Increasing Rolling Temperature Research Articles

Effects of rolling at different temperatures and subsequent recovery annealing on the mechanical properties of a metastable carbon containing FeMnCoCr high-entropy alloy

Metallic materials or alloys consisting of single face-cubic centered (FCC) phases typically face difficulties in obtaining high strength without sacrificing ductility. The introduction of different crystalline defects via pre-straining and the activation of multiple deformation mechanisms have been shown to be effective in achieving superior strength–ductility synergy. In this work, we investigated the role of varying rolling conditions and subsequent annealing on the mechanical response in an established twinning- and transformation-induced plasticity dual phase high-entropy alloy (TWIP-TRIP-DP HEA). We found that all of the annealed samples exhibited similar nano-twinned structures. Furthermore, phase transformation from FCC γ to hexagonal close-packed (HCP) ε prevailed along the nano-twins under mechanical loading. With increasing rolling temperature, the phase stability of the matrix revealed a downward trend, resulting in a significant increase in TWIP/TRIP effects along with a prominent change in the deformation microstructure. Our study presented a simple and feasible strategy for manipulating mechanical performance by modulating the microstructural characteristics and associated deformation modes.

Modulation of microstructure and improvement in the mechanical properties of TiBw/Ti65 composites by rolling at different temperatures

The effect of rolling temperature on microstructure evolution and mechanical properties of as-sintered TiBw/Ti65 composites was systematically investigated. The results showed that at 900 °C (in the low α + β phase region), the matrix microstructure primarily exhibited a deformation structure. At 1000 °C (in the high α + β phase region), a bimodal structure was observed, and at 1100 °C (in the β phase region), a basket-weave structure emerged. Additionally, silicides precipitated at 900 °C were fine but grew and coarsened at 1000 °C, eventually dissolving almost completely into the matrix at 1100 °C. This behavior is attributed to the varying solubility of silicides in the α and β phases. With increasing rolling temperature, the dynamic recrystallization (DRX) mechanism within the TiBw/Ti65 composites transitioned from continuous dynamic recrystallization (CDRX) to discontinuous dynamic recrystallization (DDRX). Rolling significantly enhanced the mechanical properties of the composites. The HR-900 composite exhibited the optimal strength-plasticity combination at room temperature, achieving an ultimate tensile strength (UTS) of 1415 ± 21 MPa and elongation (EL) of 6.2 ± 2.7%, mainly due to grain refinement and work hardening. Conversely, the HR-1100 composite demonstrated superior high-temperature mechanical performance, showing improvements of 37.18%, 27.05%, and 9.59% at 963 MPa (650 °C), 789 MPa (700 °C), and 560 MPa (750 °C), respectively, compared to those of the as-sintered materials. The strengthening mechanisms were fine-grain strengthening, dislocation strengthening, and load transfer strengthening of the as-rolled composites, and the primary strengthening mechanism shifts from dislocation to fine-grain strengthening as the rolling temperature increases.

Microstructure evolution and mechanical properties of metastable austenitic medium Mn steel fabricated by warm caliber rolling

Warm caliber rolling at 550, 600, and 650 °C were carried out to refine the austenite grains of medium Mn steel by dynamic recrystallization (DRX). The effect of rolling temperature on the microstructure characteristics and mechanical properties of metastable austenitic steel was investigated in detail. The results show that the hierarchical structure of coarse fiber grains (CFGs) and ultrafine grains (UFGs) is obtained by warm caliber rolling method. With the increasing rolling temperature, more obvious DRX behavior occurs, resulting in a high percentage of UFGs. The preactive TRIP effect shortens the yield stress plateau in tensile stress-strain curves caused by CFGs with low stability. Furthermore, the unique hierarchical structure induces crack deflection and delamination, and significantly improves the impact toughness of medium Mn steel at room temperature. However, at the low temperature of −80 °C, CFGs are easy to induce martensite transformation, which seriously deteriorates the impact toughness.

