Y. W. Wang
,
Y. L. King
,
D. H. Yuan
,
S. G. Liu and Z. Y. Yu 1 ) University of Science and Technology Beijing
,
Beijing 100083
,
China 2) Daye Special Steel Co.
,
Huangshi 435001
,
China
金属学报(英文版)
Three dimensional thermal-mechanical coupled elasto-plastic FEM has been used for simulation of round to oval single pass rolling. The analysis was conducted using MARC/AUTOFORCE1. 2 code. The material is assumed to be elasto-plastic and it obey the Von Mises yield criterion and Prandtl- Reuss rule. Deformation of the workpiece is simulated in a step-by-step manner,updating the coordinates of material points and the property after each step, so that both nonsteady-state and stendy-state deformation can be simulated. The heat transfter between the workpiece, the rolls, and enviroment and the heat generation due to plastic work and friction force, are considered in the analys- is.Predicted the deformation shape of the workpiece, distributions of strains, stresses, strain rates and temperatures, roll-separating force and roll torque are presented.
关键词:
bar rolling
,
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)
彭石高
,
丁飞
,
中国有色金属学报
采用溶胶-喷雾干燥-氢还原法制备稀土Y含量分别为0,0.4%,5%,10%和20%的超细(W,Ni,Fe,Y)复合粉末,采用XRD研究煅烧温度和还原温度以及稀土Y含量变化时复合粉末体在制备过程中的相结构变化规律.结果表明:喷雾干燥前驱体随煅烧温度的升高渐渐从非晶体向复合氧化物晶化转变,添加稀土Y的粉末前驱体经煅烧后,Y与W形成复合氧化物Y2W3O12,且稀土Y可以有效地抑制粉末颗粒长大;随着Y含量的增加,Y和W的复合氧化物明显增加,Y2W3O12在700℃才能被还原成低氧复合氧化物相:含5%稀土Y粉末中的Y2W3O12被还原生成新相Y2WO6;当稀土Y增加到10%以上时,不仅生成Y2WO6,还生成另一种新相Y6W2OB15.
关键词:
W-Ni-Fe复合粉末
,
纳米粉末
,
稀土
,
Y
姜迪友
,
刘三秋
稀有金属材料与工程
采用基于密度泛函理论的第一性原理方法研究了钇的含量对W-Y二元合金力学性质的影响,精确计算了W1-xYx(x=0.0625,0.125,0.25,0.5)合金的力学常数,并对其力学特性进行分析.结果表明,W-Y合金的弹性常数、体模量、杨氏模量以及剪切模量随Y含量(原子分数)的增加而成非单调性减小,表明Y对W材料的合金化降低了材料的机械强度.然而,基于力学特性B/G、泊松比v和柯西压力C等分析,Y的合金化对W的延展性和韧性有明显的提高.当Y含量x为0.25时,可有效改善W-Y合金的延展性和抗变形能力.通过态密度分析,W-Y合金的金属性随Y含量的增加先减弱而后增强.
关键词:
第一壁材料
,
W-Y合金
,
力学性质
,
第一性原理
,
密度泛函理论
高原
,
张维
,
王成磊
,
李冰
,
陈选楠
,
黄学锋
,
袁琳
材料热处理学报
研究Q235钢表面等离子W-Mo-Y共渗层的组织、成分、结构、显微硬度,计算渗层中不同位置、浓度下的W、Mo原子扩散系数。结果表明：渗层组织为柱状晶,W、Mo元素呈梯度分布,Y的分布不均匀。共渗层主要结构相为钨钼在α-Fe中的固溶体和Fe17Y2,共渗层显微硬度最高256 HV0.05;Y元素降低表面W、Mo的活度,W、Mo合金元素的化学势变小,表面与基体之间的化学梯度减小,W、Mo原子扩散速率减慢;W-Mo-Y共渗层厚度要比W-Mo共渗层厚度薄;通过Fick第二扩散定律计算表明,在W-Mo-Y共渗和W-Mo共渗时,不同渗层中的W、Mo扩散系数有所不同,但属同一数量级即：10-13～10-14之间。
关键词:
等离子渗金属
,
晶界
,
活度
,
化学梯度
,
化学势
,
Fick第二扩散定律
Journal of Alloys and Compounds
This work mainly investigated the mechanical properties of as-cast Mg-Zn-Y-Zr Mg alloys with Zn/Y ratio about 0.97. Tensile results show that when Zn/Y ratio is constant, the alloy (with Zn and Y contents of 3.93 and 4.14 wt.%, respectively) has the highest strength. XRD analysis shows that the alloys are mainly composed of alpha-Mg matrix and W-phase. With the contents of Zn and Y increasing, the diffraction peaks of W-phase are gradually intensified. In addition, microstructure observation indicates that with the increase of Zn and Y contents, the grain boundaries are gradually coarsened by W-phase. Based on the microstructure observation and fracture analysis, the change of the mechanical properties has been explained. (C) 2007 Elsevier B.V. All rights reserved.
