51CrV4弹簧钢低温脆性的研究

以51CrV4弹簧钢为研究对象,研究了其低温脆性.结果表明,在-60～0℃时,51CrV4弹簧钢的冲击功在20～25J,它会随温度的下降而有所降低;在-60℃时其冲击功仍保持较高水平,没有发生脆性断裂.51CrV4弹簧钢的冲击断口为混合型断口,有解理、撕裂和韧窝聚集等特征.经能谱分析可知,51CrV4弹簧钢含有少量由硅、氧组成的非金属夹杂物,属于硅酸盐类夹杂.     

GH4742合金疲劳裂纹扩展行为

研究GH4742合金在室温、700℃及750℃的疲劳裂纹扩展行为。分析温度和应力强度因子对疲劳裂纹扩展寿命与速率的影响,利用扫描电镜观察不同温度下的疲劳裂纹扩展断口。采用背散射电子衍射(EBSD)技术分析合金裂纹扩展的晶体学机制。结果表明,随着温度的升高,合金的裂纹扩展寿命降低,裂纹扩展速率增加,沿晶断裂特征更明显。应力强度因子越大,裂纹扩展速率越大。在原始大变形晶粒中裂纹以穿晶方式沿着小角度晶界扩展,裂纹扩展到再结晶晶界时以沿晶扩展为主,其扩展方式取决于相邻晶粒的面间角和取向差。     

回火温度对无碳化物贝氏体钢组织和性能的影响

研究了无碳化物高强度贝氏体钢正火后回火温度对其组织和性能的影响。结果表明,经920℃奥氏体化加热空冷及200～350℃回火,实验钢具有良好的强韧性。该温度范围回火获得的抗拉强度为1 370～1 472 MPa,断后伸长率为15%～16%,断面收缩率为47%～62%,冲击功AKV为76～86 J;组织主要为板条状贝氏体铁素体和残余奥氏体,即无碳化物贝氏体组织。550℃回火冲击值最低,出现贝氏体回火脆性,断口特征为沿晶脆性断裂。     

热处理工艺对51CrV4弹簧钢组织与性能的影响

利用光学显微镜(OM)、扫描电镜(SEM)、电子探针(EPMA)分析弹簧钢过早发生疲劳断裂的原因,研究热处理工艺对51CrV4弹簧钢的显微组织和力学性能的影响。结果表明:热处理过程中淬火温度过高导致晶粒度等级偏低,为6.5级,马氏体组织粗大,并且表面出现全脱碳层,总脱碳层厚度为301.56μm,疲劳试样的扫描形貌是沿晶断裂,属于脆性断裂;经过在860℃下保温40 min油淬、随后在450℃下回火保温90 min的优化热处理工艺处理后,弹簧钢的综合性能最佳,抗拉强度和屈服强度分别为1678 MPa和1293 MPa,断后伸长率和断面收缩率为8.9%和42.5%,回火硬度为45.2 HRC,疲劳断口为塑性断裂,疲劳寿命由6.3万次提升到11万次,满足弹簧钢的性能要求。     

ZL101A合金低温疲劳性能和断裂行为研究

研究了ZL101A合金的低温拉伸性能和低温疲劳性能,对断口形貌进行了观察,分析了疲劳断裂的微观机制。结果表明:服役温度对合金疲劳寿命及断裂机制有显著的影响。随着服役温度的降低,合金疲劳寿命提高。室温条件下断口主要以穿晶断裂为主,同时伴随局部沿晶断裂特征,而-40℃条件下合金断裂行为表现出较强的晶体学裂纹特征。与室温相比,合金在低温下的疲劳断口瞬断区面积增大,粗糙度有所升高。而相同温度下,合金随着应变幅的增加,合金低温疲劳的断口粗糙度有所降低。     

残余奥氏体韧化机理的探讨

本文通过研究20C_rM_nT_i钢碳氮共渗层中残余奥氏体数量对接触疲劳和三点弯曲疲劳寿命的影响及断口分析,探讨残余奥氏体韧化机理,同时给出了接触疲劳破坏的机制模型,并由残余奥氏体韧化机理解释了沿晶断口高寿命     

析出强化奥氏体钢的室温断裂行为

本文研究了显微组织对一种析出强化奥氏体钢室温断裂行为的影响,结果表明,在相同的时效条件下,当固溶温度≤1100℃时,断口呈穿晶韧断;当固溶温度>1100℃时,断口呈沿晶断裂.最后,讨论了穿晶韧断和沿晶断裂的原因。     

氧化时间对低合金弹簧钢奥氏体晶粒度测定的影响

氧化法可用于钢中晶粒度的测定。研究控制氧化时间对弹簧钢50CrV奥氏体晶粒度的影响。结果发现,氧化过程大致分为3个阶段:第一阶段,过剩铁素体相不断转变为奥氏体;第二阶段,基体与氧化膜之间的阴阳离子再次加快扩散,下层金属基体继续氧化脱碳,部分之前试样表面的奥氏体晶界被替代;第三阶段,一、二阶段的奥氏体晶粒逐渐长大,新旧氧化膜叠加生长,并在55SiCr、60Si2Mn、65Si2CrV钢得到验证。在不影响检测结果准确性的情况下,氧化时间可以由标准的60 min缩短至一半左右,再通过修正可得到晶粒度为10.96级,此结果与直接腐蚀法11.00级和氢致沿晶断口法11.09级相近。     

