Pass schedule of wire drawing process to prevent delamination for high strength steel cord wire

The high-speed drawing of high carbon content steel wires is usually conducted at room temperature employing a number of passes or reductions through several dies. In the multipass drawing process, the temperature rise at each pass affects the mechanical properties of the final product (such as its bending and torsion properties, and its tensile strength). This temperature rise during deformation encourages delamination in the wire, which has a deleterious influence on the torsional properties and durability of the wire. In this study, we investigated the delamination of wires using torsion tests and evaluated the wire temperature during drawing. Our data shows that one of the main reasons for delamination was an excessive rise in wire temperature. Based on our experimental results, in order to prevent delamination due to an excessive rise in wire temperature, a new isothermal pass schedule that could control the wire temperature was designed. The pass redesign for the conventional high carbon (0.75 wt%C) steel cord wire drawing process with delamination was carried out by using the isothermal pass schedule to control the wire temperature. In order to verify the effectiveness of the proposed method, wire drawing and torsion test were conducted. From the results of experiments, it was possible to produce high carbon steel cord wire without delamination.     

Evolution of cementite morphology in pearlitic steel wire during wet wire drawing

The evolution of the cementite phase during wet wire drawing of a pearlitic steel wire has been followed as a function of strain. Particular attention has been given to a quantitative characterization of changes in the alignment and in the dimensions of the cementite phase. Scanning electron microscope observations show that cementite plates become increasingly aligned with the wire axis as the drawing strain is increased. Measurements in the transmission electron microscope show that the cementite deforms plastically during wire drawing , with the average thickness of the cementite plates decreasing from 19 nm (ε = 0) to 2 nm (ε = 3.7) in correspondence with the reduction in wire diameter. The deformation of the cementite is strongly related to plastic deformation in the ferrite, with coarse slip steps, shear bands and cracks in the cementite plates/particles observed parallel to either {110}_α or {112}_α slip plane traces in the ferrite.     

Electron backscatter diffraction study of deformation and recrystallization textures of individual phases in a cross-rolled duplex steel

The evolution of microstructure and texture during cross-rolling and annealing was investigated by electron backscatter diffraction in a ferritic–austenitic duplex stainless steel. For this purpose an alloy with nearly equal volume fraction of the two phases was deformed by multi-pass cross-rolling process up to 90% reduction in thickness. The rolling and transverse directions were mutually interchanged in each pass by rotating the sample by 90° around the normal direction. In order to avoid deformation induced phase transformation and dynamic strain aging, the rolling was carried out at an optimized temperature of 898 K (625 °C) at the warm-deformation range. The microstructure after cross warm-rolling revealed a lamellar structure with alternate arrangement of the bands of two phases. Strong brass and rotated brass components were observed in austenite in the steel after processing by cross warm-rolling. The ferrite in the cross warm-rolling processed steel showed remarkably strong RD-fiber (RD//< 011 >) component {001}< 011 >. The development of texture in the two phases after processing by cross warm-rolling could be explained by the stability of the texture components. During isothermal annealing of the 90% cross warm-rolling processed material the lamellar morphology was retained before collapse of the lamellar structure to the mutual interpenetration of the phase bands. Ferrite showed recovery resulting in annealing texture similar to the deformation texture. In contrast, the austenite showed primary recrystallization without preferential orientation selection leading to the retention of deformation texture. The evolution of deformation and annealing texture in the two phases of the steel was independent of one another.     

Structural and mechanical behaviour of severe plastically deformed high purity aluminium sheets processed by constrained groove pressing technique

High purity aluminium sheets (∼99.9%) are subjected to intense plastic straining by constrained groove pressing method successfully up to 5 passes thereby imparting an effective plastic strain of 5.8. Transmission electron microscopy studies of constrained groove pressed sheets divulged significant grain refinement and the average grain sizes obtained after five pass is estimated to be ∼0.9 μm. In addition to that, microstructural evolution of constrained groove pressed sheets is characterized by X-ray diffraction peak profile analysis employing Williamson–Hall method and the results obtained fairly concur with electron microscopy findings. The tensile behaviour evolution with increased straining indicates substantial improvement of yield strength by ∼5.3 times from 17 MPa to 90 MPa during first pass corroborated to grain refinement observed. Marginal increase in strengths is noticed during second pass followed by minor drop in strengths attributed to predominance of dislocation recovery is noticed in subsequent passes. Quantitative assessment of degree of deformation homogeneity using microhardness profiles reveal relatively better strain homogeneity at higher number of passes.     

