析出粒子对钛微合金化高强钢奥氏体晶粒长大的影响

通过析出粒子与奥氏体晶粒尺寸的定量关系,建立奥氏体晶粒长大模型,计算TiN和TiC析出粒子共同作用下钛微合金化钢奥氏体晶粒尺寸. 根据析出相质点理论计算结果表明:随着加热温度的升高,析出粒子体积分数逐渐减少,粒子半径逐渐增大,TiC粒子强烈阻止奥氏体晶粒长大,TiN粒子对奥氏体晶粒长大钉扎效果一般. 采用实验测试手段测量不同加热温度下保温30 min后实验钢的奥氏体晶粒尺寸,与理论计算结果吻合较好.     

Real‐time three‐dimensional single‐particle tracking spectroscopy for complex systems

Complex systems are characterized by dynamical processes spread over multiple time and length scales. At a given instant, these systems can display spatial heterogeneities in which the local physical and chemical properties are nonuniform, depending on the location. They can also exhibit dynamical heterogeneities in which the local dynamical characteristics vary with time. These types of systems pose unique experimental challenges for their characterization and test of theoretical ideas. Recently, real‐time three‐dimensional (3D) single‐particle tracking spectroscopy has been developed to address these kinds of problems. With this approach, in principle, one can follow how a system evolves spatially as well as temporally. This article attempts to provide an introduction to this promising new technique by discussing the aims of studying a complex system and recent experimental advances towards this goal.     

过冷液体钾形核初期微观动力学机理的模拟研究

采用分子动力学方法对液态金属钾凝固过程进行了模拟,根据凝固过程体系平均原子能量、原子成键类型和成团类型,以及均方位移和非Gauss参数等动力学参数的演化特征,对过冷熔体形核初期微观动力学机理进行了研究.结果表明:根据过冷液体钾结晶形核过程热力学、动力学和结构特性的演化规律, 其过冷温度区间可以分为两个明显不同的阶段,潜在结晶核心出现在过冷液体较低温区.过冷熔体钾在形核初期,二十面体团簇结构在α-弛豫阶段逐渐解体,同时具有体心立方(bcc)结构的潜在结晶核心逐步形成,其临界晶核包含约300个原子.     

Laser Nitriding of Iron,Stainless Steel,and Plain Carbon Steel Investigated by Mössbauer Spectroscopy

Nitriding is a common method for improving the hardness, mechanical properties, wear and corrosion resistance of metals. Laser nitriding of metals is an efficient process, where the irradiation of surfaces in air or nitrogen atmospheres with short laser pulses leads to a fast take-up of nitrogen into the irradiated surfaces. This process has been extensively investigated for pure iron, but usually, no tools or functional parts are made of pure iron. Mainly steel or cast iron is used as a base material. Therefore, when looking for technical applicability, also the influence of alloying elements on the laser nitriding process is of great interest. Besides the pure iron various carbon steels and an austenitic stainless steel were studied in laser nitriding experiments in order to investigate the influence of the material itself. Here, the process is investigated via Conversion Electron and X-ray Mössbauer Spectroscopy (CEMS and CXMS), Resonant Nuclear Reaction Analysis (RNRA), and X-Ray Diffraction (XRD). It appears that carbon steels are even better suited for the laser nitriding process than pure iron, and the laser nitriding also works efficiently for the stainless steel which is normally difficult to be nitrided.     

The effect of Nb addition on the thermal stability and magnetic properties of Fe-based amorphous alloys with a wide supercooled liquid region

We have examined the effect of Nb addition on the thermal stability of the supercooled liquid before crystallization, the glass-forming ability and magnetic properties for the amorphous alloy series Fe₇₃Nb_xAl_5-xGe₂P₁₀C₆B₄ and Fe₆₃Co₇Nb_xZr_10-xB₂₀. The supercooled liquid regions (ΔT_x=T_x-T_g) have maximum values of 66 and 79K, respectively, for Fe₇₃Nb₁Al₄Ge₂P₁₀C₆B₄ and Fe₆₃Co₇Nb₄Zr₆B₂₀ alloys. The saturation magnetization σ_s of the Fe₇₃Nb_xAl_5-xGe₂P₁₀C₆B₄ alloy system is much higher than that of the Fe₆₃Co₇Nb_xZr_10-xB₂₀ alloy system, and is almost unchanged with an increasing Nb content from 0 to 3 at%. But the σ_s of the Fe₆₃Co₇Nb_xZr_10-xB₂₀ alloys decreases linearly with increasing Nb content. The coercive force H_c of the two alloy series can have a minimum value of 31A/m for Fe₇₃Nb₁Al₄Ge₂P₁₀C₆B₄ and 37A/m for Fe₆₃Co₇Nb₄Zr₆B₂₀. All these values are for the ribbons annealed at 773 and 873K for 15min in vacuum.     

过冷水滴碰撞结冰的实验与模拟研究

以宏观结冰/霜过程中过冷水滴的碰撞结冰现象为背景,实验对比了亲水和超疏水表面上常温水滴碰撞、常温水滴碰撞结冰和过冷水滴碰撞结冰的过程,建立了过冷水滴碰撞结冰过程的数值模型,研究了We数和接触角对碰撞结冰的影响。结果表明:相比于常温水滴的碰撞及其碰撞结冰过程,过冷水滴碰撞结冰过程的稳态铺展系数更大;随着过冷度和We数的增大以及接触角的减小,过冷水滴的碰撞结冰与常温水滴的碰撞在水滴形态和铺展系数上的差异逐渐增大。     

Investigation of the structure of concentrated aqueous solution of LiCl at low temperatures by the method of integral equations

Peculiarities of the formation of the structure of aqueous LiCl solution (at a salt: water molar ratio of 1:5.3) in the temperature range 298-138 K were studied by the method of integral equations. Analysis of the results obtained suggests that transition of the system into the supercooled and glassy state is accompanied by an increase in the tetrahedral ordering of solvent molecules and a decrease in the number of interactions between the water molecules in unbound solvent. Lowering the temperature leads to an increase in the degree of structurization of water molecules surrounding the cation. Preferable formation of hydrogen bonds with the anion under extreme conditions was established. The glassy state of the solution is characterized by the absence of direct anion-cation correlations and increased (compared to standard conditions) probability of the formation of ion-water chains. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1881–1886, October, 1999.     

等淬球铁的贝氏体形态

利用１００ＣＸⅡ型透射电镜对球铁的上、下贝氏体形态进行观察与分析．结果表明，球铁的上、下贝氏体均为板条状铁素体，其间有奥氏体．随着等温转变、温度降低，板条变得细小密集，奥氏体量及其含碳量也减少．在上贝氏体中未检测到碳化物，但在下贝氏体中证实有碳化物析出在铁素体片内，排列成行并与贝氏体针长轴成５５°角．