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《中国有色金属学报》2018,(11)
将"球形分流"和"膨胀挤压"概念引入传统ECAP技术,提出一种新型等通道球形转角膨胀挤压(ECAEE-SC)工艺。采用有限元模拟和实验验证的方法研究ECAEE-SC过程中工业纯铝的塑性变形行为。结果表明:ECAEE-SC工艺具有复合剧烈塑性变形的效果,球形转角和膨胀通道为两个主要变形区域;挤压过程中材料处于理想的压应力状态,坯料单道次ECAEE-SC变形累积等效应变量约为3.5,整体变形均匀性良好,挤压效率大幅提高。挤压实验与有限元模拟结果相一致,挤出坯料外形完整且宏观无裂纹,坯料显微硬度平均值从初始36.6HV增加至70.2 HV,力学性能得到显著改善。 相似文献
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通过大塑性变形可以得到超细晶,从而获得有特殊性能的材料。对于工业纯钛以及一些难变形材料,等径弯曲通道变形(ECAP)是获得超细晶的一种最有潜力的方法,但由于ECAP模具的限制,获得的坯料形状和尺寸与所要求的半成品还有一定距离。因此,还需要对ECAP坯料进行一些额外变形,如轧制、挤压或锻造,以达到最终形状要求。 相似文献
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基于等通道角挤压(ECAP)技术,开发了等通道双拐角挤压(ECDAP)技术,它是一种新的大塑性变形(SPD)工艺,可以改善冲头的偏载现象。通过有限元模拟和实验研究,定量分析了工业烧结态纯钨在单道次ECDAP过程中的变形行为。结果表明,在相同的参数下,ECDAP模具的应力分布较ECAP均匀,冲头的偏载得到改善。同时,ECDAP引入的平均等效应变与ECAP相近,但由于二次剪切变形,应变分布的均匀性也得到了很大的改善。二次剪切变形区晶粒尺寸减小到1.77μm,而且拐角区晶粒明显被拉长。细晶强化和应变强化也提高了试样的显微硬度。综合分析,ECDAP工艺是制备超细晶粒金属材料的一种有前途的方法。 相似文献
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采用有限元软件Deform-3D对室温纯钛等径弯曲通道变形(ECAP)过程进行数值模拟,分析了不同等通道截面形状条件下载荷变化、变形行为以及等效应变分布情况。结果表明:不同截面形状试样随着通道截面圆角增大,端部效应有所增加,试样与出口通道上壁之间的缝隙增大;不同通道截面挤压的行程载荷曲线趋势一致,常用的方形截面(R=0 mm)ECAP挤压时载荷最大;ECAP挤压后,试样纵向上等效应变从中部向两端递减,竖直方向上等效应变从上到下逐渐下降;方形(R=0 mm)和圆形(R=10 mm)截面ECAP挤压的等效应变较高,特别是圆形截面ECAP挤压心部等效应变要高于外表,这有别于其他塑性变形形式。 相似文献
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《塑性工程学报》2016,(4):6-12
通过对不同变形路径等径弯曲通道(Equal Channel Angular Pressing,ECAP)变形过程的数值模拟,获得了4种路径8道次ECAP变形的等效应变分布图,分析了挤压试样变形不均匀现象及其形成原因。结果表明,试样尾部与冲头的摩擦、头部未发生明显剪切变形是这两个部位变形程度低的主要原因,造成了ECAP变形的不均匀现象,而这两个部位的不同转移方式,又形成了各种挤压路径的ECAP变形差异。试样中间截面上平均等效应变排序为CBCABA,分别为10.416、10.358、8.669和8.530;试样中间截面等效应变不均匀程度的系数排序为CBCABA,分别为0.090、0.112、0.154和0.467。若追求细化效果应选择路径BC和路径C;如果追求试样材料整体均匀性,可以采用路径A。 相似文献
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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。 相似文献
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基于网格重划分技术,采用有限元软件Marc对等通道转角挤压(Equal Channel Angular Pressing,ECAP)进行数值模拟,得到了模具转角φ=90°、ψ=0°以及不同摩擦条件下圆形试样ECAP变形过程的网格、载荷变化以及等效应变分布规律。结果表明:由于剪切变形和外摩擦作用,底部网格产生畸变,出口端部形成半球形;圆形ECAP过程经历开始变形、稳定变形和终了三个阶段,在开始变形阶段载荷急剧增加,进入稳定阶段后变化平稳,但由于摩擦和加工硬化作用载荷继续增加;与无摩擦情况相比,摩擦的存在增加了试样与模具接触的接触面积、载荷值以及变形的不均匀性。此外,试样中心较表面变形更均匀,而中间截面相比头尾变形较为均匀。 相似文献
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The thermomechanical coupling simulation of the isothermal equal channel angular pressing(ECAP) of Ti-6Al-4V alloy was conducted.The effect of processing parameters,ECAP pass number and the residual billet on the effective strain,stress and temperature distribution was investigated.Based on the coupling simulation results,it is found that the shear factor,ram speed,deformation temperature,channel intersection angle and residual billet significantly affect the ECAP deformation behaviors.Meanwhile,the