L. P. Xu
,
M. H. Xu
,
L. Li
,
Y.A. Min
,
X.Z Xuand R.H .Liu (Department of Materials Science and Engineering
,
Shanghai University
,
Shanghai 200072
,
China) (Shanghai No.5 Iron and Steel Factory
,
Shanghai 200940
,
China)
金属学报(英文版)
The composition of a bearing steel was designed for limited hardenability by use of Grossmann's method. A medium frequency induction Process was applied to heat bearings to ensure penetrant heating and suitable solving of carbon and other elements in the matrix. The hardened depth measured from the end quenching test samples and actual bearings matches well with the designed one.
关键词:
: bearing steel
,
null
,
null
H.M. Geng
,
X.C. Wu
,
Y.A. Min
,
null
,
null
,
null
,
null
,
null
,
null
,
null
金属学报(英文版)
Experiments conducted to determine the effect of copper addition on the machinability of plastic mould steel 4Cr16Mo were presented. The machinability of mould steel 4Cr16Mo was improved obviously by adding Cu. The top wear of 4Cr16Mo with copper was less than that without copper. Cu-rich phase had the effect of lubricant and heat conductivity as solid lubricant, which reduced cutting-tool wear, improved machinability and increased service life of cutting-tool. With the increase of copper addition, the hot-working character of 4Cr16Mo decreased. The optimal hot-working parameters 4Cr16Mo with copper were determined by tensile test and compression test. The rate of deformation should be adopt as 0.6 s-1. The heating-up temperature, initial forging temperature and terminal forging temperature were 1200℃, 1150℃ and 950℃, respectively.
关键词:
machinability
,
cutting-tool
,
hot-shortness
Q.S. Liu1
,
2
,
3)
,
L.C. Zhao3)
,
G.X. Dong2) and N.J. Gu1) 1) Heibei University of Technology
,
Tianjin 300130
,
China 2) Tianjin Institute of Technology
,
Tianjin 300191
,
China 3) Harbin University of Technology
,
Harbin 150001
,
China
金属学报(英文版)
Theconstruction changinginthereversetransformation ofthestress induced εMin Fe 17 Mn 10 Cr 5 Si 4 Ni alloy is carefully inspected in transmission electron microscope, and then stress induced εM procedure of reverse transformation is analyzed. The behavior of reverse transformationisdissimilar when the organization of εMis different. The reversetransfor mation ofεM withtheshapeofsingle plateandstripisrelativelyeasy,anditsreversibilityincrystallographiciseasilytocarryout,fortheεM with multilayerstructure,thereversetrans formationtakes placein isolatedlayers, fortheεMthat grows well,thereversetransforma tion isrelatively difficult becauseofthe ductile harmonization between itsinternalorganiza tion structures.
关键词:
stress induced εM
,
null
,
null
徐佩
,
卢旭鑫
,
汪传斌
,
杨善中
,
孙晓红
,
丁运生
高分子材料科学与工程
为改善多壁碳纳米管(MWNT)在低密度聚乙烯(LDPE)中的分散性及复合材料的界面特性,采用溴化-1-十六烷基-3-甲基咪唑基离子液体([C16min]Br)对MWNT进行表面改性,并用Raman光谱对改性效果进行了表征.将经过修饰的碳纳米管(MIL)与LDPE熔融共混得到MIL/LDPE复合材料,采用场发射扫描电子显微镜(FESEM)和阻抗分析仪(LCR)对复合材料的结构与介电性能进行了分析.结果表明,相比与MWNT/LDPE(渗流阈值为5.2％,介电常数为82,介电损耗为0.93),MIL/LDPE(渗流阈值为9.1％,介电常数为169,介电损耗为0.51)介电常数增大,介电损耗降低.并且在低温时,MIL/LDPE介电常数随温度的变化甚小,显示出良好的温度-介电常数特性.
