纯镁细丝拉拔的有限元模拟

以热压缩本构方程为基础,控制不同的摩擦因数、拉拔速度以及道次变形量,对纯镁细丝的拉拔工艺进行了有限元模拟。结果表明,随着摩擦因数的增加,拉拔力、应变不均匀度、最大主应力均增加;随着拉拔速度的增加,拉拔力变化不大,应变不均匀度、最大主应力逐渐增加,当拉拔速度高于60mm/s时,最大主应力急剧增加;随着道次变形量的增加,断裂倾向值增加,当道次变形量大于15%时,断裂倾向值显著增加。纯镁细丝较优的拉拔工艺参数:摩擦因数为0.08,拉拔速度低于60mm/s,道次变形量为10%~15%。     

纯镁细丝冷拉拔工艺的研究

本文研究了采用不同润滑剂、拉拔速度、道次变形量对纯镁细丝累积变形量、表面质量、力学性能的影响。结果表明:选择摩擦系数较小的液体油基润滑剂,拉拔速度小于60mm/s,道次变形量为10%-15%、累积变形量约40%的多道次冷拉拔工艺参数制备的纯镁细丝表面质量以及力学性能均较高,并能满足一定的生产效率要求。     

挤压温度对往复挤压工业纯镁组织性能的影响

研究了工业纯镁的往复挤压工艺,在不同温度下用往复挤压工艺细化工业纯镁晶粒.挤压4道次,用金相显微镜观测了不同挤压温度条件下晶粒细化效果,测试了晶粒细化后的强度和硬度.结果表明,在相同挤压道次下,随着挤压温度的提高,晶粒度不断增大,拉伸强度和伸长率下降；在150℃往复挤压后,拉伸强度达到221 MPa,伸长率为23％.     

变形量对多道次拉拔和减径轧制5056铝棒组织和力学性能的影响

对5056铝棒进行了多道次拉拔和减径轧制变形处理,分析了其显微组织结构和力学强度的变化情况。研究结果表明:随着拉拔应变增大至2. 0,晶粒被拉长,晶粒发生了显著的细化。当铝棒受到大压下量轧制后,基体中形成了许多平行于轧制态结构的位错胞,生成了部分和轧制方向保持一定角度的片层晶粒位错亚结构。纯铝材料的强度随拉拔与轧制程度的上升而增大,同时伸长率发生了降低的现象;增大等效应变量后,晶粒的尺寸将会发生不断细化,由此实现强度增大的效果;受拉拔与轧制时引起的晶粒择优取向影响,强度也会随之上升。     

退火处理对热轧纯镁力学和腐蚀性能的影响

对热轧纯镁进行了退火处理,研究了退火后纯镁的显微组织、室温力学和腐蚀性能。结果表明,最佳退火工艺为175℃×2 h,此工艺下纯镁晶粒细化,内应力降低,耐腐蚀性能提高。随退火温度提高,纯镁退火后的力学和耐腐蚀性能下降。     

一种异形截面钢丝滚道全模拉拔工艺

通过计算分析异形截面钢丝滚道拉拔前后的断面收缩率以及变形特点,制定了3道次全模拉拔成形的工艺方案。利用Deform-3D有限元软件,对异形截面钢丝滚道的全模拉拔工艺过程进行数值模拟,分析了拉拔过程中的金属流动规律,研究了拉拔模具的受载荷情况和各道次钢丝拉拔过程中的等效应力分布。根据模拟结果调整试验参数,并进行生产试制,得到表面成形质量好、圆角填充完整、尺寸精度符合要求的成品钢丝。试验结果与模拟结果基本一致,表明选取的试验参数是合理有效的,同时也验证了异形截面钢丝滚道3道次全模拉拔工艺方案是可行的。     

道次间冷却工艺对厚板芯部变形及组织的影响

利用道次间冷却技术对特厚钢板轧制开展道次间冷却工艺试验,研究轧制过程中的冷却参数对钢板变形渗透性和晶粒细化的影响规律。研究结果表明:道次间冷却工艺能够促进轧制变形向特厚钢板芯部渗透,在一定程度上消除了芯部带状组织;采用再结晶低温区连续轧制并在轧制道次间进行大强度冷却工艺,特厚钢板芯部组织晶粒明显细化,晶粒尺寸可达10~15μm;粗轧道次间的冷却工艺对轧制变形渗透的提高效果优于中间坯冷却工艺,并且道次间冷却强度的增大有助于进一步提高变形渗透性。     

生物医用纯镁的腐蚀性能研究

选择纯镁为主要研究对象,应用析氢、质量损失法,从杂质Fe含量、变形状态等方面研究了纯镁在Hanks'溶液中的腐蚀规律.结果表明,纯镁中Fe元素含量越低,晶粒越细小,纯镁在Hanks'溶液耐腐蚀越好;纯镁的腐蚀速率可通过减少Fe含量、晶粒细化等方法进行控制.     

