MO Defeng
,
HU Zhengfei
,
CHEN Shujuan
,
WANG Chunxu
,
HE Guoqiu
钢铁研究学报(英文版)
Electronbeam (EB) welding was used in T250 maraging steel, microstructures of both base material and heat affected zone (HAZ) were investigated by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and microhardness was tested. The results showed that during EB welding, the HAZ of T250 maraging steel exhibited a continuous gradient structure. The microstructure of the entire HAZ, from fusion line, could be divided into four zones: fusion zone, overheated zone, transition zone, and hardened zone. The microhardness showed a distinct regularity in each area. The softest region was the fusion zone, whereas the hardest was the hardened zone. In the overheated zone, the hardness increased as the grain size decreased. Furthermore, in the transition zone, the hardness level dropped noticeably. The peak temperature during the thermal cycle had a great influence on the formation of reverted austenite and dissolution of the precipitated particles, which contributed a lot to the microstructure and hardness of this material.
关键词:
T250 maraging steel;electronbeam weld;microstructure;microhardness
ZHANG Xi-liang
,
ZHOU Chang-yu
钢铁研究学报(英文版)
The constant embrittlement curve for constant segregation concentration on grain boundary of impurity element P and relationship between equilibrium grain boundary segregation concentration and operation time for 225Cr-1Mo steel were derived based on the theory of equilibrium grain boundary segregation. The mechanism of step-cooling test and mechanism of de-embrittlement for 225Cr-1Mo steel were explained. The segregation rate will increase but equilibrium grain boundary segregation concentration of impurity element P will decrease as temperature increases in the range of temper embrittlement temperature. There is one critical temperature of embrittlement corresponding to each embrittlement degree. When the further heat treating temperature is higher than critical temperature, the heat treating will become a de-embrittlement process; otherwise, it will be an embrittlement process. The critical temperature of embrittlement will shift to the direction of low temperature as further embrittlement. As a result, some stages of step-cooling test would change into a de-embrittlement process. The grain boundary desegregation function of impurity element P was deduced based on the theory of element diffusion, and the theoretical calculation and experimental results show that the further embrittlement or de-embrittlement mechanism can be interpreted qualitatively and quantitatively by combining the theory of equilibrium grain boundary segregation with constant embrittlement curve.
关键词:
step-cooling test
,
critical embrittlement temperature
,
embrittlement mechanism
,
grain boundary desegregation
Kehai Li
材料科学技术（英文）
Modification of conventional gas metal arc welding (GMAW) process is of great potential to achieve high productivity with low cost and strong usability. Double-Electrode GMAW (DE-GMAW) is such a modified arc welding process which is formed by adding a bypass torch (gas tungsten arc welding torch) to a conventional GMAW system. The mechanism of metal transfer in DE-GMAW was proposed and verified in this paper. Experiments show that the critical current is decreased so that spray transfer can be obtained at a lower current level in DE-GMAW. Analysis of this significant change in metal transfer phenomena is conducted, and explanation is given out. It is found that the bypass arc in DE-GMAW lifts the anode point on the droplets such that the electromagnetic force becomes larger and squeezes the droplets so that spray transfer can take
place under welding current lower than that in conventional GMAW.
关键词:
Metal transfer
,
null
,
null
Materials Letters
Highly preferred (002) orientation transparent conductive Al-doped ZnO (ZAO) films were successfully prepared by de magnetron reactive sputtering from a Zn target mixed with Al of 2.0 wt.%. The film has a resistivity of 4.80 X 10(-4) n cm and a visible transmittance of as high as 90%. XPS analysis indicates Al-enrichment on the film surface. The asymmetry of Al 2p(3/2) XPS peak is resolved into two components: one centering at 72.14 eV attributed to metallic Al and the other having a binding energy of 74.17 eV due to oxidized Al. (C) 2001 Elsevier Science B.V. All rights reserved.
关键词:
Al-doped;ZnO;XPS;Al-enrichment;oxide thin-films;optical-properties;electrical-properties;rf;dc;transparent;deposition
武传松
,
张明贤
,
李克海
,
张裕明
金属学报
doi:10.3321/j.issn:0412-1961.2007.06.021
通过大量的工艺实验,找出了DE-GMAW双焊枪组合的匹配参数,测试了焊接电流波形,拍摄了熔滴过渡图像,并获得了无成型缺陷的焊缝照片.基于实验结果解释了高速焊接工艺的机理.建立了适用于DE-GMAW焊接工艺的有限元模型,并对该工艺条件下的温度场、应力-应变场进行了数值模拟.结果表明:计算出的DE-GMAW焊缝横断面形状尺寸与实验结果吻合良好;在通过焊丝的总电流相同时,DE-GMAW焊接时焊缝尺寸、热影响区宽度、应力、应变及变形均小于常规GMAW焊时的结果.这为DE-GMAW焊接工艺参数优化提供了基础数据.
关键词:
高速电弧焊接
,
工艺机理
,
DE-GMAW
,
有限元分析
武传松
,
张明贤
金属学报
根据当前制造业对高效、优质、低耗焊接技术的迫切要求，研发出低成本的高速电弧焊接新工艺DE-GMAW。该工艺在常规GMAW焊接设备的基础上，通过附加GTAW焊枪构成旁路电弧，分流了一部分通过焊丝的焊接电流，在施加于焊丝的电流较大的情况下（保证了熔敷率），减小了作用于母材的热输入，解决了高速焊接面临的矛盾，实现了高速电弧焊接。建立了适用于DE-GMAW焊接工艺的有限元模型，并对该工艺条件下的温度场和应力变形进行了数值模拟。结果表明：计算出的DE-GMAW焊缝横断面形状尺寸与实验结果吻合良好；在通过焊丝的总电流相同时，DE-GMAW焊接时焊缝尺寸、热影响区宽度、应力、应变及变形均小于常规GMAW焊时的结果。这为DE-GMAW焊接工艺参数优化提供了基础数据。
关键词:
高速电弧焊接
,
process mechanism
,
DE-GMAW
,
finite-element analysis
祁新梅
,
宗志坚
,
郑寿森
高分子材料科学与工程
应用Mooney-Rivlin、Yeoh和Ogden应变能模型研究DE材料驱动建模。首先根据单轴拉伸实验数据,分析文献中的材料常数和本文DE材料的适合程度,发现文献中的材料常数均不适合本试验中的绝缘弹胶物（DE）材料变形特性;进一步根据试验数据及理论模型回归分析求出适合本试验变形范围内的DE材料的材料常数。结果表明,Mooney-Rivlin模型不能很好地反映非线性特征,Yeoh和4参数及6参数的Ogden模型均能反映DE材料的非线性特征。
关键词:
电活性聚合物
,
绝缘弹胶物
,
类天然肌肉
,
应变能模型
