于荣
,
贺连龙
,
程志英
,
朱静
,
叶恒强
金属学报
doi:10.3321/j.issn:0412-1961.2002.z1.140
用高空间分辨分析电子显微术研究了TiAl-W-Si合金中B2相的析出行为和元素W的分布.结果表明,α2/γ相界面台阶由于W的富集而成为B2析出相的择尤形核位置.B2相中,高达三分之一的Al原子被W原子置换,而在γ相中只固溶了很有限的W.另外,W也偏析在α2/γ和B2/γ相界面上.这些结果合理地解释了W对提高TiAl合金蠕变性能的显著作用.
关键词:
分析电子显微术
,
TiAl
,
析出相
,
偏析
Journal of Physics D-Applied Physics
The effect of Co addition combined with W on the microstructure and magnetic properties of nanocomposite magnets with composition of (1 - x wt%)Nd8.55Fe84.49W0.60 B-0.636 + x wt% CO, prepared by mechanical alloying, has been investigated. The addition of W can increase the unit cell volume of soft and hard phases in nanocomposite: magnets, and cause the anisotropy field of the hard phase component to increase. Therefore, the addition of W can improve coercivity. On the other hand, addition of Co leads to a decrease of the grain size of the alpha-Fe soft phase component in nanocomposite magnets annealed at temperatures lower than 670 degrees C. It leads further to a decrease of the optimal annealing temperatures, an increase of the remanence and maximum magnetic energy product, and a slight decrease of the coercivity. With increasing the content of Co, the dependence of remanence J(r) on annealing temperature T-a changes from a convex shape, giving a maximum, to a monotonically decreasing one. These phenomena have been explained in terms of the variation of grain growth and exchange coupling between the grains, due to the addition of Co and W.
关键词:
nd-fe-b;remanence enhancement;alloys;phase;microstructure;nb
HUANG Huimin CHEN Xinmin Central South University of Technology
,
Changsha
,
China HUANG Huimin Associate Professor
,
Department of Chemistry
,
Central South University of Technology
,
Changsha
,
China
金属学报(英文版)
The nature of the oxygen contained in β-W was investigated with DSC,X-ray analysis on quenched samples and Auger spectroscope.It was shown that the oxygen contained in nonpyrophoric β-W consists of the reversibly chemisorbed oxygen and the interstitial oxygen which could form an interstitial solid solution with β-W.It seems better to consider β-W to be a metastable phase of tungsten with the interstitial oxygen as stabilizer.
关键词:
tungsten
,
null
,
null
,
null
黄远辉
,
杨海涛
,
尚福亮
,
吴国根
,
汪晓
稀有金属材料与工程
用高温固相反应法制备出A_2W_3O_(12) 型稀土钨酸盐材料(A=Y,Er,Ho,Yb),用室温及高温XRD测定其在不同温度下的结构、晶胞参数及晶胞体积,并用TOPSA软件对其结构进行精修.发现除HO_2W_3O_(12)外,都具有较大的负热膨胀系数.据A. W. Sleight预测,HO_2W_3O_(12)具有较大的负热膨胀特性,但本实验却发现它并没有负热膨胀性,反而具有非常大的正热膨胀系数.
关键词:
稀土钨酸盐
,
高温XRD
,
HO_2W_3O_(12)
韩兵强
,
李楠
材料科学与工程学报
doi:10.3969/j.issn.1673-2812.2003.06.020
以铝热法为基础制备了Al2O3/W复合材料,探讨了Al2O3含量对复合材料合成的影响.研究表明:主要物相为α-Al2O3、金属W.刚玉含量小于0 3时,温度影响不显著,大于0 3时,温度影响显著,有大量碳化物生成,且WC/W2C相对含量随Al2O3含量增加及煅烧温度的提高而增加.当刚玉含量为0 5mol时,有正交晶钨酸铝生成.随刚玉含量变化,金属钨分布从连续分布向弥散分布变化.连续分布的金属钨因被氧化铝包裹因此难以碳化,而弥散分布的金属钨则易于被碳化.
关键词:
铝热反应
,
相组成
,
显微结构
,
碳化
Physical Review B
The effect of W on the structural stability of TiAl intermetallic systems and the site preference of W in B2 and L1(0) TiAl were studied based on first-principles calculations. It was found find that about 15 at. % W addition, in good agreement with experiment, is required to stabilize the B2 structure in a TiAl base alloy. W was predicted to occupy Al sites in the B2 phase, but Ti sites in the L1(0) phase. The B2-stabilizing effect of W and its site preference can be explained perfectly on the basis of the pseudogap effect and the strong covalent W-Ti bonding. The strong W-Ti bonding pairs are maximized when W occupies Al sites in B2 TiAl. But when W occupies Al sites in L1(0) TiAl, the W-Ti bonding is weakened by the existence of Al in the alternating (002) plane, which can, however, strengthen the in-plane W-Ti bonding when W occupies Ti sites.
关键词:
gamma-titanium aluminides;electronic-structure;microstructure;deformation;systems;alloys
Journal of Materials Research
The morphology of the dark and bright regions observed by transmission electron microscopy for the Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass strongly depends on the ion beam parameters used for ion milling. This indicates that the ion beam could introduce surface fluctuation to metallic glasses during ion milling.
关键词:
room-temperature