奥氏体化温度对60Si2CrVAT弹簧钢晶粒尺寸和硬度的影响

研究了奥氏体化温度对弹簧钢60Si2CrVAT晶粒尺寸和硬度的影响。结果表明,随奥氏体化温度的提高,60Si2CrVAT钢晶粒变粗,残留奥氏体增加,硬度有增高的趋势;在890、910℃奥氏体化,晶粒尺寸和硬度得到最佳配合;回火后,60Si2CrVAT钢残留奥氏体明显减少。     

FRACTURE BEHAVIOUR OF PRECIPITATION HARDENED AUSTENITIC STEEL

本文研究了显微组织对一种析出强化奥氏体钢室温断裂行为的影响,结果表明,在相同的时效条件下,当固溶温度≤1100℃时,断口呈穿晶韧断;当固溶温度>1100℃时,断口呈沿晶断裂.最后,讨论了穿晶韧断和沿晶断裂的原因。     

Prospects of the Use of Synergetic Approach to Solution of Problems of the Science of Nanomaterials

A synergetic approach to solution of problems of self-controlled synthesis of nanostructures and creation of self-organizing nanotechnologies is considered in connection with the superproblem of creation of materials with functional properties resembling those of biosystems. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 55 – 61, July, 2005.     

Kinetics of the oxidation of metals — Influence of self-diffusion of metal

The importance of the self-diffusion of a metal during its oxidation by a gas is treated for the cases of nonstoichiometric oxides having either interstitial cation or cation vacancies. We have established a general relationship for the reaction rate when a mixed diffusion process occurs. From this relationship, we have shown that the pressure dependence can be different, according to whether the rate-determining process is the self-diffusion through the metal or through the product.     

胫骨生物陶瓷复合材料的微结构增韧机理

扫描电镜观察显示胫骨是一种由羟基磷灰石和胶原蛋白组成的自然生物陶瓷复合材料.羟基磷灰石具有层状的微结构并且平行于骨的表面排列.观察也显示这些羟基磷灰石层又是由许多羟基磷灰石片所组成,这些羟基磷灰石片具有长而薄的形状,也以平行的方式整齐排列.基于在胫骨中观察到的羟基磷灰石片的微结构特征,通过微结构模型分析及实验,研究了羟基磷灰石片平行排列微结构的最大拔出能.结果表明,羟基磷灰石片长而薄的形状以及平行排列方式增加了其最大拔出能,进而提高了骨的断裂韧性.     

Features of formation of the structure in production of blanks of disks of heat-resistant nickel alloys

Conclusions To provide a high level of mechanical properties in wrought blanks of cast ÉP741NP and ÉP962 alloys it is necessary to form controlled structures. A necklace-type structure formed in homogenizing isostatic treatment, subsequent thermomechanical working including alternation of the operations of deformation in the (+)-area and recrystallization anneals, and final heat treatment is preferable. The temperature conditions of all stages of thermomechanical working are strictly controlled, especially the final operation of deformation and heating for hardening. To eliminate hardening cracks and distortions it is necessary to use molten salts at t=600°C as quenchants. The use of multiple production operations makes it possible to significantly reduce the structural inhomogeneity related to inhertance of the original dendritic structure. However, the structure of the final semifinished product is nevertheless characterized by a difference in occurrence of the processes of polygonization and recrystallization between the former dendritic cells and the interdendritic spaces in deformation and heat treatment.To obtain structurally homogeneous blanks for gas turbine engine parts it is necessary to use basically new methods of remelting such as vacuum double electrode remelting and electron beam remelting with an intermediate vessel.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 25–29, December, 1991.     

Ab-initio calculation of enthalpies of formation of intermetallic compounds and enthalpies of mixing of solid solutions

A large number of ab-initio calculations of energies of formation of intermetallic compounds have been performed in the last 15 years. The currently used methods are listed. The paper presents a review of the aluminium based compounds which have been studied. Comparisons of calculated and experimental enthalpies of formation are provided for aluminim-3d and-4d transition metal alloys at equiatomic composition. The modelling of the enthalpies of mixing of solid solutions based on a given lattice is described.     

试论洋务派教师聘任的思想

洋务派在洋务学堂的办学活动中,为了解决西学专业学科的教学困难,采用了聘请外籍教师的应急措施.他们以真才实学,合同制管理作为主导思想,并认为这种解决师资的途径只是权宜之计,并非久远.从客观上看,洋务派的教师聘任思想有深刻的历史影响.     

面向零件形状的计算机图形库的开发

论述了CAD技术中参数化设计的三种建模方法，重点介绍了基于特征的参数化建模原理。在此基础上，分析机械设计中的机构结构，归纳出其零件的几何特征构成。设计了机构CAD图形库，并提出了该图形库生成步骤和人机交互界面。