On the texture memory effect of a cross-rolled Mg-2Zn-2Gd plate after unidirectional rolling

A Mg-2Zn-2Gd alloy subjected to a cross rolling and annealing often has a texture with c-axes of grains evenly distributing on a circle approximately 40°away from the normal direction(ND),which can completely remove the planar mechanical anisotropy.The texture memory effect and planar mechanical anisotropy of such a cross-rolled plate after an unidirectional rolling and subsequent annealing were systematically investigated.The results show that the circle-shaped texture is partially retained after the unidirectional rolling and annealing,with basal poles evenly distributing on an ellipse approximately 30°–40°away from the ND.This small texture difference will lead to quite different mechanical anisotropies between the two plates,namely,a quite low anisotropy of yield strength between the rolling direction(RD)and transverse direction(TD)before the unidirectional rolling,in contrast to an obvious mechanical anisotropy after unidirectional rolling.A quantitative calculation shows that tension along the RD of the plate after the unidirectional rolling will activate a much higher fraction of prismatic slip than tension along the TD.The much higher critical resolved shear stress for prismatic slip than that for basal slip or{10■2}twinning accounts for the much higher yield strength of TD tension than that of RDtension.The mechanisms for texture evolution during the unidirectional rolling and annealing were also discussed.     

Microstructure,texture evolution and mechanical properties of cold rolled Ti-32.5Nb-6.8Zr-2.7Sn biomedical beta titanium alloy

Ti-32.5 Nb-6.8 Zr-2.7 Sn(TNZS,wt%) alloy was produced by using vacuum arc melting method,followed by solution treatment and cold rolling with the area reductions of 50% and 90%.The effects of cold rolling on the microstructure,texture evolution and mechanical properties of the experimental alloy were investigated by optical microscopy,X-ray diffraction,transmission electron microscopy and universal material testing machine.The results showed that the grains of the alloy were elongated along rolling direction and stress-induced α' martensite was not detected in the deformed samples.The plastic deformation mechanisms of the alloy were related to {112} 111 type deformation twinning and dislocation slipping.Meanwhile,the transition from γ-fiber texture to α-fiber texture took place during cold rolling and a dominant {001} 110_(α-fiber) texture was obtained after 90% cold deformation.With the increase of cold deformation degree,the strength increased owing to the increase of microstrain,dislocation density and grain refinement,and the elastic modulus decreased owing to the increase of dislocation density as well as an enhanced intensity of {001} 110_(α-fiber)texture and a weakened intensity of {111} 112_(γ-fiber)texture.The 90% cold rolled alloy exhibited a great potential to become a new candidate for biomedical applications,since it possesses low elastic modulus(47.1 GPa),moderate strength(883 MPa) and high elastic admissible strain(1.87%),which are superior than those of Ti-6 Al-4 V alloy.     

Evolution of Microstructure and Texture during Hot Deformation of a Commercially Processed Supral100

The microstructure and texture in a commercially processed Al-6 wt% Cu-0.4 wt% Zr(Supral100) aluminium alloy have been investigated after annealing and hot tensile straining at 450 ℃,using a field emission gun scanning electron microscope(SEM) and electron backscatter diffraction(EBSD).The microstructure of commercially processed alloy had a relatively large fraction of high angle grain boundaries(HAGBs) which were aligned parallel to the rolling direction,and a strong texture.Annealing at 450 ℃ led to an increase in the fraction of HAGBs and to an increase in HAGB spacing and these changes were progressively enhanced by subsequent tensile deformation.The increasing fraction of HAGBs was due to the annihilation of low angle grain boundaries(LAGBs).A sharpening of texture during annealing was attributed to preferential textural growth,and the reduction of texture at higher tensile strains led to the development of superplastic behaviour.The present work supports the view that the evolution of the fine grain microstructure during the high temperature straining of Supral100 is primarily due to the accumulation of a large area of grain boundary during the initial thermomechanical processing,and does not involve any unusual restoration processes.     

