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1.
基于变温度场的镍钛形状记忆合金管滚珠旋压有限元模拟(英文) 总被引:1,自引:0,他引:1
作为一种新的尝试,在高温下应用滚珠旋压制造镍钛形状记忆合金管。将名义成分为Ni50.9Ti49.1(摩尔分数)的镍钛形状记忆合金棒料进行固溶处理,制成用于滚珠旋压的镍钛形状记忆合金管坯。以变温度场和本构方程为基础,用刚粘塑性有限元法来模拟镍钛形状记忆合金管的滚珠旋压,获得了温度场、应力场和应变场,并进行了旋压载荷预测。有限元模拟结果表明,在旋压件的主变形区有大约160℃的温升。从应力场和应变场可以看出,镍钛形状记忆合金管的外壁比内壁更容易满足塑性屈服准则,塑性变形区处于三向压应力状态。径向应变和切向应变为压缩应变,轴向应变为伸长应变。旋压载荷伴随滚珠旋压行程的变化对于预测旋压件的稳定流动具有重要的意义。 相似文献
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Shu-yong JIANG Ming TANG Ya-nan ZHAO Li HU Yan-qiu ZHANG Yu-long LIANG 《中国有色金属学会会刊》2014,24(6):1758-1765
Based on the local canning compression, severe plastic deformation (SPD) is able to lead to the almost complete amorphous nickel-titanium shape memory alloy (NiTi SMA), in which a small amount of retained nanocrystalline phase is embedded in the amorphous matrix. Crystallization of amorphous NiTi alloy annealed at 573, 723 and 873 K was investigated, respectively. The crystallization kinetics of the amorphous NiTi alloy can be mathematically described by the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. NiTi SMA with a complete nanocrystalline phase is obtained in the case of annealing at 573 K and 723 K, where martensite phase transformation is suppressed due to the constraint of the grain boundaries. Crystallization of amorphous NiTi alloy at 873 K leads to the coarse-grained NiTi sample, where (001) martensite compound twin is observed at room temperature. It can be found that the martensitic twins preferentially nucleate at the grain boundary and they grow up towards the two different grains. SPD based on the local canning compression and subsequent annealing provides a new approach to obtain the nanocrystalline NiTi SMA. 相似文献
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作为一种崭新的尝试,局部包套压缩被应用于实现镍钛形状记忆合金在室温下的大塑性变形。基于主应力法和塑性屈服准则,分析了镍钛形状记忆合金局部包套的压缩塑性力学。采用透射电镜、高分辨透射电镜和扫描电镜研究镍钛形状记忆合金在局部包套压缩下的显微组织演变和变形行为。静水压力随着包套外径的增加而增加,有效地抑制了显微裂纹的萌生和扩展,有助于提高镍钛形状记忆合金的塑性,避免了脆性断裂的发生。在0.15~0.50的真实应变范围内,镍钛形状记忆合金在三向压应力状态下的塑性变形满足密席斯塑性屈服准则。在更大的塑性应变下,由于非晶相的出现,镍钛合金不能满足密席斯塑性屈服准则。 相似文献
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Three-dimensional(3D)geometric models with different corner angles(90°and 120°)and with or without inner round fillets in the bottom die were designed.Some important process parameters were regarded as the calculation conditions used in DEFORMT M-3D software,such as stress—strain data of compression test for AZ31 magnesium,temperatures of die and billet,and friction coefficient.Influence of friction coefficient on deformation process was discussed.The results show that reasonable lubrication condition is im... 相似文献
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李赛毅 《中国有色金属学会会刊》2013,23(1):170-179
概述了晶体塑性模拟在面心立方金属等通道转角挤压中的典型应用.结果表明,这些模拟能够较好地解释仅基于宏观变形行为所不能解释的晶粒细化效率的路径相关性和亚结构方向性问题,能够满意地预测不同加工条件下材料的晶粒取向稳定性和织构演变.应用表明,晶体塑性模拟是探索晶粒变形的晶体学特性以及相关行为的有效手段,而这些特性常常被现有宏观理论所忽略或错误地解释. 相似文献
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通过真空自耗电极熔炼法制备等原子比镍钛形状记忆合金。为了研究其断裂力学性能,进行铸态镍钛形状记忆合金的拉伸和压缩实验。为了更好地理解镍钛形状记忆合金的组织演变及断裂行为,分析铸态镍钛形状记忆合金及其断裂样品的显微组织。在拉伸加载下,镍钛形状记忆合金在750°C时具有较高的塑性,表现为韧性断裂,但在室温和-100°C时表现出较差的塑性,具有解理断裂和穿晶断裂的特征。在-100°C的压缩加载下,铸态镍钛形状记忆合金发生剪切断裂,剪切断裂面法线与压缩轴呈45°,具有解理断裂的特征,裂纹经由穿晶断裂而扩展。 相似文献
