The effect of rolling direction on the creep process of Al–Cu bimetallic sheet

The study of the mechanical properties of aluminium–copper (Al–Cu) metal layered composite, formed by joining aluminium and copper sheets in the process of rolling have been presented in this paper. The influence of the rolling direction on the basic strength parameters and rheological properties of the composite was analysed. All tests were carried out on flat specimens cut from a sheet in the direction compatible with the rolling direction (RD) and transverse direction (TD). Preliminary tests of monotonic uniaxial tension at a temperature of 293 K were carried out and the basic mechanical properties of Al–Cu bimetal were determined. The hardening process of the material was described by the three-parameter Swift’s equation. The essential creep tests were carried out at a temperature of 523 K in the range of stress 88.5–137.9 MPa. The relation between minimum creep rate and applied stress for the specimens cut from the RD and TD directions were determined. The relationships between the time to fracture, stress, and rupture elongation, obtained from the creep tests, were determined as well. Variations of the steady creep rate with time to fracture by using the Monkman–Grant’s model and its modifications were analysed. It was found that the rolling process strongly affected the short-time monotonic deformation at 293 K and the creep process at 523 K temperature.     

Effect of crystallographic texture on precipitation induced anisotropy in an aluminium magnesium silicon alloy

The effect of crystallographic texture on precipitation induced anisotropy in yield strength of an aluminium magnesium silicon alloy was investigated. Solutionized samples were subjected to unidirectional and multi-step cross rolling to yield distinct crystallographic textures in the Al–Mg–Si alloy. The rolled sheets were then subjected to annealing followed by second solutionizing treatment to provide sheets with similar grain size and dislocation content but distinct texture. Ageing experiments were carried out on these sheets at 443 K for different time intervals. It was observed that the evolution of anisotropy in yield strength of the age hardened alloy depends on texture. The difference in age hardening response brought about by varying initial texture controls the evolution of anisotropy in mechanical properties of the alloy. This was manifested in terms of transition from anisotropic to isotropic mechanical properties in the unidirectionally rolled samples after peak ageing. On the contrary, a transition from isotropic to anisotropic yield behaviour was observed for multi-step cross rolled samples. This is attributed to enhanced precipitation hardening in crystallographically softer orientations compared to crystallographically harder orientations.     

The characterization of shape memory effect for low elastic modulus biomedical β-type titanium alloy

This work investigates the textures of biomedical TiNbTaZr alloy rolled by 99% cold reduction ratios in thickness. The relationship between textures and superelasticity of the specimens treated at 873 K and 1223 K for 1.2 ks is studied. The microstructure of tensile specimen is investigated by transmission electron microscopy. Textures of cold-rolled and heat-treated specimens are studied. During unloading, the anisotropy of superelastic strain and pure elastic strain in the heat-treated specimens is observed. Superelastic strain along rolling direction and transverse direction is larger than those along 45° from rolling direction while pure elastic strain shows the highest value along 45° from rolling direction in the specimen treated at 873 K. For the specimen treated at 1223 K, higher pure elastic strain is obtained along rolling direction. The maximum recovered strain around 2.11% is obtained along rolling direction.     

Characterization of microstructure,texture and magnetic properties in twin-roll casting high silicon non-oriented electrical steel

An Fe-6.5 wt.% Si-0.3 wt.% Al as-cast sheet was produced by twin-roll strip casting process, then treated with hot rolling, warm rolling and annealing. A detailed study of the microstructure and texture evolution at different processing stages was carried out by optical microscopy, X-ray diffraction and electron backscattered diffraction analysis. The initial as-cast strip showed strong columnar grains and pronounced < 001 >//ND texture. The hot rolled & warm rolled sheets were characterized by large amounts of shear bands distributed through the thickness together with strong < 110 >//RD texture and weak < 111 >//ND texture. After annealing, detrimental < 111 >//ND texture almost disappeared while beneficial {001}<210 >, {001}<010 >, {115}<5 − 10 1 > and {410} < 001 > recrystallization textures were formed, thus the magnetic induction of the annealed sheet was significantly improved. The recrystallization texture in the present study could be explained by preferred nucleation and grain growth mechanism.     

Microstructural evolution during annealing and rolling Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass

The microstructural evolution of the Zr_52.5Cu_17.9Ni_14.6Al₁₀Ti₅ bulk metallic glass during annealing and rolling deformation was studied. After annealing at 680 K for 0.5 h, phase separation is observed, and nanocrystallization is further induced by the subsequent rolling deformation. Increasing annealing time to 1.5 h leads to the formation of both nanocrystals and large-size particles of the Zr–Cu fcc phase. After rolling, the volume fraction of nanocrystals increases slightly while the Zr–Cu particles disappear. The presence of phase separation and nanocrystals during annealing reduce the thermal stability of the glass and accelerate the subsequent crystallization driven by rolling. During rolling the two annealed specimens exhibit the good ductility.     