Bioinspired fibrous microstructure breaks strength and toughness trade-off in plain carbon steel

Warm rolling at eight temperatures was conducted on two mixed ferrite-pearlite initial microstructures in order to develop strong but tough plain steel. The obtained wood-like fibrous microstructure in AISI 1045 plain steel breaks the strength and toughness trade-off dilemma. After rolling at 500 °C, the tensile strength reaches 1020 MPa, and the impact toughness is as high as 120 J. Intensive α-fiber (<110>//RD) and η-fiber (<100>//RD) textures, as well as necklace-like fine carbide, were developed in the fibrous microstructure. With increasing rolling temperature, the tensile strength and impact toughness decreased due to the reduced texture intensity and the increased carbide size. The high strength of fibrous steels is mainly originated from the dispersion and dislocation strengthening, while the impact toughness is controlled by the carbide size and the occurrence of delamination mechanism.

Enhancing strength and ductility of low-cost rare earth Mg-5Y-Ni alloy containing LPSO phase fabricated via multi-pass rolling based on dislocation regulation and grain refinement

A low-cost rare earth Mg-5Y-Ni alloy containing LPSO phase was fabricated via multi-pass rolling in this work, and strength and ductility were enhanced based on dislocation regulation and grain refinement at various rolling temperatures. The alloy was designed to contain about 9.6% lamellar 18R-LPSO phase after homogenization. All alloys were completely recrystallized after rolling, and the alloy rolled at 450 °C (450R) achieved the finest recrystallized grains with an average size of 3.97 μm. The {0002} basal texture intensity decreased and average Schmid factors of non-basal slips increase with increasing rolling temperature. 450R alloy exhibits the highest strength and that rolled at 500 °C (500R) exhibits the best strength-ductility synergy and work hardening capability. Accumulation of dislocations and stacking faults promotes uniform and complete recrystallization. Dislocation and grain refinement strengthening effects provide most strength increments. High-density dislocations promote dynamic recovery process during tensile deformation and results in a rapidly decrease in stage I and a low level in stage III of work hardening rates. Grain refinement induced by dislocation accumulation, dynamic recovery process promoted by high-density dislocations and high dislocation activity of non-basal slips improve the ductility. This work illustrates the feasibility of dislocation regulation to synergistically enhance the strength and ductility of Mg alloys.

Influence of warm rolling temperature on multi-scale lamellar structure and mechanical properties of medium carbon steel

Improving the synergy between strength and ductility of medium carbon steel, a multi-scale lamellar structure was developed via hot water quenching and warm rolling at different temperatures. The multi-scale lamellar structure is composed of banded proeutectoid ferrite phase, fine equiaxed ferrite and cementite. The average sizes of subgrains and grains of warm rolled samples at 550 °C is 0.53 μm and 2.3 μm, respectively. When the rolling temperature went up, the fraction of HAGBs increased while the fraction of LAGBs decreased. It is found that the dislocations gradually localized from uniformity with increasing rolling temperature. When the rolling temperature was 650 °C, an obvious substructure was formed, and a large proportion of cementite was spheroidized. The best combination of strength and uniform elongation was obtained by rolling at 550 °C with tensile strength of about 1.2 GPa. In-situ high-energy X-ray study showed that the loads of ferrites with different orientations were similar in the elastic stage, and the stress distribution after yield was significantly different. It is considered that LAGBs strengthening accounts for more than 35%. The strengthening mechanism was verified by in-situ high energy X-ray, and the accuracy of multiscale-LAGBs strengthening theory was verified.

