the microstructure and corrosion behavior of Mg−9Li−1Zn (LZ91) alloy was investigated. The test alloy sheets were cold rolled with the reduction of 50% and 75%, respectively, and then were annealed at 200 °C for 1 h. The microstructure of test alloys was observed by OM and SEM while the phase composition was determined by XRD. The corrosion property was evaluated by electrochemical measurements and immersion tests. The results show that LZ91 alloy sheet consists of α-Mg, β-Li and precipitated Mg−Li−Zn compounds (MgLi2Zn and MgLiZn phases). Dynamic recrystallization grains appear in β-Li phase during annealing process, leading to grain refinement. The results indicate that the increasing rolling reduction and performing the annealing process can enhance the corrosion resistance of LZ91 alloy. The 75% cold-rolled and annealed LZ91 alloy shows the best corrosion resistance.

Preparation, microstructure and mechanical properties of CP-Ti/AA6061-Al laminated composites by differential temperature rolling with induction heating

In this research, a new, innovative method of differential temperature rolling with induction heating was proposed to prepare CP-Ti/AA6061-Al laminated composites in an argon protective atmosphere. The homogeneous deformation of titanium and aluminium was obtained, and the effect of rolling reduction on the mechanical properties and microstructure of the laminated composites was investigated in detail. The results showed that the interfacial bonding strength gradually increased with the rolling reduction, which was attributed to the increased mechanical meshing area and the wider element diffusion layer, leading to the microstructure of shear surface changing from brittle fracture to ductile fracture. When the rolling reduction was 50.5%, the shear strength of the Ti/Al clad plates reached a peak value of 122 MPa, close to the shear strength of the aluminium matrix (131 MPa). Ti/Al composites could improve the ultimate tensile strength of a single aluminium sheet. After tensile failure, the interfacial delamination length decreased from 7.64 mm to 0.22 mm with the reduction ranging from 17.5% to 50.5%, indicating that the strong interface could effectively impede the expansion of the interfacial delamination cracks, resulting in the improved resistance to delamination of composites. In summary, through the unique form of assembly and heating, the Ti/Al laminated composites achieved satisfactory microstructure and mechanical properties.

Threshold Deformation and Mechanical Properties of Al/Al Laminated-Metal Material with Inner Grooves Fabricated by Hot Rolling

1100 Al/1100 Al laminated-metal material with inner grooves (LMWGs) were fabricated by hot roll bonding. Threshold deformation (the minimum rolling reduction in a single rolling pass that is required for metal bonding) and the mechanical properties of hot-roll-bonded LMWG and cold-roll-bonded LMWG were investigated and compared. The effects of rolling temperature and rolling reduction on the bond strength of the hot-roll-bonded LMWG were also studied. It was observed that the threshold deformation of the hot-roll-bonded LMWG decreased with increasing rolling temperature from 300 to 450 °C. However, the threshold deformations of the LMWGs rolled at 400-450 °C were smaller than those of the LMWGs rolled at room temperature, while the latter were smaller than those of the LMWGs rolled at 300-350 °C. The bond strength, ultimate tensile strength, and yield strength of the hot-roll-bonded LMWG increased with increasing rolling temperature from 300 to 450 °C. The effects of the rolling reduction were slight. When the rolling temperature and rolling reduction were 450 °C and 55%, respectively, the average bond strength reached a maximum value of 89.42 MPa.

Effect of rolling reduction on antiphase domains, grain boundary character distribution and plastic deformation of Fe-6.5 wt%Si alloy

The variation in plastic deformation of Fe-6.5 wt%Si alloy depends on antiphase domains and grain boundary character distribution. With the increase of rolling reductions from 50% to 85%, the increment of dislocation density causes decline of the sizes of antiphase domains, meanwhile the sharp and homogeneous distribution of γ-fiber texture is prone to obtaining a large fraction of CSL boundaries, thus the fracture deflection of 65% warm-rolled sheet is increased to 8.6 mm by 38.7% in comparison to that of 50% warm-rolled sheet (6.2 mm), and that of 85% warm-rolled sheet has nearly three times increment (18.2 mm).

Effects of Hot-rolling Reduction on Microstructure and Mechanical Properties of GNPs/Ti Composites

Graphene nanoplatelets (GNPs)/Ti composites were fabricated by spark plasma sintering (SPS) and hot-rolling. This work was focused on the effects of rolling reduction on microstructure and mechanical properties of GNPs/Ti composites. The SEM microstructure results show that matrix grains are gradually elongated and the amount of GNPs along the rolling direction rises with the increase of rolling reduction. The tensile test results indicate that the ultimate tensile strength and fracture elongation of the GNPs/Ti composites increase with the increase of rolling reduction. The ultimate tensile strength of the composites at 60% rolling reduction is 680 MPa, which is increased by 33% compared with pure Ti. Hot-rolling process can relieve defects and lead to GNPs aligned along the rolling direction, which improves the tensile property.

Optimum rolling speed and relevant temperature- and reduction-dependent interfacial friction behavior during the break-down rolling of AZ31B alloy

The present study aimed to determine the optimum rolling speed for break-down rolling of as-cast AZ31B alloy and investigated the friction behavior associated with temperature- and reduction-sensitivity at the roll/plate contact interface. Tensile testing, formability evaluation and microstructural studies relevant to different rolling speeds were performed and finally the optimum operating rolling speed (50.0±0.8m/min) was obtained. Further, the effects of rolling reduction and initial temperature were assessed on the temperature variation, lateral spread and interfacial friction behavior at optimum rolling speed. The results showed that lower rolling speed (18.0±0.8m/min) resulted in an incompletely recrystallized structure where twins occupied relatively high volume fraction. Twinning dominated the deformation at rolling speed exceeding the optimum, resulting in the local recrystallization with shear bands and coarse grains. Rolling at 50.0±0.8m/min could get the best overall tensile properties and rolling formability due to the relatively high recrystallization degree and microstructure uniformity. An inverse method has been developed to determine the interfacial friction coefficient during interaction of AZ31B alloy with roll surfaces. When rolling at the optimum speed, the interfacial friction coefficient ranged from 0.16 to 0.58, which was strongly positively correlated with the reduction but slightly positively correlated with the initial temperature. Depended on the rolling characteristics, external friction effect coefficient ranged from 1.25 to 2.35 and it exhibited positive correlation with both the initial rolling temperature and rolling reduction.