High Temperature Rolling Research Articles

Influence of surface state on interface bonding strength of Al/Ta laminated composite via differential temperature rolling

Al/Ta laminated composite is one of the promising space radiation shielding materials. However, due to significant differences in the properties of Al and Ta alloys, the interface bonding strength of rolled Al/Ta laminated composites is weak. In this study, we prepared 2A12 Al/Ta-2.5W laminated composite using differential temperature rolling method. The influence of surface state on the interface microstructure and interface bonding strength were systematically analyzed, and the interface bonding mechanism of Al/Ta laminated composite was revealed. It is found that 2A12 Al and Ta-2.5W alloys are successfully bonded via differential temperature rolling within rolling temperature range of 350∼450 °C and rolling reduction range of 40 %–50 % when the hardening degree of Ta-2.5W surface layer exceeds 25 %, and the roughness of Ta-2.5W and 2A12 Al surface is greater than 4.5 μm and 3.6 μm, respectively. It is demonstrated that increasing the hardening degree and roughness at Ta-2.5W surface, while decreasing the hardening degree and increasing roughness at 2A12 Al surface can facilitate cracking of the surface layer at Ta-2.5W side and the embedding of virgin Al metal into the cracks during rolling, which can promote the interface bonding process between 2A12 Al and Ta-2.5W alloys. The highest interfacial bonding strength of Al/Ta laminated composite can reach 41.2 MPa. However, when the surface layer at Ta-2.5W side is excessively hardened and the hardness reaches two times of the substrate, thick fragments could be generated at the interface, which have detrimental effect on the interface bonding strength and the value decreases to 23.05 MPa. In terms of the effects of rolling temperature and rolling reduction, it is found that the oxide film and hardening layer on the Ta-2.5W surface are more sufficiently ruptured, and more virgin 2A12 Al metals are embedded in the cracks at the surface of Ta-2.5W at higher rolling temperature and higher rolling reduction conditions, thereby leading to the increased interface bonding strength. This study provides theoretical basis for the preparation of Al/Ta laminated composites and sheds light on the relationship between surface state and interface bonding strength of laminated metal composites.

On the influence of austenite content in orientation selectivity and shear texture evolution during hot rolling of Fe-3 wt% Si grain-oriented electrical steel

A systematic investigation of the development of shear textures during hot rolling of Fe – 3 wt% Si steel has been carried out in the present work with a special focus on the influence of austenite in preferential orientation selectivity. This orientation selectivity was anticipated owing to the fact that texture evolution during thermomechanical processing is entirely an effect of crystallographic rotations and such rotations may experience constraining effects because of surrounding austenite. The influence of austenite on shear texture evolution was studied over a range of finish rolling temperatures (FRTs). The evolution of microstructure and microtexture within the surface-subsurface zone was studied adopting EBSD. Sharp Goss orientation was observed at lower FRT, while texture intensities of Brass and Copper were observed to be high at higher FRT. Additionally, it was inferred that in the surface-subsurface zone, next to the austenite, the ease of rotation about ND contributed to the higher observed frequency of the Brass orientation despite of its overall lesser fraction as compared to Copper orientation. The less observed frequency of Copper orientation near the austenite has been attributed to the resistance offered by the austenite to its adjacent ferrite grains while rotating about TD. This constraining effect of austenite has been shown to be consistent over the entire range of studied FRTs. Moreover, it has been shown that at higher rolling temperatures, the lower constraining effect by austenite paves the way for Goss orientation formation, which acts as the precursor to the formation of Brass at the FRT.

