冷轧形变量对异步轧制高纯铝箔织构的影响

应用取向分布函数(ODF)研究和分析了异步轧制高纯铝箔的形变织构和再结晶织构.结果表明:异步轧制高纯铝箔的形变织构除了C{112}<111>、B{110}<112>和S{123}<634>织构组分外,还有较强的CubeND{001}<110>和{102}织构.异步轧制高纯铝箔的再结晶织构由强的立方织构{001}<100>和弱的R{124}<211>织构组成.随着形变量的增加,异步轧制高纯铝箔的形变织构和再结晶织构呈现规律性的变化,{102}织构减少,S织构先增后减,速比较小时C织构近线性减少,速比较大时C织构则先增后减.异步轧制高纯铝箔的退火样品中有很强的立方织构,这与异步轧制提高高纯铝箔的形变储能有关,形变量过大时,立方织构随形变量的增加急剧减少.{102}织构有利于再结晶立方织构的加强.     

The study of the technology parameters on the superplasticity of the new Al–Zn–Mg–Cu–Ni–Zr base alloy

Al–Zn–Mg–Cu aluminum alloy contain 0.3% Zr and 4% Ni was processed by traditional hot and cold rolling with a total reduction from 0  to  80%. The relationship between superplastic behavior and reduction of cold deformation and casting cooling rate was analyzed. It is shown that the decrease in the reduction of cold rolling do not significantly influence on flow stress and elongation. Decrease in casting cooling rate leads to insignificantly decrease in superplastic indicators. Alloy exhibits advanced superplasticity: the elongation of 400–800% at the strain rates of (5 × 10^–3–1 × 10^–1) s^–1.     

Mechanism of warm and cold roll bonding of aluminum alloy strips

From a study of interfacial behavior at deformations up to 60%, a mechanism is proposed for pressure welding of aluminum strips by rolling at warm and cold conditions, where faying surfaces were first degreased and scratch-brushed. According to this mechanism, the scratch-brushed layers fractured coherently after entering roll gap at a reduction of approximately 21%, which is regarding to the threshold deformation for roll bonding of commercial pure (CP) aluminum strips, and some small cracks perpendicular to the rolling direction formed. As deformation proceeds and roll pressure increases, these cracks quickly expanded into fissures. This process allowed the bond to be established between the underlying metals, termed virgin metals, of base metal, which were extruded through the cracks and fissures at the scratch-brushed regions. Moreover by increasing the rolling temperature, threshold deformation required for bond formation decreases.     

Property optimization of nanostructured ARB-processed Al by post-process deformation

The effect of post-process deformation on the mechanical properties of nanostructured aluminum (99.2% purity) has been investigated by cold rolling of samples which have been processed by accumulative roll bonding (ARB) to a strain of ε_vM = 4.8. Samples have been cold rolled to 10, 15, and 50% reductions and ultimate tensile strength (UTS), yield stress and elongation have been determined by tensile testing at room temperature. The mechanical testing shows that cold rolling to low strains (10% and 15%) leads to softening and increase in elongation compared to the as-processed ARB material. In contrary, cold rolling to large strain (50%) results in significant strengthening. This leads to the suggestion of a transition strain within the range of 25–35% reduction by rolling. The microstructural evolution during post-process deformation has been followed by transmission electron microscopy showing a significant change in the dislocation structure when the strain is increased. Based on the experimental observations the mechanical behavior is related to the structural changes focusing on the characteristics of the dislocation structure present between the narrowly spaced lamellar boundaries in the deformed structure.     

Formation of textures and microstructures in asymmetrically cold rolled and subsequently annealed aluminum alloy 1100 sheets

The formation of textures and microstructures in asymmetrically cold rolled and subsequently annealed AA 1100 sheets was investigated. The asymmetrical rolling procedure in this experiment was performed in a rolling mill with different roll velocities (roll velocity ratio of 1.5/1.0). In order to enhance the shear deformation, asymmetrical rolling was performed by a large reduction per pass and without lubrication. Asymmetrical rolling led to the formation of strong shear textures. The evolution of asymmetrically cold rolled textures was analyzed by FEM simulations. After recrystallization annealing, pronounced {111}//ND orientations prevailed in all thickness layers. Intensified shear deformations by asymmetrical rolling also led to the formation of ultra-fine grains after recrystallization annealing.     

