高匹配焊接接头裂纹的J积分研究

本文研究了含有纵向裂纹或缺陷的高匹配焊接接头材料不均匀性和焊缝宽度对弹塑性断裂表征参量J积分的影响规律.高匹配焊缝被理想化为含有一平行裂纹的一个硬夹层,其屈服应力高于母材.在平面应力条件下利用弹塑性有限元计算得到数值解.研究结果表明,材料不均匀性和焊缝宽度对J积分值有显著影响,特别当名义应力或名义应变较高时影响更大.因此,估算高匹配接头的裂纹推力时必须对此加以考虑.     

HT60高拉力钢在人工海水中的腐蚀疲劳裂纹扩展特性

对高拉力钢HT60的腐蚀疲劳裂纹扩展特性和门槛值区域特性,采用紧凑拉伸试件在人工海水中进行了实验和研究,结果表明:在空气中的da/dN与ΔK_(cff)关系可以作为在海水中的da/dN与ΔK关系的一个偏保守的预测;在高应力比的高ΔK区域,由于应力诱起溶解促进了裂纹扩展的加速;该裂纹开口应力强度因子K_(op)仅反映了裂纹表面同腐蚀生成物接触的结果,从而导致了K_(op)在裂纹尖端的偏大的估计结果。     

离子渗碳层中的晶间脆性SCIEI

本文对20Cr2Ni4A钢离子渗碳层出现的沿晶断裂的原因进行了分析,结果表明,渗碳层中的残余奥氏体与在该区域产生的沿晶脆断无关。TEM分析和Auger电子能谱分析表明,形成沿晶断裂的主要原因是S,P等杂质元素在原奥氏体晶界的偏聚。采用二次加热淬火可以消除这种现象。     

TRANSFORMATION HYSTERESIS AND STABILITY OF STRAIN MARTENSITE IN A Ni_(47)Ti_(44)Nb_9 ALLOY

The transformation hysteresis and stability of strain martensite in Ni_(47)Ti_(44)Nb_ alloy have been studied by means of tensile tests at various temperatures and electrical resistance measurements as well as TEM observations.It was shown that there is a characteristic deformation temperature and a strain range,in which the critical yield stress for stress-in- duced transformation acquires optimum matching with the yield strength of the β-Nb parti- cles.In this case,deformatian can effectively increase the transformation hysteresis,while the strain recovery ratio remains usefully high.The martensite with irreguldar fine.twin substructure and martensite containing some dislocations as well as martensite intersected by the β-Nb particles possess high stability.     

MICROSTRUCTURE AND PROPERTIES OF SiC_w/6061Al COMPOSITE The Author is now with Institute of Metal Research,Academia Sinica,China

The SiC_w/Al composite prepared by squeeze casting has a combination of superior roomtemperature specific strength and modulus together with excellent thermal properties.Theextrusion can make an improvement on the strength and ductility of the composite from 582MPa as squeeze casted up to 639 MPa,and on the transformation from isotropic to theanisotropic structure.This seems to be explained by the orientation of whiskers and thedensification of dislocations in matrix.TEM observation indicates that the stacking fault isthe usual planar defect on the SiC_w surface.     

MODIFICATION EFFECT OF Sr ON Al-Si ALLOY

本文采用引入单晶Si籽晶的方法,考察Sr变质Al-22％Si合金中Si相的生长行为。结果表明Sr影响Si相的形核与生长。表面分析指出Sr在{111}_(Si)上的吸附是Sr影响Si相形核生长的原因,而变质共晶组织则是Sr使共晶领先相发生改变的结果。     

WELDING BETWEEN HIGH MANGANESE STEEL AND HIGH CARBON STEEL

1.Withthedevelopmentofthehighrunningspeedrailway,thecontinuouslyweldedlinewasreqUired.~ughthetechniqUeofweldingrailsteelhasbeenrealized,theweldingofarailwaytrackpartmadefromhighmanganesesteeltorailwasonlysolVedpclybyflashbuttweldinginFranceandAustralia{.ill.china,thisstudywasstartedin1990's.Someadvanceshavebeenobtained,buttherewasnotagoodmethodtosolvetheproblem.Thepresentinvestigationbeganin1997,andgoodresultshavebeenobtained.2.~conic2.1ExperimentalmaterialsThesampleofhighmaxlganesesteelwith…     

快速凝固Ti-48Al合金的组织及纳米硬度(英文)

研究冷却速度对熔体旋转法制备的快速凝固Ti-48%Al合金组织的影响。结果表明:同传统凝固相比,快速凝固明显细化了Ti-48%Al合金的组织,并使合金的成分变得均匀。随着冷却速度的增加,合金的晶粒明显细化。研究薄带厚度、辊速与冷却速度的关系。随着辊速的增加,冷却速度增加,薄带厚度呈减小的趋势。由于细晶强化的作用,快速凝固薄带的纳米硬度随着冷却速度的增加而增加。     

Process of friction-stir welding high-strength aluminum alloy and mechanical properties of joint

The process of friction-stir welding 2A12CZ alloy has been studied. And strength and elongation tests have been performed, which demonstrated that the opportunity existed to manipulate friction-stir welding parameters in order to improve a range of material properties. The results showed that the joint strength and elongation arrived at their maximums ( 331 MPa and 4% ) at 37. 5 mm/min and 300 rpm. As welding parameters changing, joint tensile strength and elongation had similar development. Hardness measurement indicated that the weld was softened. However, there was considerable difference in softening degree for different joint zone. The weld top had lower hardness and wider softening zone than other zone of the weld. And softening zone at advancing side was wider than that at retreating side.     

几种金属副在NaCl溶液中的抗蚀耐磨性能评价

应用电化学测试手段，针对20、2Cr13、QAl 9-2、QA l 10-3-15和QAl 10-4-4五种材料试件，分别测定了它们在NaCl溶液中的腐蚀电位及与QAl 9-2偶接时的电偶腐蚀电流的变化.并对几种铝青铜材料和QAl 9-2构成的摩擦副进行了摩擦磨损性能分析.结果表明，铝青铜材料的抗腐蚀性比钢好.其中QAl 10-4-4的腐蚀电位最为偏正，但它与QAl 9-2配副会对QAl 9-2产生较大的阳极电偶腐蚀；QAl 9-2与QAl 9-2相配时的电偶腐蚀最小，但其摩擦相溶性最差；而QAl 9-2与QAl 10-3-15材料副的抗电偶腐蚀能力和摩擦相溶性均佳.