Grain refinement and orientation of AZ31B magnesium alloy in hot flow forming under different thickness reductions

An analysis of the hot flow forming of Mg-3.0Al-1.0Zn-0.3Mn (AZ31B) alloy was conducted by experiments and numerical simulations. The effects of different thickness reductions on the microstructure and mechanical properties were investigated at a temperature of 693 K, a spindle speed of 800 rev/min and a feed ratio of 0.1 mm/rev. Thickness reductions have great influence on the uniformity of microstructure along the radial direction (RD) and the grain sizes become refined and uniform when the thickness reduction reaches 45%. The c-axes of most grains are approximately parallel to the RD, with a slight inclination towards the axial direction (AD). The best mechanical properties with UTS of 280 MPa and YS of 175 MPa near the outer surface while 266 MPa and 153 MPa near the inner surface have been achieved due to grain refinement and texture. Moreover, the material flow behavior and stress/strain distributions for single-pass reductions were studied using the ABAQUS/Explicit software. The calculated results indicate that the materials mainly suffer from triaxial compressive stresses and undergo compressive plastic strain in RD and tensile strains in other directions. The higher stress and strain rate near the outer surface lead to more refined grains than that of other regions along the RD, whereas the orientation of the maximum principal compressive stress leads to a discrepancy of the grain orientations in RD.     

Enhancing mechanical properties of Mg–Sn alloys by combining addition of Ca and Zn

We developed new wrought Mg–2Sn–1Ca wt.% (TX21) and Mg–2Sn–1Ca–2Zn wt.% (TXZ212) alloys with high strength and ductility simultaneously, produced by conventional casting, homogenization and indirect extrusion. A partial dynamically recrystallized microstructure, with the micron-/nano-MgSnCa particles and G.P. zones dispersing, was obtained in TX21 alloy extruded at 260 °C (TX21-260). The TX21-260 alloy exhibited yield strength (YS) of 269 MPa, ultimate tensile strength (UTS) of 305 MPa, while those of the TX21 alloy extruded at 300 °C decreased to be 207 MPa and 230 MPa respectively. For TXZ212-260 alloy, on the other hand, MgSnCa, MgZnCa and MgZn₂ phases were observed, and the average grain size increased to be ∼5 μm. The YS and UTS of TXZ212-260 alloy evolved to be 218 MPa and 285 MPa, and the elongation (EL) reached as high as 23%. The high strengths of TX21-260 alloy were expected due to the high number density of nano-MgSnCa phases, G.P. zones and ultra-fine grain size (∼0.8 μm). The high EL of 23% in TXZ212-260 alloy was consistent with the high work-hardening rate, which was attributed to the larger grain size, more high angular grain boundaries, presence of more nano-particles and the weaker texture.     

Microstructure and mechanical properties of high-performance Mg–Y–Er–Zn extruded alloy

The Mg–8Y–1Er–2Zn (wt.%) alloy with high strength, plasticity and heat-resistance was prepared by the hot extrusion technique and the following aging treatment. The microstructure and mechanical properties were investigated. The results show that long period stacking ordered (LPSO) phase is different from common inermetallics, and the former can be bent by plastic deformation and presents good combination with the Mg matrix. The good mechanical properties of as-extruded alloy are mainly attributed to the lamellar strips with 18R LPSO structure as well as the microstructure refinement. Aging treatment at 220 °C can further improve the strength but not at the expense of plasticity. The ultimate tensile strength (UTS) and elongation to failure (ε) of as-extruded alloy at peak hardness are 390 MPa and 18% at room temperature, and 322 MPa and 30% at 250 °C, respectively. The formation of fine α-Mg recrystallization grains with high number density of 14H LPSO structure is mainly responsible for the superior mechanical properties of extruded alloy after peak-aging.     