Study on the microstructure, texture and mechanical properties of hot-rolled and T6-treated Al1060/Al6061-TiCp/Al1060 laminated composites

The Al1060/Al6061-TiCp/Al1060 laminated composites were successfully fabricated by combining powder metallurgy and hot rolling. A subsequent T6 treatment was employed to optimize the mechanical properties of the laminated composites. The through-thickness inhomogeneity of microstructure and texture was observed in the Al1060 layer. In the hot-rolled laminated composites, the surface of the Al1060 layer suffered shear deformation, and the r-cube shear texture was developed at the surface of the Al1060 layer. After the T6 treatment, the recrystallized grains near the surface of the Al1060 layer exhibited a reduced size compared to those near the interface. The recrystallization texture at the surface was the weak r-Goss orientation. The rolling texture of the Al6061-TiCp composite layer was characterized by the Goss and β fiber components, which strengthened with increasing rolling temperature. After the T6 treatment, the Al6061-TiCp composite layer was partially recrystallized. The recrystallization texture generated from the recrystallized grains was dominated by the R fiber deviating from the β fiber. The ultimate tensile strength, yield strength and elongation of the T6 treated laminated composites indicated an enhancement compared to the hot-rolled laminated composites.

Effect of titanium addition on sub-structural characteristics of low carbon copper bearing steel in hot rolling

&lt;abstract&gt; &lt;p&gt;The low carbon copper-bearing steel exhibits high toughness and better weldability. In the present investigation, 0.05C–1.52Cu–1.45Mn stainless steel and its titanium added counterpart which is 0.05C–0.05Ti–1.52Cu–1.45Mn stainless steel were subjected to hot rolling. The hot rolling test followed by quenching to retain the microstructure was done using a hot-rolling mill. The rolling was done at two different temperatures of 800 ℃ and 850 ℃. The characterization of microstructure was done using electron back scattered diffraction and transmission electron microscopy analysis. The 0.05C–1.52Cu–1.45Mn stainless steel when subjected to hot rolling at a lower temperature envisaged a deformed microstructure rather transformed one. However, the same steel at a higher temperature envisages a transformed microstructure. There was no variation in hardness was observed. However, the addition of 0.05 wt% of titanium in 0.05C–1.52Cu–1.45Mn stainless steel influenced the softening and the microstructure showed some recrystallization; the hardness was decreased with the increasing rolling temperature because the solubility of titanium in the austenite phase increased with temperature which leads to suppression austenitic grain/sub-grain growth and hardness. The mean sub-grain size for 0.05C–1.52Cu–1.45Mn stainless steel was 2.75 µm. However, the addition of titanium leads to a decrease in the mean sub-grain size. A marginally larger mean sub-grain size was observed when 0.05C–0.05Ti–1.52Cu–1.45Mn stainless steel was rolled at a higher temperature. A comparatively finer precipitate of copper, titanium and oxy-silicates of Ferrous/Manganese in order of nanometer was formed during rolling at a higher temperature.&lt;/p&gt; &lt;/abstract&gt;

Microstructure characteristics and enhanced properties of network-structured TiB/(TA15-Si) composites via rolling deformation at different temperatures

Discontinuously reinforced titanium matrix composites (DRTMCs) with network structure have attracted much attention in recent years due to their superior strengthening effect and ductility. To figure out their microstructure characteristics of the as-rolled network-structured composites under different rolling temperatures, hot rolling deformation processes at α+β region, upper α+β region, β region were performed on a series of TiB whiskers reinforced Ti–6.5Al–2Zr–1Mo–1V–0.3Si (TA15) composites (TiB/TA15–Si). The results showed that with the increase of rolling temperature, primary α (αp) phases and silicides gradually decreased, while transformed β (βT) phases, secondary α (αs) phases and TiB aspect ratio gradually increased, which is attributed to the phase transformation, Si dissolution and lower deformation resistance. And the silicides were fractured into several parts at 900 °C due to the low solid solubility and excessive growth. Besides, the composite rolled at α+β region exhibited dominant dynamic recrystallization (DRX) of α phase, while the composite rolled at β region presented an elongated deformation of prior β phase inside the network and DRX behavior near the network. With the increasing rolling temperature, the composites showed an increasing trend in strength and a decreasing trend in ductility. The composite rolled at 1100 °C can obtain better overall ultimate tensile strengths of 1260 MPa (at RT), 843 MPa (at 600 °C), 729 MPa (at 650 °C) and 595 MPa (at 700 °C), which increased by 13.4%, 38.2%, 36.3%, 21.9% compared with those of the as-sintered composite, respectively. The superior strengthening mechanism of the as-rolled composites can be mainly attributed to grain refining of the matrix and load transfer of TiB.