关键词:
咪唑基离子液体
,
碳纳米管
,
低密度聚乙烯
,
介电性能
材料科学技术（英文）
6 mm thick ZK60 and ZK60-Y alloy plates were successfully friction stir welded (FSW) at a tool rotation rate of 1200 r/min and a traverse speed of 100 mm/min. FSW resulted in the dissolution of MgZn(2) particles in the ZK60 and the breakup and dispersion of W-phase (Mg(3)Zn(3)Y(2)) particles in the ZK60-Y alloy, thereby leading to a decrease in the hardness of the nugget zone (NZ) for the ZK60 alloy and an increase in the hardness of the NZ for the ZK60-Y alloy, respectively. While two FSW joints exhibited similar joint efficiency (87%-89% of ultimate tensile strengths of the parent materials), the yield strength of the FSW ZK60-Y joint was substantially higher than that of the FSW ZK60 joint. The fracture occurred in the NZ and the heat affected zone for the ZK60 and ZK60-Y joints, respectively, which were consistent with the lowest hardness distribution of the welded joints.
关键词:
Friction stir welding;Magnesium;Microstructure;Mechanical properties;az91d magnesium alloy;evolution
Journal of the American Ceramic Society
Combining Clarke's model with first-principles calculation of average sound velocity, the minimum lattice thermal conductivities (kappa(min)) of Y3Al5O12 (YAG), YAlO3 (YAP) and Y4Al2O9 (YAM) are predicted to be 1.59, 1.61, and 1.10 W.(m.K)(-1), respectively. The weak Y-O polyhedra provide "weak zones" that scattering phonons and lead to the low kappa(min) of ternary Y-Al-O compounds. In addition, the extremely low kappa(min) of YAM is attributed to its higher levels of local disorder of crystal structure and weaker chemical bonding compared with those of YAG and YAP. Inspired by theoretical predictions, dense and phase-pure YAM is synthesized and the experimental thermal conductivity is only 1.56 W.(m.K)(-1) at 1273 K. Finally, YAM is highlighted as a potential thermal barrier material for its low thermal conductivities at temperatures from 473 to 1273 K.
关键词:
barrier coatings;single-crystal;gas;stability
舒大禹
,
赵祖德
,
胡传凯
,
康凤
,
王艳彬
,
宁海青
材料科学与工艺
为了改善镁合金在熔铸及加工过程中抗氧化燃烧性能,用合金化阻燃方法在Mg-4Zn合金中添加适宜的Y元素制备了阻燃效果优异的Mg-4Zn-3Y合金.采用俄歇电子能谱仪、X射线衍射仪和扫描电镜(SEM+EDS)研究了氧化膜的显微形貌、合金元素分布及其物相组成.结果表明,Mg-4Zn-3Y合金在高温下暴露于大气中时,燃点提高250℃,合金表面生成一层以Y2O3为主的氧化膜,改善镁合金氧化膜的粘附性,提高高温抗氧化和燃烧能力.基于高温氧化热力学分析,建立了Mg-4Zn-3Y合金在高温下的氧化物理模型.Mg-4Zn-3Y合金能在1065 K时于大气中保温30 min而不燃烧,实现了低Y元素含量镁合金在大气条件下的无保护熔炼.
关键词:
Mg-4Zn-3Y合金
,
阻燃特性
,
燃点
,
热力学
YU Fanghua YANG Guohua Shanghai Institute of Nuclear Research
,
Academia Sinica
,
Shanghai
,
ChinaHAN Rongdian WENG Huimin University of Science and Technology of China
,
Hefei
,
ChinaSHEN Jianian Corrosion Science Laboratory
,
Institute of Corrosion and Protection of Metals Academia Sinica
,
Shenvang
,
China
金属学报(英文版)
The effects of small amount(≥0.05%)of active elements Y and Ce in Fe-25Cr-40Ni al- loy have been investigated on the kinetics of early stage of high temperature oxidation as well as composition and microsructure of oxide film by ion backscattering and slow positron beam.The results show that Y and Ce can reduce evidently the high tem- perature oxidation rate of FeCrNi alloy at early stage and can effectively enhance the Cr_2O_3 formation and retard the oxide formation of Fe and Ni in the surface layer thus the microstructure of the oxide film is improved.Y and Ce enter the oxide film and concentrate within several tens nanometres from surface of the outer layer.The mech- anism of oxidation resistance for Ce is different from Y.Ce can decrease the density of vacancy defects in oxide layer,so the cations are restrained from diffusion outward through vacancies.While Y can control the outward diffusion of cations through va- cancies at the early statge of oxidation(shorter than 12 min),aften that restrained the cations from diffusion outward along grain boundaries up to 60 min oxidation.
关键词:
ion backscattering
,
null
,
null
,
null
,
null