Analysis of through-thickness heterogeneities of microstructure and texture in nickel after accumulative roll bonding

The through-thickness heterogeneities of the microstructure and texture have been investigated in pure nickel processed by six cycles of accumulative roll bonding (ARB) with lubrication applied during each rolling pass. Strong rolling textures are found in the intermediate and center layers of the deformed sample, whereas increased fractions of the shear texture are observed near the surface. Significant differences at different depths are also revealed in the fractions of areas containing either predominantly low angle misorientations or predominantly high angle misorientations. It is found that the fractions of such areas are much more sensitive to the deformation history than the average parameters based on the measurements of the boundary spacing and fractions of high angle boundaries. For the material studied in this work, the area fraction of the low misorientation regions appears to correlate with the summed fraction of the rolling texture components. The observed microstructural and textural variations are discussed and compared with literature data, taking into account the influence of large-draught rolling and lubrication on the distribution of strain imposed during the ARB process.     

Recrystallisation textures in cold rolled low carbon steel containing ferritic and bainitic microstructures

Abstract

Low carbon steel strip was heat treated to generate four different starting microstructures (fine and coarse polygonal ferrite, acicular ferrite and bainite) for investigating their influence on texture development during cold rolling and annealing. The starting materials were cold rolled to 50–90% reduction and annealed for various times in the temperature range 853–953 K. The resultant microstructures and textures were examined mainly by electron backscatter diffraction and X-ray diffraction. The initial microstructure strongly influenced the crystallographic rotation paths during cold rolling, whereby high strain deformation generated strong {223}〈110〉 texture components in the polygonal ferritic microstructures, whereas a strong {001}〈110〉 texture was produced in the acicular/bainitic microstructures. Subsequent annealing generated, to varying degrees, the classic {111}〈uvw〉 (γ-fibre) recrystallisation texture in all materials. Unexpectedly, coarse polygonal ferrite produced the strongest γ-fibre recrystallisation texture after 70–90% cold rolling reduction. Based on arguments involving the effect of carbon in solution, initial grain size and deformation textures on recrystallisation texture development, it was shown that a strong γ-fibre texture can indeed be generated in coarse polygonal ferrite.     

罩式退火无间隙原子钢的最优冷轧压下率的确定

以工业生产的含钛、铌和含钛的两种无间隙原子(IF)钢热轧钢板为试验材料,在实验室研究了冷轧压下率对两种IF钢的显微组织、力学性能和再结晶织构的影响。结果表明:在试验条件下,两种试验钢经不同冷轧压下率冷轧和720℃×5 h罩式退火后,再结晶完成,随着冷轧压下率的增加,晶粒变得细小均匀,退火后得到的织构也增强,并且织构类型有转向{111}织构的趋势;塑性应变比r90在压下率为70%时达到最大值,随着冷轧压下率的进一步增大,r90值减小;应变硬化指数n90值逐渐降低。最后提出工业生产中冷轧压下率最佳范围为70%~80%,可获得良好的深冲性能。     

Microstructures and properties of ultrafine-grained pure titanium processed by equal-channel angular pressing and cold deformation

Equal-channel angular pressing (ECAP) has been used to refine the grain size of commercially pure (CP) titanium as well as other metals and alloys. CP-Ti is usually processed at about 400 degrees C because it lacks sufficient ductility at lower temperature. The warm processing temperature limits the ability of the ECAP technique to improve the strength of CP-Ti. We have employed cold deformation following warm ECAP to further improve the strength of CP-Ti. Ti billets were first processed for eight passes via ECAP route Bc, with a clockwise rotation of 90 degrees between adjacent passes. The grain size obtained by ECAP alone is about 260 nm. The billets were further processed by cold deformation (cold rolling) to increase the crystalline defects such as dislocations. The strength of pure Ti was improved from 380 to around 1000 MPa by the two-step process. This article reports the microstructures, microhardness, tensile properties, and thermal stability of these Ti billets processed by a combination of ECAP and cold deformation.     

