深冷轧制制备高性能金属材料研究进展

相对于传统热轧、温轧、冷轧,深冷轧制是一项变革性技术,它利用某些金属材料在深冷情况下具有优异的塑性变形能力以及深冷环境阻碍塑性变形过程中位错运动和再结晶行为,促使材料晶粒细化,材料具有更高的强度与韧性。系统地介绍了近年来深冷轧制制备高性能金属材料的研究进展,包括深冷轧制在铝合金、铜合金、钛合金、复合层状金属带材中的应用。对深冷轧制制备高性能金属材料的研究进行了展望。     

[学科发展]深冷轧制制备高性能金属材料研究进展

相对于传统热轧、温轧、冷轧，深冷轧制是一项变革性技术，它利用某些金属材料在深冷情况下具有优异的塑性变形能力以及深冷环境阻碍塑性变形过程中位错运动和再结晶行为，促使材料晶粒细化，材料具有更高的强度与韧性。系统地介绍了近年来深冷轧制制备高性能金属材料的研究进展，包括深冷轧制在铝合金、铜合金、钛合金、复合层状金属带材中的应用。对深冷轧制制备高性能金属材料的研究进行了展望。     

对影响金属材料塑性变形的重要指标——应变速率敏感性指数的探讨

本文对影响金属材料塑性变形的应变速率敏感性指数进行了分析研究,并介绍了一些测试这一指标的方法。对研究金属材料的塑性变形有一定的指导意义。     

轧态Zn-5Al-RE合金的超塑性研究

用恒载荷法研究了轧态Zn-5Al-RE合金的组织超塑性和相变超塑性的蠕变特征,测定了轧态Zn-5Al-RE合金超塑变形的激活能Q值和应变速率敏感指数m值。试验结果表明：当载荷减小、温度降低和淬火保温时间延长时,组织超塑性变形中稳态蠕变阶段延长;粗晶粒可降低组织超塑性变形时的伸长率,但对相变超塑性变形的伸长率影响不大;组织超塑性变形的m值大于相变超塑性变形的m值;轧态Zn-5Al-RE合金的表观激活能略大于Zn-5Al-RE合金的激活能。     

基于红外热象技术的金属材料疲劳性能研究方法

金属材料的疲劳极限或疲劳寿命等性能是长寿命机械和结构抗疲劳设计的基本数据,探讨效率高、成本低而又准确的试验新方法,成为相关研究者十分感兴趣的课题.材料在循环载荷作用下产生的塑性变形经不断累积会引起疲劳破坏,这个过程所耗的塑性功绝大部分以热量形式耗散,因此寻找热耗散温度变化过程与疲劳极限及寿命之间的关系很有意义.就此问题,文中引入利用先进的红外热成象技术确定金属材料疲劳性能的试验研究方法,主要从原理和试验方法两方面进行介绍,并对45钢的试验过程和现象作较为详细地阐述,得到较准确的疲劳极限值和基于红外热象技术确定疲劳寿命的重要参量 M.     

累积叠轧工艺对AA3003铝合金显微组织和性能的影响

对AA3003铝合金板进行4道次累积叠轧加工,研究了不同道次累积叠轧后铝合金板的显微组织、拉伸性能和成形性能。结果表明:随着叠轧道次的增加,铝合金板中晶粒发生细化并趋于等轴形状,板厚方向上的组织均匀性增强;累积叠轧铝合金板的中心层主要为轧制织构,表层主要为剪切织构;累积叠轧工艺提高了铝合金板的强度,但降低了其塑性和成形性能,随着叠轧道次的增加,铝合金板的屈服强度和抗拉强度增大、伸长率变化不大、成形性能略微下降。     

铝合金单道次热轧过程的温度模拟

为精确预测轧件的温度场、优化轧制工艺和提高最终产品的质量,通过轧制试验和二维弹塑性有限元法,用MSC、Merc软件建立了3104铝合金板材单道次热轧有限元温度模型,分析了空冷、接触传热、塑性变形热和摩擦热等传热方式对轧板温度的影响以及轧板初始温度、轧制速度、接触传热系数和压下量等轧制参数的轧板温降灵敏度系数。结果表明:在单道次热轧过程中,接触传热对轧板温度的影响最大,塑性变形热的影响次之,摩擦热的影响较小,空冷的影响最小;轧板初始温度、轧制速度、接触传热系数和压下量等轧制参数的轧板温降灵敏度系数依次减小。     

