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     

Ag合金化对热挤压前后耐热Al-Cu-Mg合金组织和性能的影响

采用拉伸力学性能测试和金相分析 ,研究了Ag合金化对热挤压前后耐热Al Cu Mg合金组织与性能的影响。结果表明 ,Ag的微合金化可以改善热挤压后Al Cu Mg合金的显微组织 ,明显提高合金的强度、延伸率及高温热稳定性。显微组织分析认为 ,这主要归功于合金化后析出的Ω相的沉淀硬化。     

Ni－Cr－Al电极材料的组织与性能

研究了Ｎｉ３Ａｌ—ＸＣｒ、ＮｉＡｌ—ＸＣｒ二个系列合金的显微组织与结构，并对合金的导电率、维氏硬度和三点弯曲性能进行了测试。本文还就不同Ｃｒ含量对合金性能的影响关系以及Ｎｉ—Ｃｒ—Ａｌ合金作为真空断路器（ＶＣＢ）电极材料的应用前景作了进一步的讨论．     

L12型Al3Ti合金室温变形超位错的分解及计算机图像模拟

利用透射电子显微镜和计算机图像模拟技术研究了ＬＩ２型Ａｌ３Ｔｉ合金室温变形的位错核心结构，结果表明：α（１１０）超位错在｛１１１｝面上分解成两个α／３｛１１２｝型超偏位错，其间为超点阵内禀层错。     

微量Ag对Al-5.3Cu-0.8Mg合金组织和耐热性能的影响

通过拉伸测试和透射电镜研究了Al-5，3Cu-0.8Mg合金中Ag的合金化作用，结果表明，合金中加入少量Ag元素后，改善了合金时效硬化特性，使合金高温力学性能得到较大提高，合金耐热性能提高原因在于Ag的加入改变了合金时效过程，析出了一种新的片状Ω相，Ag原子在{111}α面的层错中偏聚以及Ag和Mg的强烈作用形成的Ag-Mg-cluster对Cu原子的扩散作用，为Ω相形核提供了结构和成分条件。     

马氏体相变的界面吸引子模型

从经典的马氏体相界面运动方程出发,利用相平面分析,证明具有界面摩擦的马氏体相界面是吸引子,与理想的马氏体相界面的孤立子特征不同.通过对非线性方程解的分析,得到发生应力诱发马氏体相变的相界面趋向为焦点型定常吸引子,而热诱发相变的马氏体相界面趋向为结点型定常吸引子,因此考虑界面摩擦后相界面的运动与理想相界面的运动具有不同的非线性特征.     

Electronic structure of FCC phase in Fe-Mn-Si based shape memory alloys and its stability

The relationship between the electronic structure of FCC phase in Fe-Mn-Si alloy and its stability has been studied by using the discrete variational method based on the first principle. The reason why Mn and Si elements have different influences on the stacking fault energy may be related to the electron concentration ( e/a). Si reduces the hole number of 3d band while Mn is rather complicated . The binding energy has been calculated and the experimental results that martensite start temperature (Ms) varies with Si and Mn are explained. When the external stress is exerted in three directions, the electronic structure, the total density of states, the energy gap at Fermi energy level( EF) and the energy degeneracy will change into other states. When the different external stresses are exerted in one direction, 3d or 4s orbital occupations of the central atom decrease, the partial density of states seems to be thinner and its peak increases at EF, the bond orbit shrinks in the direction of the external st     

Al67Mn8Ti25合金的解理裂纹

利用Ｓｔｒｏｈ 位错塞积模型解释了Ｌ１２ 结构Ａｌ６７ Ｍｎ８Ｔｉ２５ 合金室温解理裂纹的萌生。计算表明,位错塞积优先在与滑移面成３５ ．３°方向诱发微裂纹, 导致解理断裂。经室温弯曲断口解理面取向的电子背散射衍射（ＥＢＳＤ） 测试结果验证表明,Ｌ１２ 结构Ａｌ６７ Ｍｎ８Ｔｉ２５ 合金室温解理断裂裂纹优先在｛１１０｝ 晶面萌生     

PST双相TiAl类单晶中的微孪晶变形

利用透射电子显微镜研究了ＰＳＴ双相ＴｉＡｌ类单晶中的微孪晶变形行为，研究结果表明，孪晶面为（１１１），是由（α／６）Ｓｈｏｃｋｌｅｙ不全位错在（１１１）面上运动产生的，当该位错遇到到互在孪晶关系的两片ＴｉＡｌ界面时，将在另一片ＴｉＡｌ相中诱发出新的微孪晶，其孪晶系统不变，这说明互成孪晶关系的ＴｉＡｌ相界面对微孪晶变形阻碍作用不大，本文讨论了微孪晶变形对材料变形的影响。     

PST双相TiAl类单晶高温变形位错特征

利用透射电子显微镜研究了ＰＳＴ双相ＴｉＡｌ晶体高温变形后的位错组态。发现微孪晶变形、１／２＜１１０］单位位错、＜０１１］超点阵位错、１／２＜１１２］超点阵位错均参与了变形。螺型＜０１１］超点阵位错可在｛１００｝面上分解，构成Ｋｅａｒ－Ｗｉｌｓｄｏｒｆ锁。４００℃，６００℃变形时由１／２＜１１２］位错分解形成的层错偶极子仍然存在，但数量减少。８５０℃变形时未发现层错偶极子，但这时１／２＜１１２］刃型可动位错数量增加。原位加热观察表明，层错偶极子在６５０℃时完全消失。本文讨论了这些位错特征对ＴｉＡｌ合金韧脆转变特征的影响。