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为了研究夹杂物尺寸对粉末高温合金低周疲劳寿命的影响,将夹杂分别位于试样中心、表面、亚表面并改变其尺寸,研究同一位置下,不同夹杂物尺寸对应力应变分布的影响,结果表明:当夹杂物界面上不含微孔洞时,夹杂物与基体尺寸比例在实验室尺度(1:25)到工程尺度(1:10 000)范围内,夹杂物尺寸对应力应变影响很小;工程实际中,缺陷往往会与基体形成不完好的连接界面,即初始损伤破坏——微孔洞。缺陷对寿命的影响原因:夹杂物尺寸越大,它与基体的界面就越大,出现不完好连接和缺陷的概率就会增加,容易在界面处产生初始损伤破坏;当夹杂物界面上含有微孔洞时,随着夹杂物尺寸变大,界面正应力明显增大,界面切应力微弱减小,基体最大正应力和最大塑性应变均明显增大。 相似文献
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本文采用金相及电子探针方法,分析了1Cr18Ni9Ti旋压薄壁管内壁黑丝缺陷的成因。结果表明,钢中夹杂物含量较高、且呈串状分布时,在酸洗过程中易被酸蚀掉呈条状空隙。当钢管内壁涂上含有氧化铝高硬度粒子的牛油石灰作润滑剂时,在随后的冷拔过程中,氧化铝硬粒子嵌入软态金属基体的条状空隙中,再经冷轧、旋压便产生黑丝缺陷。 相似文献
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为探明Cr5支承辊出现探伤缺陷的原因,截取本体检测试片,开展组织观察和断口分析,研究了夹杂物微观形貌。结果表明:支承辊心部存在密集性夹杂物缺陷,缺陷呈条状或断续链条状分布;能谱分析结果表明夹杂物主要为Ca和Si的氧化物,是冶炼过程复合脱氧剂形成的脱氧产物。 相似文献
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Donovan Verkens Reynier I. Revilla Ali Kosari Mert Günyüz Cemil Işıksaçan Johannes M.C. Mol Iris De Graeve Herman Terryn 《工业材料与腐蚀》2020,71(1):60-69
Aluminum alloy (AA) 3003 is widely used as fin and tube material in heat exchangers. In these heat exchangers, the tube and fin material are brazed together by means of an AA4xxx alloy. In this study, the effect of a simulated brazing step on the microstructure and corrosion behavior of a twin roll casted (TRC) AA3003 was studied. In particular, the effect of simulated brazing on the corrosion properties of the centre line segregation (CLS) of alloying elements and the interaction of the intermetallic particles with the surrounding matrix is explored. It is shown that the cross sections are significantly more active than the surface of the TRC AA3003, revealing the importance of the CLS on the corrosion behavior. Furthermore, it is shown that the number of pits and their depths decreased considerably on the exposed cross sections after simulated brazing, especially near the CLS. Scanning Kelvin probe force microscopy measurements show that after the simulated brazing step the Volta potential difference between the intermetallic particles and the matrix reduced significantly. This change in the Volta potential could be caused by the slight increase of Si content in the matrix. 相似文献
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电子显微术在原位金属基复合材料界面研究中的应用 总被引:2,自引:0,他引:2
原位金属基复合材料的增强颗粒是在基体中原位生成,因而增强颗粒和基体间不存在界面反应,两者间为直接的原子结合.界面对原位金属基复合材料的性能有着重要的影响.本文综述了扫描电子显微镜、普通透射电子显微镜、高分辨电子显微镜和电子能量损伤谱仪等现代电子显微技术在原位金属基复合材料界面研究中的应用及部分研究结果.利用现代电子显微技术和先进的实验方法在原子尺度上对界面的精细结构、结合方式、界面缺陷、界面稳定性及其影响因素等进行研究,从而在较深的层次上认识原位金属基复合材料的界面,对在该领域做进一步研究探讨起到促进作用. 相似文献
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《International Journal of Machine Tools and Manufacture》2005,45(12-13):1368-1374
The buckling mechanism of a thin metal tube during laser forming with axial preloads was investigated numerically and experimentally in this study. Metal tubes made of 304 stainless steel were heated by a CO2 Gaussian laser beam, which induced the buckling phenomenon on the tube surface due to elastic–plastic deformation. This uncoupled thermal–mechanical problem was solved using a 3D finite element method (FEM) and was subsequently satisfactorily verified with axial force measurements. The transient force response and residual stress of the thin metal tube under specific operation conditions were also studied. 相似文献
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Effect of solution heat treatment on galvanic coupling between intermetallics and matrix in AA7075-T6 总被引:1,自引:0,他引:1
Susceptibility to localised corrosion is strongly affected by heat treatments performed on Al-Zn-Cu-Mg alloys. In order to study how galvanic coupling between intermetallics and matrix is affected by solution heat treatment, AA7075-T6 and solution heat treated AA7075 have been characterised by means of scanning electron microscopy and scanning Kelvin probe force microscopy. Solution heat treatment strongly increased the Volta potential difference between the intermetallics and the surrounding matrix showing a strong increase in galvanic coupling. This is explained by Zn and Mg enrichment of the matrix caused by dissolution of strengthening particles during solution heat treatment. 相似文献
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螺旋槽管材滚压成形过程的有限元分析 总被引:2,自引:0,他引:2
利用ANSYS有限元分析软件中的LS-DYNA求解器,分别采用球形和带过渡圆弧的三角形滚压辊,对螺旋槽管材滚压成形过程进行了数值模拟,得到了应力和应变分布规律、金属变形流动规律以及滚压力大小.根据有限元计算结果,分析了不同辊型的滚压辊和螺旋槽管的主要结构参数对滚压力的影响规律以及螺旋凹槽处壁厚的变化规律.通过试验验证了用有限元法进行螺旋槽管材滚压成形过程数值模拟的可靠性,为确定滚压力和槽深之间的关系提供了必要的指导依据.同时,为进一步研究螺旋槽管在滚压过程中的力学性能奠定了一定的理论基础. 相似文献