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991.
脉冲磁场下铝合金定向凝固磁场分布数值模拟 总被引:2,自引:0,他引:2
采用ANSYS 8.0有限元分析软件对铝合金脉冲磁场定向凝固磁场分布作了数值模拟,得到了凝固过程中的磁场分布状态.结果表明:在试样中心附近磁感应强度较强,而在端部较弱.模拟结果和实验测得结果相符合.通过数值模拟,不仅可以初步了解凝固过程中的磁场分布状态,而且有助于进一步研究凝固组织细化的原因. 相似文献
992.
对斜轧技术的发展和传统斜轧“横锻效应”的副作用作的介绍和分析,并列举几种新型的斜轧穿孔和轧管设备的特点,提出用三步成型轧管工艺代替老式多工序轧管工艺以改造现有自动轧管机组。 相似文献
993.
Friction stir welding of AZ31 magnesium alloy 总被引:3,自引:0,他引:3
Friction stir welding (FSW) is an new solid-phase joining technology which has more advantages over fusion welding methods in welding of aluminum and other non-ferrous metals. The effects of welding parameters on mechanical properties and microstructure during friction stir welding of AZ31 magnesium alloy were studied in this paper. Microstructures and mechanical properties of the joints were investigated by means of optical microscopy, scanning electric microscopy ( SEM ) , micro-hardness analysis, and tensile test. Experimental results show that the magnesium alloy can be successfully welded by FSW method, and the ultimate tensile strength (UTS) of FSW joint reaches up to 90 percent of base metal. The microstructures of welded joints exhibit the variation from dynamically recrystallized fine grains to greatly deformed grains. Hardness in nugget zone was found lower than the base metal but not too obvious. 相似文献
994.
995.
J. H. Li P. Deshpande R. Y. Lin 《Journal of Materials Engineering and Performance》2004,13(4):445-450
The objective of this study is to investigate an innovative infrared (IR) technique to enhance adhesion of electroplated copper
(Cu) on Ti-6Al-4V without dichromate dipping. The ultimate goal is to develop a Cu coating process on Ti-6Al-4V without hazardous
hexavalent chromium (Cr) solution treatments. Cu coatings of around 50 μm were electroplated on Ti-6Al-4V specimens at a current
density of 0.03 A/cm2 in an acidic Cu solution. To improve adhesion of coatings, IR heat treatments were performed on the Cu-coated samples at
different temperatures and durations: 860 °C for 600 s and 875 °C for 20–120 s. This process was accomplished in an attempt
to replace the use of dichromate dipping before electroplating. For samples heat treated at 860 °C, no bonding existed, even
after 600 s. It is believed that solid-state diffusion prevailed at 860 °C and that 600 s was not enough for sufficient diffusion
to occur. Adhesion was poor when samples were heat treated at 875 °C for 20 s. Excellent adhesion was observed when the heat
treatment holding time was increased to 40 s. For 90 s, the surface appearance of coatings partially changed from Cu-colored
to a grayish color. There was no Cu left on the surface after a 120 s heat treatment. From optical microscopic observations
on sample cross sections, an interlayer between the Cu and Ti-6Al-4V formed when heat treated at 875 °C for 40 s and longer.
The interlayer thickness increased as the holding time increased, until depletion of Cu. The sheet resistivity of coated specimens
was on the order of pure Cu for samples heat treated at 875 °C and less than 90 s. During the 875 °C heat treatment, the following
occurred: solid-state diffusion of Cu in Ti-6Al-4V, formation of eutectic solutions, dissolution of Cu and Ti-6Al-4V into
the liquid phase, and the formation of intermetallic compounds. The lowest eutectic temperature of 875 °C played a key role
in this innovative process of Cu coating on Ti-6Al-4V.
This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September
15–17, 2003, in Indianapolis, Indiana and appears on pp. 403–10 of the Proceedings. 相似文献
996.
997.
Nanocrystallized Cr1−xAlxN films with various Al contents (0 to 68 at.%) were deposited by pulsed closed field unbalanced magnetron sputtering (P-CFUBMS). The effects of aluminum content on the microstructure, mechanical and tribological properties of the Cr1−xAlxN films have been investigated. It was found that the hardness and elastic modulus of Cr1−xAlxN films increased with increasing Al contents in the films and reached the highest value of 36 GPa and 370 GPa, respectively, at an Al content of 58.5 at.%. Addition of Al beyond 64.0 at.% resulted in a change in crystal structure from B1 cubic to B4 hexagonal phase. The wear resistance improved gradually with the increase of Al in the Cr1−xAlxN films. A combination of the abrasive and adhesive wear mechanism was proposed based on the SEM and EDS analysis of the wear track. The steady state dry coefficient of friction measured against a WC ball for the Cr1−xAlxN films were in the range of 0.36-0.55, and the wear rate was in the 10− 6 mm3 N− 1 m− 1 range. 相似文献
998.
LIU Lin FU Hengzhi SHI Zhengxing Northwestern Polytechnical University Xi''''an China Dr.LIU Lin Lecturer Department of Applied Physics Northwestern Polytechnical University Xi''''an China 《金属学报(英文版)》1990,3(1):46-51
The SEM analysis of decply etched specimens of Ni-base superalloys K38 and K19H+Ta in-dicates that both the primary morphologies under normal growth conditions and the finalmorphologies near equilibrium of MC carbides are octahedral blocks.The classification ofMC crystal faces by means of PBC(Periodic Bond Chains)theory confirms that{100},{110}and{111}are F faces,and that{212}are S faces.The calculations of the attachmentenergy for each F face show that{111}are most easily appeared.It has also been inferred thatone of the MC growth units is a coordination octahedron composed of one metal atom sur-rounded by six carbon atoms.The octahedral growth units can be attached to the growth sur-faces of MC carbides through laver stacking mechanism on the{111}faces. 相似文献
999.
1000.
2006年11月16日至24日,笔者受浙江省再生资源有限公司总经理室指派,带领四名员工赴台州对废旧金属市场进行调查.
台州是我国进口废金属拆解基地之一.目前建有约1 900亩标准化再生资源加工园区.园区内建有标准厂房28万平方米,总投资达10.5亿元,同时建有拆解工场50多个,相关市场7个,直接从业人员6万多人. 相似文献