共查询到19条相似文献,搜索用时 96 毫秒
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机械合金化—新型的固态合金化方法 总被引:27,自引:1,他引:26
介绍了一种新型的固态合金化方法-机械合金化。阐述了机械合金化的基本原理,金属粉末机械合金化形成非晶,纳米晶和超饱和固溶体的基本机理。这是一种很有发展前途的固态合金化方法,正在新型材料的开发中显示出独特作用。 相似文献
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非晶态材料具有优异的力学、磁学和电学等性能,并得到了广泛的应用。但是在用传统的熔体急冷法只能获得厚度约几十微米的薄带,使其应用范围受到一定限制。自1983年以来,人们采用机械合金化方法成功地获得了非晶态粉末,从而为制成大块的非晶态金属材料开辟了广阔的前景。目前国外已将这种非晶态粉末,经过低温压制,制备出了性能优异的大块非晶材料。此外,机械合金化与传统的急冷法相比,还具有非晶态形成范围大的特点,并能制备一些传统方法不能得到的新的非晶合金。本文介绍了用机械合金化方法制备非晶态Cu_(60)Zr_(40)和Ni_(50)Zr_(50)粉末的形成机制和结构分析结果。 相似文献
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The conventional route for preparation of silicon carbide ceramics is by the use of pressureless sintering, hot pressing, or hot isostatic pressing of silicon carbide starting powders. High sintering temperatures (2073–2473 K) and the addition of sintering additives are normally used to enhance densification. These sintering additives, however, form second phases at grain boundaries which impair the mechanical properties of the material, particularly at high temperatures. It is therefore desirable that new processing routes are developed that overcome these difficulties. A proposed route is to use a polymeric pressure which can provide a Silicon carbide matrix as binding agent for silicon carbide powders, thus making the requirement for high temperatures and sintering additives unnecessary. This paper reports observations of the direct transformation of a polymeric precursor into amorphous Si–C, and crystalline SiC at low temperatures, and the use of this precursor as a binder for the production of SiC powder/ex-precursor SiC composites. 相似文献
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采用热压非晶粉末成型的方式,制备了块状Nd2Fe14B/α-Fe复合纳米晶磁体,在此过程中,同时完成非晶晶化和粉末成型。文中研究了不同压力下磁体的致密性及磁性的变化。 相似文献
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J. DUTKIEWICZ L. LITYSKA-DOBRZYSKA A. KOVACOVA† . ROGAL & W. MAZIARZ 《Journal of microscopy》2009,236(2):132-136
Amorphous powder of composition corresponding to Ni60Ti20Zr20 (in at%) was obtained by ball milling in a high-energy mills starting from pure elements. Formation of the amorphous structure was observed already after 20 h of milling, although complete amorphization occurred after 40 h. The microhardness of powders increased from about 30 HV for pure elements to above 400 HV (1290 MPa) after 40 h of milling. Transmission electron microscopy (TEM) allowed to identify nanocrystalline inclusions of intermetallic phases of size 2–10 nm. Uniaxial hot pressing was performed in vacuum at temperature below the crystallization Tx it is 510°C and pressure of 600 MPa, Mixed amorphous powders and nanocrystalline silver powders were used to form a composite, in which microhardness was near 970 MPa HV and 400 HV for the amorphous phase and nanocrystalline silver, respectively. The compression strength of the composite containing 20 wt% of nanocrystalline Ag powder was equal to 600 MPa and plastic strain was 2%. Microstructure studies showed low porosity of composites of less than 1%, uniform distribution of the silver phase and a transition zone between both components, about 150 nm thick, where diffusion of nickel, niobium and zirconium into silver was observed. High-resolution TEM allowed identifying the structure of nanocrystalline inclusions in the amorphous matrix after hot pressing as either Ni3 Zr or Ni17 Nb3 . The identification was performed basing on measurements of angles and interatomic distances using inverse Fourier transformed images with enhanced contrast using Digital Micrograph computer program. 相似文献
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J. DUTKIEWICZ M. KUBÍEK† M. PASTRÁK† W. MAZIARZ M. LEJKOWSKA T. CZEPPE & J. MORGIEL 《Journal of microscopy》2006,223(3):268-271
ZrNiTiCu and ZrNiTiCuAl alloys were amorphized using either a melt‐spinning or ball‐milling process in a high‐energy planetary mill. The elemental powders were initially blended to the desired composition (in at.%) of Zr, 65; Cu, 27.5; Al, 7.5 and of Ti, 25; Zr, 17; Cu, 29; Ni, 29, respectively. The composition of alloys was chosen to be the same as for the bulk amorphous ZrCuAl and easy glass‐forming ZrNiTiCu alloys. An almost fully amorphous structure was obtained after 80 h of milling in the case of both compositions. Transmission electron microscopy studies of ball‐milled powders revealed the presence of nano‐crystallites [2–5 nm for ZrCuAl and smaller (1–3 nm) for the ZrTiNiCu alloy]. High‐resolution transmission electron microscopy of melt‐spun ZrNiTiCuAl ribbons provided evidence of the amorphous structure. 相似文献
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机械合金化合成TiB2/Fe3Al纳米复合粉体 总被引:1,自引:0,他引:1
采用铁、铝、钛、硼四元粉体机械合金化与后续热处理的方法合成纳米TiB_2/Fe_3Al复合粉体,并利用XRD、DSC、SEM和TEM等对粉体进行了表征。结果表明:在球磨过程中,四元粉体形成了Fe(Al,Ti,B)过饱和固溶体,有序度不断降低,逐渐向非晶态转变,同时粉体晶粒尺寸逐渐细化,球磨40h后Fe(Al,Ti,B)的晶粒尺寸为9.6nm;并在热处理过程中Fe(Al,Ti,B)分解生成纳米Fe_3Al和TiB_2复合粉体,同时发生组成相晶粒生长,结构有序度提高等转变。 相似文献
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