Effect of electroplastic rolling on the ductility and superelasticity of TiNi shape memory alloy

The brittle TiNi shape memory alloy strips were processed by electroplastic rolling (EPR) without intermediate annealing. The maximum thickness reduction of the alloy strip in the individual EPR pass can be 21.6% and the total deformation in terms of thickness reduction can reach 74% in the seven passes of EPR processing. The ductility of the TiNi alloy is enhanced by electropulse due to the dynamic recrystallization in the process. The rolling separating force in EPR drops compared to the cold rolling. Furthermore, the EPR processed TiNi after annealing exhibits an excellent superelasticity and the recoverable strain of 6% is obtained.     

Consolidated Al/Al2O3 Nanocomposites by Equal Channel Angular Pressing and Hot Extrusion

This work is aimed at producing Al-matrix nanocomposites through the powder metallurgy (PM) process. An initial study on pure aluminum powder was performed to analyze the performance of different PM techniques. In particular, Al powder was refined via high-energy ball milling and consolidated by hot extrusion and equal channel angular pressing. The latter revealed to be a very efficient procedure for powder compaction (high density and hardness of the products) and it was adopted for the production of Al-based composites reinforced with 2% and 5 wt% of Al₂O₃ nanoparticles. The composites exhibited higher hardness than the pure aluminum sample.     

Texture and microstructure evolution in cold rolled AZ31 magnesium alloy

Microstructure and texture evolution of an AZ31 magnesium alloy during cold roll was investigated. Shear bands formed and fine recrystallized grains appeared in the shear bands at the reduction of 22% during cold roll process. Texture of hot-extruded AZ31 magnesium alloy can be expressed by (0002) texture, while those of cold roll sheet were characterized by (0002) texture with a double-peak distribution, showing that basal texture tilted about ± 10°away from the normal direction toward the rolling direction.     

激光加热下铜的再结晶织构及其机制探讨

冷变形金属再结晶织构受加热速度的影响很大。利用激光超快速加热方法对冷轧纯铜进行再结晶处理，其织构转变动力学过程与普通加热时不同，并受冷轧量的影响。     

压下率对轧制单层晶极薄带晶界滑移特性的影响

采用退火态单层晶轧制铜箔为原料,进行不同压下率的箔轧.以多晶体位错滑移及塑性流动机制为基础,建立了考虑潜在硬化和晶格转动效应的率相关晶体滑移本构模型,分析了压下率对轧制单层晶极薄带晶界附近区域变形分布特性、取向演化和滑移系激活规律的影响,并探讨其机理.确定了合理的材料本构参数,铜箔拉伸实验与晶体塑性有限元模拟得到的应力-应变曲线一致.所建立的晶体塑性有限元模型,可很好的模拟最大压下率达到80%时轧制单层晶铜箔的变形过程.结果表明:1)由于晶粒形状、晶界及晶粒取向的作用导致晶内-晶间变形分布非均匀性;2)由于晶粒间复杂的相互作用导致晶粒取向主要绕横向(TD)进行旋转,且旋转角度和取向分散度随压下率的增加而增大;3)在晶内-晶间不同区域的滑移系启动存在显著差异,启动滑移系随压下率的增加而增多,当压下率小于等于60%时,在晶粒表层和晶界处,滑移系成对发生启动,当压下率达到80%时,表层和晶界处为多滑移系启动情形;4)滑移最先从晶粒表层和晶界处开始,然后向晶粒内部延伸.     