Influence of Grain Size and Texture on the Yield Asymmetry of Mg-3Al-1Zn Alloy

The yield asymmetry between compression and tension of magnesium alloy Mg-3Al-1Zn(AZ31) with different grain sizes and textures has been studied by tensile and compressive testing of as-cast,as-extruded and equal channel angular pressed(ECAPed) specimens.The significant yield asymmetry(the ratio of yield strength between compression and tension σyc/σyt is ～0.44) was found in as-extruded specimens and the corresponding microstructure evolution during deformation revealed that {10 ˉ 12} tensile twinning is the underlying reason for the large yield asymmetry.Strong texture and grain size are influential factors for large yield asymmetry.The separate contributions of grain size and texture on yield asymmetry were investigated.     

Variation in Texture and Lankford Value of 1070 Aluminum Sheet Rolled by Cone-shaped Roll

A rolling with cone-shaped roll, the diameter of which continuously varies along the axial direction, has been proposed as a new shear rolling for controlling the texture of an aluminum alloy sheet. In this study, variations in the texture and Lankford value of a 1070 aluminum sheet rolled by the cone-shaped roll were investigated. Rolling with the cone-shaped roll was found to impose intense shear strain at the edges of the specimen, specifically near the surface. The shear directions in the left and right portions of the specimen were opposite to each other. The surface and middle layer of the specimen rolled by the cone-shaped roll and the reference specimen were characterized by a shear texture and typical recrystallization texture components, respectively. Notably, the specimen rolled by the cone-shaped roll exhibited smaller texture intensity than the reference specimen, especially at the surface, and the shear texture-components were observed at relatively deeper positions. As a result of Lankford value measurements, the specimen rolled with the cone-shape roll exhibited a smaller planar anisotropy than the reference specimen and an average Lankford value close to unity, which are likely due to the texture modifications introduced during rolling with the cone-shaped roll.     

Growth Behavior of a Phase in Ti-5.6Al-4.8Sn-2.0Zr-1.OMo-0.35Si-0.7Nd Titanium Alloy

The thermal stability of the microstructure of a near-αtitanium alloy after aging at 750℃was investigated using optical microscope and transmission electron microscope as well as composition analysis. Aging treatment brings about significant coarsening of grain boundaryαandαplatelets within the colonies for martensitic microstructure. The observed changes are related to the growth steps or ledges of the interface and lamellar termination presented in the microstructure. The composition analysis of the coarsenedαplate is consistent with the growth kinetics. TheαWidmanstatten plates were coarsened due to the movement ofα/βinterface for Widmansta'tten microstructure, and the phase boundaries of primaryα(αp) phase directly moved into the transformedβfor bimodal microstructure.     

Experimental Study and Finite Element Polycrystal Model Simulation of the Cold Rolling Textures in a Powder Metallurgy Processed Pure Aluminum Plate

Ingot metallurgy (IM) aluminum has long been the subject and attracted the attention of many metallurgists and textural researchers of materials. Due to the introduction of large amounts of ex situ interfaces, however, the textures in powder metallurgy (PM) processed aluminum has been rarely reported. In this article, a pure aluminum plate was prepared via PM route. The starting billet was first produced with uni-axially cold compaction and flat hot-extrusion and then followed by cold rolling processes. The hot-extruded and cold rolling deformation textures of the pure PM aluminum at 50%, 80% and 90% cold rolling reductions were studied by orientation distribution functions (ODFs) analysis. The finite element polycrystal model (FEPM) was finally utilized to simulate the cold rolling textural     

Microstructure and Mechanical Properties of Hybrid Laser-Friction Stir Welding between AA6061-T6 Al Alloy and AZ31 Mg Alloy

For the purpose of improving the strength of this dissimilar joint,the present study was carried out to investigate the improvement in intermetallic layer by using a third material foil between the faying edges of the friction stir welded and hybrid welded Al6061-T6/AZ31 alloy plates.The difference in microstructural and mechanical characteristics of friction stir welded and hybrid welded Al6061-T6/AZ31 joint was compared.Hybrid buttwelding of aluminum alloy plate to a magnesium alloy plate was successfully achieved with Ni foil as filler material,while defect-free laser-friction stir welding(FSW) hybrid welding was achieved by using a laser power of 2 kW.Transverse tensile strength of the joint reached about 66% of the Mg base metal tensile strength in the case of hybrid welding with Ni foil and showed higher value than that of the friction stir welded joint with and without the third material foil.This may be due to the presence of less brittle Ni-based intermetallic phases instead of Al12Mg17.     

