通过原位腐蚀观察和基于密度泛函理论的第一性原理计算方法,从微观角度研究了稀土元素铈(Ce)对J5不锈钢中夹杂物的改性和夹杂物诱导腐蚀的机理.采用扫描电子显微镜与能谱分析了稀土元素Ce改性夹杂物的过程中夹杂物成分和类型的变化,观...通过原位腐蚀观察和基于密度泛函理论的第一性原理计算方法,从微观角度研究了稀土元素铈(Ce)对J5不锈钢中夹杂物的改性和夹杂物诱导腐蚀的机理.采用扫描电子显微镜与能谱分析了稀土元素Ce改性夹杂物的过程中夹杂物成分和类型的变化,观察到的代表夹杂物为Ce Al O_(3)-Ce_(2)O_(2)S、Ce_(2)O_(3)-Ce_(2)O_(2)S、Mn S等.根据形成能计算,经稀土元素Ce处理后,生成了稳定的Ce_(2)O_(3)、Ce_(2)O_(2)S、Ce Al O_(3)夹杂物.通过表面能判断了晶面的稳定性,Fe(100)-2面的表面能经收敛测得为2.4374 J·m^(-2),该晶面的功函数为4.7352 e V.通过对比夹杂物与钢基体的功函数与计算电势差,分析了不同含Ce夹杂物诱导点蚀的趋势,探讨了不同原子位置、原子数量和不同slab模型对功函数的影响.研究表明,与Fe(100)-2面的电子功函数相比,Mn S以及改性后3种夹杂物Ce S、Ce_(2)O_(3)和Ce_(2)O_(2)S电势差大多小于0,Ce Al O_(3)的电势差在0 e V左右.夹杂物不同晶面对功函数影响很大,O、S等非金属原子数量多的晶面功函数平均值较高,添加稀土元素Ce可以有效降低晶面功函数.5种夹杂物和钢基体的平均功函数大小顺序为Ce Al O_(3)>Fe>Mn S>Ce S>Ce_(2)O_(2)S>Ce_(2)O_(3).结合不锈钢中复合夹杂物的实验结果可知,Ce_(2)O_(3)诱导点蚀发生的概率最高,Ce Al O_(3)可以有效提高钢的耐腐蚀能.展开更多
The formation and the growth of Cu-Sn intermetallic compound (IMC) layer at the interface between Sn-3.0Ag-0.5Cu-xCe solder and Cu substrate during soldering and aging were studied. The results show that Cu6Sn5 IMC is...The formation and the growth of Cu-Sn intermetallic compound (IMC) layer at the interface between Sn-3.0Ag-0.5Cu-xCe solder and Cu substrate during soldering and aging were studied. The results show that Cu6Sn5 IMC is observed at the interface between solder and Cu substrate in all conditions. After aging for 120 h,the Cu3Sn IMC is then obtained. With increasing aging time,the scalloped Cu6Sn5 structure changes to a plate structure. The Cu3Sn film always forms with a relatively planar interface. By adding a small amount of the rare earth element Ce (only 0.1%,mass fraction) into the Sn-3.0Ag-0.5Cu solder alloy,the growth rate of the Cu-Sn IMC at the interface of solder alloy system is decreased. When the time exponent is approximately 0.5,the growth of the IMC layer is mainly controlled by a diffusion over the studied time range.展开更多
Three observation methods were used to investigate the existing form and the behavior of rare earth during the sintering process of high activity mischmetal （RE, with lanthanum and cerium） doped WC-8%Co-0.048%RE（ma...Three observation methods were used to investigate the existing form and the behavior of rare earth during the sintering process of high activity mischmetal （RE, with lanthanum and cerium） doped WC-8%Co-0.048%RE（mass fraction） alloy with low carbon-containing level by scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDXS）, considering the fact that the addition amount of rare earth in the alloy is very minute. The directional migration process and mechanism of cerium were discussed. First, the sinter skin （surface） is observed. oxide on the sinter skin, and lanthanum in these cerium observed, and lanthanum containing phase/micro-zone in It is shown that there exists a dispersedly distributed cerium containing enrichment positions is very minute. Secondly, the polished section is the alloy is identified. Finally, based on the fact that the fracture of cemented carbide is resulted from the heterogeneous phase or other defects within the microstructure, the fracture surface is observed and cerium containing phase/micro-zone in the fracture source approximately 260 μm from the surface is identified. These combined observations reveal adequately the fact that lanthanum and cerium get separated and cerium predominantly migrates towards the surface during the sintering process.展开更多