纯镁切应力变形后的微观组织演变、力学性能、腐蚀行为

纯镁为密排六方结构,具有较少的独立滑移系导致其塑性较差。研究了纯镁变形后的微观组织演变、力学性能、腐蚀行为。结果表明,纯镁经过等径角挤压（ECAP）变形后晶粒明显细化以及基面织构发生了弱化,导致纯镁的塑性得到了显著地提高。等径角挤压变形后纯镁强度降低主要是因为基面织构弱化影响大于晶粒细化。此外,等径角挤压变形后纯镁自腐蚀电位和腐蚀电流密度明显增加,纯镁的抗腐蚀性能显著提高。纯镁的腐蚀机理可能从局部腐蚀向均匀腐蚀转变,从而减少了样品在标准模拟体液浸泡中的腐蚀脱落,确保了试样的完整性。     

AZ91镁合金模拟累积叠轧过程中组织演化行为

采用Gleeble-3500热/力动态模拟试验机研究了AZ91镁合金在变形温度为250～400℃、应变速率为10-3～1 s-1条件下的热压缩变形行为。并在此基础上,采用Gleeble-3500模拟累积叠轧焊轧制方法,对其在累积叠轧焊(ARB)过程中的组织演变和晶粒细化的机制进行了研究。结果表明:AZ91镁合金在热压缩变形过程中,适宜的变形工艺为变形温度350～400℃、应变速率10-3～10-2 s-1。AZ91镁合金在变形温度350℃、应变速率0.01 s-1和变形量80%为工艺条件的累积叠轧焊过程中,晶粒在第一次轧制过程中明显细化,其机制发生了动态再结晶,在随后的叠轧过程中,晶粒细化程度有限,但组织均匀程度增加。     

铜包铝线材室温拉变形后的显微组织和力学性能

研究经室温拉变形后的纯铜包覆铝合金的不同线径的线材的显微组织及力学性能。结果表明:显微组织自原始的等轴晶变为细长条纤维状,纤维直径与形变量近似地成反比,纤维长度与形变量的平方近似地成正比;经室温拉变形的铜包铝线的极限抗拉强度随形变量增大而增大,与形变量平方根呈直线关系;延伸率随形变量增大逐渐降低,但延伸率波动较大。根据原始纯铜和合金铝的极限抗拉强度值,可以用复合材料强度的混合法则近似地预测不同线径的铜包铝线的极限抗拉强度。     

Continuous bending-drawing process to manufacture the ultrafine copper wire with excellent electrical and mechanical properties

New continuous bending-drawing process to manufacture ultrafine electric wire is proposed. This process is capable of manufacturing ultrafine wire with excellent electrical and mechanical properties, by controlling the microstructure and grain orientations affected by the loading directions during drawing and bending. The mechanical properties and microstructure evolution of copper alloy deformed by the process was systematically investigated. It was confirmed that change of grain size and deformation induced texture that was introduced by the process have great effects on the successful manufacturing of ultrafine wire of 210 μm diameter with excellent mechanical properties, such as good ultimate strength and total elongation.     

Combination of the Upper Bound and Potts Models for Simulation of Microstructure in Wire Drawing and Annealing Processes

For microstructure modeling of copper wire after wire drawing process and annealing, an algorithm based on the Upper Bound Method and Potts Model is developed. In the algorithm, the Upper Bound Method is utilized to calculate the stored energy distribution in the drawn wire and then the stored energy is used in the Potts Model to obtain the grain size distribution of the drawn wire after annealing. The microstructure modeling is carried out at different deformation and annealing conditions. In all of the conditions, the fine and coarse grains are achieved at the surface and center of the wire, respectively. Also, the grain size of the drawn wire after annealing is decreased with increasing die angle and reduction in area. The modeling results are verified by the experimental results and a good agreement is achieved.     

FE-based coupling simulation of Ti60 alloy in isothermal upsetting process

A constitutive equation was proposed to describe the effect of grain size on the deformation behavior. And a coupling simulation of deformation with heat transfer and microstructure was carried out in isothermal upsetting process of Ti60 alloy. The effects of processing parameters on the equivalent strain, the equivalent stress, the temperature rise and the grain size distribution in isothermal upsetting process of Ti60 alloy were analyzed. It is concluded that the uniformity of equivalent strain and equivalent stress increases with the increase of deformation temperature. However, the temperature rise and the grain size decreases with the increase of deformation temperature. The non-uniformity of equivalent strain, equivalent stress, temperature field and grain size increases with the increase of height reduction. And the calculated grain size using simulation is in good agreement with the experimental one.     