Enhanced Strength and Ductility Due to Microstructure Refinement and Texture Weakening of the GW102K Alloy by Cyclic Extrusion Compression

The cyclic extrusion compression(CEC) was applied to severely deform the as-extruded GW102K(Mg–10.0Gd–2.0Y–0.5Zr, wt%) alloy at 350, 400, and 450 °C, respectively. The microstructure, texture, and grain boundary character distribution of the CECed alloy were investigated in the present work. The mechanical properties were measured by uniaxial tension at room temperature. The crack initiation on the longitudinal section near the tensile fracture-surface was investigated by high-resolution scanning electron microscopy(SEM). The result shows that the microstructure was dramatically refined by dynamic recrystallization(DRX). The initial fiber texture was disintegrated and obviously weakened. The 8-passes/350 °C CECed alloy exhibited yield strength of 318 MPa with an elongation-to-fracture of 16.8%, increased by 41.3% and 162.5%, respectively. Moreover, the elongation-to-fracture of the 8-passes/450 °C CECed alloy significantly increased more than 3 times than that of the received alloy. The cracks were mainly initiated at twin boundaries and second phase/matrix interfaces during tensile deformation. The microstructure refinement was considered to result in the dramatically enhanced of the strength and ductility. In addition, the texture randomization during CEC is beneficial for enhancing ductility. The standard positive Hall–Petch relationships have been obtained for the CECed GW102 K alloy.     

Microstructure, Elastic Modulus and Tensile Properties of Ti-Nb-O Alloy System

In the present study Ti-Nb binary alloy system was chosen because it has excellent biocompatibility as well as reasonable mechanical properties,aiming at understanding oxygen content on microstructural formation, elastic modulus and tensile properties in Ti-Nb alloy system.Small alloy buttons of 50 mm in diameter were prepared by arc melting on a water-cooled copper hearth under an argon gas atmosphere with a non-consumable tungsten electrode.The button ingots were then heat treated in a vacuum atmosphere at 1273 K for 0.5 h followed by water quenching in a specially designed heat treatment furnace.Microstructure,elastic modulus and tensile properties were investigated in order to understand the effect of oxygen content in quenched Ti- Nb alloy system.The orthorhombic structuredα″martensite was changed to bcc structuredβ-phase with increasing Nb content.Interestingly,it was found that oxygen makesβ-phase stable in quenched Ti-Nb alloy system.Elastic modulus values were sensitive to phase stability of constituent phases.Yield strength increased with increasing oxygen content.Details will be explained by phase formation and stability behavior.     

Friction stir spot welding of SPCC low carbon steel plates at extremely low welding temperature

Friction stir spot welding(FSSW) was applied to 2.0 mm thick steel plate cold-rolled commercial(SPCC)low carbon steel plates at a very low rotation speed that ranged from 5 to 50 rpm, which was much lower than that generally used for the conventional FSSW technique. Due to the very low heat input, the welding processes could therefore be completed at a peak welding temperature below 160℃. As a result,a significantly refined microstructure with an average grain size of about 0.41 μm was formed in the stir zone of the joints and the J1{0–11}-211 and J2{1–10}-1–12 shear textures were the dominant components, which are different from the D1{11–2}111 and D2{-1–12}111 shear textures formed in the conventional FSSW joints. In addition, no heat affected zone could be detected along the crosssectional plane of the joints. Although a few void-like non-bonded areas were still observed along the interface between the upper and lower steel plates, the shear tensile loads of the joints increased to about 10.0 kN when welded at a condition of 8 t, 20 rpm and 30s, and the joints fractured through the plug failure mode.     

