C晶界偏析对α-Fe纳米晶高温力学性能的影响

纳米晶在常温下具有很高的强度,然而其高温力学性能往往低于其对应粗晶.C是钢中的重要成分,由于其原子半径较小,容易在纳米晶中发生晶界偏析.通过分子动力学模拟,探讨了利用C的晶界偏析来提升纳米晶高温力学性能的可能性.在不同温度和应力水平下模拟了Fe-C与纯Fe纳米晶的拉伸蠕变试验,得到对应的应变速率,并根据Mukherje...     

普通碳钢脱碳伴随的P在晶界偏析和晶间裂纹

普通碳钢只有脱碳后在晶界有P轻微偏析时的冷却过程中的内脱碳区产生晶间表面裂纹,脱碳区内热拉伸应力的变化取决于在此温度下的晶界强度。     

晶界磷偏析和添加硼对超高强度钢韧性的影响

研究了磷含量和添加硼对强度级超过１５００ＭＰａ的中碳钢韧性的影响。韧性随磷含量的增加而降低，而添加硼可以改善韧性。俄歇电子光谱法（ＡＥＳ）观测表明，添加硼由于减少了晶界磷偏析，因而减少了晶间断裂。用麦克林（Ｍｃｌｅａｎ）理论计算指出，在奥氏体化温度硼向晶界偏析比磷快得多，并指出硼减少了磷偏析的晶界能。     

稀土元素对耐候钢元素偏析的影响

应用金属原位统计分布分析技术(OPA)研究了耐候钢铸锭中C、P、S、Cu、Si和Mn的宏观偏析规律,并分析了稀土元素对耐候钢中元素偏析的影响.结果表明,在30%～40%等轴晶率,20℃过热度下,元素C、S、P和Cu能产生严重的宏观偏析,C、S呈中心正偏析,P、Cu呈中心负偏析并伴随有反偏析,而Si和Mn的分布较为均匀.各个元素中心偏析位置完全相同.稀土元素在钢中的固溶度为10-5～10-4,固溶稀土元素可以细化枝晶,提高等轴晶率.钢中加入质量分数0.38%～0.55%的稀土元素可以有效改善C、S、P和Cu的宏观偏析.     

合金元素对CrMoV钢偏析的影响

1 前言 CrMoV钢是高温强度优质的低合金钢,用于发电工业。由于要求相应的高韧性,因此必须降低P、S等杂质元素及Si、Mn等助长脆化的元素,同时还须最佳地设计Ni、Cr、Mo等合金成分。 由于钢锭的大型化对偏析的影响,在生产蠕     

利用直读光谱仪检测铸坯偏析的探索与实践

通过对快速直读光谱和原位分析的工作原理对比分析,为解决实际生产中利用酸洗检验铸坯偏析无法定量化描述的问题,将铸坯切割成光谱小样利用快速直读光谱模拟原位分析对连铸坯质量进行检测,直读光谱检测铸坯偏析结果与传统酸洗检验结果不仅趋势相同,而且还可以将各种元素的偏析度及成分偏析曲线描述清楚,具有直观数字化作用。实现了使用快速光谱分析仪将铸坯偏析定量化检测,为酸洗检测铸坯偏析提供一种借鉴和补充。     

晶间脆性断裂的非平衡偏聚机理研究

 中温脆性、回火脆性是困扰材料学界百年的两大晶间脆性难题,其发生机理一直是材料科学与工程学界研究的热点。根据溶质非平衡偏聚恒温动力学特征,总结出了中温脆性的非平衡偏聚机理。另外,依据溶质非平衡偏聚的临界时间现象,综述了回火脆性的非平衡偏聚研究最新进展。通过对以上两种晶间脆性断裂发生机理的分析发现,他们都是由溶质的非平衡偏聚临界时间引起的。     

The Influence of Alloying Elements on Impurity Induced Grain Boundary Embrittlement

A nonequilibrium thermodynamic model which describes the effect of solute grain boundary segregation on grain boundary cohesion was extended to Fe ternary systems. The extended model directly and simply predicts the effect of alloying elements on impurity-induced grain boundary embrittlement. According to the extended model, Mo, W, and Zr strongly reduce, Ni, Ti, and V slightly reduce, and Cr and Mn enhance impurity-induced grain boundary embrittlement in an Fe ternary system. For the evaluation of the extended model, Fe-P, Fe-P-Mn, Fe-P-Mo, and Fe-P-W alloys were studied by Auger electron spectroscopy, scanning electron microscopy, 4-point slow bend tests, and tension tests. The experimental results show that for a given amount of P grain boundary segregation the grain boundary strength increases with increasing Mo or W grain boundary segregation and decreases with increasing Mn grain boundary segregation. These experimental results showing the remedial effect of Mo or W and the embrittling effect of Mn on P-induced grain boundary embrittlement are consistent with the predicted results from the extended model. The nonequilibrium model is also used to evaluate impurity-induced interfacial embrittlement in continuous fiber metal matrix composite materials.     

Recursive Determination for Effectof Alloying Element on Impurity Induced Low Angle Grain Boundary Embrittlement

It has been known for decades that P is one ofthe principal impurities responsible for temperingembrittlement in alloying steels[1] ,and it is general-ly believed that the equilibrium segregation of impu-rities to grain boundaries(GB) is the fundamentalmechanism of inter- granular embrittlement and thatthis is somehow influenced by the alloying elementspresent,such as nickel and chromium,which areknown to play an important role in the process[2 ] .For example,Mulford R A et al[3] have demons…     

Nonequilibrium Grain Boundary Segregation of Sulfur and Its Effect on Intergranular Corrosion for 304 Stainless Steel

 The data obtained by bending tests for intergranular embrittlement after 45 h and 450 h exposure to Strauss solution have been reported for 304 stainless steel. The results show that an embrittlement peak appears at 650 ℃ for all samples quenched from 1260 ℃ and then sensitized for 150 h at 480, 565, 650, 730, 815 and 900 ℃ respectively. The temperature corresponding to the embrittlement peak is decreased to 565 ℃ when the sensitizing time is prolonged to 1500 h. In this paper, these data are analyzed with an isothermal kinetic model of nonequilibrium grain boundary segregation, indicating that the embrittlement peak is related to the critical time for nonequilibrium grain boundary segregation of sulfur.     

