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191.
REHEATING TEMPERATURE CONTRAST AND MICROSTRUCTURES OF 7075 Al ALLOY CAST BY LIQUIDUS SEMI-CONTINUOUS CASTING 总被引:4,自引:0,他引:4
J. Dong G.M. Lu J.Z. CuiThe Key Lab. of Electromagnetic Processing of Material Ministry of Education Northeastern University Shenvane China 《金属学报(英文版)》2002,(6)
In this study, reheating of liquidus semi-continuous cast billets of 7075 Al alloy was carried out in a resistance furnace, and the temperature contrast of the outer and the center of the reheated billets was investigated, then the reheating microstructures were investigated. Results show that: the difference of temperature between the outer and center is small and the difference of their microstructures are also small. During reheating at 576℃ the spheroidization of grains is significant after 5min and no rosettes are visible after 20min by optical microscopy. Similar observations were madeon materials reheated at 596℃, but the ripening process is faster. The grains growup to 30-60μm, fine enough for thixoforming. 相似文献
192.
The effect of Zr on reduction of hardness and microstructure in an FS weld of equal channel angular-pressed Al alloy was investigated. Zr addition to Al suppressed dynamic recovery in the thermomechanically affected zone and enabled retention of the high hardness of the ECA-pressed material throughout the weld. 相似文献
193.
Ali Bayram Agah Uguz Ali Durmus 《Journal of Materials Engineering and Performance》2002,11(5):571-576
Three types of material whose fracture toughness tests were previously performed by using circumferentially notched bars,
namely (1) a dual-phase steel with three different morphologies; (2) an Al-Zn-Mg-Cu-wrought alloy; and (3) Al-Si-cast alloys
with three different Si contents, were investigated in terms of accuracy and reliability of the testing method. Also, the
advantages of using circumferentially notched bars for fracture toughness determination of metallic materials were discussed.
With the help of stress concentration factors, which are associated with the bluntness of the notch, correction factors for
the fracture toughness calculations are derived. The corrected fracture toughness values are found to be close to the uncorrected
ones, implying that the testing procedure is reliable. 相似文献
194.
原始组织及加热方式对Al-5.8wt%Cu合金熔化行为的影响 总被引:3,自引:0,他引:3
利用DSC分析手段,研究了具有3种不同凝固组织的Al-5.8wt%合金在7种不同加热方式下的熔化开始温度和熔化热,发现凝固组织中存在的非平衡共晶在加热过程中大部分扩散溶解,溶入基体,剩余部分参与共晶熔化,其熔化开始温度与组织状态无关,随加热速度的增大略有升高,溶解部分的体积分散与组织状态和加热方式有关,随加热时间和非平衡相表面积的增大而增大。 相似文献
195.
196.
低碳钢热浸Zn-0.15%Ni合金镀层组织及第二相粒子 总被引:1,自引:0,他引:1
采用热浸Zn-Ni合金镀锌方法,在含0.03%-0.36%Si的低碳钢上获得Zn-Ni合金镀层,研究了镀浴中Ni含量和钢中Si含量对镀层中δ相和ζ相生长速率的影响,以及Zn-Ni合金镀层η相中的第二相粒子即Zn-Fe-Ni三元化合物Γ2相粒子的形成和长大过程,结果表明,在Zn-0.15%Ni镀浴中,含硅0.03%-0.215%钢镀层的ζ相明显受到抑制,δ相厚度略有增加,Γ2相粒子的形成和长大过程包括ζ相的溶解,Γ2相的形核和成比例吸收铁,镍而长大。 相似文献
197.
探讨了0Cr12Ni6Mn16Si5形状记忆合金的工业化生产工艺,0Cr12Ni6Mn16Si5可以采用EF1+AOD+EF2进行冶炼.合金具有强的热敏感性和高温变形抗力,高温可加工热塑性温度区间比较窄,温度超过1*!100℃,塑性直线下降.铸锭的开锻温度为1*!080℃,终锻温度为900℃;锻造管坯只有采用挤压方法实施管材成型.挤压成型的毛管可以采用冷轧与冷拔相接合方法进一步加工成薄壁管. 相似文献
198.
Positron annihilation lifetime spectroscopy and Doppler-broadened annihilation radiation (DBAR) experiments were performed on polypropylene-polystyrene (PP-PS) alloys (0-100% styrene) prepared by in situ polymerisation of styrene in a PP host matrix. The mean size of free-volume holes estimated from the ortho-positronium lifetime τ3 shows a continuous decrease from 0.119 nm3 in PP to 0.095 nm3 in PS. The intensity of the o-Ps component, I3, the average positron lifetime τav, the curve-shape parameter S and the peak height H of the DBAR spectra increase linearly with the styrene concentration. This is attributed to a linear superposition of the Ps yields of PP and PS in the PP-PS alloys. The DBAR spectra were fitted by a sum of three Gaussians, the narrowest of them is attributed to self-annihilation of para-positronium confined within holes. After its subtraction, a ‘broad component’ is obtained which represents the momentum distribution of electrons bound to molecules. Its normalised peak height does not show any change with the composition which reflects the fact that both constituents of the PP-PS alloys contain only hydrogen and carbon atoms in their chemical units. Immersing of PP into styrene liquid leads to a very pronounced increases in the lifetime parameters which is attributed to the plasticisation of PP. 相似文献
199.
钛硅选择性氧化催化剂的研究进展 总被引:6,自引:1,他引:5
过渡金属钼、钨、钛、钒等的高价态络合物能有效催化有机过氧化物进行烯烃的环氧化反应。以Mo(Ⅵ)络合物在有机相中催化过氧化烃来氧化丙烯生产环氧丙烷的方法称之为间接氧化法,是生产环氧丙烷的主要方法之一。70年代初,荷兰Shel研究所发现Ti(Ⅳ)高分散负... 相似文献
200.