微合金钢凝固前沿脆性区溶质的偏析特性

 针对目前微合金钢凝固过程中产生大量裂纹缺陷的现状。以B-F偏析模型为基础对微合金钢凝固过程进行了理论分析,并结合Gleeble-1500热模拟试验,系统研究了SAPH440微合金钢凝固前沿脆性区的溶质偏析及裂纹敏感性。结果表明：微合金钢凝固过程中,固相率在0.75~1.00之间时,C、Mn元素偏析较轻,S、P、Ti元素偏析严重,Mn对S偏析有抑制作用,Mn的质量分数增加到1.2%时,S的偏析度降低至20.7;对凝固脆性区的影响程度顺序为Mn>S>C>P>Ti,S的质量分数由0.002%增加至0.02%,凝固脆性区由25K扩大至33K;Mn的质量分数从0.2%增大到1.6%时,裂纹敏感区间由15K扩大至38K。同时Gleeble-1500热模拟试验证实钢脆化的原因与试样的凝固组织无直接关系。     

An analytical model for solute mixing in surcharged manholes

A mathematical model has been developed to describe solute mixing in surcharged manholes using the submerged jet theory. The model has been applied for straight-through flow manholes and for manholes with a difference in the level of the inlet and outlet pipes. The model is applicable to dissolved substances, i.e. the model has not been validated for high sediment concentrations (above 1 g/l) and care should be taken in such cases. Simulation results from the new model are compared with laboratory measurements and are further compared to conventional modelling techniques currently available in commercial software specially developed for modelling the water quality in sewers. The results prove that the new model produces considerably better results compared to the traditional assumption of full mixing in a manhole. The new model compares well to the laboratory measurements and hence improves the accuracy of modelling soluble pollutant transport in sewers. The applicability of the new modelling approach is discussed and further studies are recommended.     

基于Excel的一维地下水溶质运移数值模拟简易方法

针对地下水数值模拟软件难于推广使用问题,利用Excel办公软件并基于Crank-Nicolson差分方法,提出了一种简易的一维地下水溶质运移的数值模拟方法,再采用地下水模拟专业软件GMS7.1进行验证,发现两者模拟结果吻合。该方法为解决实际的地下水溶质运移问题提供了便利。     

高强度汽车大梁钢合金减量化生产实践

在优化AG610L的加热、轧制和层流冷却工艺、提高钢强度的基础上,进行了去除钒合金化的减量化生产实践.生产统计数据表明,减量化后钢的强度与含钒钢相比,屈服强度和抗拉强度的波动范围都有一定的降低,同规格的铁素体晶粒度提高了1级,实物质量较好,能够满足用户的冷加工要求,降低了生产成本.     

晶界元素偏聚及其机理的研究进展

晶界成分偏聚对多晶材料的力学性能有很大影响,探明影响晶界成分偏聚的因素和偏聚机理,对改善材料性能和优化设计合金系统具有重要意义。本文通过归纳近几年来国内外原子尺度研究晶界成分偏聚及其机理的研究进展,分析了间隙原子,置换型原子和空位在晶界的偏聚及其对材料性能的影响,讨论了成分偏聚与合金元素择优占位行为的关系,总结了晶界成分偏聚对材料力学性能影响的根本原因。     

边界层理论在裂隙水运移的研究进展

简要评述近几十年来,裂隙介质地下水运移过程中存在的问题,回顾了边界层理论的形成发展过程,重点评述了溶质非费克运移峰提前、拖尾和双峰现象。分析了边界层内部的流速分布,边界层厚度与非费克运移特征之间的联进一步指出今后研究方向,为裂隙介质地下水非费克溶质运移研究提供了新的思路和理论基础。     

Relating reverse and forward solute diffusion to membrane fouling in osmotically driven membrane processes

Osmotically driven membrane processes, such as forward osmosis (FO) and pressure retarded osmosis (PRO), are attracting increasing interest in research and applications in environment and energy related fields. In this study, we systematically investigated the alginate fouling on an osmotic membrane during FO operation using four types of draw solutions (NaCl, MgCl₂, CaCl₂ and Ca(NO₃)₂) to elucidate the relationships between reverse (from draw solution to feed solution) and forward (from feed solution to draw solution) solute diffusion, and membrane fouling. At the same water flux level (achieved by adjusting the draw solution concentration), the greatest reverse solute diffusion rate was observed for NaCl draw solution, followed by Ca(NO₃)₂ draw solution, and then CaCl₂ draw solution and MgCl₂ draw solution, the order of which was consistent with that of their solute permeability coefficients. Moreover, the reverse solute diffusion of draw solute (especially divalent cation) can change the feed solution chemistry and thus enhance membrane fouling by alginate, the extent of which is related to the rate of the reverse draw solute diffusion and its ability to interact with the foulant. The extent of fouling for the four types of draw solution followed an order of Ca(NO₃)₂ > CaCl₂ >> MgCl₂ > NaCl. On the other hand, the rate of forward diffusion of feed solute (e.g., Na⁺) was in turn promoted under severe membrane fouling in active layer facing draw solution orientation, which may be attributed to the fouling enhanced concentration polarization (pore clogging enhanced ICP and cake enhanced concentration polarization). The enhanced concentration polarization can lead to additional water flux reduction and is an important mechanism governing the water flux behavior during FO membrane fouling. Findings have significant implications for the draw solution selection and membrane fouling control in osmotically driven membrane processes.     

Effect of Solute Drag and Precipitate Pinning on Austenite Grain Growth in Ti-Nb Microalloyed Steels

A metallurgical model concerning the co-effect of the Nb solute drag and the complex carbonitride precipitates pinning is proposed to predict the recrystallization austenite grain growth of low carbon Nb-containing microalloyed steels.The analysis,both predicted and experimental,reveals the precipitate pinning plays a dominate role in suppressing the austenite grain growth with less Nb solute drag effect in high temperature region whereas the Nb solute drag predominates in relatively low temperature region.A factor p is suggested to assess the effectiveness of drag and pinning.The pinning and the drag are more effective in restraining grain growth as p>0 and p<0,respectively.A low carbon Nb microalloyed steel and a kind of Ti-modified low carbon Nb steel by Ti substituting for part of Nb are employed to validate the modeling results.The theoretical calculations show a good agreement with experimental results.     

深过冷凝固Co80Pd20合金中的枝晶生长

采用玻璃熔体净化与循环过热相结合的深过冷凝固技术实现了Co80Pd20合金的深过冷,获得了高达415 K的最大过冷度.采用OM观察了不同过冷度下凝固合金的微观组织,分析了枝晶形成的过冷度区间及过冷度对枝晶形貌的影响.运用BCT模型对深过冷凝固Co80Pd20中的枝晶生长进行了理论分析,获得了深过冷凝固过程中的枝晶生长速...