共查询到20条相似文献,搜索用时 5 毫秒
1.
2.
3.
4.
The normal reflectivities of Al and Al alloys which are important as cryogenic materials are measured mainly in the infrared region below room temperature down to 16 K. A new model is proposed which assumes that in the Drude equation, additional scattering of conduction electrons occur at the surface layer which explains the temperature dependence of the radiative properties. This model can predict the radiative properties of metals at low temperatures better than the anomalous skin effect theory. 相似文献
5.
T. Vignesh Kumar Rama Thirumurugan B. Viswanath 《Materials and Manufacturing Processes》2017,32(16):1789-1805
The research area “Cryogenic Treatment of Materials” has been the subject of a multitude of research studies and therefore needs a proper review article to highlight the present state of understanding and to define the future research direction. Though reviews on cryogenic processing of tool steels are available, there has not been a review that attempts to systematically discourse the effect of cryogenic treatment on the metallurgy of various ferrous alloys. While previous reviews address transformation of retained austenite and the formation of fine precipitated carbides as the major phenomena of cryogenic treatment, developments such as the refinement of pearlite matrix, formation of fine martensite, and enhancement of properties in low carbon steel and cast iron are discussed in detail in this article. In addition, the influence of individual treatment parameters, their sequence, and the effect of room temperature stabilization on the metallurgical changes are extensively addressed. Moreover, many of the contradicting observations/conclusions such as detwinning of martensite and dissolution of secondary carbides during cryogenic treatment are highlighted for further clarification. Finally, applicability of cryogenic treatment for a range of ferrous alloys is presented with an emphasis on scope for future research. 相似文献
6.
7.
The success of deep cryogenic treatment (DCT) of austenitic stainless steels (AusSSs) relies heavily on martensitic transformation. For AusSSs that are not prone to martensitic transformation, thermomechanical treatments (such as high-temperature solution treatment, plastic deformation, and sensitisation) may expedite DCT by encouraging martensite formation. This paper looks into the influences of the aforementioned thermomechanical treatments on the cryogenic treatability of a slightly unstable AusSS regarding tensile properties. Overall, no noticeable strengthening could be achieved through DCT, but a slight improvement in ductility was observed for all the thermomechanical treatment conditions mentioned above. Preliminary results indicated that the pitting corrosion resistance of the AusSS was almost unaltered by DCT. 相似文献
8.
The effect of the deep cryogenic treatment on the micro-structure and mechanical properties (tensile strength, toughness, residual stress and fatigue strength) of the medium carbon spring steel, which is subjected to different heat treatment steps, is investigated. Deep cryogenic treatment causes spring steel to keep compressive residual stress more efficiently due to an increase in the density of the crystalline defects, retardation in the stress relief after the phase transformations and nano-cluster carbide formations. If deep cryogenic treatment is applied before the tempering then the homogeneously distributed fine carbides form after the tempering and the grains remain relatively fine. The microstructure with homogeneously distributed fine carbides and fine grains cause spring steels to have simultaneously enhanced tensile strength, ductility and fatigue strength. If deep cryogenic treatment is applied after the conventional heat treatment (quenching+tempering), however, the coarse carbides form in the micro-structure and the improvement in the mechanical properties of the spring steel is limited. 相似文献
9.
10.
11.
Effect of deep cryogenic treatment on microstructure, creep and wear behaviors of AZ91 magnesium alloy 总被引:3,自引:0,他引:3
Kaveh Meshinchi Asl Alireza Tari Farzad Khomamizadeh 《Materials Science and Engineering: A》2009,523(1-2):27-31
This paper focuses on the effect of deep cryogenic treatment (−196 °C) on microstructure and mechanical properties of AZ91 magnesium alloy. The execution of deep cryogenic treatment on samples changed the distribution of β precipitates. The tiny laminar β particles almost dissolved in the microstructure and the coarse divorced eutectic β phase penetrated into the matrix. This microstructural modification resulted in a significant improvement on mechanical properties of the alloy. The steady state creep rates were measured and it was found that the creep behavior of the alloy, which is dependent on the stability of the near grain boundary microstructure, was improved by the deep cryogenic treatment. For the AZ91 alloy, the results indicate a mixed mode of creep behavior, with some grain boundary effects contributing to the overall behavior. However for the deep cryogenic samples dislocation climb controlled creep is the dominant deformation mechanism. After the deep cryogenic treatment the sliding of grain boundaries was greatly suppressed due to morphological changes. As a result, the grain boundaries are less susceptible for grain boundary sliding at high temperatures. Dry sliding wear tests were also applied and the wear resistance of the alloy improved remarkably after deep cryogenic treatment. 相似文献
12.