Influence of Rolling Temperatures on Interface Microstructure and Mechanical Properties of Multi-Pass Rolling TA1/Q235B Explosive Welded Sheets

The effect of rolling temperatures on the interface microstructure and mechanical properties is investigated using 2-mm-thick TA1/Q235B composite sheets, which were prepared after nine passes of hot rolling of explosive welded plates. The results show that the vortex region and the transition layer exist in the interface at the explosive welded plate, while only the transition layer exists in the interface after hot rolling. The transition layer is composed of α-Ti, TiC, Fe, and FeTi, and the thickness increases with the increasing rolling temperature. The microhardness of the explosive welded plate is higher than that of the hot-rolling sheet, and the microhardness of interface are higher than that of matrix metals. The interface shear strength and tensile elongation of the hot-rolled sheet increase with the increasing hot rolling temperature, while the ultimate tensile strength (UTS), yield strength (YS) and Young modulus decrease with the increase of hot rolling temperature. The shear strength of sheets is related to the interfacial compounds, and the tensile strength is mainly affected by the grain morphology of the matrix.

The dependence of fatigue crack growth on hydrogen in warm-rolled 316 austenitic stainless steel

The fatigue crack growth rate of warm-rolled AISI 316 austenitic stainless steel was investigated by controlling rolling strain and temperature in argon and hydrogen gas atmospheres. The fatigue crack growth rates of warm-rolled 316 specimens tested in hydrogen decreased with increasing rolling temperature, especially 400 °C. By controlling the deformation temperature and strain, the influences of microstructure (including dislocation structure, deformation twins and α′ martensite) and its evolution on hydrogen-induced degradation of mechanical properties were separately discussed. Deformation twins deceased and dislocations became more uniform with the increase in rolling temperature, inhibiting the formation of dynamic α′ martensite during the crack propagation. In the cold-rolled 316 specimens, deformation twins accelerated hydrogen-induced crack growth due to the α′ martensitic transformation at the crack tip. In the warm-rolled specimens, the formation of α′ martensite around the crack tip was completely inhibited, which greatly reduced the fatigue crack growth rate in hydrogen atmosphere.

Densification Mechanism for the Precursor of AFS under Different Rolling Temperatures.

The effect of rolling temperature on the precursor of aluminum foam sandwich (AFS) prepared by powder metallurgy through Pack Rolling method is investigated in this work. The cross-section along rolling direction of the precursors was observed. It was found that periodic corrugated morphology with micro-cracks on the composite interface as well as cracks and micro-holes among core powder particles emerged abundantly at room temperature rolling. These defects degraded with increasing rolling temperature and completely disappeared when the rolling temperature reached 400 °C. Combining with foaming ability of these precursors, the densification mechanism of core powders was discussed. Powder particles deformed with difficulty at low rolling temperature; the gap between them cannot be effectively filled through their plastic deformation. Fracture occurred in powder core layer during co-extension with the outer panel and was partly embedded by it, resulting in corrugated composite morphology at the interface. The precursors of high density and excellent bonding interface were prepared at the rolling temperature of 400 °C. A more suitable foaming condition was determined.

Effects of Hot Asymmetric Rolling on Microstructure and Formability of Aluminum Alloys

In order to analyze the effect of hot asymmetric rolling on the microstructure and texture of aluminum alloy and to investigate the effect of the texture on the formability and plastic anisotropy of aluminum alloy, aluminum 6061 alloy is asymmetrically rolled at room temperature, 200 °C, 350 °C, and 500 °C, and the results are compared with symmetrically rolled results. In the case of asymmetric rolling, the equivalent strain (εeq) is greatest in the upper roll part where the rotational speed of the roll is high and increases with increasing rolling temperature. The increase rate of the mean misorientation angle with increasing temperature is larger than that during symmetrical rolling, and dynamic recrystallization occurs the most when asymmetrical rolling is performed at 500 °C. In the case of hot symmetric rolling, the {001}<110> rotated cube orientation mainly develops, but in the case of hot asymmetric rolling, the {111}<110> orientation develops along with the {001}<100> cube orientation. The hot asymmetric rolling improves the formability (r) of the aluminum 6061 alloy to 0.9 and reduces the plastic anisotropy (Δr) to near zero due to the {111}<110> shear orientation that develops by asymmetric rolling.

