汽车车身用6000系铝合金板材微观组织与热处理工艺的研究进展

本文介绍了6000系铝合金在汽车车身上的应用现状及其性能特点,并详细论述了该系合金的时效析出特征、强化机理、织构演化和合金元素对性能的影响。此外,分析了6000系铝合金的传统热处理工艺,阐述了固溶后预时效和预变形对合金烘烤硬化性的影响,并探讨了汽车车身用6000系铝合金目前存在的问题及当前的主要研究方向。     

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材料的织构导致其性能的各向异性。例如取向硅钢要求有高斯织构,这样高压变压器漏磁最小,能量损失最低。纯钛金属材料及其合金应用十分广泛,在常温下是六方晶体,其织构表现形式有别于立方晶体。在本期刊载的论文“工业纯钛金属织构标准极图的计算及分析”中,昆明理工大学材料科学与工程学院陈亮维等给出了纯钛任意织构对任意投影晶面理论极图的绘制方法,并提供了纯钛常见织构的参考极图。这为钛材研制与生产中出现的织构测试提供了分析标准,也为其他六方金属材料如镁、锌金属等材料的织构测试提供了极图分析参考。     

WS2软涂层刀具的材料优选及涂层制备

运用有限元软件分析了不同基体材料和过渡层的基体表面WS2软涂层的残余热应力。结果表明弹性模量和热膨胀系数等参数是影响涂层残余热应力大小的主要因素。采用中频磁控溅射、多弧离子镀外加离子束辅助沉积工艺制备了4种WS2软涂层刀具并对其性能进行了测试,分析结果符合有限元计算的结论,发现残余热应力对WS2软涂层刀具的性能产生很大的影响,并发现Zr过渡层能有效促进WS2Ⅱ型织构的生长。     

钽材轧制和再结晶织构演变研究进展

钽作为一种稀有难熔金属,耐化学腐蚀、电子迁移率低、延展性好、价格昂贵,常用在具有特殊性能要求的苛刻环境中。近些年来,钽材的生产工艺逐步改进,性能不断提高,但生产过程中其晶粒不可避免地会出现择优取向,即织构。织构能明显影响钽材的性能,不同用途的钽制品对织构的要求也不同,深冲时要求有强烈的{111}织构,溅射时需要织构均匀分布。轧制工艺和再结晶退火作为改变晶体材料各向异性的主要手段,前者可影响滑移系的激活和晶粒的转动状态,形成不同的轧制织构,后者能使特定取向的晶粒优先形核并快速长大,形成再结晶织构。国内外对金属材料的织构进行了大量研究,然而主要集中于钢铁和面心立方晶粒材料,对于钽这样的稀贵金属的织构研究较少。主要综述了钽材在轧制和再结晶过程中织构的变化规律,重点介绍了钽材冷轧和再结晶织构演变的研究现状及最新进展。     

激光表面织构化对材料摩擦学性能影响的研究进展

总结了激光表面织构化技术的特点,并介绍了其在摩擦学中应用的现状,分别讨论了激光表面织构的不同几何形状、尺寸和织构密度等因素,以及织构引起的金属材料表面硬度的升高对摩擦学性能的影响,展望了激光表面织构化技术未来的研究和发展方向及应用领域,指出应加强理论模拟和计算研究,以期与实验研究相辅相成;实验研究应注重规律的摸索和总结;机理方面应深入研究织构引起的组织和力学性能变化的规律,及其对材料摩擦学性能、力学性能和化学性能的影响。     

织构分析在材料检测中的应用

控制织构的类型和含量可以发掘材料最大潜能，因此织构材料广泛应用于各种功能器件和工程构件中。阐述了织构存在的多样性，织构的测量和表征以及织构的应用。重点讨论了如何利用织构分析对材料物相定性和修正物相含量的计算，以及以弹性模量为例介绍如何利用织构分析对材料的宏观性能进行计算和预测。     

铝合金氩弧焊与搅拌摩擦焊残余应力对比分析

铝合金材料由于其重量轻、耐腐蚀等优点被广泛应用于石油海洋工程中。铝合金的焊接及焊接接头的性能,备受关注。不同的焊接方法和焊接工艺产生的焊接残余应力对接头的疲劳寿命影响极大。以氩弧焊和搅拌摩擦焊工艺,选用不同的铝合金材料,采用小盲孔法测试焊接残余应力。比较了两种焊接方法、工艺所产生的接头焊接残余应力值,为今后铝合金焊接接头中,疲劳性能的计算提供初步的数据。试验结果表明,在铝合金的氩弧焊和搅拌摩擦焊对接接头中,残余应力的最大值均出现在焊缝中心到热影响区的范围内,随着与焊缝中心距离的增加,残余应力的数值逐渐减小。     