文摘通过原位腐蚀观察和基于密度泛函理论的第一性原理计算方法,从微观角度研究了稀土元素铈(Ce)对J5不锈钢中夹杂物的改性和夹杂物诱导腐蚀的机理.采用扫描电子显微镜与能谱分析了稀土元素Ce改性夹杂物的过程中夹杂物成分和类型的变化,观察到的代表夹杂物为Ce Al O_(3)-Ce_(2)O_(2)S、Ce_(2)O_(3)-Ce_(2)O_(2)S、Mn S等.根据形成能计算,经稀土元素Ce处理后,生成了稳定的Ce_(2)O_(3)、Ce_(2)O_(2)S、Ce Al O_(3)夹杂物.通过表面能判断了晶面的稳定性,Fe(100)-2面的表面能经收敛测得为2.4374 J·m^(-2),该晶面的功函数为4.7352 e V.通过对比夹杂物与钢基体的功函数与计算电势差,分析了不同含Ce夹杂物诱导点蚀的趋势,探讨了不同原子位置、原子数量和不同slab模型对功函数的影响.研究表明,与Fe(100)-2面的电子功函数相比,Mn S以及改性后3种夹杂物Ce S、Ce_(2)O_(3)和Ce_(2)O_(2)S电势差大多小于0,Ce Al O_(3)的电势差在0 e V左右.夹杂物不同晶面对功函数影响很大,O、S等非金属原子数量多的晶面功函数平均值较高,添加稀土元素Ce可以有效降低晶面功函数.5种夹杂物和钢基体的平均功函数大小顺序为Ce Al O_(3)>Fe>Mn S>Ce S>Ce_(2)O_(2)S>Ce_(2)O_(3).结合不锈钢中复合夹杂物的实验结果可知,Ce_(2)O_(3)诱导点蚀发生的概率最高,Ce Al O_(3)可以有效提高钢的耐腐蚀能.
基金Project(06GK2002) supported by the Major Project of Hunan Provincial Science and Technology Development Strategy
文摘The formation and the growth of Cu-Sn intermetallic compound (IMC) layer at the interface between Sn-3.0Ag-0.5Cu-xCe solder and Cu substrate during soldering and aging were studied. The results show that Cu6Sn5 IMC is observed at the interface between solder and Cu substrate in all conditions. After aging for 120 h,the Cu3Sn IMC is then obtained. With increasing aging time,the scalloped Cu6Sn5 structure changes to a plate structure. The Cu3Sn film always forms with a relatively planar interface. By adding a small amount of the rare earth element Ce (only 0.1%,mass fraction) into the Sn-3.0Ag-0.5Cu solder alloy,the growth rate of the Cu-Sn IMC at the interface of solder alloy system is decreased. When the time exponent is approximately 0.5,the growth of the IMC layer is mainly controlled by a diffusion over the studied time range.
基金Project(50574104) supported by the National Natural Science Foundation of China
文摘Three observation methods were used to investigate the existing form and the behavior of rare earth during the sintering process of high activity mischmetal （RE, with lanthanum and cerium） doped WC-8%Co-0.048%RE（mass fraction） alloy with low carbon-containing level by scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDXS）, considering the fact that the addition amount of rare earth in the alloy is very minute. The directional migration process and mechanism of cerium were discussed. First, the sinter skin （surface） is observed. oxide on the sinter skin, and lanthanum in these cerium observed, and lanthanum containing phase/micro-zone in It is shown that there exists a dispersedly distributed cerium containing enrichment positions is very minute. Secondly, the polished section is the alloy is identified. Finally, based on the fact that the fracture of cemented carbide is resulted from the heterogeneous phase or other defects within the microstructure, the fracture surface is observed and cerium containing phase/micro-zone in the fracture source approximately 260 μm from the surface is identified. These combined observations reveal adequately the fact that lanthanum and cerium get separated and cerium predominantly migrates towards the surface during the sintering process.