关键词:
Mg-Zn-Y-Zr alloys;the mechanical properties;W-phase;icosahedral phase;microstructure;behavior
Journal of the American Ceramic Society
Combining Clarke's model with first-principles calculation of average sound velocity, the minimum lattice thermal conductivities (kappa(min)) of Y3Al5O12 (YAG), YAlO3 (YAP) and Y4Al2O9 (YAM) are predicted to be 1.59, 1.61, and 1.10 W.(m.K)(-1), respectively. The weak Y-O polyhedra provide "weak zones" that scattering phonons and lead to the low kappa(min) of ternary Y-Al-O compounds. In addition, the extremely low kappa(min) of YAM is attributed to its higher levels of local disorder of crystal structure and weaker chemical bonding compared with those of YAG and YAP. Inspired by theoretical predictions, dense and phase-pure YAM is synthesized and the experimental thermal conductivity is only 1.56 W.(m.K)(-1) at 1273 K. Finally, YAM is highlighted as a potential thermal barrier material for its low thermal conductivities at temperatures from 473 to 1273 K.
关键词:
barrier coatings;single-crystal;gas;stability
李冰
,
高原
,
陈选楠
,
黄学锋
,
赖涛
,
陈文琦
表面技术
doi:10.3969/j.issn.1001-3660.2011.01.025
采用辉光等离子渗金属技术对Q235钢进行W-Mo-Y三元共渗,探讨了极间距、气压、保温时间、温度对共渗层厚度的影响,并分析了共渗层的金相显微组织、合金元素分布及物相组成.结果表明:在试验涉及的条件下,以极间距25 mm,气压30 Pa,保温时间3 h,温度1000℃为最佳工艺参数;共渗层主要由Fe3Mo,Fe(Mo,W,Y),Fe17Y2等组成,组织为柱状晶,W和Mo的含量由表及里逐渐减少,而Y元素由于在晶界处发生偏聚而分布不均匀.
关键词:
等离子渗金属
,
W-Mo-Y共渗
,
Q235钢
马运柱
,
黄伯云
,
范景莲
,
熊翔
,
魏定池
,
汪登龙
中国稀土学报
以喷雾干燥法制备的(W,Ni,Fe)复合氧化物粉末为原料,采用700 ℃,保温90 min的条件进行还原,研究了La-Y含量对还原制备纳米级W-Ni-Fe复合粉末特性的影响;采用XRD及高倍SEM分别对所制备的复合粉末进行了物相分析、晶粒尺寸测试和形貌观察;并对所制得复合粉末的Fsss粒度、比表面进行了测定与分析.研究结果表明: 不加La-Y时还原粉末由W和γ-(Ni,Fe)两相组成,添加一定量La-Y的还原粉末有W,γ-(Ni,Fe),Y(Ni0.75W0.25)O3和La (Ni0.75W0.25)O3四相组成;当La-Y的质量分数在0～0.8%范围时(占90W-7Ni-3Fe复合粉末的质量分数),随着La-Y含量的增加,粉末dBET粒度由96.6降到50.3 nm,粉末Fsss粒度由0.64降到0.33 μm,粉末晶粒尺寸由26.1降到22.2 nm;未添加La-Y时粉末颗粒为球形,添加一定量的La-Y,粉末颗粒变为近球形或多面体;添加一定量的La-Y不仅可以有效地抑制晶粒长大,还可以在一定程度上提高粉末的分散性.
关键词:
材料学
,
W-Ni-Fe复合粉末
,
纳米级粉末
,
氢还原
,
稀土