Microstructure evolution during high temperature rolling and effect on the mechanical properties of TiBw/Ti65 composites with network structure

In this paper, the rolled TiB whisker (TiBw)/Ti65 composites with different rolling reductions were obtained by high temperature (HT) rolling in the β single-phase region. The changes in TiBw, silicide and grain size after rolling deformation were analyzed by microstructure characterization. Based on this, the strengthening mechanism and HT deformation behavior of rolled composites were analyzed in combination with room temperature and HT tensile experiments. The results show that TiBw fractured after rolling deformation, leading to a decrease in the aspect ratio and an increase in matrix connectivity. Silicide with an average diameter of 80 nm appeared in the rolled composites. The grain was continuously refined as the rolling reduction increased. A T-type texture with the crystal C-axis parallel to the transverse direction appeared at 40% rolling reduction. The strength and plasticity of sintered TiBw/Ti65 composites were increased after rolling. With an increase of rolling reduction, the composites exhibited fine-grain strengthening below 650 °C. When tensile above 700 °C, a softening effect occurred with the decrease of grain size, that is, the yield strength decreased for grain size <3.6 μm. The strengthening mechanisms of rolled TiBw/Ti65 composites include fine grain strengthening, load transfer strengthening of TiBw, Orowan strengthening of silicide, and dislocation density strengthening. Among them, fine grain strengthening and load transfer strengthening predominated and increased as the rolling reduction increased. After tensile at 750 °C, many recrystallized grains with large misorientation appeared around the initial coarse grains and TiBw.

Hot Rolling on Microstructure and Properties of NbHfTiVC0.1 Refractory High-Entropy Alloy

NbHfTiVC0.1 refractory high-entropy alloy (RHEA) exhibits excellent comprehensive mechanical properties and demonstrates great potential for applications. However, the mechanical properties need to be improved further. In this work, hot rolling on NbHfTiVC0.1 RHEA at temperatures of 650 °C, 850 °C, and 1050 °C, with total reductions of up to 30%, 50%, 70%, and 80%, was conducted. The microstructure and mechanical property evolution of the samples were further investigated. The hot-rolled samples at 650 °C and 850 °C exhibit a composition consisting of BCC, carbide, and Laves phases, whereas the samples rolled at 1050 °C only consist of BCC and carbide phases. The 650-80 sample displays the highest ultimate tensile strength (1354 MPa), and the 1050-80 sample demonstrates the highest elongation (16%). The highest strength observed in the 650 °C-80% sample can be attributed to the presence of fractured and refined carbides, fine-grains, and the hindrance of dislocation slip by the fine Laves phase. At a higher rolling temperature (1050 °C), the Laves phase disappears, resulting in a reduction in strength but an increase in plasticity. Furthermore, the dislocation slipping mechanism within the BCC matrix also contributes positively to plastic deformation, leading to a notable increase in ductility for the 1050 °C-80% sample. These research findings provide valuable insights into enhancing the strength and ductility simultaneously of NbHfTiVC0.1 RHEA through hot rolling.

Analysis of the mechanism of orientations evolution during hot rolling and mechanical properties of TiBw/TA15 composites based on crystal plasticity finite element model

An in-depth understanding of the crystal orientation evolution during hot rolling of TiB whisker (TiBw) /TA15 composites and the anisotropy of the as-rolled plates can help fully utilize the material properties. In this paper, the crystal plasticity finite element models of high-temperature (HT) β-phase and room-temperature (RT) α-phase were constructed from electron backscattering diffraction data. Based on this, the orientation evolution during hot rolling in the single-phase region and the effects of the matrix texture on the mechanical properties of the as-rolled plates were analyzed. The effect of TiBw on the anisotropy was studied by the composites finite element model. Results showed that the α-fiber texture of the β-phase was formed during HT rolling. This texture was converted to the T-texture of the α-phase at RT during cooling according to the Burgers orientation relationships. The TiBw had little effect on the matrix texture composition. The TiBw and matrix texture caused the matrix to have higher strength along the rolling direction and the transverse direction, respectively. The matrix texture dominated the difference in mechanical properties because its effect exceeded that of TiBw. The effect of the matrix on the mechanical properties was caused by the Schmid factors (SFs) and the critical resolved shear stress (CRSS) of the slip system together. The slip mode was influenced by SFs determined by the angular relationship between the crystal orientation and the loading direction. The CRSS of the activated slip system determined the yield strength.