Rolling and annealing textures of a SiCw/Al composite

A SiC whisker reinforced pure aluminum composite (SiC_w/Al) was fabricated using a squeeze casting route and cold-rolled to 50% reduction in thickness. Some cold-rolled composites were then annealed at 500 °C for 1 h. The pure aluminum was also cold-rolled and annealed in the above way for comparison purpose. The textures of the cold-rolled and annealed materials were examined using XRD technique. It was found that the dominant texture components in the cold-rolled composites consisted of {112}〈111〉, {100}〈011〉 and {123}〈634〉. They were much weaker than those in the cold-rolled aluminum. When the cold-rolled composites were annealed, the new texture components {211}〈213〉, {013}〈131〉 and {011}〈211〉 occurred and had the similar intensity as the texture components remained from the deformation state. This indicated that the recovery reaction and recrystallization occurred simultaneously when the cold-rolled composite was annealed 1 h at 500 °C. Like the situation of the deformed materials, the annealing texture was also much weaker in the composite than in the aluminum. The weaker deformation and annealing textures in the composites can be attributed to the introduction of the whiskers.     

无取向硅钢形变储能取向依赖性及其对再结晶织构的影响

采用晶体塑性有限元模拟与实验相结合的方式,研究无取向硅钢冷轧过程中不同初始织构组分的取向流动与形变储能累积。结果表明:冷轧后形成了较强的α,γ形变织构和较弱的λ形变织构。再结晶织构由γ,α,η和λ织构组成,其取向密度依赖于冷轧压下率。随冷轧压下率增大,λ再结晶织构逐渐增强,η织构先增强后减弱,γ织构先减弱后增强,α织构稍有弱化。冷轧过程中形变储能累积具有明显的初始取向依赖性,初始γ取向储能累积速率在低于50%压下率时与初始α取向接近,高于50%压下率时则明显大于后者,初始λ取向储能累积速率始终显著低于γ和α取向,转至同一形变取向的不同初始取向间的储能累积也会产生差异。冷轧过程中不同初始织构组分的取向流动与形变储能累积规律,决定了无取向硅钢再结晶织构组分的发展。     

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.     

Cu-Cr-Zr系合金变形过程中的织构分析

对Cu-Cr-Zr系合金铸锭进行热轧、固溶和冷轧,利用X射线衍射仪测试合金材料不同状态下的织构,分析各个状态下的织构种类及其演变规律.结果表明:热轧后材料中主要织构为Copper{112}〈111〉(C)织构、Brass{011}〈211〉(B)织构和S{123}〈634〉织构,存在微弱的立方织构{001}〈100〉;固溶后材料中织构的强度降低,立方织构消失;冷轧后材料中织构的强度随着变形量的增加而强度增加,冷轧过程中主要织构也是C织构、B织构和S织构,在冷轧初期出现Goss{011}〈100〉(G)织构,随后G织构慢慢减弱,直至消失.     

室温ECAP和冷轧复合变形工业纯钛的组织和性能

采用ECAP技术和常规冷轧复合变形工艺制备了高强度工业纯钛,研究了复合变形后试样的力学性能与显微组织的关系.结果表明,工业纯钛经室温单道次ECAP和冷轧复合变形后,晶粒被严重拉长,形成了明显的纤维状组织,试样的抗拉强度高达805MPa;随着冷轧变形量的增大,变形组织的细化程度和均匀性提高,使试样的强度和塑性进一步提高.位错滑移和孪生是工业纯钛室温ECAP和冷轧复合变形的主要变形机制.     

高纯铜冷轧形变组织及织构演变规律研究

采用纯度99.99%的高纯铜进行30%、50%、70%、90%形变量冷轧加工,对不同形变量下高纯铜的晶粒尺寸、分布等微观组织及织构进行了定量研究。结果发现,随着形变量的增加,平均晶粒尺寸、晶粒尺寸方差不断减小,晶粒高宽比(形状因子)逐渐增加,晶粒逐渐转变为纤维状;冷轧织构(Brass、S、Copper)含量逐渐增加,其中Brass织构最多,S织构次之,Copper织构最少。形变量至90%后,冷轧织构含量增至85%以上,晶粒逐渐向标准极射三角形中间部位聚集,在{101}方向有显著聚集,{111}方向始终无明显聚集。α取向线及β取向线上织构含量逐渐增加,均出现明显的集中织构,形变量从70%增加至90%时织构的增加最明显。