Multi billet extrusion technology for manufacturing bi-layered components

The development of the multi billet extrusion technology for manufacturing bi-layered aluminum based semi-products for heat radiators is the subject of this work. To obtain increased strength of the product, ultra fine grained ECAP billets were prepared and used during the extrusion. Appropriate deformation route to get desirable level of grain refinement and billet quality were identified by a series of experiments and numerical simulations performed with the implemented microstructure evolution model. Similar combination of experimental and numerical research was used within the paper for identification of dies geometry and process parameters during development of the multi billet extrusion technology.     

铝合金挤压时的摩擦与摩擦因数

对挤压铝合金时锭坯与工模具接触面上摩擦的性质和行为进行了研究。结果表明，由于铝锭坯与粘附在挤压筒内壁、穿孔针和模具工作带上的铝套或铝层是同种金属，粘着变形使得接触表面微结构自发地趋于相称，从而导致很大的摩擦；其摩擦因数与铝合金的牌号和变形抗力有关。建立了摩擦因数与变形抗力的关系式。     

Severe plastic deformation of commercially pure aluminum using novel equal channel angular expansion extrusion with spherical cavity

Equal channel angular expansion extrusion with spherical cavity (ECAEE-SC) was introduced as a novel severe plastic deformation (SPD) technique, which is capable of imposing large plastic strain and intrinsic back-pressure on the processed billet. The plastic deformation behaviors of commercially pure aluminum during ECAEE-SC process were investigated using finite element analysis DEFORM-3D simulation software. The material flow, the load history, the distribution of effective strain and mean stress in the billet were analyzed in comparison with conventional equal channel angular extrusion (ECAE) process. In addition, single-pass ECAEE-SC was experimentally conducted on commercially pure aluminum at room temperature for validation, and the evolution of microstructure and microhardness of as-processed material was discussed. It was shown that during the process, the material is in the ideal hydrostatic stress state and the load requirement for ECAEE-SC is much more than that for ECAE. After a single-pass ECAEE-SC, an average strain of 3.51 was accumulated in the billet with homogeneous distribution. Moreover, the microstructure was significantly refined and composed of equiaxed ultrafine grains with sub-micron size. Considerable improvement in the average microhardness of aluminum was also found, which was homogenized and increased from HV 36.61 to HV 70.20, denoting 91.75% improvement compared with that of the as-cast billet.     

Material physical response in the extrusion process

The mechanical properties and surface quality of the extruded profiles depend on the final microstructure which has been developed during the extrusion process. The final microstructure is a result of a billet microstructure, material deformation history and post-processing treatment. In order to understand the role of the metal flow in the deformation history both physical and numerical process modelling techniques have been applied. Physical modeling of the extrusion process using modelling materials allows quick and inexpensive evaluation of the flow conditions through different die configurations. Additional information can be obtained from the crystallographic characterization of the typical deformation zone regions such as dead metal zone, main deformation zone and recrystallized zone on the billet-container interface. The electron backscattering diffraction (EBSD) technique has been utilized to follow in detail the orientation aspects of the deformed grains in extruded aluminum. This analysis provides information which can be utilized in the die and process design to improve metal flow uniformity and therefore the microstructure of the final product. It also allows prevention of the typical extrusion defects like surface tearing.     

铝合金锭接锭挤压过程中横向焊缝的有限元分析

应用三维有限元法对铝合金锭接锭挤压过程进行了详细分析,探讨了挤压过程中金属的流动规律及横向焊缝的形成过程.模拟结果显示,挤压过程中金属表现为不均匀的流变行为;在新旧坯料接触顶端形成了一个空隙;同时在高压及剪切变形作用下,新旧坯料接触面形成了一条横向焊缝;讨论了横向焊缝质量的影响因素.模拟分析表明,通过改变平锥模的锥面长度,可有效缩短包含横向焊缝的制品长度.     

Microstructure and flow behaviour during backward extrusion of semi-solid 7075 aluminium alloy

The microstructure and flow behaviour during thixo backward extrusion of 7075 aluminium alloy were investigated. Reheating the steel die and the aluminium billet placed into the die at the same time using an induction furnace provides rapidly a very homogeneous microstructure suitable for thixoforming. During thixoextrusion, despite the high solid fraction, the solid globules are weakly connected and slide over each other without any plastic deformation. The flow remains quasi homogeneous resulting in homogeneous induced microstructure of the component.     