The microstructure evolution and the effect of grain size, temperature, and TiBw on the deformation mechanism of TiBw/TA15 composites during high temperature deformation

In this paper, the deformation mechanism and microstructure evolution of TiB whisker (TiBw)/TA15 composites during high temperature (HT) rolling and tensile were investigated. The effects of grain size and temperature on the HT mechanical properties, deformation mechanism, and strengthening/softening effects were studied. The influence of temperature on the TiBw fracture mode was analyzed within the range of 600–750 °C. The results show that grain boundary slip (GBS) and dislocation motion were more prone to promote the occurrence of discontinuous dynamic recrystallization (DRX) and continuous DRX, respectively. TiBw could withstand higher forces and fractured when the orientation was consistent with the loading direction and at a lower temperature, while it was easier to debond with temperature increasing. TiBw/TA15 composites had Hall-Petch (H–P) and inverse H–P (I–H–P) regions in the range of 4.5–7.0 μm with a critical grain size of 5.8 μm under HT tensile at 600 °C and 0.001 s−1. The grain boundary strength decreased with the temperature increased, which caused the transformation of the deformation mechanism and the H–P/I–H–P regions at different temperatures. The deformation was dominated by GBS when the strength of grain boundary was lower than that of intracrystalline. The deformation mechanism transformation temperature of TiBw/TA15 composites was 700 °C under HT deformation at 0.001 s−1.

Deformation behavior of high-chromium cast iron / low-carbon steel laminates based on hot rolling and finite element simulation

In this study, the hot deformation behavior of high-chromium cast iron (HCCI)/low-carbon steel laminates during hot rolling was studied via finite element simulation and experimentation. The effects of different rolling processes, including rolling reduction (30%, 45%, and 60%), rolling temperature (1000, 1100, and 1200 °C), and rolling speed (0.17, 0.26, and 0.34 r/s), on the forming quality of laminates were discussed. Results show that the shape of the laminates is straight without warping and grid distortion. The middle layer of the low-carbon steel plays a role in stress release. In terms of mechanics, large rolling reduction (60%), high rolling temperature (1200 °C), and low rolling speed (0.17 r/s) are favorable for increasing the interface stress and stress release time. This promotes interface recombination, reduces damage to the brittle HCCI layer, and effectively improves the bending and impact strengths of the laminates. In terms of microstructure, increasing the atomic active energy and diffusion time is beneficial to the formation of the microinterface morphology with high bonding quality and refinement of the HCCI carbide.

Effect of Alkylation Chain Length on Inhibiting Performance of Soluble Ionic Liquids in Water-Based Drilling Fluids.

This work investigated the effect of the alkyl chain length of soluble methylimidazolium bromide ionic liquids (ILs) on their inhibition performance. The IL with a shorter alkyl chain length showed superior inhibition performance by suppressing clay swelling, mitigating clay dispersion, at room temperature. Particularly, the IL with an alkyl chain length of two (EmBr) reduced the sodium bentonite (Na-BT) swelling degree to 89% and achieved a cutting recovery of 81.9% after being rolled at room temperature, performing the best among all ILs. To systematically analyze the inhibition mechanism of ILs, X-ray diffraction (XRD), ζ potential, and particle size distribution have been carried out. The results revealed that the methylimidazolium with shorter alkyl chain length had better ability to enter the interlayer void by ion exchange and decrease interlayer distance, suppress the electrical double layer of the Na-BT particles and decrease the ζ potential, and promote the aggregation of Na-BT in water. It is also observed that high hot rolling temperature reduced the shale inhibiting performance of all ILs, and ILs with longer alkyl chain length had better ability to prevent cutting disintegration at high temperature. It is attributed to the variation of the hydrophilic characteristic of Na-BT at high temperature where EmBr no longer adsorbed the most on the surface and entered the interlayer voids of Na-BT. This study can be used as a reference to systematically explore the effect of the structure of shale inhibitors on their inhibiting performance and develop effective shale inhibitors.

