材料期刊网

Numerical Simulation of Macro-Segregation in Steel Ingot During Solidification

C.W. Ma , H.F. Shen , T.Y. Huang , B.C. Liu

金属学报(英文版)

A mathematical model coupling the momentum, energy and species conservation equa- tions was proposed to calculate the macro-segregation of Fe-C alloy ingot during solidification. The corresponding simulation software which concurrently solves the macro- scopic mass, momentum, energy and species conservation equations has been developed by applying the SIMPLE algorithm. The thermo-solutal convection in a NH4Cl-H2O ingot is verified and the result shows good agreement with that reported. Then macro-segregation in a steel ingot is simu- lated by using the developed program. The steel ingot is in a rectangular mold with a riser. The fluid flow is mainly induced by the temperature field and the solid fraction. The macro-segregation pattern is mainly affected by the thermo-induced convection in the mushy zone. The negative segregation forms along the walls of the casting. The positive segregation forms at the top center of the casting into the riser. The species concentration reaches the peak in the center of the ingot where solidi¯cation ends lastly.

关键词: macro-segregation , null , null , null

基于(火积)耗散率最小的T-Y形肋片构形优化

冯辉君 , 陈林根 , 谢志辉 , 孙丰瑞

工程热物理学报

基于构形理论,以导热和对流换热总(火积)耗散率最小为优化目标,对T-Y形肋片进行构形优化,得到同时考虑导热和对流换热(火积)耗散性能的T-Y形肋片最优构形.结果表明:存在最佳单元级直肋和中部空腔高度和长度比使得T-Y形肋片无量纲当量热阻取得二次最小值.增大肋片高度和长度比和肋片占比有助于提高T-Y形肋片整体传热性能.T-Y形肋片与T形肋片相比,T-Y形肋片二次最小无量纲当量热阻降低32.33％,此时T-Y形肋片温度梯度场更均匀,整体传热性能得到明显提高.

关键词: 构形理论 , (火积)耗散率最小 , T-Y形肋片 , 对流换热 , 广义热力学优化

AA6061-T6铝合金表面纳米Y2 O3改性硅烷膜的耐蚀性

张明明 , 李文超 , 张圣麟

腐蚀与防护

采用动电位极化曲线，电化学阻抗谱（EIS）和中性盐雾试验（NSS）研究了溶液中加入不同含量纳米Y2 O3对铝合金AA6061-T6表面硅烷膜耐蚀性的影响，采用扫描电镜（SEM）对其形貌进行了观察。结果表明，在1，2-双-三乙氧基硅烷（BTSE）溶液中加入少量纳米Y2 O3可提高硅烷膜在3．5％ NaCl溶液中的耐蚀性。硅烷膜对铝合金的保护只起到物理屏障作用。纳米Y2 O3抑制了电化学腐蚀过程中阴极还原反应的发生，但不影响电极反应的动力特征。SEM表明在BTSE硅烷溶液中添加10～20 mg/L的纳米Y2 O3后，硅烷膜表面变得平滑致密。

关键词: 硅烷膜 , 纳米Y2 O3 , 耐蚀性能 , 铝合金

纳米Y2O3预处理对T91钢抗高温水蒸汽氧化的影响

刘光明 , 张都清 , 任善平

表面技术 doi:10.16490/j.cnki.issn.1001-3660.2015.12.017

目的 研究纳米Y2 O3 预处理对T91钢抗水蒸汽氧化性能的影响,分析稀土元素作用的机理及长期氧化后的失效机制. 方法 采用将Y2 O3、铝粉、粘结剂制备成料浆涂覆于T91钢表面,并在720 ℃水蒸汽中预处理48 h. 预处理样品和空白样品同时置于在700 ℃高温水蒸汽中氧化,获取循环氧化动力学曲线并进行对比,检验预处理对提高材料抗高温水蒸汽腐蚀的效果. 对氧化的样品采用XRD、SEM/EDS对氧化物结构、形貌、成分进行分析. 结果 预处理后在样品表面形成了含Y2 O3 的富铬氧化物薄膜. 在高温水蒸汽环境的氧化过程中,试样处理600 h时,质量增加轻微,仅为0. 152 g/cm2. 但在600 h后质量增加明显,预处理膜层逐渐退化,表面出现Fe2 O3 突出物. 空白样在腐蚀初期即明显增加,氧化70 h后,质量增加达12. 17 mg/cm2 ,氧化过程中可见氧化产物的剥落,氧化膜附着力差. 结论 纳米Y2 O3预处理可提高T91钢抗水蒸汽氧化性能,但随着氧化时间延长,富铬氧化膜将逐渐退化.

关键词: 纳米Y2O3 , T91钢 , 预处理 , 水蒸汽 , 高温氧化 , 富铬氧化膜

Mg-9Gd-4Y-0.6Zr合金挤压T5态的高温组织与力学性能

肖阳 , 张新明 , 陈健美 , 蒋浩

中国有色金属学报

研究了Mg-9Gd-4Y-0.6Zr合金挤压T5态在250～400℃之间的高温组织与力学性能. 结果表明:该合金具有非常优异的高温力学性能,其力学性能明显优于WE54;该合金在250、300、350和400℃时的抗拉伸强度分别为348、262、150和62MPa;该合金在400℃拉伸时还具有粗晶超塑性,晶界上有再结晶的细晶,晶内有大量孪晶同时共存.