UBET analysis of process of extruding aluminum alloy ribbed thin-wall pipes through a porthole die

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块体材料连续变断面循环挤压形状参数的优化

采用连续变断面循环挤压(Continuous Variable Cross-section Recycled Extrusion,CVCE)法对矩形截面的铸态铅块进行挤压和回复镦粗变形,研究了原始坯料高径比、挤压角度等形状参数对块体变形后的外部形状和内部金属流动规律的影响。结果表明:经CVCE工艺镦粗后的试样,由于金属的径向流动和侧面金属翻平的共同作用,导致上底面面积增大,这种变形自上而下依次渗透并逐层减少;坯料在竖直方向上受到挤压而产生的变形有传递的作用,自上而下,各层的压缩量逐渐减少。当挤压角度为6°、原始坯料高径比为1.83时,循环挤压回复到原始形状的效果最好,且制品表面质量更好,内部金属流动较为均匀。     

Damage prediction for magnesium matrix composites formed by liquid-solid extrusion process based on finite element simulation

A damage prediction method based on FE simulation was proposed to predict the occurrence of hot shortness cracks and surface cracks in liquid-solid extrusion process. This method integrated the critical temperature criterion and Cockcroft &; Latham ductile damage model, which were used to predict the initiation of hot shortness cracks and surface cracks of products, respectively. A coupling simulation of deformation with heat transfer as well as ductile damage was carried out to investigate the effect of extrusion temperature and extrusion speed on the damage behavior of C_sf/AZ91D composites. It is concluded that the semisolid zone moves gradually toward deformation zone with the punch descending. The amplitude of the temperature rise at the exit of die from the initial billet temperature increases with the increase of extrusion speed during steady-state extrusion at a given punch displacement. In order to prevent the surface temperature of products beyond the incipient melting temperature of composites, the critical extrusion speed is decreased with the increase of extrusion temperature, otherwise the hot shortness cracks will occur. The maximum damage values increase with increasing extrusion speed or extrusion temperature. Theoretical results obtained by the Deform?-2D simulation agree well with the experiments.     

Preparation and thixoforging of semisolid billet of AZ80 magnesium alloy

Semisolid billet of AZ80 magnesium alloy was prepared by new strain induced melt activated (new SIMA) process and thixoforging experiment was performed. The results show that after as-cast AZ80 magnesium alloy is processed by equal channel angular extrusion, microstructure is refined well due to heavy dynamic recrystallization occurring in severe plastic deformation. Compared with semisolid isothermal treatment and conventional SIMA, semisolid billet with fine and spheroidal grains are achieved in new SIMA. Thixoforging process of semisolid billet prepared by new SIMA has many advantages such as good surface quality of final component, high ability to fill cavity and net-shape. The fine and spheroidal grains and high mechanical properties such as tensile strength of 298 MPa and elongation of 28% can be developed in final part thixoforged.     

喷射成形7475铝合金的显微组织与力学性能

采用全自动控制往复喷射成形工艺制备了大规格7475铝合金锭坯。研究工业规格喷射成形7475铝合金的初始组织、挤压工艺及热处理制度对显微组织和力学性能的影响。结果表明,喷射成形7475铝合金锭坯规格可达Ф360mm×1200mm,晶粒为等轴状,粒度宏观均匀,主要在30～40μm,组织无明显宏观偏析,锭坯致密度达到97%。喷射成形锭坯经小挤压比变形后达到全致密,T6态(480℃×4h+135℃×16h)合金性能最优,σb为625～635MPa,δ为12%～12.6%,表明控制往复喷射成形铝合金锭坯冶金质量优越。     

Deformation behavior in the compression process of L-shaped aluminum alloy components

In order to discover the deformation mechanism in compression, L-shaped components of aluminum alloy are taken as specimen to investigate the influence of metal flow and deformation behavior in the forming process. Research results show that when the sectional shape is fixed, the range of plastic zone in the deformation body is expanded with the increase of the height of the billet. In addition, the deformation billet has a tendency to change from convexity both inside and outside to convexity inside outside and concavity outside inside, and the complexity degree of deformation also increases. Flow interface in the deformation body deviates along the radial direction to the inside billet gradually. Moreover, when the height of billet is a constant, the flow interface disappears and the metal on the deformation billet has an outflow tendency entirely. The results agree with the numerical simulation through experiments verification.     

转向节热挤压方案工艺性对比分析

采用有限元数值模拟方法以某汽车转向节不同热挤压方案为研究对象,从填充性能、飞边铺展均匀性和流线分布等方面分别作了对比分析研究.结果表明:转向节挤压生产时应避免采用大高径比的坯料直接挤压;采用大直径规格的坯料具有最好的杆部填充性能;采用镦挤加拍扁的预制坯方案可获得较好的综合填充性和变形均匀性.变形方式对锻件最终流线分布的影响最大;初始坯料的流线状态和变形程度对最终锻件的流线状态有重要影响;采用镦挤加拍扁的预制坯方案可获得最好的挤压件流线分布状态.镦挤加拍扁的转向节热挤压预制坯方案具有最优的综合工艺性能.     