Mechanical and microstructural characterizations of ultrafine grained Zircaloy-2 produced by room temperature rolling

The effect of deformation strain at room temperature on the microstructural and mechanical properties of Zircaloy-2 was investigated in the present work. The sample was initially heat treated at 800 °C in argon environment and quenched in mercury prior to rolling. The deformed alloys were characterized by using EBSD and TEM. It reveals the misorientation of incidental grain boundaries (IDBs) due to large plastic strain induced in the sample. The recovery of deformed alloy upon annealing leads to the formation of ultrafine and nanostructured grains in the alloy. The hardness achieved after 85% room temperature rolling (RTR) is found to be 269 HV, while the tensile strength is 679 MPa and 697 MPa in the rolling and transverse direction, respectively. The improvement in strength is due to generation of high dislocation density and ultrafine grains in the deformed alloy with 85% thickness reduction, during rolling. The deformed alloy subjected to annealing at 400 °C for 30 min sample shows increase in ductility (6% and 7.2%) in rolling and transverse direction, respectively, due to the annihilation of dislocations as evident from the TEM study.     

Influence of cold rolling on the precipitation in an Al–Mn–Zr alloy

The aim of the experiments was to study the influence of the rolling reduction (39, 87, and 96%) on the size and distribution of secondary particles and recrystallization behaviour of Al–Mn sheets with Zr addition prepared by twin-roll casting (TRC) in the industrial conditions. Samples, cold rolled on a laboratory mill, were subjected to a two-step precipitation annealing. Their microstructure (grain structure, substructure, particle analysis) as well as mechanical and physical properties (microhardness, electrical conductivity, resisitivity) were then characterized. The material cold worked with 39% reduction shows a moderate decrease of microhardness due to recovery, while sheets cold worked with 87 and 96% reduction soften more due to recrystallization. Regardless of the cold rolling reduction, the highest density of precipitates of α-Al(Mn,Fe)Si phase form during heating to 450 °C in the temperature range from 350 °C to 450 °C. Quantitative particle analysis of the sheets after the whole annealing cycle indicate that the alloy deformed 96% shows the highest density of particles in the size range from 50 to 140 nm. In addition, many spherical particles up to 15 nm were observed by transmission electron microscopy, some of them were identified by electron diffraction as Al₃Zr phase with L1₂ crystal structure.     

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.     

Effect of anisotropy on fatigue properties of 2198 Al–Li plates joined by friction stir welding

Al–Li alloys are characterized by a strong anisotropy in mechanical and microstructural properties with respect to the rolling direction. In the present paper, 4 mm sheets of 2198 Al–Li alloy were joined via friction stir welding (FSW) by employing a rotating speed of 1000 mm/min and a welding speed of 80 mm/min in parallel and orthogonal direction with respect to the rolling one. The joints mechanical properties were evaluated by means of tensile tests at room temperature. In addition, fatigue tests were performed by using a resonant electro-mechanical testing machine under constant amplitude control up to 250 Hz sinusoidal loading. The fatigue tests were conducted in axial control mode with R = σ_min/σ_max = 0.33, for all the welding and rotating speeds used in the present study.     

Achieving a weak basal texture in a Mg–6Al–3Sn alloy by wave-shaped die rolling

An innovative rolling approach was proposed to achieve weak basal texture in rolled Mg alloy sheets, by laying a wave-shaped die during rolling. It was shown that, Mg–6Al–3Sn (AT63) alloy sheets processed by this wave-shaped die rolling (labeled as WDR) exhibited basal textures with low intensity and tilted basal peak. A substantial basal texture weakening was found to occur during WDR after a single pass. Moreover, the WDRed alloy sheets exhibited basal texture gradients through the center to the surface, reflecting the asymmetric deformation mode of the sheets during rolling. In addition, WDR was effective to refine the grain size of AT63 alloy, from ~ 35 μm to ~ 10.3–11.5 μm. Tensile tests revealed that, the WDRed AT63 sheets presented much enhanced strain hardening ability (n = 0.295) and high elongation to failure (ε_f = 22.5%), as compared with the equivalent AT63 sheet rolled without wave-shaped die.     

Phase change and optical band gap behavior of Se0.8S0.2 chalcogenide glass films

Se_0.8S_0.2 chalcogenide glass films have been prepared by thermal vacuum evaporation technique with thickness 583 nm. Annealing process at T ≥ 333 K crystallizes the films and nanostructured films are formed. The crystallite size was increased to 24 nm as the annealing temperature increased to 373 K. Orthorhombic crystalline system was identified for the annealed films. SEM micrographs show that films consist of two parallel surfaces and the thickness was determined by cross section imaging. The optical transmittance is characterized by interference patterns as a result of these two parallel surfaces, besides their average value at longer wavelength decreases as a result of annealing process. The band gap, E_g is red shifted due to crystallization by annealing. As the phase of the films changes from amorphous to crystalline in the annealing temperature range 333–363 K, a non sharp change of the band gap (E_g) is observed. This change was explained by Brus’s model of the energy gap confinement behavior of the nanostructured films. The optical refractive index increases suddenly when the system starts to be crystallized by annealing.     