Comparative study on local and global mechanical properties of bobbin tool and conventional friction stir welded 7085-T7452 aluminum thick plate

7085-T7452 plates with a thickness of 12 mm were welded by conventional single side and bobbin tool friction stir welding (SS-FSW and BB-FSW, respectively) at different welding parameters. The temperature distribution, microstructure evolution and mechanical properties of joints along the thickness direction were investigated, and digital image correlation (DIC) was utilized to evaluate quantitatively the deformation of different zones during tensile tests. The results indicated that heat-affected zone (HAZ), the local softening region, was responsible for the early plastic deformation and also the fracture location for SS-FSW samples, while a rapid fracture was observed in weld nugget zone (WNZ) before yield behavior for all BB-FSW specimens. The ultimate tensile strength (UTS) of SS-FSW joints presented the highest value of 410 MPa, 82% of the base material, at a rotational speed of 300 rpm and welding speed of 60 mm/min, much higher than that of BB-FSW joints, with a joint efficiency of only 47%. This should be attributed to the Lazy S defect produced by a larger extent of heat input during the BB-FSW process. The whole joint exhibited a much higher elongation than the slices. Scanning electron microscopic (SEM) analysis of the fracture morphologies showed that joints failed through ductile fracture for SS-FSW and brittle fracture for BB-FSW.     

Structure deformation and failure of sintered steel wire mesh under torsion loading

Sintered steel wire mesh materials with total porosities of 36.3–61.8%, which are subjected to torsion loading, have been investigated in terms of deformation mode and failure mechanism. The experiments reveal that the twisted wire’s stretching, moving and rotating are main deformation mode, which leads to most of wires orientating towards the torsion direction. The failure occurs when the oriented wires fracture continuously, and leave behind a 45° fracture surface. The shear strength and shear modulus of the tested wire mesh samples are evaluated in the range of 44–103 MPa and 47–718 MPa, respectively. With an increase in porosity both the shear strength and the shear modulus decrease.     

Effects of Ag addition on microstructures and mechanical properties of Mg–6Zn–2Sn–0.4Mn-based alloy system

We investigated the effects of Ag addition on the microstructure and mechanical properties of hot-extruded Mg–6Zn–2Sn–0.4Mn-based alloys. Ag addition resulted in the formation of fine submicron-sized Mg–Ag particles, grain refinement, and weaker basal texture in the alloys. The Ag-containing extruded alloys had better mechanical properties than the alloys without Ag. The ultimate tensile strength (UTS) and elongation of alloys containing 1 wt.% Ag were 352 MPa and 19%, respectively.     

Dynamic recrystallization behavior and microstructural evolution of Mg alloy AZ31 through high-speed rolling

High-speed rolling (HSR) is known to improve the workability of Mg alloys significantly, which makes it possible to impose a large reduction in a single pass without fracture. In the present study, dynamic recrystallization (DRX) behavior and microstructural and textural variations of Mg alloy AZ31 during a HSR process were investigated by conducting rolling with different imposed reductions in the range of 20%–80% at a high rolling speed of 470 m/min and 400 °C. High-strain-rate deformation during HSR suppresses dislocation slips but promotes twinning, which results in the formation of numerous twins of several types, i.e., {10–12} extension twins, {10–11} and {10–13} contraction twins, and {10–11}–{10–12} double twins. After twinning, high strain energy is accumulated in twin bands because their crystallographic orientations are favorable for basal slips, leading to subsequent DRX at the twin bands. Accordingly, twinning activation and twinning-induced DRX behavior play crucial roles in accommodating plastic deformation during HSR and in varying microstructure and texture of the high-speed-rolled (HSRed) sheets. Area fraction of fine DRXed grains formed at the twin bands increases with increasing rolling reduction, which is attributed to the combined effects of increased strain, strain rate, and deformation temperature and a decreased critical strain for DRX. Size, internal strain, and texture intensity of the DRXed grains are smaller than those of unDRXed grains. Therefore, as rolling reduction increases, average grain size, stored internal energy, microstructural inhomogeneity, and basal texture intensity of the HSRed sheets gradually decrease owing to an increase in the area fraction of the DRXed grains.     

Effects of Zr and B on the structure and tensile properties of Al–20%Mg alloy

In current research, the effects of different Zr and B contents on the structure and tensile properties of Al–20%Mg alloy have been investigated by using Al–15Zr and Al–8B master alloys. Optical and scanning electron microscopy (SEM) were utilized to study the microstructures and fracture surfaces. Microstructural analysis of the cast alloy showed dendrites of primary α-phase within the eutectic matrix which consists of β-Al₃Mg₂ intermetallic and α-solid solution. After tensile testing, the optimum amounts for both Zr and B were found to be 0.5 wt.%. Ultimate tensile strength (UTS) value of the unrefined alloy increased from 168 MPa to 243 MPa and 236 MPa by adding 0.5% Zr and 0.5%B, respectively. The main mechanism for UTS enhancement was found to be due to the refinement of grains and also altering large dendrites of Al(α)-phase to finer structure. The study of fracture faces revealed that B/Zr addition changes the mode of fracture from brittle to rather ductile.     