Cross-sectional structure,microstructure and mechanical property evolutions of brass cladding pure copper stranded wire composite during drawing

A solid/liquid continuous casting and composite technology was used to produce d8.5 mm brass cladding pure copper stranded wire composite billet and the composite billet was then drawn. The results showed that the composite billet had good surface quality, metallurgical bonding interface between brass and pure copper as well as elongation of 53.1%. Synergistic deformation degree between pure copper wire and brass cladding layer was high during drawing. With an increase of the total deformation amount, the plastic deformation of the pure copper wire reduced triangular arc gaps between the pure copper wires and the triangular arc gaps were fully filled at 50%. When the total deformation amount was increased to 63%, dislocation cells and microbands successively formed in the pure copper wire. In the brass cladding layer, planar dislocation networks, twins and shear bands formed successively, and the main deformation mechanisms were dislocation sliding, twinning and shear deformation. The tensile strength increased from 240 MPa of the composite billet to 519 MPa of the one with the deformation amount of 63%, but the elongation decreased from 53.1% to 3.2%. A process of solid/liquid continuous casting and composite forming→drawing can work as a new compact method to produce brass cladding pure copper stranded wire composite as railway through grounding wire.     

An extrusion−shear−expanding process for manufacturing AZ31 magnesium alloy tube

A new severe plastic deformation method for manufacturing tubes made of AZ31 magnesium alloy with a large diameter was developed, which is called the TCESE (tube continuous extrusion?shear?expanding) process. The process combines direct extrusion with a two-step shear?expanding process. The influences of expanding ratios, extrusion temperatures on the deformation of finite element meshes, strain evolution and flow velocity of tube blanks during the TCESE process were researched based on numerical simulations by using DEFORM-3D software. Simulation results show that the maximum expanding ratio is 3.0 in the TCESE process. The deformation of finite element meshes of tube blanks is inhomogeneous in the shear?expanding zone, and the equivalent strains increase significantly during the TCESE process of the AZ31 magnesium alloy. A extrusion temperature of 380 °C and expanding ratio of 2.0 were selected as the optimized process parameters from the numerical simulation results. The average grain size of tubes fabricated by the TCESE process is approximately 10 µm. The TCESE process can refine grains of magnesium alloy tubes with the occurrence of dynamic recrystallization. The (0001) basal texture intensities of the magnesium alloy tube blanks decrease due to continuous plastic deformation during the TCESE process. The average hardness of the extruded tubes is approximately HV 75, which is obviously improved.     

铜包钢线加工工艺对其电阻率的影响

本研究采用包覆焊接法制备铜包钢线,并对其进行拉拔变形及退火处理。给出了经拉拔变形后的铜包钢线电阻率的计算公式。研究了不同的拉拔变形量和退火处理对其电阻率的影响;分析了其电阻率随加工工艺的变化规律。研究结果表明,铜包钢线的电阻率随其形变量的增加而升高。根据纯铜和钢丝原材料的电阻率,可计算经过不同拉拔变形量的导线的电阻率。随着铜包钢线退火时间的延长和退火温度的升高,其电阻率降低。通过实验数据分析,得到了铜包钢线的退火温度和退火时间分别与其电阻率关系的回归方程。     

Evolution of microstructure and mechanical properties of steel in the course of pressing–drawing

The combined continuous pressing–drawing process is proposed after a comprehensive analysis of available plastic structure-forming techniques taking into account the promising trends in their development. This combination of severe plastic deformation in equal-channel step die and drawing allows one to obtain a wire of desired size and shape in the cross section with an ultrafine-grained structure after a few deformation cycles. It also enables initial workpieces of any length to be processed and, therefore, allows one to obtain finished products up to several tens of meters in length. The aim of this study is to investigate the effect of new combined pressing–drawing technique of plastic deformation on the structure and mechanical properties of the steel. These studies have shown that the proposed deformation technique has a significant advantage of the techniques currently used to manufacture a steel wire.     

高槽满率绕组专用窄矩形截面电磁线拉拔均匀性研究

针对小型轻量化汽车驱动电机的高峰值扭矩和高持续功率要求,对槽满率电机绕组专用窄矩形截面电磁线拉拔成形过程中截面塑性变形均匀性控制进行研究,运用有限元软件对铜扁线拉拔过程进行了建模仿真,验证了多道次成形方案的可行性。研究结果表明:在特定的长宽比下圆角处变形程度远大于窄边处,窄边也大于宽边处,为了解决横截面金属塑性流动不均匀的问题,采用控制变量法,通过优化拉拔模的拔模角和定径带长度,并引入不均匀系数N表征坯料变形的均匀程度,最终获得截面变形较均匀的工艺参数与模具结构参数组合,为企业生产窄矩形截面铜扁线提供工艺参考。     

剧烈塑性变形对AZ31镁合金显微组织和力学性能的影响(英文)

通过等通道转角挤压技术(ECAP)对镁合金进行剧烈塑性变形,使用有限元法实现对ECAP加工过程及相关工艺参数的数值模拟,分析成形过程中的网格的变化、应力应变分布规律及其加载载荷规律,确定主要工艺参数影响规律。通过分析,得出晶粒细化程度与力学性能的关系,为镁合金的晶粒细化方法提供更合理的理论指导和参考依据。