金属切削过程中晶体塑性变形的有限元分析

基于金属材料塑性变形理论,利用有限元分析软件,建立了金属切削过程中的晶体变形模型,对二维正交金属切削过程中的晶体塑性变形进行了数值模拟。将仿真结果与实验数据进行了对比,验证了相关理论和模型的有效性。     

《塑性力学及其在工程中的应用》讲座(五) 滑移线法的原理及应用

塑性力学中的滑移线法是利用滑移线的性质求解塑性力学问题的一种方法。金属材料在塑性变形时所产生的滑移是沿着最大剪应力方向的,所谓滑移线就是塑性变形过程中最大剪应力的迹线。如将塑性变形过程中     

高颈法兰数控辗环机精辗成形高效节能新工艺的研究

通过对高颈法兰辗轧生产中塑性变形分析,总结其变形特点和原理,提出数控辗环机辗轧高颈法兰的短流程工艺和模具设计方案、操作注意事项,从而达到高效节能的目的.     

ARB法制备超细晶材料的组织与性能研究

采用累积叠轧焊方法（ARB）对MB2镁合金和1060工业纯铝进行试验,分析了它们变形前后内部微观组织结构的演变和力学性能的变化。结果表明,MB2镁合金平均晶粒细化到1.2μm,抗拉强度由轧制前的235 MPa提高到300 MPa;1060工业纯铝晶粒细化到约400 nm,抗拉强度由轧制前的87MPa提高到220 MPa,硬度由轧制前的37 HV提高到83 HV;2种材料的延伸率在ARB 1道次后下降,并随着轧制道次的增加,材料组织均匀程度提高,抗拉强度变化平缓;MB2镁合金的延伸率回升幅度较大。     

Severe wear of rolling/sliding contacts

The wear of wheel flanges against the sides of rails is shown to be caused by rolling/sliding contacts sustaining high cyclic stresses at low slide/roll ratios. When these conditions are reproduced in the laboratory severe metallic wear is initiated when the resultant shear stress, which is dependent on both normal (pressure) and tangential (friction) forces, exceeds a critical value. The results are discussed in terms of Johnson's shakedown limit and the material's stress/strain characteristics. It is concluded that the severe wear of contacts at low slide/roll ratios is caused by high resolved cyclic stresses that result in continual plastic deformation of the surface layers.     

An approximate method for a three-dimensional analysis of rolling

A theory, based on the extremum principle for rigid perfectly plastic materials, is given for the analysis of three-dimensional deformation in rolling. Theoretical solutions are obtained for single-pass rolling in terms of sideways spread, roll torque and the location of neutral points. The results on spread and roll torque showed excellent agreement with those found by experiments in the literature.     

轧机油膜轴承锥套微动损伤机理和多极边界元法

为揭示大型轧机油膜轴承等过盈量弹性结合锥套与辊颈粘结事故的产生机理,采用多极边界元法定量描述锥套与辊颈在液压胀形装配过程中的接触应力分布规律,发现锥套与辊颈装配就位时两端区域接触压力高度集中现象,其最大值超过辊颈屈服极限致使辊颈表面生成对应塑性变形的高应力区.通过过盈配合轴套与悬臂轴组成的旋转试验装置,对油膜轴承锥套与辊颈在轧制负荷下进行微动损伤模拟试验,证明辊颈与锥套随着轧辊转动存在相互微动现象,讨论轧制过程中锥套与辊颈两端高接触应力区域微动疲劳损伤导致两者发生粘结的机制.阐明等过盈量弹性结合锥套结构的不合理性,否定原有锥套淬火硬度低而导致粘结事故发生的观点.     