experimental study of the isothermal ECAP process of Ti-6Al-4V alloy using route C,in which the repeated rotation angle around the longitudinal billet axis before reinsertion in the die was 180°,were conducted at a deformation temperature of 750°C,a ram speed of 0.3 mm·s-1,an outer arc of curvature of 60° and a channel intersection angle of 120°.Furthermore,a large amount of recrystallization occurs and some prior α phase grains grow in the post-ECAP process of Ti-6Al-4V alloy.The yield strength of post-ECAP Ti-6Al-4V alloy increases compared with that of as-received Ti-6Al-4V alloy. 相似文献
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M. M. Myshlyaev S. Yu. Mironov E. V. Konovalova M. M. Kamalov M. A. Prokunin M. M. Myshlyaeva 《The Physics of Metals and Metallography》2006,102(3):328-332
The structural-phase state of rods processed by different regimes of equal-channel angular pressing (ECAP) has been studied. A microcrystalline structure has been shown to be formed during the pressing process. A dislocation substructure and subgrains are formed in the grains. In the rods subjected to ten ECAP passes at 370°C, a uniform structural state is formed in the entire bulk material. The mechanical behavior of rods processed by ECAP has been investigated. Temperature and strain-rate conditions that are necessary to obtain the maximum deformation to fracture have been determined for the specimens of each structural state. It was established that the maximum deformation to fracture corresponds to the rods subjected to ten ECAP passes at 370°C. It corresponds to the deformation rate equal to 10?2 s?1 at 370°C. The maximum degree of deformation was ~1900%. The plasticity of the specimens with the smallest grain size proved to be low. 相似文献
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Conclusions 1. We have developed a technological setup for isothermal equal-channel angular pressing (ECAP) for hard-to-deform materials
that serve at up to 500°C and specific loads on the punch of up to 2000 MPa.
2. We established the process parameters that provide fabrication of defectless preforms from titanium of grade VT1-0 with
a nanostructure and obtained specimens 100 mm long and 20 mm in diameter.
3. We used the method of grids to study the strain state of preforms obtained by the ECAP method and established the great
influence of the geometry of the channels, in particular, of the back angle of intersection of the pressing channels, on the
uniformity of the distribution of shear strain in the plane of flow of the material.
4. Rotation of a preform of titanium VT1-0 after each cycle of ECAP by 90° about the longitudinal axis provides a homogeneous
structure with grains 0.2 – 0.5 μm in size after eight treatment cycles.
Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 9, pp. 27 – 31, September, 2000. 相似文献
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E. G. Astafurova G. G. Zakharova E. V. Naydenkin S. V. Dobatkin G. I. Raab 《The Physics of Metals and Metallography》2010,110(3):260-268
Results are presented of the investigation of mechanical properties, microstructure, and phase composition of low-carbon steel
10G2FT (Fe-1.12Mn-0.08V-0.07Ti-0.1C) before and after equal-channel angular pressing (ECAP). It has been established that
the ECAP of steel 10G2FT at T = 200°C in the case of the ferritic-pearlitic state and at T = 400°C in the case of the martensitic state leads to the formation of a predominantly submicrocrystalline structure with
an average size of structural elements of approximately 0.3 μm, causes an increase in the strength properties, a decrease
in the plasticity, and the localization of plastic flow. It has been experimentally shown that the initially martensitic structure
after ECAP causes higher strength properties in comparison with the ferritic-pearlitic structure. 相似文献
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平面板料斜刃冲裁的冲裁力研究 总被引:1,自引:0,他引:1
通过对斜刃冲裁和倾斜板料冲裁的大量研究,笔者发现长期使用的斜刃冲裁的冲裁力计算公式是不完整的。本文对斜刃冲裁的冲裁力进行了推求,得到了一个新公式。该公式与以前的公式共同表达了斜刃冲裁的冲裁力。 相似文献
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针对三通管接头在模锻成形中易出现破裂、材料折叠、冲头载荷大等问题,研究了冲头速度、坯料初始温度、摩擦系数对锻件模锻质量的影响。通过Deform软件,研究了水平冲头和垂直冲头等速进给、水平冲头和垂直冲头差速进给、水平冲头进给而垂直冲头不运动3种工艺条件下锻件的成形规律,并基于上述最佳工艺,研究了坯料初始温度对模锻过程中温度分布的影响,以及摩擦系数对锻件等效应变的影响,以获得最优的工艺参数。结果表明:在水平冲头和垂直冲头差速进给的情况下锻件质量较好,最优工艺参数能够显著降低冲头载荷,通过与试验结果对比,验证了有限元仿真结果的正确性,为类似管件模锻工艺的研究提供了理论参考。 相似文献
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I. Yu. Khmelevskaya R. D. Karelin S. D. Prokoshkin V. A. Andreev V. S. Yusupov M. M. Perkas V. V. Prosvirnin A. E. Shelest V. S. Komarov 《The Physics of Metals and Metallography》2017,118(3):279-287
The effect of severe plastic deformation by equal-channel angular pressing (ECAP) under normal and quasi-continuous regimes on the structure and the mechanical and functional properties of a Ti–50.2 at % Ni shape-memory alloy (SMA) has been studied. ECAP was carried out at an angle of intersection of channels of 120° in the normal regime with heating between passes at 450°C for 20 passes and in the quasi-continuous regime at the temperature of 400°C for three, five, and seven passes. The hot screw rolling with subsequent annealing at 750°C for 30 min and cooling in water was used as a control treatment (CT). A mixed submicrocrystalline and nanosubgrained structure was formed. The increase in the number of passes from three to seven led to a decrease in the average size of structural elements from 115 ± 5 to 103 ± 5 nm and to an increase in the fraction of grains/subgrains having a size less than 100 nm. After ECAP (seven passes) and post-deformation annealing at the temperature of 400°C for 1 h, a completely recoverable strain was 9.5%; after normal ECAP, 7.2%; after CT, 4.0%. 相似文献
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L.M.A. Hezam M.A. Hassan I.M. Hassab-Allah M.G. El-Sebaie 《International Journal of Machine Tools and Manufacture》2009,49(10):773-780
In this article, a new process for increasing the drawability of square cups has been developed. A circular blank is pushed by a flat-headed square punch through a conical die with a square aperture. The deformed blank conforms to the square shape of the die throat and finally a square cup is obtained. The developed technique has a simple tooling set in which the drawing process can be efficiently preformed in a single-acting stroke without using draw beads or blankholder. A commercial finite element simulation package, DYNAFORM, is used to investigate the developed setup in order to determine the optimum die cone angle. An experimental setup is built accordingly with a half cone angle of 18°. Brass alloy (67/33 Cu–Zn) and commercially pure aluminum (Al99.5w) sheets are used in the experimentations. The effects of the original blank thickness (to=1, 1.5, 2, 2.5, and 3 mm) and the orientation of the blank rolling direction (0°, 22.5°, 45°, and 67.5°) to the punch side on the limiting drawing ratio (LDR) and punch load are experimentally investigated. The present process successfully produces square cups with drawing ratios of 2.92 for brass and 2.74 for aluminum. The new process has shown superiority over the conventional methods through achieving high drawing ratio especially for thick sheets (2–3 mm). Comparison between experimental results and the available published work showed that the required punch force in the new process is significantly reduced while the LDR is increased. 相似文献