针对林德公司对大型低温液体贮罐日蒸发率的高要求,联合国内制造商进行技术攻关,选择质量符合要求的保温材料,根据国产保温材料的参数修改贮罐的设计参数。按照国内相关规范对2000m3液氧贮罐进行日蒸发率实际测试,其结果达到林德公司的标准。 相似文献
13.
14.
介绍了一种特殊的辐轮式低温支撑,针对这种不同材质和辐条数量及其截面形状的辐轮式结构,分别从热学性能和力学性能两方面进行了实验研究,测量了聚醚醚酮(PEEK)和玻璃钢(GRP)两种材料的热导率以及由这两种材料组成的多种结构形式的支撑轮的热阻,对试样进行力学拉伸破坏实验,并对实验结果进行了分析与比较,给出了误差分析。实验结果表明,温度在200 K以下时PEEK材料热导率小于GRP材料,200 K以上时两者相当;支撑轮的热阻随着辐条数量和截面积的增加而减小,且实验测得的热阻是固体传热和辐射换热的综合结果;支撑轮的力学性能随着辐条数量和截面积的增加而提高,GRP材料的支撑轮径向承受载荷能力较强、轴向偏弱,而PEEK材料的支撑轮各方向上承载能力较为均匀,这主要是因为GRP材料是各向异性的。综合热性能和力学性能实验结果,PEEK材料6辐带肋结构的支撑轮是最佳选择。 相似文献
15.
16.
17.
An apparatus for measuring the integral thermal expansions at cryogenic temperatures is described. The thermal expansions are given for a number of commercial epoxy resins, commercial polyester resins and inorganic cements. A method to reduce the thermal expansion of the resins by the use of quartz powder fillers is reported. 相似文献
18.
Investigating the effect of holding duration on the microstructure of 1.2080 tool steel during the deep cryogenic heat treatment 总被引:1,自引:0,他引:1
This study concerns the effect of the holding time at liquid nitrogen temperature during the deep cryogenic heat treatment on the microstructural changes, carbide distribution, carbide percentage, hardness and microhardness of 1.2080 tool steel. These analyses were performed via the scanning electron microscope (SEM), optical microscope (OM), transmission electron microscope (TEM) and X-ay diffraction (XRD). The obtained results showed that there is an optimum holding duration in which the carbides exhibit a maximum percentage and the most homogenous distribution as compared to the other soaking durations. It was also shown that by increasing the holding duration beyond the optimum holding duration, the hardness, microhardness, carbide percentage, carbide distribution homogeneity and particle size reach a constant value and do not change. 相似文献
19.
20.
Processing of materials at cryogenic temperature has improved the properties of materials such as hardness, toughness, wear resistance, tensile strength, dimensional stability, corrosion resistance, etc. However, the extent of improvement in the properties of materials subjected to cryogenic treatment as claimed in the literature is diverse and sometimes contradictory to each other. Contradictions have also been reported regarding its various aspects like tempering prior and postcryogenic treatment, tempering temperature, aging before cryogenic treatment and cryogenic parameters like soaking temperature, soaking time, and cooling rate. There is need of investigating the cryogenic treatment in relation to pre and postheat treatment conditions. In this study, an attempt has been made to review the various research articles published in the literature on the subject matter extensively. Cryogenic processing of cutting tools and workpiece material has also emerged as a potential technique for improving the performance of cutting tools during metal cutting as well as for improving the machinability and weldability of workpiece materials. The implications of cryogenic treatment in the perspective of manufacturing have been revealed clearly through review of related studies. The various findings reported in the literature have been highlighted systematically and futuristic directions have been proposed to encourage research work in the area of cryogenic treatment. 相似文献