A plane-strain elastoplastic finite-element model for cold rolling of thin strip

In cold rolling of thin strip, elastic roll deformation is a prominent phenomenon which may indeed govern the whole process. Analysis of the literature suggests a number of methods to solve this coupled problem; for the most severe operations, the coupling technique is more important than the precision of the computation of stress and strain. To perform as general an analysis as possible, a completely coupled finite element model is formulated, meshing a global strip-roll system with internal interface with sliding and friction. The model is two-dimensional and only analyzes roll flattening. The basic equations and numerical formulation are described. Application to several kinds of rolling passes is examined (temper rolling, thin foil rolling) with special emphasis on roll deformed shape and behaviour of metal in the roll gap (sliding/sticking zones, elastic/plastic zones).     

Analysis of the forming process of sintered powder metals by a rigid-plastic finite-element method

A finite-element method for analyzing plastic deformation of sintered powder metals is developed. To give a theoretical basis, a variational principle for rigid-plastic deformation of porous metals is derived. The effect of the change in density during plastic deformation due to expansion or contraction of the internal pores is accommodated to the rigid-plastic finite-element method. As an example of analysis, plane-strain continuous rolling of sintered powder plates is treated. The distributions of density, strain, strain rate and stress in the plate and the pressure distribution over the roll surface are calculated. It is shown that the deformation behaviour of sintered powder metals is significantly influenced by the initial density.     

棒材高精度二辊矫直质量控制策略研究

高精度矫直辊辊型设计及工艺参数控制是二辊矫直机的核心技术。为了满足高精度棒材矫直要求,在辊型设计过程中依据矫直辊磨损状态、弹塑性理论、塑性变形硬化系数求解模型及中性层偏移理论,提出“凹三凸二”分段辊型的矫直辊组合形式及辊型设计方法。在此基础上,根据棒材与矫直辊的局部线接触状态,建立棒材二辊矫直倾角及辊缝估算模型,进而探讨二辊矫直工艺参数（倾角、辊缝、矫直速度和导板间距）的变化规律和控制策略,并给出具体设计实例和有限元模拟分析。从矫直力、塑性变形深度、直线度及残余应力等角度,证明该辊型设计方法和工艺控制策略的有效性,且现场试验矫后的棒材直线度小于1 mm/m,完全满足棒材高精度矫直标准。     

On properties at interfaces of friction welded near-nanostructured Al 5083 alloys

Equal-channel angular pressing is a material processing method that allows very high strains to be imposed, which leads to extreme work hardening and micro-structural refinement, with minimal change of external sample dimensions. It offers possibilities of good mechanical properties, such as high strength and ductility, while allowing flexibility of choice of alloy composition for better corrosion behavior, lower materials costs, and so on. This study characterizes for the first time the microstructure and properties of aluminum friction welded after severe plastic deformation via the equal-channel angular pressing method. In this study, 5,083 aluminum alloys, which were exposed to severe plastic deformation using square cross-sectional equal-channel angular pressing die, were joined with friction welding method. It was found that tensile and fatigue strengths of severe plastic deformed and welded specimens were higher than those of the purchased specimens. Hardness values were also consistent with the strength results. However, the refining of grain size as shown from microstructures results in a significant increase in hardness and mechanical properties.     

Formation of nanosized ferromagnetic phases during plastic deformation and subsequent annealing of stable austenitic steels

The effect of severe plastic deformation on the destabilization of the g phase in metastable and stable austenitic steels is considered. An increase in the degree of deformation and a decrease in the deformation temperature were shown to lead to the formation of a ferromagnetic phase in the materials under study.     

多曲面复杂卡箍的弯制及模具的设计

介绍了多曲面复杂卡箍的特点,分析板料在塑性变形过程中尺寸偏移的情况,明确中性层材料在弯曲过程中尺寸基本不变,绘制弯曲卡箍的展开图及其计算出弯曲部分的展开尺寸是卡箍弯制的前提。卡箍的形状、大小及其精度是设计弯曲模具的依据,确定多曲面卡箍弯制造的先后顺序,设计卡箍弯制模具及确定凸、凹模具间隙,使压制出的零件符合图样要求。