朱杰武
,
柳永宁
,
许雁
,
冯耀荣
机械工程材料
doi:10.3969/j.issn.1000-3738.2005.06.007
在不同温度下测试了X70管线钢动态断裂韧度K1d、J1d和止裂韧度K1a以及夏氏V型缺口冲击韧度Ak,对三者的关系进行了分析.结果表明:温度和加载速率都对断裂韧度产生影响;加载速率变化引起的韧-脆断裂转变具有热激活特征,在热激活分析基础上,在应力强度因子速率K=15 MPa·m1/2s-1条件下,得出断裂韧度、止裂韧度和冲击韧度三者的关系:Ak=4.84×106T-2.8K1d(或K1a).可以用小试样Ak数据计算得到K1d和K1a.
关键词:
管线钢
,
断裂韧度
,
止裂韧度
,
韧-脆断裂转变
T.L. Wang 1
,
2)
,
J.T. Guo 1)
,
D.S. Xia 2)
,
Y.Wang 1) and H.C. Yang 2) 1) Institute of Metal Research
,
Chinese Academy of Science
,
Shenyang 110015
,
China 2) Material and Metallurgical Institute Northeastern University
,
Shenyang 110006
,
China
金属学报(英文版)
Effect of revert cycles on microstructure and fatigue properties of cast cobalt base superalloy K640S has been investigated. The results show that: at 70 times of cool heat cycles, there were microcracks found in seven times revert and ten times revert. With the increasing of thermal fatigue cycles, the crack of revert grows a little faster than virgin. When the cycle time reaches 200, the crack length for both virgin and reverts have been as long as 2mm. The low cycle fatigue life has no remarkable change, with the increase of revert cycles at 815℃, 360MPa ,0 5Hz. With the times of cycles increasing, it is found that the content of impurity and gas in alloy change a little, and there is no obvious change for dendrite microstructure.
关键词:
revert
,
null
,
null
,
null
,
null
Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science
Surface modifications were investigated for an AISI D2 steel after 25 pulses of high current pulsed electron beam (HCPEB) treatment. In particular, X-ray diffraction (XRD) was used to determine the thickness, nature of phase, and texture in the top surface melted layer. The mechanisms responsible for the structure and texture evolutions were further asserted by scanning electron microscopy (SEM) and electron backscattering diffraction (EBSD) results. Under the action of the beam, the large carbides present in the steel were melted and dissolved so that the top surface rapidly solidified as a 3-mu m-thick layer of ultra-fine-grained metastable austenite without any martensite formation. The growth of the phase led to an unusual < 100 > + < 110 > fiber solidification texture. In addition, Sigma 3-twin boundaries were observed to bridge, most often, near < 110 > domains. These features, observed here in a Fe supersaturated and highly undercooled melt, are discussed in light of recent findings on atypical growth in directionally solidified Al-based alloys. ([40-42]) Comparatively, the a phase present in the heat-affected zone remained randomly oriented.
关键词:
dendrite growth directions;ion-beams;phase formations;alloys;transformations;temperatures;irradiation;simulation;metals;ti
Wu YAO
,
Jie LI
材料科学技术（英文）
A superfine slag powder (SP) made from granulated blast furnace slag incorporating activators by using special milling technique, was used as supplementary cementitious material in high performance concrete (HPC), replacing part of the mass of normal Portland cement. The effects of the SP on the workability, mechanical and crack self-healing properties of HPC were studied. The hydration process and microstructure characteristics were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, respectively. The crack self-healing capacity was evaluated by Brazilian test. The test results indicate that the SP has especially supplementary effect on water reducing and excellent property of better control of slump loss. The concrete flowability increases remarkably with the increase of SP replacement level in the range of 20% to 50%. The compressive and splitting tensile strengths of HPC containing SP are higher than the corresponding strength of the control concrete at all ages. The crack self-healing ability is highly dependent on SP content of HPC.
关键词:
Superfine slag powder
,
null
,
null
Journal of Materials Engineering and Performance
The effect of high cooling rate of approximately 10(2) K/s and subsequent hot isostatic pressure (HIP) and high temperature (HT) treatment on the microstructure and mechanical properties of NiAl-based inter-metallic alloys was investigated. The results reveal that rapid solidification refines the microstructure of the NiAl-Cr(Mo)-0.5Hf eutectic alloy and transforms the Ni(2)AlHf Heusler phase, which is present in the equilibrium state to a metastable Hf(Ni, Al, Cr) solid solution phase. Simultaneously, the shape and distribution of the Hf(Ni, Al, Cr) solid solution phase were considerably improved. After the HIP treatment, the Hf(Ni, Al, Cr) solid solution phase has changed from continuous distribution along eutectic cell boundaries into semicontinuous distribution, and the primary NiAl(Cr, Mo) phase has coarsened. The HT treatment reduces the volume fraction of the primary NiAl(Cr, Mo) phase and optimizes the distribution of the Hf(Ni, Al, Cr) solid solution phase. Rapid solidification and the resulting fine-grained microstructure will significantly improve the mechanical properties of the alloy in compression tests. However, additional HIP and HT treatments enhance the high-temperature strength properties obviously.
关键词:
mechanical property;microstructure;NiAl-Cr(Mo)-Hf eutectic alloy;rapid solidification;magnetic-field treatment;cr
Physical Review B
Calculating the S-state splitting of a d5 ion (Fe3+, Mn2+) in a crystal has been a long-standing difficult problem since 1934 when it was discussed by Van Vleck and Penney. Low and Rosengarten have concluded that crystal-field theory is not capable of providing a unified interpretation for the spectrum and for the S-state zero-field splitting of d5 6S ions. In the present paper, by utilizing a method of combined perturbation composed of the electrostatic, crystal-field, and spin-orbit-coupling energies, and by diagonalizing a set of complete energy matrices constructed for a d5 configuration and having a total order of 252, a reasonable interpretation is obtained for the d-d spectrum and the EPR cubic zero-field splitting of Fe3+ ions located at octahedral and tetrahedral sites in yttrium gallium garnet. This shows that crystal-field theory is as well suited for application to d5 ions and to other d(n) ions and that the earlier Low-Rosengarten conclusion is wrong. It is also shown that contributions to the ground-state splitting arising from various excited states of the d5 configuration or from various components of the crystal field do not obey a linear-superposition rule. In the Appendix, a detailed explicit description of the matrices is given.
关键词:
ion;spectra
