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991.
用透射电镜和X-射线能谱仪对经自然和人工时效的18Cr2Ni4WA钢的微观组织、析出相及其分布进行了研究。结果表明,在应力作用下,组织的回复趋于不均,沿晶界析出的脱溶物增多。回复较充分的铁素体板条中析出粗大的(Fe、Cr)3C,局部均匀分布;回复不充分处,沿晶界还析出长杆状的(Fe、Cr)3C和更细小的杆状W2C。时效后组织中元素C、Cr和W趋于沿晶界偏聚,其中W几乎全部以碳化物的形式存在于晶界附近。析出相(Fe、Cr)3C的[001]晶带轴与α铁素体的[121]晶带轴近似平行。晶界脆性相的增多是该材料的螺栓在服役期间变脆和在腐蚀环境下失效的内在原因。 相似文献
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993.
994.
Jinfu LU Yaohe ZHOUSchool of Materials Science Engineering Shanghai Jiao Tong University Shanghai ChinaWanqi JIE Gencang YANGState Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi''''an Chin 《材料科学技术学报》2002,18(4):295-298
Solidification structure variation of single phase alloy with undercooling prior to nucleation has been widely studied.The progress,especially during the last decade,is reviewed so as to give a comprehensive knowledge for it ,in which the emphases are laid on the structure evolution mechanism and the potential application.Lastly, the future interesting subjects are presented. 相似文献
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996.
The effects of Si,Mn and Al on the microstructure and mechanical properties of ADl weld have been studied.The microstructure of ADl weld metal mainly consists of bainitic ferrite and retained austenite.Mechanical properties of Adl weld increase with increasing Si content,but an excess of Si(3.79%) results in decreasing the austemperability owing to decreasing the carbon content of the matrix austenite.Mn increases the retained austenite volume fractio,but the ductility and impact toughness of weld obviously decrease with increasing Mn content because of increased amount of martenite and twin martenite.In the range of 0.13%-0.64%Al ,increasing Al content favours improving the mechanical properties of ADl weld.Therefore,it is very important to select suitable Si,Mn and Al contents to improve mechanical properties of ADl weld . 相似文献
997.
David G. McIntyre Shawn J. Cunningham Judd S. Carper Paul D. Jaramillo Svetlana Tatic-Lucic Larry E. Starr 《Sensors and actuators. A, Physical》1997,60(1-3):181-185
Single-crystal silicon microstructures, of identical design, exhibit different failure rates (following fabrication or mechanical shock testing) due to various processes. The microstructures fabricated with a boron diffusion and subsequent removal of the boron-diffused layer have a higher survival rate to the fabrication process and to mechanical shock. The survival rate (a survivor has an intact proof mass and beam) through the process is increased by 26.5%. At a 3680g shock, the boron-diffused devices have a 2.3% lower failure rate but the difference is not statistically significant. These results have been developed with wafer-level shock testing, which permits bulk testing of many samples in a cost-effective manner. 相似文献
998.
数字序列抗原的淋巴细胞的演化方法 总被引:3,自引:0,他引:3
论文对计算机免疫学中Self集的物理空间分布和识别器的构造进行了探讨性的分析,并针对传统方法识别效果差、缺乏灵活性等缺点,提出了一种基于遗传算法的具有空间自适应能力的识别器构造方法,并通过实验比较了该算法与传统识别器构造算法的效果。 相似文献
999.
Liquid immiscible alloys 总被引:8,自引:0,他引:8
The microstructure formation, during casting, of alloys being immiscible in the liquid state such as copperlead or aluminium-lead has gained renewed scientific and technical interest during the last fifteen years. Especially, a new experimental tool, research under reduced gravity conditions, was able to cast new, unexpected results and theories into the discussion on the nature of the complex process of microstructure evolution in such alloys. Prior to the first experiments performed at reduced levels of gravity acceleration, it was generally agreed that the process of phase separation during cooling through the miscibility gap is dictated solely by gravity-induced effects such as natural convection and sedimentation. Fundamental and applied research in space and in earth laboratories could show that there are other mechanisms operating concurrently and under suitable conditions with equal strength. In addition applied research was able to utilize the often unexpected results from space experimentation to develop new casting processes which allow one to produce microstructures on earth suitable for bearings in automotive applications. Therefore this article describes the extensive progress that has been made during the last decade and also the fundamentals of immiscibles. In addition it will be shown that the combination of classical laboratory research, research under reduced gravity conditions and a newly developed computational modelling technique seems to be just becoming available to solve the problems of decomposition, spatial phase separation and microstructure evolution during cooling of an alloy through the liquid miscibility gap. 相似文献
1000.
The microstructure of high chrome bricks made at dif-ferent sintering temperature are analyzed by SEM. The re-sults indicate that the sintering temperature of high chromebricks has an optimum range, it is not the higher, the ber-ter. The high chrome. bricks made at this sintering temper-ature have the moderate crystal size in the matrix and ofdense structure. The closed bonding structure could be ob-tained between grains and matrix and no crackle occurred.The high chrome bricks with this microstructure have thebest dynamic properties. 相似文献