Qin LIN+
,
Aisheng LIU
,
Wen YE
,
Zongsen YU
,
Dept. of Physical Chemistry
,
University of Science and Technology Beijing
,
Beijing
,
100083
,
China
材料科学技术（英）
In steels 16Mn and X60 with low S content (0. 003～0. 005%), rare earth metals (REM) still show ef- fects on purifying the molten steel and controlling the sulphide morphology. The optimum ratio of RE/S is about 2. 0, which causes lower content of oxygen and inclusions and higher impact toughness. The amount of REM in solid solution in the steel was determined by means of inductive coupling plasma (ICP) spectroscopy. The dissolved REM in low S steel could decrease the propor- tion of pearlite and increase the strength of the steel.
关键词:
rare earths
,
null
,
null
LIN Qin
,
YE Wen
,
DU Yuansheng
,
YU Zongsen Department of Physical Chemistry
,
University of Science and Technology Beijing
,
100083
,
China.
材料科学技术（英）
The contents of rare earth metals(REM) in solid solution in 16 Mn steel were determined by means of inductive coupling plasma (ICP) spectroscopy.The amount of REM in solid solution is only a few ppm in the steel with MnS inclusions, which rises slightly with the increasing of REM content in steel.At RE/S>1.9,the MnS inclu- sions in steel disappear completely,the REM con- tent in solid solution increases rapidly with the in- creasing of REM content.The solubility of cerium in 16 Mn steel(st 52)is less than 0.011 wt—% at room temperature. The results obtained indicate that REM in sol- id solution reduce the amount of pearlite and in- crease that of ferrite and its microhardness.Dis- solved REM oculd increase temperature of critical points,alleviate band structnre and suppress growth of austenite grains.
关键词:
rare earth
,
null
,
null
Y.S.Wang
,
Q.D.Wang
金属学报(英文版)
Mg-9Al-xRE magnesium alloys were studied,where x is0,0.4,0.8,1.2and 1.6(in weight percent,wt),respectively.Influence of rare earths(RE) on microstructure and strength in both T4(solute heat treatment)and T6(solute heat treatment and artificial ageing treatment)were investigated.Strength of specimen was tested at am-bient temperature.The microstructure was analyzed by optical microscopy,scanning electron microscopy(SEM)and X-ray diffreation analysis.RE additions improved T4 tensile strength of the treated alloys.Small addition (0.4wt) of RE greatly im-proved the strength of ageing treated(T6)Mg-9Al alloy,but further additions caused decreasing.
关键词:
Mg-Al alloy
,
null
,
null
L.J.Shang
金属学报(英文版)
A gradient coating of Fe-based alloy was manufactured with rare earths (RE) by plasma surfacing on Q235 steel substrate. The coatings were studied by using X-ray diffraction (XRD), scanning electron microscope (SEM), differential thermal analyzer (DTA), and electron probe micro-analyzer (EPMA). The results show that the phases of the two kinds of coatings(with and without RE) both include α-Fe, Fe7C3， Fe3C, Cr2B, Fe2B and FeB. The microstructure of F314 coating is mainly hypereutectic, the pro-phases Cr7C3 and Cr2B are loose, crassi, spiculate and contain microcracks. The brittleness of the coating is high, and the average hardness is 787 HV. When 0.8wtRE was added into the F314 alloy, the microstructure varied from hypoeutectic to hypereutectic continuously, The hardness appears as gradient distribution with the highest value of 773 HV, meanwhile, the brittleness decreases significantly. The formation of gradient structure depends on the fallowing factors: (i) the conversion of RE. The addition of RE lowers the elements point and Fe-C eutectic temperature, thus the base metal melting acutely. (ii) the heating of plasma arc.Graded temperature results in directional solidification, thus the gradient structure forms easily. The main reasons for the hardness decrease with RE addition in the alloy are the ratio of hard phase lowering and the hardness of the hard phase decreasing.
关键词:
rate earth
,
null
,
null
Journal of Materials Science
This investigation studied the effects of rare earths (RE) and chromium on the high temperature oxidation resistance and aqueous corrosion resistance of iron base self-fluxing alloy coatings. Four coatings were prepared through smelting-atomizing and oxide-acetylene flame spraying. The properties of the coatings were evaluated by cyclic oxidation tests, weight loss experiments, electrochemical impedance spectroscopy (EIS), potentiodynamic scanning technique, scanning electron microscopy (SEM) and electron dispersive X-ray analysis (EDAX). The addition of RE greatly enhanced the oxidation resistance of the coatings. This effect was attributed to the fact that RE changed the ion diffusion patterns of the coatings in the process of scale forming, resulting in more protective scales with high adhesion. The increase of chromium content in the coatings enhanced the corrosion resistance of the coatings in nitric acid solution, but in hydrochloric acid and sulfuric acid solutions the result was reversed. Rare earth addition had a beneficial effect in sulfuric acid and nitric solutions, but in hydrochloric acid, the samples with RE had a corrosion rate slightly higher than that of the samples without RE addition. These results are explained by the effect that the addition of RE minimized the cathodic area of the coatings. (C) 2002 Kluwer Academic Publishers.
关键词:
oxidation
Journal of Physics-Condensed Matter
The mixing effects of light and heavy rare earths in cubic Laves phase compounds Nd1-xHRxCO2 (HR = Gd, Tb) have been investigated by means of x-ray powder diffraction and magnetic measurements. In Nd1-xTbxCo2, the saturation moment M-S exhibits in anomaly and could be ascribed to an abrupt jump of the Co moment at a critical concentration x approximate to 0.33, whereas, in Nd1-xGdxCo2, M-S does not show such an anomaly and a relatively simple magnetic behaviour is observed at x(c) approximate to 0.43. The different behaviours of these two systems can be understood by considering the structural distortion of a cubic unit cell at low temperature. A field-induced metamagnetic transition from weak ferrimagnetism to strong ferrimagnetism is observed in both systems. This can be interpreted by the evolution of magnetization with the help of percolation theory. The compensation points are observed in both systems, which are well explained within the two-sublattice model. A double peak of the AC susceptibility observed in Nd1-xTbxCo2 near x(0) approximate to 0.19 does not necessarily mean the occurrence of a first-order phase transition. The observed second-order magnetic phase transition near x(0) can be well described by Landau theory of the phase transition.
关键词:
itinerant-electron metamagnetism;intermetallic compounds;rco2;transition;moment;order;er1-xluxco2;cobalt;yco2
