The influence of temperature on stacking fault energy in Fe-based alloys

Temperature has great influence on the stacking fault energy (SFE). Both SFE and dr0/ d T for Fe-based alloys containing substitutional or interstitial atoms increase with increasing tempera-ture. Based on the thermodynamic model of SFE, the equation dr0/dT=drcn/dT+drseg/dT+drMG/dT and thoseexpressions for three items involved are established. The calculated dr0/dT is generally consistent with the experimental. The influence of chemical free energy on the temperature dependence of SFE is almost constant, and is obviously stronger than that of magnetic and segregation contributions. The magnetic transition and the segregation of alloying elements at stacking faults cause a decrease in SFE of the alloys when temperature increases; that is, drMG/dT<0 and dyseg/dT<0. Meanwhile, such an influence decreases with increasing temperature, except for the drseg/d 7 of Fe-Mn-Si alloys. With these results, the experimenal phenomena that the SFE of Fe-based alloys is not zero at the thermo-dynamically equilibrated tem     

自主创新发展超高强度钢

经总结有关钢的显微组织与力学性能之间的关系,以及超高强度钢发展历史的文献,作出超高强度组织、成分和热处理设计.含＜0.5wt%C,(1～2)%Si,低Mn(Ni)及碳化物形成元素的钢,如0.48C-1.19Mn-1.18Si-0.95Ni-0.2Nb-0.2Mo(wt%)钢,经淬火-碳分配-回火(Q-P-T)新热处理工艺,具抗拉强度>2000MPa,并总伸长率＞10%的性能,且价格低廉.含较低碳的Q-P-T钢也显示良好的综合性能.     

贝氏体相变研究的进展

本文对贝氏体相变研究的进展作概括的综述,包括钢中贝氏体的形态、贝氏体的定义,从动力学、晶体学、形状改变、热力学及奥氏体强度和扩散系数对相变的影响探讨贝氏体相变的机制;有色合金贝氏体的形态和结构、从贝氏体形成时成分改变、晶体学及热力学判断贝氏体相变的机制;简介贝氏体预相变和贝氏体的应用。     

Thermodynamic Analysis of the Fracture Inheritance in Overheated Steels

Based on the experimental result that Crand C segregated on the prior grain boundariesof austenite in overheated steels,causing theinheritance of fracture mode after re-austeni-tization,a thermodynamic analysis is conductedthrough the calculation of equilibrium segregationamount of Cr and C in grain boundary at 860and 1050℃ and the segregation kinetics of Cris also calculated.Thermodynamic calculationgives an evidence that the segregation of Crand C at grain boundaries may be regarded asone of the mechanisms of the fracture inheritancein overheated steels.     

纳米材料的马氏体相变

简述了纳米材料的定义、制备、结构、性能和应用。总结了马氏体相变的尺寸效应。概括了近十年来，纳米材料的马氏体相变和热力学研究的最新结果。     

热力学在材料工程中的应用(续)

五、晶界偏聚杂质元素 P、Sb、As 等在钢中原奥氏体晶界上的偏聚促使高温回火脆性,而合金元素Ni、Cr、Mn 等则助长杂质在晶界的偏聚。Guttmann 曾以合金元素(M)与杂质(Ⅰ)的交互作用系数α′_(MI)>0定性说明这一问题。他虽列出定量的计算式,却难以作实际运     

一种新型热敏材料——形状记忆合金在热保护器上的应用

介绍了形状记忆合金的热-机械动作特性,感温与驱动的控制原理以及单程和双程记忆效应在热保护器和热继电器上的应用实例.试验结果表明,铜基形状记忆合金,完全能作为热敏元件代替双金属片用在热保护器,热继电器或温度控制器上.并具有结构简单,动作灵敏,寿命长,成本低的特点,有较高的经济效益和发展前景.     

热力学在材料工程中的应用

示例简介热力学在材料工程中的应用。应用相图热力学计算了 Fe—C—N 相图580℃的等温截面,作为 C、N 共渗处理的参考;和计算了钢中α/γ平衡相界,供双相钢及临界区热处理工艺制订的依据。以热力学方法计算 Fe——C、Fe—X、Fe—X—C(Fe—Ni—C、Fe—一Cr—C、Fe—Mn—C 及 Fe—高 Ni—C)和多元低合金钢,包括渗 C、N 后渗层的 Ms.建立磷在奥氏体晶界偏聚的模型。分析了回火马氏体脆性的机制。以热力学判定贝氏体相变的机制。对材料的裂纹扩展和晶界断裂作了热力学讨论。