Amorphization and magnetic properties of Fe62Nb38 mechanically alloyed powders

The amorphization and magnetic properties of Fe62Nb38 mechanically alloyed powders were investigated. In the initial mechanical alloying processes, the lattice structure of pure Fe is destroyed due to the cold-welding and fracturing, accompanying the reduction of ferromagnetic properties. The Ms value of Fe62Nb38 powders with ball-milling time t=6 h is only 48.1 A.m^2/kg. With prolongating of mechanical alloying processes, a solid state amorphization reaction (SSAR) takes place and the Fe-Nb ferromagnetic amorphous phase is formed. With the milling time increasing from 6 to 18 h, the saturation magnetization of Fe62Nb38 powders increases with enhancement of the proportion of ferromagnetic amorphous phase in milled powders. The Ms value of the Fe62Nb38 amorphous powders is 98 A.m^2/kg, which is very close to the value estimated from dilute model. However, the Curie temperature of the Fe62Nb38 amorphous phase is only 206℃, which is much smaller than that of the pure Fe. This implies that the exchange interaction between Fe atoms in amorphous alloyed Fe62Nb38 becomes weak due to the Nb dilution. Investigation shows that the variation of magnetic properties of milled powders is one of important tools for describing the amorphization by mechanical alloying.     

Formation and crystallization of Zr-Ni-Ti metallic glass

The metallic Zr65 Ni25 Ti10 (mole fraction, ％) glass has been fabricated by a single roller melt-spinning method. The glass forming ability(GFA) and thermal stability of the Zr65 Ni25 Ti10 melt-spun ribbons were investigated by using X-ray diffraction(XRD) and differential scanning calorimetry(DSC) in the mode of continuous heating. It is shown that the reduced glass transition temperature (Trg) is 0. 506 and the supercooled liquid region (△Tx) is 30 K. Two exothermic peaks were observed in the DSC curves of the as-quenched ribbon, which indicates that the crystallization process undergoes two different stages. The phase transformation during the isothermal annealing was investigated by X-ray diffraction(XRD) and transmission electronic microscope(TEM). It is observed that the metastable FCC Zr2 Ni(Fd3m, a= 12.27 A) precipitated while annealing in the suppercooled region(615 K) and the stable BCT Zr2Ni(I4/mcm, a= 6.499 A, c= 5.270 A) precipitated while annealing at higher temperature(673 K or 723 K). The crystallines are on nanoscale, with grain size of 15-30 nm. The reason for the precipitation of the different structural Zr2 Ni from the glassy matrix under different annealing conditions was discussed based on the concept of multi-component chemical short range order(MCSRO).     

国内外金属针布组织及性能对比研究

通过对比分析瑞士Graf的OK40与OB20和国内的SWRH72B与SWRH57B针布齿条的化学成分、金相组织、力学性能,从材质方面提出了提高针布高耐磨性的若干意见。     

渗碳体高温高压金刚石化的显微分析

片状触媒合成金刚石有一个重要现象：金刚石总包覆着一层很薄的金属膜，金属包膜在金冈4石的生长过程中起着重要作用。本文利用扫描电镜（SEM）、X射线衍射仪（XRD）和透射电镜（TEM）研究了金属包膜的组织形貌、相结构组成和微观结构。通过研究金属包膜，探讨金刚石相交合成机理，进而优化合成工艺。结果表明：渗碳体在高温高压作用下发生金刚石化，形成金刚石单晶；同时当铁基金属包膜内的渗碳体分布较均匀时金刚石单晶的晶形较完整，反之则晶形较差。     

钨丝增强ZrTiCuNiBeNb金属玻璃基复合材料界面

采用渗流铸造工艺制备了钨丝增强ZrTiCuNiBeNb金属玻璃基复合材料,利用X射线衍射、扫描电镜、电子探针以及Nano IndenterⅡ纳米显微力学探针考察了复合材料的界面结构以及界面微区力学性能.结果表明:钨丝增强ZrTiCuNiBeNb金属玻璃基复合材料界面仅由单纯的界面溶解和扩散形成,并未发生界面反应,该界面应属于金属基复合材料的Ⅱ类界面;并且溶解和扩散的存在使界面微区的硬度和弹性模量高于基体,界面结合较强,没有沿界面的裂纹扩展.     

Q235钢双层辉光等离子Mo-Cr共渗及其热处理工艺研究

对比研究了Q235钢进行双层辉光等离子Mo—Cr共渗和不同热处理工艺处理的表面层组织和性能。结果表明：Q235钢等离子Mo—Cr共渗＋超饱和渗碳＋淬火＋深冷处理＋回火的试样，表面渗层组织结构细小，碳化物分布弥散，尺寸小于1μm，表面硬度达到1600HV。摩擦磨损试验表明：Q235钢经过渗碳＋淬火＋低温回火、等离子Mo—Cr共渗＋离子渗氮、等离子Mo-Cr共渗＋超饱和渗碳＋淬火＋低温回火、等离子Mo-Cr共渗＋超饱和渗碳＋淬火＋深冷处理＋低温回火处理的试样的相对耐磨性分别为：1，1．32，1．6和2．74。     

COMPUTER OPTIMIZATION OF DENSITY AND VISCOSITY FOR BINARY METALLIC MELTS

ＣＯＭＰＵＴＥＲＯＰＴＩＭＩＺＡＴＩＯＮＯＦＤＥＮＳＩＴＹＡＮＤＶＩＳＣＯＳＩＴＹＦＯＲＢＩＮＡＲＹＭＥＴＡＬＬＩＣＭＥＬＴＳ￥Ｚｈａｎｇ，Ｊｉａｙｕｎ；Ｚｈｏｕ，Ｔｕｐｉｎｇ；Ｆｅｎｇ，Ｘｕｅｌｉａｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓｉｃａｌＣｈ...     

内生枝晶增塑锆基块体金属玻璃复合材料

利用熔体水淬法制备了内生bcc β-Zr固溶体增塑的Zr56．2Ti13.8Nb5．0Cu6．9Ni5．6Be12．5块体金属玻璃基体复合材料．β相呈发达的树枝状，体积分数约为30％．室温单轴压缩时，复合材料失效前的纯塑性应变达到10．2％，并具有2．0％的弹性应变极限和1788MPa的极限断裂强度．显微观察表明，压缩变形后的试样表面均匀分布着大量波浪形剪切带．     

金属纳米微粒熔化热力学性能的尺寸形状效应

利用表征纳米微粒形状效应的形状因子与金属纳米微粒结合能的尺寸效应表达式，建立了金属纳米微粒尺寸形状效应的熔化热力学模型，预测了金属纳米微粒存在的最小临界尺寸为rc=5r0/μ^1/2{1-exp[-2Sm(∞）/3κ]}，最低熔化温度为Tc(r)=Tm(∞)exp[-2Sm(∞)／3κ]．对纳米微粒Au，In，Al和Sn熔点、熔化熵及熔化焓的预测值与实验结果相一致。     

WC-Ni硬质合金研究

研究以Ni替代Co作硬质合金粘结剂，通过在Ni中添加适量的金属添加剂，来提高和改善WC－Ni硬质合金性能，采用此方法生产出来的WC－Ni硬质合金的机械性能和使用性能完全可以达到WC—Co硬质合金的水平．