铝合金表面特性对其胶接性能影响的研究进展

不同的表面处理方法会导致铝合金表面的表面理化特性发生改变,从而对铝合金板材与胶黏剂的界面结合强度以及胶接接头的耐腐蚀性能有很大的影响。本文从铝合金表面粗糙度、微观织构、表面氧化层和涂层化学特性等方面入手,对铝合金胶接接头的界面强度和耐腐蚀性能影响的研究现状进行了综述。探讨了铝合金胶接研究发展趋势,并认为铝合金表面理化特性的参数化表征以及表面特性与胶接性能的关系模型建立等方面是今后研究的重要方向。     

晶体塑性模型描述多晶体循环加载中的Bauschinger效应

为了研究循环加载过程中织构对多晶材料Baushinger效应的影响,利用经典晶体塑性模型及含随动硬化的晶体塑性模型模拟AA6104铝合金循环加载力学行为.研究了多晶体中晶粒取向差异对材料宏观塑性行为的影响.详细分析了经典晶体塑性模型可描述多晶体循环加载Bauschinger效应机理,定量分析了多晶有限元模型中晶体取向差异对模拟结果的影响.结果表明多晶体中由于晶粒取向差异而造成的晶粒间相互作用力使得多晶体模型宏观卸载时晶粒内的残余应力是产生Bauschinger效应的主要原因,采用含随动硬化的晶体塑性模型能够较好地模拟具有织构的AA6014铝合金的循环加载过程.     

层状钴氧化物热电材料的结构调控研究进展

层状钴氧化物热电材料具有性能稳定、可在氧化气氛下长期工作、无毒无污染等优点,已成为热电转换领域研究的热点之一.综述了结构调控技术对层状钴氧化物热电性能的调控和优化,重点介绍了织构取向优化、纳米结构复合化、低维化等结构调控技术的特点,分析了结构调控技术对层状钴氧化物材料热电性能的影响,初步探讨了结构调控技术提高材料热电性能的原因并介绍了层状钴氧化物材料的研发应用现状,并对其发展前景进行了展望.     

析产品设计之肌理

肌理,设计中不可忽视的一个重要因素.设计师对肌理运用的好坏,直接影响到一个产品设计的成功与否.通过对肌理的含义及产品设计中肌理运用进行了分析,从材料、加工工艺以及组织结构等因素与肌理的关系的角度对产品设计中的肌理进行了探讨,使设计师能够对产品设计中的肌理的含义及其运用有一个大概的了解,以便在设计中将其良好运用,设计出更多优秀的产品.     

预拉伸厚铝板内 部残余应力 与晶粒取向均匀性的研究

目的消减预拉伸铝板内部残余应力。方法利用短波长X射线衍射仪(SWXRD),分别对某公司国产25 mm厚2024-T351预拉伸铝板,以及美国铝业公司(ALCOA)20 mm厚7075-T651预拉伸铝板的内部残余应力、内部织构及其沿板厚的分布,进行了无损测定。结果 ALCOA的20mm厚7075预拉伸铝板内部残余应力小于25 MPa,其内部晶粒取向沿板厚均匀分布;而某公司原工艺生产的25 mm厚2024预拉伸铝板,内部残余应力高达100 MPa左右,其内部晶粒取向沿板厚分布很不均匀。结论源自于轧制的内部织构沿板厚分布的不均匀性,使得以消减残余应力为目的的预拉伸处理中的铝板塑性变形不均匀,导致某公司国产预拉伸铝板内部残余应力的消减效果差,在其后续加工中容易产生加工变形超差的问题,需要抑制强剪切织构的产生,减小织构在整个板材厚度上的不均匀分布程度。     

Development of texture and texture gradient in Al-Cu-Li (2195) thick plate

Texture resulting from micromechanical processing plays an important role in the anisotropy of materials. The determination of texture components is a useful way to present texture data. The types of components present in the texture of a material can be related to other material aspects including predictions of yield loci using polycrystal methods. Al-Cu-Li 2195 thick plate was cold rolled to produce various reductions in thickness. Texture analysis was performed on the various rolled materials at different positions through the thickness of the plates. The texture components are consistent among the various rolled specimens at equivalent thickness positions. A texture gradient is observed to exist through the plate thickness that may indicate other microstructural information about the alloy. This texture gradient evidences the effects of increasing amounts of deformation on texture intensity, texture components observed, and changing modes of deformation.     