Effect of Rolling Temperature on the Microstructural Characteristics of High-Speed-Rolled Mg Alloy with Initial Non-Basal Texture

In this study, the effects of rolling temperature on the microstructural characteristics of a highspeed-rolled Mg alloy with a non-basal texture were investigated. To this end, commercial AZ31 alloy samples in which the basal poles of most grains were tilted at an angle of 45° from the normal direction (ND) to the transverse direction were hot-rolled with a rolling reduction of 80% at a rolling speed of 470 m/min at various temperatures (300 °C, 350 °C, and 400 °C). With increasing rolling temperature, the area fraction of dynamically recrystallized (DRXed) grains increased and the internal strain energy accumulated in the rolled material decreased. This is attributed to the occurrence of homogeneous nucleation throughout the material at higher temperatures. When the rolling temperature increased from 300 °C to 350 °C, the area fraction of coarse unDRXed grains decreased, but the size of the relatively fine DRXed grains increased. Consequently, the average grain size of the rolled material remained nearly unchanged. However, when the rolling temperature increased from 350 °C to 400 °C, the size of the DRXed grains increased considerably owing to enhanced grain growth behavior. This increase led to an increase in the average grain size of the rolled material. The basal poles of the high-speed-rolled materials were mainly tilted 25° - 29° from the ND. This indicates that application of single-pass high-speed rolling causes the non-basal texture of the initial material to transform into a basal texture similar to the typical texture of rolled Mg alloys. Key words: Mg alloy, high-speed rolling, rolling temperature, texture, dynamic recrystallization, microstructure

Mechanical properties and degradation behavior of binary magnesium-silver alloy sheets

The application of Mg–Ag alloys is suggested as biodegradable implant materials in the form of sheets with controllable mechanical properties and appropriate degradation behavior. This study aimed on the understanding of influence of rolling temperature and silver content (2–8 wt %) on the microstructure development, mechanical properties and the degradation behavior of the sheet material. Besides an increase of the average grain size with increasing rolling temperature, precipitates of Mg54Ag17 formed during processing at lower temperatures and resulted in grain growth restriction during recrystallization. A typical alignment of basal planes parallel to the sheet plane was confirmed by texture measurements along with a strengthening of such textures when grains grew larger during recrystallization. As a result, an increase of the Ag-content corresponds to an increase in the hardness and strength properties of the sheets. In immersion tests, the as-rolled and annealed Q6 and Q8 rolled at 400 °C or 450 °C had similar degradation rate but an obvious difference of the degradation morphology due to the existence of precipitates at grain boundaries. By elevating the rolling and annealing temperature, the degradation rate decreased and the elimination of precipitates led to homogeneous degradation even when the silver in magnesium was up to 8 wt%. Appropriate short time annealing procedures below 60 s allow the tailored regulation of hardness, mechanical properties and ductility via controlled static recrystallization.

Microstructural characteristics of magnesium alloy sheets subjected to high-speed rolling and their rolling temperature dependence

Microstructural and textural variations of an AZ31 Mg alloy during its high-speed rolling (HSR) and their dependence on the rolling temperature are investigated by performing HSR at temperatures of 300°C, 350°C, and 400°C at a rolling speed of 470m/min with 80% reduction in a single pass. Shear band formation is observed in all the high-speed-rolled (HSRed) materials; however, with increasing rolling temperature, the density and intensity of the shear bands decrease considerably because of an increase in deformation homogeneity. With increasing rolling temperature, the area fraction of dynamically recrystallized (DRXed) grains gradually increases owing to the promoted twinning-induced recrystallization behavior. With an increase in the rolling temperature from 300°C to 350°C, the average grain size of the HSRed materials decreases owing to the reduced area fraction of coarse unDRXed grains; however, at 400°C, the average grain size increases owing to the increased DRXed grain size. With decreasing rolling temperature, the basal texture of the HSRed materials tilts from the normal direction toward the rolling direction, owing to the intensive shear deformation at lower temperatures. The texture intensity also increases with decreasing rolling temperature because of an increase in the area fraction of the unDRXed region, which has a considerably strong texture.