关键词: Mg-Gd-Y-Zr合金 , 耐热镁合金 , 高温力学性能 , T5态 , 粗晶超塑性

Ni液中Y-S平衡的研究

王龙妹 , 杜挺

金属学报

用直接平衡法研究了1500,1550,1600℃Ni液中Y-S平衡关系,测定了钇的脱硫常数lgK_(YS)及Y,S的一阶活度相互作用系数e_S~Y与温度的关系,并进行了有关的热力学计算。由测得的数据算出Ni液中YS的标准生成自由能△G_((Y)S),钇的标准溶解自由能△G_((Y)(l)→[Y]Ni),活度系数γ_Y~o,以及钇的克原子分数自相互作用系数∑_Y~Y和百分浓度自相互作用系数e_Y~Y与温度的关系。 对于反应[Y]_(Ni)+[S]_(Ni)=YS_(s) △G_((Y)S)=-215000+95.53T(cal/mol)脱硫常数: lgK_(YS)=-47000/T+20.86 e_S~Y=-350200/T+179 △G_((Y)(l)→[Y]Ni)=126200-79.31T(cal/mol) lgγ_(Y)=27584/T-15.151 ∑_Y~Y=-127T05/T+69.79 e_Y~Y=-364.8/T+0.2018

关键词:

Multiferroic phase diagram of Y partially substituted Dy(1-x)Y(x)MnO(3)

Applied Physics Letters

The effect of nonmagnetic Y partial substitution at the Dy site in Dy(1-x)Y(x)MnO(3) up to x=0.2 on magnetism, specific heat, and ferroelectricity is investigated, which resulted in a preliminary multiferroic phase diagram. It is revealed that the Y partial substitution suppresses the Dy-spin ordering point (T(Dy)) and ferroelectric ordering point (T(FE)) but enhances the Mn-spin ordering point (T(N)). The interaction between the spins of Dy and Mn is remarkably affected by Y substitution. The measured electrical polarization depends on the Y substitution in a complex way because the ferroelectricity is sensitive to the interaction between the spins of Dy and Mn. (c) 2011 American Institute of Physics. [doi: 10.1063/1.3536506]

关键词: ferroelectricity;polarization

Prediction Models on Distribution of Inherent Strains in T Type Welding Structure

Peng HE , Jicai FENG , Jiecai HAN , Yiyu QIAN

材料科学技术（英）

A fundamental theory for the analysis of residual welding stresses and deformation based on the inherent strain distribution along the welded joint is introduced. The method of predicting maximum hardness Hv(y, z) and maximum inherent strain gmax is given. The model T.E.P-Tav-hardness calculation is proposed to predict distribution of inherent strains in T type welding structure. By T.E.P-Tav-hardness calculation, distribution of longitudinal inherent strains can be predicted in T type welding structure, and calculation and experimental results are consistent.

关键词: Inherent strain , null , null

HIGH T_c SUPERCONDUCTOR YBa_2 Cu_3 O_x SYNTHESIZED BY UNIDIRECTIONAL REACTION

FAN Zhanguo , JI Chunlin , WANG Kuihan , CUI Chuanmeng , LIU Sulan , Northeast University of Technology , Shenyang , China

金属学报(英文版)

A unidirectional reaction for synthesis of the high T_c superconductor YBa_2Cu_3O_x has been proposed, Its T_c is 90-94.5 K and △T is 1 K. The phase relationships in the system Y_2BaCuO_5-Y_2Cu_2O_5-CuO-YBa_2Cu_3O_x were studied and discussed.

关键词: unidirectional reaction , null , null

Y含量对铸造Mg-Gd-Y-Nd-Zr合金组织与性能的影响

唐昌平 , 刘文辉 , 陈宇强 , 刘筱 , 邓运来

材料导报 doi:10.11896/j.issn.1005-023X.2016.16.019

采用金相观察、硬度测试、扫描电镜观察、能谱分析、透射电镜观察、X射线衍射及室温拉伸等手段,研究了元素Y对铸造Mg-Gd-Y-Nd-Zr合金组织与性能的影响,结果表明:Y对该系合金的铸态组织无明显影响,在研究的成分范围内,不同成分合金的铸态组织均由α-Mg和非平衡共晶Mg5.05 RE组成;经固溶处理后,非平衡共晶可溶入基体,但在晶界残留富稀土粒子,随着合金中Y含量降低,残留富稀土粒子的数量也降低;经T6处理后,合金中形成了大量的析出相β',高Y含量合金中析出相的体积分数高于低Y含量合金,导致高Y含量合金T6态的硬度较高,但残留更多数量的富稀土粒子反而使高Y含量合金的拉伸强度和延伸率更低.经成分优化,较优的化学成分为Mg-5.5Gd-3.0Y-1.0Nd-1.0Zr,其铸造-T6态的抗拉强度为322MPa,延伸率为4.0％,力学性能优于总稀土含量与之相当的商用WE54合金.

关键词: Mg-Gd-Y合金 , 化学成分 , 微观组织 , 力学性能 , 富稀土粒子