Texture control by {10-12} twinning to improve the formability of Mg alloys: A review

Texture control of wrought Mg alloys, particularly in rolled Mg alloy sheets, has been an important research topic for the past several decades because it has significant influence on stretch formability at room temperature. For Mg alloys, {10-12} twinning can be easily activated and causes a ˜86.3° lattice rotation. Thus, pre-twinning deformation is considered as an effective and low-cost method for texture control in wrought Mg and its alloys. Furthermore, it has been verified that texture control via pre-twinning deformation can remarkably improve stretch formability of rolled Mg alloy sheets. In this review, recent researches on texture control via twinning deformation and its influence on stretch formability will be critically reviewed. The main contents include the micro-mechanism and impact factors of control in twin-orientation, plastic processing techniques of pre-inducing twins and the application of pre-induced twins in improvement of stretch formability. Finally, further research directions on this field were proposed.     

搅拌摩擦加工对AZ31镁合金微观组织及力学性能的影响

采用搅拌摩擦加工技术(Friction stir processing,FSP)对AZ31镁合金板材进行了单道次加工,研究了加工区域微观组织对力学性能的影响。结果表明,相同前进速度下,旋转速度升高,平均晶粒尺寸增大。搅拌摩擦加工后,晶粒尺寸和织构变化显著影响AZ31镁合金的力学性能,平均晶粒尺寸越大,越易发生孪生变形。织构类型主要包括基面织构和纤维织构。基面织构位于软位向时,屈服强度降低,但纤维织构会弱化基面织构对力学性能的影响。     

Quantifying the recrystallization of cold rolled AA 3015 aluminum alloy by X-ray diffraction

The recrystallization kinetics of continuous cast (CC) AA 3015 aluminum alloy with and without pre-treatment has been investigated by X-ray diffraction and measurements of hardness. The variation in texture volume fractions with annealing time reflects better the progress of recrystallization. The JMAK exponent and the activation energy for recrystallization derived from texture data are in good agreement with those from hardness data. Monitoring the change of texture volume fractions during annealing is shown to be a feasible method of determining the recrystallization kinetics of aluminum alloys. The recrystallization kinetics and recrystallization texture of CC AA 3015 aluminum alloy are strongly affected by concurrent precipitation. Concurrent precipitation significantly retards the recrystallization of CC AA 3015 aluminum alloy, decreases the JMAK exponent, enhances the activation energy for recrystallization, and results in a strong P recrystallization texture.     

Texture and microstructure development during hot deformation of ME20 magnesium alloy: Experiments and simulations

The influence of deformation conditions and starting texture on the microstructure and texture evolution during hot deformation of a commercial rare earth (RE)-containing magnesium alloy sheet ME20 was investigated and compared with a conventional Mg sheet alloy AZ31. For all the investigated conditions, the two alloys revealed obvious distinctions in the flow behavior and the development of texture and microstructure, which was primarily attributed to the different chemistry of the two alloys. The presence of precipitates in the fine microstructure of the ME20 sheet considerably increased the recrystallization temperature and suppressed tensile twinning. This gave rise to an uncommon Mg texture development during deformation. Texture simulation using an advanced cluster-type Taylor approach with consideration of grain interaction was employed to correlate the unique texture development in the ME20 alloy with the activation scenarios of different deformation modes.     

AA6111合金在热轧过程中保持时间对晶体织构的影响

使用EBSD研究了AA6111合金在两次热轧过程中不同保持时间对晶体织构演变的影响.结果显示:变形织构主要由α和β纤维组成.从主要织构组分的取向强度看出,随着保持时间的增加,Brass和Copper理想织构组分显著增加,S织构没有明显变化.     

Texture evolution in two phase Zr – 2.5 wt-%Nb through modified route

Abstract

Two phase Zr – 2.5 wt-%Nb is used as pressure tube material in water cooled and moderated reactors. The in service behaviour of this hcp zirconium based alloy is dependent on strong textures developed during thermomechanical processing. In the present study, the texture evolution during fabrication of this material, using a modified route, was investigated. Texture, evaluated by the orientation distribution function, was correlated to microstructure during various stages of processing. It was observed that a strong orientation fibre parallel to the working direction develops with hot working (extrusion). With subsequent cold working, the texture formed after extrusion alone becomes strengthened. This observation is attributed to the presence of a soft secondary phase (β) at the α-phase grain boundary. In contrast to the above, in the case of single phase Zircaloy 4, new components of texture are generated with cold deformation after hot extrusion, as a result of interaction between grains.