Simulation on extrusion process of TiAl alloy

The rigid-plastic finite element Deform-3D software was employed to describe the plastic deformation behavior of TiAl billet (Ti-46.5Al-2.5V-1.0Cr-0.3Ni alloy) during its axisymmetric extrusion through a conical die. Under various extrusion conditions, the present numerical analysis investigated the strain distribution, the damage factor distributions and the die load during the extrusion process. The relative influences of the die semi-angle and the extrusion ratio were examined. The results show that the extrusion force was enhanced from 1.54 × 10⁶ N to 2.81 × 10⁶ N with a certain slop coefficient (about 0.04) when die semi-angle increased in the range 40°≤ α ≤ 70°. The uniform effective strain and the lower propensity for fracture could be obtained at the 60° die semi-angle. The 60° die semi-angle will be an appropriate choice for the extrusion of TiAl alloy. With the raising of extrusion ratio, the effective strain, extrusion load and the damage factor in billet would also be increased.     

不锈钢管接头成形过程的有限元模拟与实验研究

根据不锈钢管接头的形状结构特点和材料成形性能，确定该零件可采用正挤压——镦粗二次成形和一次正挤压成形两种工艺进行加工。运用有限元软件Deform-3D对确定的成形工艺过程进行模拟分析，得到金属变形和载荷变化等规律，通过工艺实验，验证模拟分析结果。结果表明：采用正挤压——镦粗二次成形时工艺力较小、变形均匀性好，采用一次正挤压成形工艺力大。     

挤压比对热挤压AZ80镁合金管材组织和性能的影响

选用不同的挤压比对变形镁合金AZ80进行管材热挤压工艺试验研究,对挤压前后材料组织与力学性能的变化进行分析。结果表明,热挤压可以显著细化AZ80镁合金的晶粒,而且随着挤压比的增加,晶粒变得更加细小;增大挤压比也可以提高AZ80镁合金的抗拉强度和屈服强度。结果表明,挤压比为18.2,坯料温度为390℃,模具预热温度为360℃,凹模的半模角为60°～70°,可得到均匀的合金组织和良好的力学性能。     

Evolution of microstructure and texture of AZ61 Mg alloy during net-shape pressing of extruded perform

The micro orientation theological behavior of AZ61 Mg alloy during net-shape forming of tensile specimens via close-die pressing of extruded preformed and the effect of the press deformation rate on the microstructure characteristics were characterized with electron back-scattering diffraction (EBSD) orientation imaging microscopy and metallography. The results indicate that the intensity distribution of basal {0001}<10(1)0 > texture on the cross-section of the extruded perform is uniform and parallel to the extrusion direction. Subjected to pressing in extrusion direction, deformation shear stress leads to grain rotation and basal texture {0001}<10(1)0> deviation from the extrusion direction, spreading in the direction perpendicular to pressing direction. The texture intensity increases with the press deformation rate and reaches its peak value at 50%, which is considerably lower than the value reached in extrusion deformation. Then, the texture intensity decreases with the press deformation rate reversely.     

基于有限体积法的铜母线连续挤压扩展成形的数值模拟

对连续挤压几何模型进行简化,基于MSC.SuperForge软件平台,成功实现10mm×80mm铜母线连续挤压扩展成形的有限体积数值模拟,避免了刚塑性有限元法模拟大变形需要多次网格重划,体积损失等难题。获得了金属在模腔内的流动-应力-温度-组织耦合变化规律,详尽的分析了整个扩展变形流动过程与各物理场之间的关系,进一步探明了模腔结构对成形过程的影响。结果表明,在成形过程中,坯料最高温度约为872K,出现在坯料与挡料块接触的表面上;当趋于稳定状态时,扩展腔内坯料温度分布比较均匀一致,约为660K;坯料密度发生了明显变化,镦粗段坯料密度最高,为8.962×103kg/m3,产品成形区域坯料密度最低,在8.750×103kg/m3~8.771×103kg/m3之间。在镦粗段内,坯料与挤压轮的打滑量为32%,在镦粗前,坯料与挤压轮保持同步。坯料作用在腔体上的压力高点出现在腔体挡料块顶端,压力为473MPa。扭矩校核表明,数值模拟结果和实测结果吻合较好。     

空心坯料反挤压省力成形方法及应用研究

采用主应力法与数值模拟相结合的方法,研究分析空心坯料反挤压成形力变化规律。结果表明,空心坯料反挤压在减少接触面积的同时,减小了接触面上的单位变形力,大幅度降低了挤压成形力。经在重型车辆铝合金轮辋成形中验证和应用表明,该方法可行,为底部带中心孔的大型薄壁筒形零件的成形,提供了新思路。     

TC6合金等温锻造过程中晶粒尺寸的数值模拟

通过引入一个与微观组织相关的函数对稳态流动应力模型进行修正,建立了金属材料高温变形时的稳态流动应力模型.并将该耦合微观组织参数的流动应力模型写入有限元程序中,模拟了TC6合金叶片在等温锻造过程中初生α相晶粒尺寸的变化.研究了变形工艺参数(压下量,变形温度,变形速度和摩擦因子)对零件内部初生α相晶粒尺寸的影响.