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NiTi形状记忆合金的本构关系及有限元模拟研究进展 总被引:1,自引:0,他引:1
NiTi合金是目前记忆合金中研究最多和应用最广泛的一种,而描述NiTi形状记忆合金超弹性和记忆效应的本构模型及其有限元模拟技术是国内外研究的重点和难点。简要介绍了描述NiTi形状记忆合金超弹性的宏观唯象模型和细观力学模型这两种本构关系的研究进展。重点对近十年来NiTi记忆合金血管支架和管接头的有限元建模、分析及优化进行了评述。 相似文献
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等通道弯角挤压变形机理模拟与工艺参数优化 总被引:10,自引:0,他引:10
通过等通道弯角挤压工艺 (EqualChannelAngularPressing ECAP)能够获得块状超细晶粒材料 (包括亚微米和纳米材料 )。模具几何形状、摩擦条件等工艺参数对挤压过程具有重要影响。本文应用作者自主开发的商品化软件 ,通过大量的有限元模拟 ,研究了过程参数对挤压件变形分布、挤压载荷的影响规律 ,给出了不同模具拐角和圆心角对ECAP挤压件变形区产生的累积等效应变、等效应力和载荷 行程曲线的影响 ,为优化模具形状和获得所要求的挤压件变形分布提供了大量有效的结果和规律。 相似文献
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Anumalasetty Venkata Nagasekhar Hyoung Seop Kim 《Metals and Materials International》2008,14(5):565-568
Plastic deformation behavior in T-shaped equal channel pressing, a modified equal channel angular pressing (ECAP) using T-shaped
channel instead of conventional L-shaped channel, is analyzed by using the commercial finite element code DEFORM. Simulations
were carried out under realistic conditions by considering the strain hardening of material and friction. The deformation
behavior is more complicated and the strain induced is highly localized. Severe plastic strain is localized in the bottom
region of the workpiece and very small strain is developed in the other region, which is in good agreement with the experimental
results reported in the literature showing the nonuniformity in microstructure and hardness distribution. In addition, the
load requirements of the T-ECAP are much higher compared to conventional ECAP. 相似文献
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Electrochemical behaviors of laser-welded Ti-50.6%Ni(mole fraction) shape memory alloy and the base metal in 0.9% NaCl solution were investigated by electrochemical techniques as corrosion potential measurement, linear and potentiodynamic polarization. The results indicate that the laser-welded NiTi alloy is less susceptible to pitting and crevice corrosion than the base metal, which is demonstrated by the increase in polarization resistance(Rp) and pitting potential(φpit) and decrease in corrosion current density(Jcorr) and mean difference between φpit and φprot values. It is confirmed by scanning electron microscope micrographs that pits could be observed on the surface of base metal but not on the surface of laser-welded alloy after potentiodynamic tests. An improvement of corrosion resistance of laser-welded NiTi alloy could be attributed to almost complete dissolution of inclusions upon laser welding. 相似文献
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Xiaoning ZhangChenglong Huang Baoyu XiaBin Chen Xiaogang SunChaoying Xie 《Journal of Alloys and Compounds》2011,509(6):3006-3012