底面集合組織の形成を抑制したAZ31Bマグネシウム合金板材の室温深絞り成形性に及ぼすプロセス因子の影響

The effects of process parameters on room-temperature (RT) deep drawability were investigated for AZ31B magnesium alloy sheets, in which the formation of basal texture was suppressed by high-temperature rolling. When the blank holder force was set to the minimum value to prevent wrinkling, high RT drawability was obtained. In particular, a significantly high limiting drawing ratio (LDR) of 1.83 was obtained by the optimization of the process parameters of the servo-press machine. At higher punch speeds, the drawability tended to be deteriorated; however, a high LDR of 1.72 was obtained even at a high punch speed of 50mm/s by the optimization of the process parameters of the servo-press machine. Furthermore, when the punch speed in the initial stage of deep drawing was reduced, it was possible to perform deep drawing without fracture even if the punch speed in the later stages was increased. The results of the study of the effect of lubricants indicated that relatively high RT drawability was obtained when molybdenum disulfide was utilized. It was also suggested to be important to select a lubricant that reduces punch load and does not delaminate during deep drawing.

Unraveling the effects of hot rolling on microstructure and mechanical properties of cold sprayed Mg/Al clad plates

In this work, the evolution of microstructure and mechanical properties of the cold sprayed Mg/Al clad plates were examined in detail in relation to various combinations of rolling parameters. For this purpose, three different rolling temperatures (350, 400, and 450 °C) and rolling reduction ratios (10%, 20%, and 30%) were applied to the As-Sprayed samples. The macroscopic morphology, interfacial microstructure, tensile strength, and shear bond strength (SBS) of the samples were investigated in detail. Results reveal that the ultimate tensile strength (UTS) of the samples is positively related to the rolling temperature and reduction ratio. However, high rolling temperature facilitates the formation of thick intermetallic compounds (IMCs) layer, which is harmful to the SBS. In addition, a high rolling reduction ratio promotes edge cracking in clad plates. Finally, the optimized rolling parameters (400 °C and 30%) are pinpointed, which result in the best combination of macroscopic morphology, interfacial microstructure, and mechanical properties (UTS: 392.7 ± 3.3 MPa; EL: 4.5 ± 0.1%; SBS: 91.7 ± 6.3 MPa) for the clad plate.

Twinning-mediated texture weakening in a basal-textured Mg-6Al-1Zn (mass%) alloy sheet by a novel cold-sample rolling method

In this paper, we report the use of cold-sample rolling (CSR) processing, which induced a high fraction of double twins and a substantial texture-weakening effect in an Al-concentrated commercial Mg-6Al-1Zn (mass%) alloy sheet. A CSR-processed and subsequently annealed sheet showed a weak basal texture with a broad distribution of the (0001) poles toward the rolling and transverse directions. This led to moderate stretch formability with a limiting dome height of 5.5 mm. High-temperature rolling (HTR) processing has been reported to weaken the basal texture in Mg-Al-based alloy sheets because of the activation of non-basal <c+a> dislocations, resulting in texture weakening. However, the processing induced a relatively low fraction of double twins. Consequently, CSR processing led to a relatively high texture-weakening effect. The results showed that twinning-mediated static recrystallization is essential for texture weakening in Al-concentrated Mg-alloy sheets.

Influential mechanisms on interface bonding of hot-rolled TB9/TC4 laminated composites

To promote the application of laminated composites with high strength and plasticity in armor field, the feature of interface bonding and the influential mechanisms accounting for the interface quality need clarification. In this work, laminated composites of high-strength TB9 and good-toughness TC4 were successfully manufactured by high temperature rolling with different thickness reduction. Microstructural observations indicate that the plastic deformation and recrystallization at the edge position of the laminated composites are greater than that at the center position. By contrast, the center position of the composites has better bonding quality than the edge position. Besides, holes are detected at the interfaces when the reduction is low. With the reduction increased, the interface bonding is improved and the positional quality difference of the interfaces is reduced. The shear and tensile tests show higher bonding strength and tensile strength with larger rolling reduction. LS-DYNA finite element simulation is performed to study the formation mechanism of the holes and the influential mechanisms on the positional difference in interface bonding quality of the laminated composites. A parameter δ considering the relative strain of the TB9 and TC4 is introduced to quantitatively evaluate the deformation coordination. When the reduction was 70%, the δ is the smallest with the largest bonding strength up to 676 MPa at the center position.