Design and mechanical characterization of a Zr–Nb–O–P alloy

In this study, Sn-free Zr–1.5Nb–O–P alloys were manufactured and their mechanical properties were characterized. The ultimate tensile strength (UTS) of cold rolled Zr–1.5Nb–O–P alloy with 160 ppm phosphorous (680 MPa) were close to that of a commercially available Zr–1Nb–1Sn–0.1Fe alloy (720 MPa), achieving a good mechanical strength without the addition of Sn, an effective solution strengthening element. The UTS of recrystallized Zr–1.5Nb–O–P alloy with 160 ppm phosphorous (533 MPa) was far greater than that of a commercially available Zr–1Nb–O (323 MPa) because of the strengthening due to higher Nb and oxygen content combined with phosphorous strengthening. The activation volumes for the cold rolled Zr–1.5Nb–P alloys were not much different from those of annealed Zr–1.5Nb–P alloys despite the higher dislocation density in the cold rolled alloys. Insensitivity of the activation volume to the dislocation density and the decrease of the activation volume with the addition of phosphorous support the suggestion linking the activation volume with the activated bulge of dislocations limited by segregation of oxygen and phosphorous atoms.     

Fatigue properties of strongly textured bulk NiW

The cyclic plasticity of Ni–5at.%W with a strong cube texture was investigated for two different deformation directions and at two different plastic strain amplitudes of 2.5 ⋅ 10⁻⁴ and 5 ⋅ 10⁻⁴ in a symmetric push–pull-mode. To prevent bending of the thin samples during the compression half-cycles, a novel sample suspension was successfully integrated into the mechanical tests.Samples deformed parallel to a 〈0 0 1〉 or a 〈0 1 1〉 direction of the cube texture displayed significant differences in both plastic behavior (i.e., lifetime, correlation of saturation stress amplitude and plastic strain amplitude) and microcrack characteristics. The majority of these effects can be interpreted as a consequence of the peculiar grain structure of the material, consisting of a “matrix” of cube oriented grains with small embedded grain regions of differing orientations. The hysteresis loops of all samples exhibit a short region of concave curvature shortly before the inversion points, possible reasons of which are discussed.     

Controlled retting of hemp fibres: Effect of hydrothermal pre-treatment and enzymatic retting on the mechanical properties of unidirectional hemp/epoxy composites

The objective of this work was to investigate the use of hydrothermal pre-treatment and enzymatic retting to remove non-cellulosic compounds and thus improve the mechanical properties of hemp fibre/epoxy composites. Hydrothermal pre-treatment at 100 kPa and 121 °C combined with enzymatic retting produced fibres with the highest ultimate tensile strength (UTS) of 780 MPa. Compared to untreated fibres, this combined treatment exhibited a positive effect on the mechanical properties of hemp fibre/epoxy composites, resulting in high quality composites with low porosity factor (α_pf) of 0.08. Traditional field retting produced composites with the poorest mechanical properties and the highest α_pf of 0.16. Hydrothermal pretreatment at 100 kPa and subsequent enzymatic retting resulted in hemp fibre composites with the highest UTS of 325 MPa, and stiffness of 38 GPa with 50% fibre volume content, which was 31% and 41% higher, respectively, compared to field retted fibres.     

Wear properties of high pressure torsion processed ultrafine grained Al–7%Si alloy

In this paper, Al–7 wt% Si alloy was processed via high pressure torsion (HPT) at an applied pressure 8 GPa for 10 revolutions at room temperature. The microstructure and hardness of the HPT samples were investigated and compared with those of the as-cast samples. The wear properties of as-cast and the HPT samples under dry sliding conditions using different sliding distances and loads were investigated by reciprocated sliding wear tests.The HPT process successfully resulted in nanostructure Al–7 wt% Si samples with a higher microhardness due to the finer Al matrix grains and Si particles sizes with more homogeneous distribution of the Si particles than those in the as-cast samples.The wear mass loss and coefficient of friction values were decreased after the HPT process. The wear mechanism was observed to be adhesive, delamination, plastic deformation bands and oxidization in the case of the as-cast alloy. Then, the wear mechanism was transformed into a combination of abrasive and adhesive wear after the HPT process. The oxidization cannot be considered as a mechanism that contributes to wear in the case of HPT samples, because O₂ was not detected in all conditions.     

