火车用C级钢的高温流动应力

C级钢因其优越的机械性能而广泛应用于火车车轮、车钩等重要零部件上。该材料零部件通常经热锻成形,因此对该材料在高温下的流动应力进行研究具有重要意义。该文采用Gleeble热力学模拟机对C级钢在温度为1 050～1 250℃、应变速率为0.01～10 s-1条件下的流动应力进行测试,获得C级钢的流动应力数据以及C级钢在不同热变形条件下的峰值及稳态流动应力。实验结果预测了C级钢存在动态再结晶现象,得到了变形温度、应变速率和变形程度对C级钢流变应力的影响规律。基于Sellers-Tegart方程拟合本构参数,包括应力水平参数、应力指数、变形激活能和结构因子,建立了C级钢的本构关系式,可作为C级钢零部件热成形加工工艺选择和参数确定的依据,同时也可作为C级钢零部件锻造工艺数值模拟的基础数据。     

以乙醇、乙醇/水为溶剂提取白桦树皮中桦木醇的工艺研究

分别以乙醇、乙醇/水、水为提取剂,研究从白桦树皮中提取桦木醇的工艺,确定了用乙醇作提取剂的最佳提取工艺条件:固液比(g∶mL)为0.083,抽提时间6,h;分别用异丙醇和乙醇作溶剂,通过两步重结晶操作,纯化桦木醇,得到桦木醇产品的产率达19.8%,熔点257.7～258.9,℃,纯度98%.     

AZ31镁合金无缝管挤压动态再结晶数值模拟研究

通过热压缩实验得出温度在300~450℃,应变率为0.01~1 s-1时的应力-应变曲线,建立了AZ31镁合金的动态再结晶模型。该模型用于AZ31镁合金无缝管挤压过程中动态再结晶过程的数值模拟,并通过金相观察得以实验验证。结果表明,在挤压速度确定的情况下,挤压温度对动态再结晶分数的影响最为明显。随着挤压温度的升高,动态再结晶体积分数明显增大。预测的动态再结晶体积分数与实验结果吻合。     

大压下率冷轧无取向硅钢再结晶织构演变

研究了冷轧95%变形量无取向硅钢不同退火温度(710~1050℃)下再结晶织构特征.再结晶刚完成时(710℃退火),呈现强γ(｛111~)与弱｛114｝织构特征;随退火温度升高至900℃,γ明显减弱,｛114｝组分持续增强,形成典型的｛h,1,1｝织构;进一步升温至1050℃,再结晶织构不再发生明显变化.基于EBSD分析,｛114｝组分的持续强化可归因于其明显的尺寸优势以及较高频率的高能晶界(取向差角为20°~45°).     

Forming mechanism of refined granular crystalline of Cu70Ni30 alloy by undercooled solidification

Moth glass fluxing and cyclic superheating techniques were adopted to effectively uudercool the Cu₇₀Ni₃₀ alloy in vacuum. Within the undercooling range of 21 K to 270 K, the microstructure evolution ol the alloy was investigated. When the inell was undercooled to △T > △T', (210 K) , the grain refinement took place abruptly, liascd on the observation of the solidified microstructure, the rnierocheinieal-analysis and the calculated results with UCT model, it is found that the secondary grain refinement mechanism consists of two stages. The dendrite is, firstly, broken into hag-ments owing to the stress caused by uneven shrinking during rapid solidilication, then the fragments, under the driving force of surface and strain energies, merge through the migration of l>ouinlaries, i. c. recryslallization, thus leading to the formation of secondary granular-crystalline .     

N-甲基-2-对二甲氨基苯乙烯吡啶碘盐的合成及分析

研究了N-甲基-2-对二甲氨基苯乙烯吡淀碘盐的合成及分离方法,通过可见吸收光谱、MS谱、HNMR谱分析,证实了其结构和理论预期的一致性。     

热形变工艺参数对珠光体转变动力学的影响

本文研究了热形变工艺参数对40Cr 钢珠光体转变动力学的影响.研究结果表明,晶粒大小,形变温度和形变量对珠光体转变动力学都有影响,从而影响了动态再结晶过程.对生产各种形状和尺寸的模锻件来说,可通过调节热形变工艺参数来控制高温形变组织,从而达到控制室温组织与性能的目的.     

从混合二元酸中分离提纯戊二酸

结合企业的生产,本研究中采用重结晶的方法对混合二元酸结片中的戊二酸进行提纯,探索了料水比、结晶温度、结晶时间等结晶条件对戊二酸纯度和回收率的影响,在不引入新杂质的条件下,得到戊二酸的纯度大于99.0%.     

Microstructural evolution during ultra-rapid annealing of severely deformed low-carbon steel: strain,temperature, and heating rate effects

An interaction between ferrite recrystallization and austenite transformation in low-carbon steel occurs when recrystallization is delayed until the intercritical temperature range by employing high heating rate. The kinetics of recrystallization and transformation is affected by high heating rate and such an interaction. In this study, different levels of strain are applied to low-carbon steel using a severe plastic deformation method. Then, ultra-rapid annealing is performed at different heating rates of 200–1100℃/s and peak temperatures of near critical temperature. Five regimes are proposed to investigate the effects of heating rate, strain, and temperature on the interaction between recrystallization and transformation. The microstructural evolution of severely deformed low-carbon steel after ultra-rapid annealing is investigated based on the proposed regimes. Regarding the intensity and start temperature of the interaction, different microstructures consisting of ferrite and pearlite/martensite are formed. It is found that when the interaction is strong, the microstructure is refined because of the high kinetics of transformation and recrystallization. Moreover, strain shifts an interaction zone to a relatively higher heating rate. Therefore, severely deformed steel should be heated at relatively higher heating rates for it to undergo a strong interaction.     

反溶剂重结晶法制备无定形依贝沙坦微粉

采用反溶剂重结晶法对疏水性药物依贝沙坦了进行微粉化研究。实验考察了依贝沙坦的质量浓度、体系温度、溶液与反溶剂的体积比以及搅拌转速等因素对微粉化过程的影响。结果表明较优的微粉化条件为：溶液中依贝沙坦的浓度0.01g/mL,体系温度15℃,溶液与反溶剂体积比1∶20,搅拌转速1000r/min;鼓风干燥后得到的依贝沙坦微粉粒度分布在1～2μm。红外分析显示所制得的样品与原料药化学结构基本相同;XRD分析结果表明微粉化产品的晶型为原料药的结晶形转变为无定形;溶剂残留检测结果表明微粉化后的依贝沙坦中甲醇的残留量符合药典标准;溶解速率实验表明微粉化后的依贝沙坦微粉溶解速率显著提高。