Uniform texture in Al-Zn-Mg alloys using a coupled force field of electron wind and external load

Cylindrical Al-Zn-Mg alloys were processed by electroplastic compression with forced air cooling.Compared to a simple compression process,an unequal intensity of {110} <111> was obtained,and other textures were eliminated by electroplastic compression,that is,electroplastic compression can promote a uniform texture.The various textures formed in different regions along the radial direction under a simple compression process were illuminated by analyzing the relationship between the crystal rotation and stress state.Furthermore,the interaction between the electrons and dislocations was studied in electroplastic compression.The electrons enhanced {110} <111> by promoting slipping of the dislocations when the Burgers vectors of the dislocations were parallel to the drift direction of the electrons.However,the electrons also inhibited crystal rotation by pinning the dislocations with the Burgers vectors perpendicular to the drift direction of the electrons.Therefore,textures other than {110} <111>have difficulty forming under electroplastic compression.The effect of the current energy on the texture(enhancement or attenuation) was in accordance with the law of conservation.The results provided reasonable explanations for the test phenomena.     

Development of Microstructure and Texture Heterogeneities during Static Annealing of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si Alloy Preformed by Hot Working

The effect of annealing temperature on the development of microstructure and texture in an α+β titanium alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si (TC11) preformed by hot working was investigated with the aid of electron back-scattered diffraction and X-ray diffraction measurements. It is shown that considerable microstructure and texture heterogeneities were developed in the cross-section of the hot-worked rod due to the non-uniform deformation. Subsequent annealing at 940℃ and 990℃ led to homogeneous microstructures with globular α grains, whereas a typical lamellar α+β microstructure was obtained after annealing at 1040℃. In the latter case, the Burgers orientation relationship was well preserved between the two phases in a single colony. The α lamellar within a given colony depicted similar crystallographic orientations and the boundary α grains shared the orientation of one of the neighboring α lamellar. In contrast, subsequent annealing had very limited effect on the main features of the textures, indicating strong inheritance of the texture heterogeneity in annealing. It is thus crucial to control the hot working process in order to achieve a high level of texture homogeneity in the final parts.     

Effect of corrosion on mechanical behaviors of Mg-Zn-Zr alloy in simulated body fluid

The main purpose of this paper is to investigate the effect of corrosion on mechanical behaviors of the Mg-Zn-Zr alloy immersed in simulated body fluid （SBF） with different immersion times. The corrosion behavior of the materials in SBF was determined by immersion tests. The surfaces of the corroded alloys were examined by SEM. The tensile samples of the extruded Mg-2Zn-0.8Zr magnesium alloy were immersed in the SBF for 0, 4, 7, 10, 14, 21 and 28 d. The tensile mechanical behaviors of test samples were performed on an electronic tensile testing machine. SEM was used to observe the fracture morphology. It was found that with extension of the immersion time, the ultimate tensile strength （UTS）, yield strength （YS） and elongation （EL） of the Mg-2Zn-0.8Zr samples decreased rapidly at first and then decreased slowly. The main fracture mechanism of the alloy transformed from ductile fracture to cleavage fracture with the increasing immersion times, which can be attributed to stress concentration and embrittlement caused by pit corrosion.     

Microstructures,mechanical properties and degradability of Mg-2Gd-0.5(Cu/Ni) alloys: A comparison study

Low alloying Mg-2 Gd-0.5(Cu/Ni) alloys for sealing tools in the oil and gas industry were prepared.The differences in the effects of minor Cu and Ni additions on microstructures and properties of the Mg-2 Gd alloy were compared.The results showed that adding Ni was more effective than adding Cu in refining grain sizes,strengthening the basal fiber texture,and promoting the formation of LPSO phases,resulting in higher strength.The tensile yield strength/elongation of the Mg-2 Gd-0.5 Cu alloy,Mg-2...     

Dependence of mechanical properties on the microstructure characteristics of a near β titanium alloy Ti-7333

In this work, the microstructure and the corresponding tensile properties of the rolled Ti-7Mo-3Nb-3Cr-3Al(Ti-7333) alloy before and after the thermal treatments were investigated. The results show that a strong α-fiber texture is developed in the rolled Ti-7333 alloy. The deformed matrix and the texture significantly induce the variant selection of β phase. The high strength of the rolled Ti-7333 alloy is attributed to the 110 texture parallel to the tensile direction and the dispersed α phase within the matrix. After the solution treatment followed by the aging treatment, the texture decreases and the microstructure consists of the equiaxed β grains, the spheroidal α_p phase and various needle-like α variants. Eventually, the alloy could achieve an optimal combination with the strength of about 1450 MPa,the ductility of about 10.5% and a considerable shear strength of about 775 MPa. This balance can be ascribed to the performance of the spheroidal α_p phase and various needle-like α_s variants. The results indicate that the Ti-7333 alloy could be a promising candidate material for the high-strength fastener.     