Weakened anisotropy of mechanical properties in rolled ZK60 magnesium alloy sheets with elevated deformation temperature

The rolling direction (RD) and the transverse direction (TD) samples were obtained from an as-rolled ZK60 magnesium alloy sheet with strong anisotropy of initial texture and their mechanical properties were tested at various deformation temperatures. Meanwhile, the microstructure and texture of these samples after fracture were investigated. Results revealed that a higher flow stress along the RD than that along the TD at room temperature were ascribed to the strong anisotropy of transitional texture, and this texture effect was remarkably weakened with the increase of deformation temperature. Deformation structure was dominant at 100 °C, and was replaced by dynamic recrystallization structure when the deformation temperature increased to 200 °C and 300 °C. The texture presented a strong texture (transitional texture in the RD sample and basal texture in the TD sample) at 100 °C, but its intensity visibly decreased and texture components became more disperse at 200 °C and 300 °C. These microstructure and texture results were employed in conjunction with calculated results to argue that raising deformation temperature could increase the activity of non-basal slip by tailoring the relative critical resolved shear stress of each deformation mode and finally result in low texture effect on mechanical anisotropy.     

Microstructure evolution and mechanical properties of a Ti–35Nb–3Zr–2Ta biomedical alloy processed by equal channel angular pressing (ECAP)

In this paper, an equal channel angular pressing method is employed to refine grains and enhance mechanical properties of a new β Ti–35Nb–3Zr–2Ta biomedical alloy. After the 4th pass, the ultrafine equiaxed grains of approximately 300 nm and 600 nm are obtained at pressing temperatures of 500 and 600 °C respectively. The SEM images of billets pressed at 500 °C reveal the evolution of shear bands and finally at the 4th pass intersectant networks of shear bands, involving initial band propagation and new band broadening, are formed with the purpose of accommodating large plastic strain. Furthermore, a unique herringbone microstructure of twinned martensitic variants is observed in TEM images. The results of microhardness measurements and uniaxial tensile tests show a significant improvement in microhardness and tensile strength from 534 MPa to 765 MPa, while keeping a good level of ductility (~ 16%) and low elastic modulus (~ 59 GPa). The maximum superelastic strain of 1.4% and maximum recovered strain of 2.7% are obtained in the billets pressed at 500 °C via the 4th pass, which exhibits an excellent superelastic behavior. Meanwhile, the effects of different accumulative deformations and pressing temperatures on superelasticity of the ECAP-processed alloys are investigated.     

Effects of thickness and texture on mechanical properties anisotropy of commercially pure titanium thin sheets

Simultaneous effects of thickness and texture on the anisotropy of mechanical properties and fracture behaviors of commercially pure titanium thin sheets were studied. The activation of different deformation systems, due to the split distribution of basal texture, led to mechanical properties anisotropy. The crack initiation and propagation energies, when the loading direction was parallel to the initial rolling direction, decreased with increasing thickness ranges from 0.25 to 1 mm. The changes of size, shape and distribution of dimples with increasing thickness confirmed the restriction of deformation systems and the development of triaxial stress state and plane-strain condition at the notch tip. However, in transverse-directed specimens, the energy release rate increased with increasing specimen thickness up to 0.75 mm and then decreased. The fractography of these specimens explained the simultaneous effects of thickness and texture on structural stability and high accommodated plastic deformation at the notch tip.     

An investigation into the mechanical behavior of a new transformation-twinning induced plasticity steel

In recent years, the transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP) steels have been the focus of great attention thanks to their excellent tensile strength-ductility combination. Accordingly the mechanical behavior of an advanced microalloyed TRIP–TWIP steel, the compression tests were conducted from 25 to 1000 °C. This experimental steel shows a high compressive strength of 1280 MPa with the yield strength of 385 MPa as well as an outstanding strain hardening rate of about 14,000 MPa at the 25 °C. In addition the results indicate that the plastic deformation in the range of 25–150 °C is controlled by both the strain-induced martensite formation and mechanical twinning. However the mechanical twinning has been speculated as the only deformation mechanism in the temperature range of 150–1000 °C. This as well has led to an outstanding grain refinement via grain partitioning. The occurrence of mechanical twinning at such high temperatures is a novel observation in this grade of TRIP–TWIP high manganese steels.