W.M. Mao
,
A.M. Zhao
,
X.Y. Zhong
金属学报(英文版)
The nondendritic semi-solid slurry preparation of high chromium cast iron Cr20Mo2
has been studied in this paper. The experiments show that the proeutectic austenitic
particles are more spherical under a larger stirring power condition, even if the stirring
time is shorter, while the proeutectic austenitic particles are not very much spherical
under a smaller stirring power condition and some proeutectic austenitic dendrites
also exist, even if the stirring time is very long. The experiments also show that when
stirred for 5{6 minutes under the test condition, the semi-solid slurry with 40vol.%{
50vol.% solid fraction and spherical proeutectic austenite in the size of 50{80¹m can
be obtained.
关键词:
high chromium cast iron
,
null
,
null
W.M. Mao
,
Z.S. Zhen
,
H.T. Chen
,
X.Y. Zhong
金属学报(英文版)
With the help of an electromagnetic stirring device and alloy melt quenching technology, the microstructure of semi-solid AZ91D magnesium alloy slurry stirred by a rotationally electromagnetic field was studied and the experimental results are shown as the following. The primary α-Mg grains are refined obviously when the slurry is stirred by a rotational electromagnetic field during continuously cooling and they are eventually changed to fine rosette grains or spherical grains. If the above semi-solid slurry is further stirred isothermally for some time, much more spherical primary α-Mg grains can be obtained. If the melt is first cooled down to a given semi-solid temperature and then starts being stirred by the rotational electromagnetic field, the primary α-Mg dendrites will be large, and a longer time will be taken and a larger stirring power will be needed for the secondary arms of the dendrites to be remelted on the roots to prepare an ideal semi-solid slurry. Theoretical analysis indicates that the strong flow motion leads to a more even temperature field and a solute field and stronger man-made temperature fluctuation in the AZ91D magnesium alloy melt so that the spherical primary α-Mg grains are increased in the slurry. Moreover, all the measures promoting the temperature fluctuation will be favorable to the formation of spherical primary α-Mg grains and all the factors increasing the arm's root remelting difficulty will be favorable to the formation of rosette-type primary α-Mg grains.
关键词:
AZ91D magnesium alloy
,
null
,
null
TIAN Baohong ZHENG Shi'an WU Lei Luoyang Institute of Technology
,
Luoyang
,
China ZHENG Shi'an
,
associate professor
,
Department of Materials Engineering
,
Luoyang Institute of Technology
,
Luoyang 471039
,
China
金属学报(英文版)
Determination was carried out of fatigue crack propagation rate of steel 65Cr5Mo3W2VSiTi (LM2)with various bainite contents and M/B duplex structure tempered at various tempera- tures.The threshold value of fatigue for each processing was estimated by experimental data. The mechanism for fatigue crack propagation of M/B duplex structure in steel LM2 seems to be non-continuous.The calculated fatigue crack micro-propagation rates are found to agree with the experimental data.
关键词:
duplex structure
,
null
,
null
,
null
Journal of Alloys and Compounds
Bulk metallic glasses (BMGs) Fe56Co7M2Zr10Mo5B20 (M = W or Ni) with diameters of 1.5 mm were fabricated by copper mould casting method. There is no significant difference in the glass properties such as glass transition temperature (T-g), onset temperature of crystallization (T-x), supercooled liquid region (Delta T-x), and offset temperature of melting (T-1) except that the onset melting temperature T-m, which are 1454 and 1464 K for the alloy containing W and Ni, respectively. The alloy containing W exhibits some paramagnetic properties while the Ni containing alloy shows fully ferromagnetic. The potentiodynamic polarization experiments show that these alloys have a high corrosion resistance in 3.5 % NaCl solution with strong passivation ability. The alloy containing W shows excellent pitting resistance with a wide passive range (Delta E = 852 mV) and low passive current density in the order of mu A m(-2). Electrochemical impedance spectroscopy (EIS) for either alloy consists only of single capacitive loop. (c) 2005 Elsevier B.V. All rights reserved.
关键词:
amorphous materials;casting;bulk metallic glasses;glass forming;ability;high saturation magnetization;p-c alloys;ferromagnetic glasses;amorphous-alloys;1.5 t;hcl;resistance;behavior;system
何立子
,
孙晓峰
,
郑启
,
侯贵臣
,
张承忠
,
管恒荣
,
胡壮麒
材料工程
doi:10.3969/j.issn.1001-4381.2004.02.011
研究了一种高W,Mo的Ni基高温合金M963中碳化物的种类、形态、分布及产生的相关工艺条件和形成机理.实验研究发现,根据碳化物产生的热力学条件不同,可以把M963合金中出现的碳化物分为:遗传型碳化物、自发形核型碳化物和析出型碳化物三类.未熔体处理的合金组织中以粗大的块状遗传型MC碳化物为主,遗传型碳化物多分布于晶界和枝晶间.经过熔体处理后,合金中开始出现自发形核的共晶型汉字碳化物,在更高的熔体处理温度1850℃以上,出现了自发形核的非共晶型颗粒碳化物,自发形核碳化物多分布于枝晶间.随熔体处理温度的升高,碳化物形态的变化顺序为:块状→汉字形→颗粒状,碳化物的尺寸变小,分布更加均匀.