Effect of different annealing atmospheres on crystallization and corrosion resistance of Al86Ni9La5 amorphous alloy

The effect of different annealing atmospheres (H₂, air, Ar and N₂) on precipitated phases, corrosion resistance and hardness of Al₈₆Ni₉La₅ amorphous alloy was investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), thermogravimetry (TG), electrochemistry experiment and microhardness tester. During annealing at 523 K, the primary crystallized fcc-Al is independent on the annealing atmospheres. During annealing at 584 K, the final crystalline phases, i.e. fcc-Al + Al₁₁La₃ + Al₃Ni, are also independent on the different annealing atmospheres. However, during annealing at 523 K, H₂ and air can promote the eutectic crystallization process, and induce the formation of metastable Al₃Ni₂ phase. The promoting effect of different annealing atmospheres is in the order of H₂ > air > Ar > N₂. The microhardness and corrosion resistance in the 3.5 wt.% NaCl solution are improved by annealing in H₂ and air atmospheres. The property promotion caused by annealing process can be ascribed to the formation of nanocrystalline phases, which is possibly helpful to develop the alloy's application in the seawater environment.     

Annealing and anomalous (bimodal) grain growth of Zr 702

Zirconium’s superior corrosion resistance capabilities have lead to its increasing use in the fabrication of chemical processing equipment and nuclear reactors. The purpose of this study was to find a critical temperature, above which bimodal grain growth takes place, in cold worked sheets after annealing was applied. The critical temperature above which there is abnormal grain growth was 1275 °F (691 °C). Additionally, the abnormal grain growth occurs only after bending and not rolling.     

Effects of inter-critical temperatures on martensite morphology,volume fraction and mechanical properties of dual-phase steels obtained from direct and continuous annealing cycles

Homogenizing and normalizing heat treatments were performed on low carbon–manganese steel. Then, direct and continuous annealing heat treatments were carried out at 800 °C, 770 °C, 750 °C and 725 °C. Finally; dual phase ferrite–martensite steel was obtained. Thereafter, hardness and tensile tests were applied at ambient temperature, and impact tests for the initial sample and the dual-phase steels obtained from continuous and direct annealing heat treatment in the temperature ranges of (−67 to +70), (−70 to +60), (−70 to +29), respectively, were accomplished. The ductile–brittle transition temperature (DBTT) and the fracture modes of the samples were obtained, and the fracture surface of the steel was observed through scanning electron microscopy (SEM). The results revealed that the best mechanical properties in dual-phase steels, like impact toughness and flexibility, appear at the inter-critical temperature of 725 °C for both continuous and direct annealing cycles. The (DBTT) for the specimens obtained from direct and continuous annealing and the initial sample were −49 °C, −6 °C, and −34 °C, respectively. The dual-phase specimen achieved through the direct annealing method had better toughness and impact properties than the initial specimen or the one obtained through continuous annealing.     

Development of through-thickness texture gradient and persistence of shear-type textures during annealing of commercial purity aluminium sheet processed by accumulative roll-bonding

Ultrafine-grained commercial-purity aluminum (AA1070) sheets produced by four cycles of accumulative roll-bonding (ARB) without lubrication are subjected to annealing treatments in the temperature range from 250 °C to 400 °C. Microstructures and microtextures in the surface and center regions of the ARBed and annealed sheets are measured by electron backscatter diffraction. The results show that annealing treatments at 325 °C or above lead to a reduction in the microstructure gradient but a significant through-thickness texture gradient different from that in the as-deformed state. The center region is featured by the development of a strong cube texture at the expense of rolling components. In the surface region, shear-type components are either enhanced or largely retained, showing a high persistency upon annealing. While the grain structures are restored predominantly by continuous recrystallization in the surface region, a mixture of continuous and discontinuous recrystallization is envisaged for the center region.     