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 Temperature on the Microstructure and Mechanical Properties of Mg-2Zn-0.4Y Alloy Subjected to Large Strain Rolling

Large strain rolling (LSR) has been conducted on the Mg-2Zn-0.4Y alloy. After the 1st rolling process at 250, 300, 350, and 400 °C, the alloy demonstrates a fully recrystallized microstructure. The grain size increases from 6, 8, 12, to 17 μm with an increasing rolling temperature. After the 2nd rolling process at 300 °C, twinning and shear bands were introduced. During the 3rd rolling process at 350 °C, dynamic recrystallization (DRX) was observed and resulted in a more uniform microstructure. DRX occurred because of temperature increase and large dislocation density induced by LSR. For the room temperature tensile tests, the plates rolled at 300 and 350 °C in the 1st rolling process demonstrate higher strength and lower elongation due to twinning. The one rolled at 400 °C in the 1st rolling process, shows the most uniform rolling microstructure and the best combination of strength and elongation at room temperature.

Microstructure, texture and mechanical properties of Ti-43Al-9V-0.2Y alloy hot-rolled at various temperatures

Using the hot-pack rolling method, β-solidifying Ti-43Al-9V-0.2Y alloy sheets were rolled (thickness reduction: 85%) within the α(α2) + β + γ ternary-phase region at temperatures ranging from 1100 °C to 1200 °C. The microstructure and texture evolution occurring during dynamic recrystallization of the γ phase and their effect on the mechanical properties were systematically investigated. After hot-rolling, residual lamellar structures of the as-forged TiAl alloy were completely broken down and the fraction of dynamically recrystallized grains increased significantly with increasing rolling temperature. Lower-temperature and higher-temperature rolling were conducive for dynamic-recrystallization nucleation and growth, respectively, of the γ grains. At 1100 °C, the precipitation of numerous fine (thickness: ∼200 nm) γ laths from the β-phase ribbon was accompanied by the emergence of γ twins in the new grains. The texture evolution was also strongly dependent on the hot-rolling temperature, as evidenced by the transformation of recrystallization textures into random deformation components when the temperature was increased to 1200 °C. Moreover, compared with those rolled at higher temperatures, the sheet hot-rolled at 1100 °C had a significantly higher tensile strength (ultimate tensile strength (UTS): 945 MPa, yield strength (YS): 840 MPa) at room temperature. A good combination of high strength (UTS: 550 MPa, YS: 480 MPa) and sufficient ductility (80%) of this alloy sheet was also achieved at 750 °C.

Mechanical Properties and Interface Evaluation of Al/AZ31 Multilayer Composites Produced by ARB at Different Rolling Temperatures

Many researchers have studied the microstructure and mechanical properties of Al/Mg composites rolled at a unique temperature; however, the effect of rolling temperature, which is one of the more decisive accumulative roll bonding (ARB) parameters, has not been investigated. In this work, laminated Al/Mg composites were fabricated by ARB at different temperatures using AZ31 magnesium alloy and commercially pure aluminum sheets. The microstructure of the layers and the mechanical properties of the rolled Al/AZ31 composites were investigated. Tensile and bending properties of the multilayer materials were examined by tensile and three-point bending tests. The results showed that mechanical bonding of the layers was improved with increasing rolling temperature. As a result, the intermediate rolling temperature (300 °C) indicated the best mechanical properties. Moreover, hot rolling caused an accelerated formation of intermetallic compounds.