关键词:
M963合金
,
熔体处理
,
碳化物
,
形态
,
分布
刘路
,
李世燕
,
樊荣
,
陈仙辉
低温物理学报
doi:10.3969/j.issn.1000-3258.2000.05.005
分别用固相反应和柠檬酸盐溶胶-凝胶法制备名义组成为Sr2(Gd1 5Ce0.5)Cu2Oz的前驱物,再用真空烧结的方法合成了(Hg,M)-1222相铜氧化合物(Hg0.75M0.25)Sr2(Gd1.5Ce0.5)Cu2Oz(M=W,Mo,V,Cr,Ti).溶胶-凝胶法同固相法相比混合更均匀,反应温度低,成相情况好.改进该方法后,用溶解度较高的Ce(NO3)3代替不溶于硝酸的CeO2,制得了纯1222相.研究了不同退火条件对样品电阻温度特性的影响,发现高氧压退火有助于超导转变.M=W,Mo时得到超导体,Tc(onset)在13～27K之间.
关键词:
刘勤
,
裔式珙
材料研究学报
在250℃以■=0.025min~(-1)测到的Zn-5%Al 合金的超塑性m-δ曲线均属式。w_0/l_0值加大使m_0,m_L 和δ_F 值增大,但对δ_L 和m_F 值无大影响。试样厚度的加大(由1增大到2mm)仅使δ_L 和δ_F 值增大,考虑w_0/l_0比值的影响,C_3~((m_0-m_L))-(m_L=m_(mas))型C.L.m-δ方程式规划为:或其中,m′_0(W_0/l_0)=m_0,m′_0>m_0;m′_L(w_0/l_0)=m_L,m′_L>m。w_0/l_0=0.15—0.39。当w_O/l_0=1时,缺口效应消失,δ(或δ_F)值为最大。
关键词:
Zn-5%Al合金
,
mechanics of superplasticity
,
C.L.m-δequation
柏广海
,
胡锐
,
李金山
,
钟宏
,
寇宏超
,
傅恒志
稀有金属材料与工程
采用差示扫描量热法(DSC)、扫描电镜(SEM)和透射电镜(TEM)系统研究了Ni-Cr-W基高温合金二次M23C6的析出行为.结果表明,合金中二次M23C6的析出温度范围为648～1147℃,当温度高于1160℃时M23C6发生固溶；初生M6C在1349℃发生分解；合金在1400℃时完全熔化.由于时效温度不同,合金中析出两种不同形貌的M23C6.在较低温度时(655～900℃)粗大片层状M23C6在晶界析出;在900℃以上M23C6的形貌由片层状转变为不连续颗粒状.降温速率对M23C6的析出形貌产生一定影响；同时,降温过程中晶界上不连续颗粒状M23C6的析出是导致弯曲晶界形成的主要原因.
关键词:
Ni-Cr-W基高温合金
,
DSC
,
M23C6
,
析出
,
弯曲晶界
Applied Surface Science
A novel kind of micro-arc oxidation (MAO) coating was prepared on magnesium alloy surface coated with rare earth conversion film (RE-film) in an alkaline aluminum oxidation electrolyte by AC power source. Inspection of scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) microspectroscopy, the structure and composition of MAO coating formed on AZ91D with RE-film under different applied voltages were investigated and the performance of the optimized MAO coating compared with the MAO coating directly formed on magnesium alloy. As the pretreatment of magnesium alloy with RE-film, the cerium oxides can be incorporated into the MAO coatings, reduce porosity of the MAO coating surface and enhance the thickness of MAO coating. These structure features and the cerium oxides incorporated into the MAO coating result in greatly improved corrosion resistance. Base on electrochemistry impedance spectroscopy (EIS) measurement, the electronic structure and composition analysis of the MAO coating, a double-layer structure, with a compact inner layer and a porous outer layer, of the coating was proposed for understanding its corrosion process. (C) 2010 Elsevier B.V. All rights reserved.
关键词:
Magnesium alloy;Rare earth conversion film;Micro-arc oxidation;Porosity;az31 magnesium alloys;micro-arc oxidation;mg-al alloys;electrolyte;resistance;cerium;phosphate