Enhanced tensile properties of a reversion annealed 6.5Mn-TRIP alloy via tailoring initial microstructure and cold rolling reduction

The feasibility of improving the overall performance of medium Mn steels was demonstrated via tailoring the initial microstructure and cold rolling reduction.The combined effects of cooling patterns after hot rolling(HR) and cold rolling(CR) reductions show:(1) as the cooling pattern varied from furnace cooling(FC) to oil quenching(OQ),the intercritically annealed microstructure was dramatically refined and the fraction of recrystallized ferrite dropped,regardless of CR reductions.This resulted in both high yield/ultimate tensile strengths(YS/UTS) but low total elongation to fracture(El);(2) as the CR reduction increased from 50% to 75%,the OQ-samples after annealing exhibited a more refined microstructure with relatively higher fractions of retained austenite and sub-structure,leading to higher YS and UTS but lower El; whereas the FC samples appeared to exhibit little difference in overall tensile properties in both cases.The differences in microstructural evolution with cooling patterns and CR reductions were explained by the calculated accumulated effective strain(εAES),which was considered to be related to degrees of recovery and recrystallization of the deformed martensite(α').The optimal tensile properties of ~1 GPa YS and ~40 GPa·% UTS×El were achieved in the OQ-50%CR annealed samples at 650?C for 1 h.This was quite beneficial to large-scale production of ultra-high strength steels,owing to its serious springback during heavy cold working.     

Effects of Composition and Thermal Cycle on Transformation Behaviors, Thermal Stability and Mechanical Properties of CuAlAg Alloy

The phase transformation behavior, mechanical properties, and the thermal stability of CuAlAg alloy were studied and minor rare earth (0.1 wt pct La Ce) was added to improve the mechanical property of the studied alloy. It was found that Ag addition in the CuAl binary alloy can improve the stability of martensitic transformation and high Al content leads to the disappearing of martensitic transformation. The tensile strength and strain of the Cu-10.6Al-5.8Ag (wt pct) alloy were measured to be 383.5 MPa and 0.86%, respectively. With rare earth addition, the tensile strain increased from 0.86% to 1.47%. The CuAlAg alloy did not exhibit martensitic transformation on the second heating process. Its poor thermal stability still needs to be improved.     

Finding of Gray Points on the Surface of the Sn-Fe Alloy Layer and Its Effects on the Corrosion Resistance of the Alloy Layer

After removing tin coating of tinplates offered by some steel works, we discovered massive, highly disperse gray points outspreading along rolling direction on the surface of the alloy layer. Morphology of the alloy layer was observed by scanning electron microscope (SEM), and many cavities of the alloy layer were found out in the gray point. After analyzing the composition of the alloy layer, we found that content of Fe in the gray points was more than that in the normal alloy layer. Moreover, corrosion resistance of the alloy layer declines with increase of amount of gray points. In addition, the hot-humidity testing was carried out for some plates whose surface has many gray points. After 14 days, there were many rust points occurring in the edge of gray points and in the small gray points. The morphology of rust points was observed by atomic force microscope (AFM). The reason why rust points generated in the edge of gray points and in the small gray points was discussed.     

Study on Steel-Mushy Al-20Sn Alloy Bonding

Steel-mushy Al-20Sn alloy bonding was studied for the first time. The relationship model about preheat temperature of steel plate, solid fraction of Al-20Sn alloy mushy, rolling speed and interfacial shear strength of bonding plate could be established by artificial neural networks perfectly. This model could be optimized with a genetic algorithm. The optimum bonding parameters were: 505℃ for preheat temperature of steel plate, 34.3% for solid fraction of Al-20Sn alloy mushy and 10 mm/s for rolling speed, and the largest interfacial shear strength of bonding plate was 71.2 MPa.