铸坯取样位置对经济型双相不锈钢2101热塑性的影响

为了解大型铸锭在轧制过程中产生边裂的原因,通过对比铸坯中部和边部的成分、不同温度下相比例、两相硬度差等的变化规律,利用光学显微镜,扫描电子显微镜和电子背散射衍射观察分析试验钢的微观组织和断口形貌,分析了边部容易开裂的原因.结果表明,和中部相比,边部晶粒细小,且铁素体含量较多,但边部开裂更严重.这说明晶粒尺寸和相比例并不是影响使边部开裂严重的主要原因.而和中部比,铸锭边部试样两相硬度差较大,使两相在热变形过程中应变分配不均匀,容易在相界处产生应力集中,导致开裂.同时边部析出物较中部多,相界析出物的产生破坏了基体的连续性,容易在相界处产生显微裂纹,导致开裂.     

经济型双相不锈钢2101中氮化物在基体中的平衡固溶度计算

为了解析出物对经济型双相不锈钢2101热塑性的影响机制,对比了相同工艺下2101和2205双相不锈钢在热变形过程中相界析出物产生的规律.结果表明:2101钢比2205钢的相界处更倾向于产生析出物,促使后续热变形过程中相界产生裂纹,进而影响材料的热塑性.根据热力学相关数据,通过Thermo-Calc和实验测试数据,推导出2101和2205双相不锈钢析出物Cr₂N的平衡固溶度公式,计算实验钢中析出物Cr₂N的全固溶温度,同时引入Wagner相互作用系数,考虑了Ni、Mn、Mo和Si对固溶度积公式的影响.发现2101双相不锈钢中Cr₂N的全固溶温度比2205钢高100℃左右,计算结果和实验结果吻合较好.实际生产过程中必须控制双相不锈钢热轧的终轧温度到全固溶温度以上,否则相界容易产生氮化物析出,影响材料热塑性.     

高酸性气田用油管材料G3、825合金的高温变形特性

采用Thermomacmaster-Z热模拟试验机分别对G3、825耐蚀合金在应变量为0.8、变形温度1 030～1 300℃、应变速率1～25 s-1及大气条件下进行压缩及拉伸试验,对其变形抗力及发生动态再结晶的影响因素进行了分析;通过温度-断面收缩率曲线对合金的高温热塑性进行了探讨.结果表明:G3、G3-Z、825合金的最大变形抗力均随着温度的升高而降低;G3、G3-Z和825合金适宜的热加工温度范围分别为1 100～1 240℃,1 130～1 220℃和1 050～I 240℃.     

TC6钛合金的热塑性变形行为研究

采用热模拟试验机对TC6钛合金轧制态试样进行了不同温度和不同应变速率的应力—应变试验,研究TC6钛合金的高温变形行为。试验结果表明,TC6钛合金在相同的温度下,应变速率越小,热塑性越好,越容易变形;应变速率对TC6钛合金热塑性的影响还与温度有很大的关系,温度越低,热塑性受应变速率的影响越明显。800～900℃时,TC6钛合金热塑性受温度影响较大,变形温度越低,热塑性越差;900℃以上时,几乎不受变形温度和应变速率的影响。TC6钛合金在920～950℃,应变速率1.0 s-1时具有良好的热塑性和很好的热加工性能。     

一种环境友好橡胶——配位交联橡胶的研究进展

简要介绍了配位化合物、高分子配位交联的定义;详细阐述了配位交联橡胶的热塑性、耐高温特征,建构配位交联体系时胶种、交联剂和胶料制备方法的选择依据,以及影响配位交联的重要因素;指出了目前配位交联橡胶研究存在的不足,并展望了相关发展趋势。     