Ni-rich TiNi shape memory alloys were subjected to the effect of equal channel angular extrusion (ECAE) processes at 773 K by Bc path. The effects of ECAE processes on microstructures evolution and phase transformation behaviors were investigated. The initial 60-80 μm equiaxed coarse grains of samples were elongated along the shearing force direction of ECAE and refined to 300-400 nm after eight passes ECAE. The R phase transformation of Ni-rich TiNi shape memory alloys was stimulated by ECAE processes within a larger temperature range. The martensite transformation peak temperature (Mp) dropped in previous 1-3 ECAE treatments, but the dropped Mp increased gradually with the increase of ECAE processes. Ti3Ni4 phase was observed in the regions with high density of dislocations after ECAE treatment. Reasons for microstructures evolution and phase transformation changes were also discussed. 相似文献
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模具外角对等通道转角挤压(ECAE)变形过程影响较大,文章利用有限元软件(MSC.Marc)模拟研究了模具外角对ECAE过程中等效应变、变形机理的影响。模拟结果表明,模具外角Ψ>0°~30°的范围内,等效应变的分布较为均匀;当模具外角Ψ>30°时,等效应变的分布越来越不均匀;当模具外角Ψ=0°~90°范围内逐渐增大时,试样的变形机理由单一剪切变形逐渐变为剪切变形与弯曲变形相结合的复合变形行为。为了验证模拟结果,对大尺寸纯铝进行了等通道转角挤压实验(模具内角Ф=90°,模具外角Ψ=30°),纯铝实验应变值的分布与大小和模拟应变值的分布与大小近似吻合。由光学显微组织可知,经ECAE挤压一次后,变形试样组织较为均匀,晶粒得到一定程度细化。 相似文献
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镍钛形状记忆合金在热压缩变形下的动态回复和动态再结晶 总被引:1,自引:0,他引:1
通过获得镍钛形状记忆合金在应变速率(0.001~1 s-1)和变形温度(600~1000℃)下的压缩真实应力—应变曲线,研究镍钛形状记忆合金在热变形下的力学行为.通过显微组织演变研究镍钛形状记忆合金的动态回复和动态再结晶,获得应变速率、变形温度和变形程度对镍钛形状记忆合金的动态回复和动态再结晶的影响规律.镍钛形状记忆合金在600℃和700℃下,动态回复和动态再结晶共存,但在其他温度下表现出完全动态再结晶.增加变形温度或降低应变速率,导致较大的等轴晶粒.变形程度对镍钛形状记忆合金的动态再结晶具有重要的影响.在镍钛形状记忆合金的动态再结晶中存在临界变形程度,当大于临界变形程度时,较大的变形程度有助于获得细小的等轴再结晶晶粒. 相似文献
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Microstructure evolution of processed Mg-Al-Zn alloy by equal channel angular extrusion in semi-solid isothermal treatment 总被引:1,自引:3,他引:1
1Introduction Thixoforming is one of the best methods regarding manufacture of Mg-Al-Zn alloy components because of its low resistance of deformation compared with solid metal forging and high mechanical properties of formed components compared with liqui… 相似文献
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This research investigates the use of equal channel angular extrusion (ECAE) processing to produce a superplastic form of
the aluminum alloy 2098. The starting material was a hot-rolled and precipitation-hardened plate with elongated grains of
width 67–92 μm, and a composition in weight percent of 2.2% Li, 1.3% Cu, 0.73% Mg, 0.05% Zr, balance Al. Microstructural evolution
was investigated with optical and transmission electron microscopy (TEM) and microhardness measurements after each step of
a multipass ECAE process. ECAE produced a submicron grain structure with an average size of about 0.5 μm. The sub-grain microstructure
size was a function of the magnitude of the input strain and the extrusion temperature. Misorientation angles of the developed
submicron structure increase with increasing number of passes at warm working temperatures. Superplastic behavior of the ECAE-processed
alloy was achieved. However, the low zirconium content of the 2098 alloy resulted in grain growth of the refined structure
at the superplastic processing temperatures, placing a lower limit on the deformation rates that can be used. 相似文献
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采用数值模拟和实验研究方法分析圆形纯铝挤压件多道次等通道弯角挤压工艺,发现单道次挤压获得的挤压件的变形分布沿挤压件中心横截面竖直方向变形分布不均匀.通过节点映射法实现各工艺路线的多道次挤压,不同的工艺路线对应的多道次挤压变形分布具有明显差异.多道次挤压后晶粒得到显著细化,变形后晶粒结构较挤压前的退火等轴晶粒大为不同,而且各工艺路线的晶界取向也各不相同,其中旋转90.挤压能够获得大角度晶界分布的等轴晶粒试样,实验结果与有限元分析结果十分吻合. 相似文献