Microstructure evolution of three-roll skew-rolling formed hollow axles with uniform wall thickness

The uniform thickness hollow axle is one of the lightest weight axles in the high-speed rail industry. It can effectively reduce unsprung mass and further improve the train speed. Therefore, due to its importance and significance, it is crucial to research and develop the uniform thickness hollow axle. To understand the microstructural evolution during three-roll skew-rolling (TRSR) forming, 30CrMoA alloy steel was used in this study. A constitutive model of 30CrMoA was established by SIMUFACT FORMING finite element software and utilized to simulate the deformation, heat transfer, and microstructure coupling during TRSR. Via analyzing the influence of process parameters on the average grain size, the microstructural evolution of the forming part at each deformation stage is revealed. The result shows that the dynamic recrystallization of the rolled piece produces a fine and uniform grain structure during the forming process. The refinement level is enhanced with the increase of the radial compression; the grain size is gradually increased from the outer surface to the inner surface of the rolled piece. At a higher rolling temperature, it was found the initial grain size and final average grain size were larger compared to the lower temperature. By increasing the axial traction speed, not only can the rolling time be shortened, but also the appearance of coarse grains can be avoided. Therefore, the mechanical properties can be improved.

Microstructure Evolution of Graphene and the Corresponding Effect on the Mechanical/Electrical Properties of Graphene/Cu Composite during Rolling Treatment.

Rolling enables the directional alignment of the reinforcements in graphene/Cu composites while achieving uniform graphene dispersion and matrix grain refinement. This is expected to achieve a breakthrough in composite performance. In this paper, the process parameters of rolling are investigated, and the defects, thickness variations of graphene and property changes of the composite under different parameters are analyzed. High-temperature rolling is beneficial to avoid the damage of graphene during rolling, and the prepared composites have higher electrical conductivity. The properties of graphene were investigated. Low-temperature rolling is more favorable to the thinning and dispersion of graphene; meanwhile, the relative density of the composites is higher in the low-temperature rolling process. With the increase of rolling deformation, the graphene defects slightly increased and the number of layers decreased. In this paper, the defect states of graphene and the electrical conductivity with different rolling parameters is comprehensively investigated to provide a reference for the rolling process of graphene/copper composites with different demands.

Strength-ductility synergy in Mg98.3Y1.3Ni0.4 alloy processed by high temperature homogenization and rolling

A new Mg98.3Y1.3Ni0.4 alloy containing long period stacking ordered (LPSO) phases with good strength-ductility synergy was prepared by high temperature homogenization and rolling, which possesses a high ultimate tensile strength of 320 MPa and elongation of 17.0% and low work hardening rate during tensile deformation. Bulk LPSO phases with lamellar morphology exist in original grains after homogenization. Refined grains, broken LPSO phases and high-density geometrically necessary dislocations provide a good strength for as-rolled alloy with the strength increment of 146.3 MPa, 51.7 MPa and 68.3 MPa, respectively. Good ductility and low work hardening rate are attributed to weak basal texture, activation of non-basal slips with high Schmid factors and annihilation of high-density dislocations. In situ tensile testing result shows deformation coordination by non-basal slips, deformation twinning, grain rotation and absorption of plastic deformation energy by LPSO phases, which suggests a good ductility as well.

Thermomechanical Simulation of Ferritic Rolling of Titanium-Niobium Interstitial-Free Steel