600—1200℃温度范围内含钒低合金钢高温热塑性影响因素的研究

应用ＧＬＥＥＢＬＥ－１５００热力模拟机，采用正交分析法测定量研究了低合金风中含钒量、变形温度、变形速率、冷却速率等因素对含钒钢温度热塑性的影响，用数学回归法建立了各影响因素与钢的热塑性间的数学模型，为制定含钒钢连铸工艺提供了依据。     

Thermoplasticity with diffusion in welding problems

A thermomechanical model for the analysis of thermoplasticity with a diffusion term is presented. This model is defined in infinitesimal strain thermoplasticity framework. Thermal hardening is coupled with a diffusion process. The example presents thermodiffusion process in titanium friction welding parts. The migration of hydrogen in the process of thermoplastic deformation is described. Copyright © 2007 John Wiley & Sons, Ltd.     

Effect of 0.3 wt% hydrogen addition on the friction stir welding characteristics of Ti–6Al–4V alloy and mechanism of hydrogen-induced effect

The α + β titanium alloy, Ti–6Al–4V, was thermohydrogen processed with 0.3 wt% hydrogen. The friction stir welding characteristics of Ti–6Al–4V alloy and the hydrogenated alloy with 0.3 wt% hydrogen were investigated in contrast. The results showed that welding parameters range for the unhydrogenated alloy was narrow and flash was prone to occur in the welding process. Hydrogenation could help to widen welding parameters range, improve weld appearance, and increase service life of pin tool. The reason was attributed to the hydrogen-enhanced thermoplasticity of titanium alloys, while the fundamental cause was the hydrogen-induced microstructural evolution in titanium alloys. Hydrogen almost did not escape from the hydrogenated alloy during the friction stir welding and could be successfully removed through post-weld vacuum annealing. The mechanism of hydrogen-induced effect during the friction stir welding and post-weld dehydrogenation was discussed in detail.     

Local and non‐local thermomechanical modeling of elastic‐plastic materials undergoing large strains

This paper deals with the numerical analysis of instabilities for elastic‐plastic materials undergoing large deformations in non‐isothermal conditions. The considered isotropic model is fully thermomechanically coupled and includes temperature‐induced softening, which is another source of strain localization next to geometrical effects. Due to complexity of the model, a symbolic‐numerical tool Ace is used for the preparation of user‐supplied subroutines for the finite element method. The computational verification is performed using two benchmark tests: necking of circular bar in tension and shear banding of elongated rectangular plate in plain strain conditions. The attention is focused on mesh dependence of the numerical results and the regularizing effect of heat conduction. The research reveals that the conductivity influences the shear band width and ductility of the material response; however, for the adiabatic case, the results are discretization sensitive, and another regularization is needed. A new gradient‐enhanced thermomechanical model is developed that introduces an internal length parameter governing the size of the shear band caused by thermal softening. The numerical verification of the non‐local model is performed for the adiabatic case. Subsequently, the simultaneous application of the gradient enhancement and heat conduction in the model is analyzed, which reproduces an evolving shear band. Copyright © 2016 John Wiley & Sons, Ltd.     

0Cr25Ni7Mo4N双相不锈钢高温热塑性及组织演变

采用热拉伸实验研究了两种不同元素(O、N)含量的双相不锈钢0Cr25Ni7Mo4N在1 000~1 200℃范围内、1s-1应变速率条件下的热变形行为。利用光学显微镜(OM)、扫描电镜(SEM)和透射电镜(TEM)观察并分析了实验钢的组织和夹杂物。结果表明,经铝和硅铁脱氧后的实验钢热塑性良好,而未经脱氧的高O、N含量的实验钢在1 150℃以上才具有良好塑性,故双相不锈钢0Cr25Ni7Mo4N的热加工过程中应该控制温度在1 150℃以上;热加工过程中实验钢以铁素体的动态回复和奥氏体的动态再结晶为主要软化机制;高O、N含量钢中,在相界析出的含铬的氧化物夹杂引起的相界结合强度降低,及高温加工中不恰当的两相比例,是其热塑性较低的主要原因。