共查询到17条相似文献,搜索用时 187 毫秒
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The liquid–solid extrusion process for forming composite products was simulated by the three-dimensional thermo-mechanical finite element method. The mechanism for forming defects was analyzed based on the distribution of temperature and flowage of the work piece. The surface annular cracks occurring at the initial stage was caused by the high deformation temperature together with the axial tensile stress which was caused by uneven axial flow rate. However, the low deformation temperature in the terminal stage led to high resistance of deformation and interfacial strength, resulting in the fracture of fibres during severe deformation. The deformation condition in the middle stage was feasible to obtain composite products that were defect free. The simulation was verified through the comparison of the deforming force between the calculated and the measured one in laboratory conditions. The results indicate that the forming quality depends on the thermal and deformation state of the work piece, which can be controlled by the selection and adjustment of the process parameters. 相似文献
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研究了时效方式对FeMnSiCrNi系合金形状记忆效应和低温松弛性能的影响。结果表明,形变后时效比未变形时效析出的碳化物更多、更细小、分布更均匀,有利于提高基体的强度,抑制不可逆的塑性变形的发生,从而显著提高合金的形状记忆效应和回复应力。合金经过10%变形后时效比未变形时效的回复量提高38%139%,回复应力提高12%-22%。不同时效方式的低温松弛率都不大,在213K时只有16%左右,尽管形变时效后回复应力的提高会提高低温松弛率,但并不显著,仅为0%~3.0%。 相似文献
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《Intermetallics》1999,7(3-4):363-369
Based on microstructural observations, the deformation resistance of lamellar Ti48Al–2Nb–2Cr in the temperature range between 1000 and 1200 K is expressed by treating the material as a composite of regions with lamellar and globular structure deforming independently of each other. For stresses below 1000 MPa the dislocation velocity is lower in the lamellar regions compared to the globular ones due to a larger athermal hardening component caused by interfaces (lamella boundaries in the lamellar structure and (sub)grain boundaries in the globular structure). Combining deformation kinetics and structural evolution allows the modelling of the maximum deformation resistance and the subsequent softening resulting from the increase in globular volume fraction. The model is applied to predict the creep life. 相似文献
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通过热模拟试验,对比分析不加V和加V两种中碳锰非调质试验钢的高温力学性能和组织,探讨V的析出对热塑性及组织的影响。结果表明,高温形变诱导析出的V(C、N)可抑制动态再结晶行为、提高变形抗力并促进晶内铁素体转变,使热塑性降低、高塑性温度区变窄、低塑性温度区变宽,而VC主要在奥氏体向铁素体转变时沿γ/α界面的形核析出,并有利于铁素体向晶内长大。不加V和加V的试验钢经1280 ℃固溶处理后,高温变形分别在900~1100 ℃和1000~1130 ℃时,可获得高的热塑性。 相似文献
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7075铝合金热压缩变形流变应力 总被引:42,自引:10,他引:42
在Gleeble-1500热模拟试验机上,采用高温等温压缩试验,对7075铝合金在高温压缩变形中的流变应力行为进行了研究。结果表明,应变速率和变形温度的变化强烈地影响合金流变应力的大小,流变应力随变形温度升高而降低,随应变速率提高而增大;可用Zener-Hollomon参数的指数形式来描述7075铝合金高温压缩变莆时的流变应力行为。 相似文献
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