Abstract Austenitic or two-phase rolling of ultra-low carbon steels face temperature control issues and generate shape defects. Ferritic rolling has been developed as a solution, and ferritic hot-rolled sheets are used as final products, replacing hot-rolled followed by cold-rolled sheets. However, it is not in regular industrial production because of mill limitations. Hence, ferritic hot rolling must be optimized for developing a ferritic cold-rolled and close-annealed sheet through subsequent processing. In this work, industrial ferritic rolling process was simulated for a titanium-niobium interstitial-free steel using a thermomechanical simulator. Multi-hit plane strain compression tests were carried out at three different regimes below the lower transformation temperature (Ar1). Steels were processed under high strain and strain rates as experienced during industrial hot rolling operation, and the results were compared with the conventional austenitic rolling. The flow stress of the material in the ferritic regime decreased with decreasing deformation temperatures but increased at temperatures below 700°C. Nonuniformity in grains and texture also increased with decreasing temperatures. High-temperature rolling in ferritic condition close to Ar1 temperature does not differ significantly from the austenitic condition, whereas the low-temperature ferritic rolled material had through-thickness microstructural nonuniformity and unwanted goss and brass fibers. The intensity of gamma-fiber {111} || normal direction (ND) required for formability was highest in the intermediate temperature zone. Deformation between temperatures of 850°C and 800°C was found to be ideal. Based on simulation studies, full-scale plant rolling was carried out under the optimized ferritic regime. The microstructure and texture matched closely with the simulation results. This work provides a working window for ferrite rolling in an industrial hot strip mill for developing ferritic cold-rolled close-annealed products.

Effect of High-Temperature Rolling and Annealing on the Structure and Properties of a Zirconium Based Amorphous Alloy

Effect of High-Temperature Rolling and Annealing on the Structure and Properties of a Zirconium Based Amorphous Alloy

Effect of finish rolling temperature on microstructures and mechanical properties of 1000 MPa grade tempered steel plate for hydropower station

With the decreasing of finish rolling temperature, the microstructure of the hot rolled steel was changed from lath martensite to complex microstructures composed of lath martensite, ferrite, granular bainite and lath bainite, unrecrystallized prior austenite grains are the main reason for the formation of complex microstructures. After tempering, the steels are mainly composed of ferrite and cementite. For the steel with high finish rolling temperature, the proportion of high misorientation boundary is less, and it has rod-like precipitates with the length of 25−85 nm and punctate precipitates with the size of 4−16 nm, the intensities of {111}<110> and {001}<110> textures are enhanced. The experimental steel has the best combination with strength and toughness as yield strength of 996 MPa, tensile strength of 1023 MPa, total elongation of 19.1 %, impact value at -60 ℃ of 125 J. Grain refinement, higher density of dislocation, fine and dispersed precipitates could enhance the yield strength and tensile strength. Stronger intensity of {332}<113> texture and weaker intensity of {001}<110> texture could improve the impact toughness.

The Role of Recrystallization and Local Misorientation on the Biodegradation Behavior of Mg

Most biomedical implants are predominantly Mg-based because of their degradable properties. The effect of recrystallization and local misorientation induced by various rolling parameters on the biodegradation of pure Mg has been systematically studied. The results reveal that an increase in recrystallization fraction and a reduction in local misorientation of grains as the rolling temperature increased was beneficial to the degradation rate of pure Mg. There is basal texture variation arising from the occurrence of high twinning activity at a lower rolling temperature which suppresses the maximum texture intensity and also increases the degradation rate. This result also reveals that grain growth was beneficial to the degradation rate of Mg, as larger grain size give a lower degradation rate. The degradation rate generally increased with decreasing rolling temperature (i.e., 350°C < 250°C < 100°C), indicating that the higher rolling temperature was beneficial to the degradation rate. This work is expected to give a better insight into the rolling process optimization of pure Mg to improve its degradation rate for biomedical applications.

Development of a high-strength Mg–11Gd–2Ag (wt%) alloy sheet with extra-low anisotropy

A high-performance Mg–11Gd–2Ag (wt%) alloy sheet was prepared via a procedure of high-temperature rolling combined with aging. The sheet showed a tensile yield strength of 393 MPa, an ultimate tensile strength of 435 MPa, and an elongation of 5.2% along the rolling direction while possessing a near-isotropic mechanical response and a weak planar anisotropy. The grain refinement, the basal texture, the stabilized band-like structure boundaries, and the promoted precipitation of γ'' and β′ nanoplates synergistically enhanced the strength. Especially, the grain orientation with a-axis randomly distributed in the rolling plane gave rise to the extra-low anisotropy. The present work is contributing to developing high-performance Mg alloy sheets and the broadening of their application.