磷元素在钢中的晶界偏聚

磷元素在钢中的晶界偏聚可以分为两类,即平衡偏聚和非平衡偏聚.介绍了这两类偏聚现象以及偏聚理论.以磷对晶界结合力、晶界扩散和晶界能的影响机理为基础,分析了磷元素对钢力学性能的影响和磷在钢中发生晶界偏聚的原因.     

Effect of Carbon on Grain Boundary Segregation of Phosphorus and Phosphorus-Induced Intergranular Fracture in High Purity Iron with Phosphorus

Ａｓｗｅｌｌｋｎｏｗｎ ,ｔｈｅａｄｄｉｔｉｏｎｏｆｃａｒｂｏｎｃａｎｐｒｅ ｖｅｎｔｔｈｅｐｈｏｓｐｈｏｒｕｓ ｉｎｄｕｃｅｄｉｎｔｅｒｇｒａｎｕｌａｒｆａｉｌｕｒｅｉｎｉｒｏｎ .ＢｕｔｉｔｉｓｔｈｅｒｅｓｕｌｔｏｆｕｓｉｎｇＡＥＳ (Ａｕｇｅｒｅｌｅｃ ｔｒｏｎｓｐｅｃｔｒｏｓｃｏｐｙ)ａｎａｌｙｓｉｓｉｎｆｒａｃｔｕｒｅｄｓｕｒｆａｃｅａｎａｌ ｙｓｉｓ .ＥｒｈａｒｔＨｅｔａｌ[1] ,ｉｎｏｒｄｅｒｔｏｅｘｐｌａｉｎｔｈｅｍｅｃｈ ａｎｉｓｍｏｆｃａｒｂｏｎｓｕｐｐｒｅｓｓｉｎｇｔｈｅｉｎｔｅｒｇｒａ…     

Relationship Between Grain Boundary Segregation of Antimony and Temper Embrittlement in TitaniumDoped Nickel-Chromium Steel

 The observations given by Ohtani et al are analyzed in the present paper and it is concluded that the kinetics of temper embrittlement in titanium-doped low carbon NiCr steel agree well with those of non-equilibrium grain-boundary segregation of Sb. Besides, the mechanism of non-equilibrium grain-boundary segregation of Sb is determined to be the most satisfactory one among the existed mechanisms in the literature to interpret the Sb-induced embrittlement kinetics in the NiCr steel. Based on the conclusion and the determination, the activation energy and frequency factor of diffusion of Sb-vacancy complexes are obtained for the first time according to the concept of critical time in non-equilibrium grain-boundary segregation theory. The calculated results can give theoretical basis for predicting and controlling over the Sb-induced embrittlement in steels.     

Relationship Between Grain Boundary Segregation of Antimony and Temper Embrittlement in Titanium-Doped Nickel-Chromium Steel

The antimony segregation at grain boundary was observed and the temper embrittlement in titanium-doped nickel-chromium steel was analyzed. It is concluded that the antimony segregation at grain boundary is nonequilibium and the kinetics of temper embrittlement agrees well with those of nonequilibrium antimony segregation at grain boundary. Besides, the mechanism of nonequilibrium antimony segregation at grain boundary proved to be the most satisfactory one among the existing mechanisms to interpret the antimony-induced embrittlement kinetics in the nickel-chrominm steel. Based on these, the activation energy and frequency factor of diffusion of antimony-vacancy complexes were obtained according to the concept of critical time in nonequilibrium grain boundary segregation theory.     

合金元素对GH220合金弯曲晶界的影响

本文对GH220合金弯晶形成机制以及加入W、Mo、C、Ce（微量）等元素的作用进行了初步探讨。试验结果表明:对于GH220合金,慢速缓冷时形成弯晶为γ′机制;快速冷却和采用等温工艺时为碳化物机制。并摸索到上述各元素最佳含量范围,对生产有一定参考价值。     

Method of Evaluating Hydrogen Embrittlement Susceptibility of Tempered Martensitic Steel Showing Intergranular Fracture

A stress application method in delayed fracture susceptibility tests was investigated using 1450 MPa class tempered martensitic steel. Its fracture mode under hydrogen charging was mainly intergranular because of its relatively small Si content of 0.21 mass pct. The conditions for consistency in fracture strength between tensile tests and constant load tests (CLTs) were clarified: first, to conduct hydrogen precharging before stress application; and second, to choose a sufficiently low crosshead speed in tensile tests. When hydrogen precharging was not conducted before CLTs, the fracture strength was higher than the values in CLTs with hydrogen charging and in tensile tests. If the crosshead speed was too high, the fracture strength obtained was higher than the values in CLTs. The dependence of the fracture strength on crosshead speed was seen for both notched and smooth bar specimens. These results suggested that plastic deformation, i.e., dislocation motion, was related to intergranular fracture with a tear pattern as well as to quasi-cleavage fracture. In addition, cathodic electrolysis in an alkaline solution containing NaOH should be used as the hydrogen charging method to avoid the effects of corrosion.