Crystallographic texture evolution in Ti–35Nb alloy deformed by cold rolling

This work presents the results of a microstructural characterization of the Ti–35Nb alloy deformed by cold rolling. Initially, samples of the Ti–35Nb (wt%) alloy were obtained by electric arc melting. After melting, these samples were solution heat-treated at 1000 °C for 8 h and water quenched. The resulting microstructure was composed of β-phase (bcc) combined with orthorhombic martensite (α″). Samples were cold-rolled in multiple passes to reduce their thickness by up to 85% without intermediary annealing. They were then characterized by light optical microscopy, X-ray diffraction and Vickers hardness measurements. Young’s modulus was determined by ultrasonic methods and nanoindentation measurements. The texture evolution and orientation relationship between phases were studied by X-ray diffraction and electron backscatter diffraction (EBSD). The results reveal the presence of shear bands in the deformed samples, an orientation of the orthorhombic martensite phase in relation to the rolling direction, and variations of Young’s modulus in response to deformation. The textural results of the β-phase show a typical bcc rolling texture with strong (1 1 0) fiber and weak (1 1 1) fiber. The intensity of the (1 1 0) fiber increases with deformation.     

Mechanical properties of aluminium–copper–lithium alloy AA2195 at cryogenic temperatures

Tensile testing was performed on a 4 mm thick sheet of the aluminum–lithium alloy AA2195 in T87 (solution treatment + water quenching + 7% cold work + peak aging) temper which was subjected to 7% cold working by combination of cold rolling and stretching, over a temperature range from ambient to liquid hydrogen (20 K) conditions. Properties were evaluated in longitudinal as well as transverse directions to characterize anisotropy with respect to strength and ductility. Strength and ductility were compared to the conventional aluminum alloy AA2219-T87, developed for similar cryogenic applications. Decreases in test temperature led to higher strengths with little or no change in ductility. As the temperature decreases, the differences between ultimate tensile strength as well as yield strength for two different combinations of cold roll and stretch studied in the present work, narrows down and become equal at 20 K.     

Tensile properties of hot rolled Mg–3Sn–1Ca alloy sheets at elevated temperatures

Mechanical behavior of hot rolled Mg–3Sn–1Ca (TX31) magnesium alloy sheets were studied in the temperature range 25–350 °C. The microstructure of the alloy consisted of the eutectic structure of α-Mg + Mg₂Sn and a dispersion of needle-like CaMgSn. The highest room-temperature ductility of 18% was obtained by hot rolling of the cast slabs at 440 °C, followed by annealing at 420 °C. The high temperature tensile deformation of the material was characterized by a decrease in work hardening exponent (n) and an increase in strain rate sensitivity index (m). These variations resulted in respective drops of proof stress and tensile strength from 126.5 MPa and 220 MPa at room temperature to 23.5 MPa and 29 MPa at 350 °C. This was in contrast to the ductility of the alloy which increased from 18% at room temperature to 56% at 350 °C. The observed variations in strength and ductility were ascribed to the activity of non-basal slip systems and dynamic recovery at high temperatures. The TX31 alloy showed lower strength than AZ31 magnesium alloy at low temperatures, while it exhibited superior strength at temperatures higher than 200 °C, mainly due to the presence of thermally stable CaMgSn particles.     

Effect of annealing on the magnetic properties of solution synthesized Zn1−xMnxO nanorods

Mn-doped ZnO nanorods with ～30 nm in diameter and ～200 nm in length were synthesized by a seed-mediated solution method. The structures, magnetic properties, as well as the annealing effect were characterized by transmission electron microscopy, electron energy loss spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectrum and physical properties measurement system. Magnetic properties measurement revealed that the Zn_0.97Mn_0.03O nanorods exhibited ferromagnetism with a saturation magnetization of 0.005 emu g^?1 and a coercivity of 110 Oe at 305 K. After annealing the samples at 900 °C for 2 h in air, the nanorods were transformed into nanoparticle aggregates. The coercivity and saturation magnetization increased obviously. Detailed analyses proved that a phase-separation process was happened at the high temperature. In this process, most of the particles preserved the wurtzite ZnO structure, while a few small ones evolved into spinel-structured particles. The increasing of the ferromagnetism of the annealed sample is attributed to the formation of secondary phase Zn_xMn_3?xO_4.     

Enhanced initial permeability and magneto-impedance ratio of Co67Fe4Mo2Si15B12

Co-based amorphous alloy exhibits superior soft magnetic properties after appropriate annealing treatment below the crystallization temperature by devitrification of the amorphous phase. The initiation of crystallization temperature has been found as 518 °C from differential thermal analysis for the heating rate of 10 °C/min. Ultra-soft magnetic properties manifested by enhanced initial permeability, μ′ of the order of 5.1 × 10⁴ and reduction of relative loss factor, tan δ/μ′ of the order of 9 × 10^− 6 has been achieved for the annealing temperature of 500 °C for 30 min. This has been achieved because at this stage local anisotropy is averaged out by exchange coupling between nanograins embedded in the residual amorphous matrix. Since enhanced magneto-impedance is a typical characteristic of Co-based amorphous alloy, field dependence of magneto-impedance has been measured for as-cast and annealed samples at current driving frequency of 4.5 MHz. Field dependence of magneto-impedance shows hysteresis at low field, which is related to the changes in the magnetization process of the sample.