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排序方式: 共有216条查询结果,搜索用时 15 毫秒
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Yosuke Yamazaki Takayuki Otsuka Kazuo Okamura Yoji Shibutani 《Materials Science & Technology》2020,36(6):750-758
ABSTRACTHeat treatment, such as quenching and carburising, often involves volume change caused by phenomena such as thermal expansion, phase transformation, and carbide precipitation during tempering. During the tempering process, an external force induces additional plastic deformation. The authors termed this phenomenon ‘tempering plasticity’. In this study, we performed crystal plasticity analysis using fast Fourier transform considering the volume change in carbides to assess the mechanism of tempering plasticity. As a result, tempering plastic strain occurred as the volume fraction of carbide increased, and the tempering plastic phenomenon could be reproduced based on the transformation model proposed by Greenwood–Johnson. The result supports the idea that the volume change accompanied by carbide precipitation is an important mechanism that invokes tempering plasticity. 相似文献
3.
The integral diaphragm pressure transducers machined out of precipitation hardened martensite stainless steel (APX4) are widely used for propellant pressure measurements in space applications. These transducers are expected to exhibit dimensional stability and linearity for their entire useful life. These vital factors are very critical for the reliable performance and dependability of the pressure transducers. However, these transducers invariably develop internal stresses during various stages of machining. These stresses have an adverse effect on the performance of the transducers causing deviation from linearity. In order to eliminate these possibilities, it was planned to cryotreat the machined transducers to improve both the long-term linearity and dimensional stability. To study these effects, an experimental cryotreatment unit was designed and developed based on the concept of indirect cooling using the concept of cold nitrogen gas forced closed loop convection currents. The system has the capability of cryotreating large number of samples for varied rates of cooling, soaking and warm-up. After obtaining the initial levels of residual stress and retained austenite using X-ray diffraction techniques, the pressure transducers were cryotreated at 98 K for 36 h. Immediately after cryotreatment, the transducers were tempered at 510 °C for 3 h in vacuum furnace. Results after cryo treatment clearly indicated significant reduction in residual stress levels and conversion of retained austenite to martensite. These changes have brought in improvements in long term zero drift and dimensional stability. The cryotreated pressure transducers have been incorporated for actual space applications. 相似文献
4.
S. Bhattacharya G.P. DindaA.K. Dasgupta J. Mazumder 《Materials Science and Engineering: A》2011,528(6):2309-2318
In the current investigation AISI 4340 steel was laser deposited on a rolled mild steel substrate by Direct Metal Deposition (DMD) technology. The microstructural investigation of the clad was performed using optical and electron microscopes and X-ray diffraction techniques. The microstructure consisted of ferrite, martensite and cementite phases. Two types of martensite, lathe-type and plate-type, were observed in the microstructure. Decrease in microhardness values from the top layer to the alloy layer proves that the degree of tempering of the martensite phase increases in the same direction. The lattice parameters of the identified phases were found to be shorter than those reported in literature. The reported parameters in literature are from samples processed under equilibrium conditions. 相似文献
5.
借助于内耗仪研究了不同退火工艺(退火温度和冷却速度)和平整工艺对镀锡板固溶碳含量的影响。结果表明:(1)随着退火温度的升高,镀锡板中固溶碳含量逐渐增加;(2)随着冷却速度的增加,镀锡板中固溶碳含量逐渐降低;(3)随着平整量的增加,镀锡板中固溶碳含量逐渐减小。 相似文献
6.
通过对Q550中厚板轧后直接淬火+回火(DQ—T)替代调质的工艺研究,摸索最佳的生产工艺,批量生产出具有良好和稳定综合力学性能的Q550高强度中厚钢板。 相似文献
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B. M. Huang H. W. Yen C. H. Hsu C. Y. Huang H. Mohrbacher 《Materials Science & Technology》2014,30(9):1014-1023
AbstractThe effect of Mo additions on the development of bainitic ferrite in hot rolled low carbon (0·05 wt-%C) Nb containing steel strips has been studied. The steel strips were fabricated by a combined process of controlled rolling and accelerated cooling. Microstructural characterisation and mechanical testing for the corresponding strips were investigated. The results indicated that a small amount of Mo addition (0·1–0·3 wt-%) causes the production of a high volume fraction of bainite, which undergoes significant secondary hardening after tempering treatment at 600°C for 1 h. It is noticeable that the secondary hardening effect provides an additional way to significantly increase the strength of low carbon Nb–Mo containing bainitic steels. 相似文献
9.
To study the effect of tempering temperature on strain hardening exponent and flow stress curve, one kind of 1000 MPa grade low carbon bainitic steel for construction machinery was designed, and the standard uniaxial tensile tests were conducted at room temperature.A new flow stress model, which could predict the flow behavior of the tested steels at different tempering temperatures more efficient-ly, was established.The relationship between mobile dislocation density and strain hardening expo-nent was discussed based on the dislocation-stress relation.Arrhenius equation and an inverse propor-tional function were adopted to describe the mobile dislocation, and two mathematical models were established to describe the relationship between tempering temperature and strain hardening expo-nent.Nonlinear regression analysis was applied to the Arrhenius type model, hence, the activation energy was determined to be 37.6 kJ/mol.Moreover, the square of correlation coefficient was 0.985, which indicated a high reliability between the fitted curve and experimental data.By comparison with the Arrhenius type curve, the general trend of the inverse proportional fitting curve was coincided with the experimental data points except of some fitting errors.Thus, the Arrhenius type model can be adopted to predict the strain hardening exponent at different tempering temperatures. 相似文献
10.
研究了回火温度及回火时间对27 mm厚610 MPa级压力容器用钢组织及力学性能的影响.研究结果表明,该厚度的钢材在回火温度630-650 ℃、回火时间70 min左右时可以获得均匀的回火贝氏体组织,综合力学性能达到较高水平. 相似文献