连铸钢液过滤

本文在水力学模拟试验的基础上,运用自行研制的三种不同材质的过滤器,在连续铸钢中间包内成功地进行了过滤的实机试验。所过滤的钢液量最高达350吨,夹杂物总量去除率最高达63.63%。从使用情况看,刚玉质和石灰质过滤器均能满足要求,但从对非金属夹杂物的去除效率方面来说,石灰质更具有吸引力。     

激光表面熔凝改善热喷涂纯铝涂层的抗氢渗透性

采用激光表面熔凝工艺,封闭热喷涂纯铝涂层中的孔隙减少了微裂纹。此法不仅提高了涂层质量,而且还使其抗氢渗透性能得到明显的改善。     

PLD制备生物陶瓷薄膜的研究现状

脉冲激光沉积法制备HAP生物陶瓷涂层是近年来发展的制备生物陶瓷涂层的一个十分活跃的研究领域.本文简要介绍了它的研究背景、原理与特点,并对其四个研究方向-溅射机理,沉积条件与涂层质量的关系,脉冲激光沉积新工艺,HAP涂层的生理功能的研究现状进行了概括与总结.     

Al－45％Cu合金的熔剂净化与过冷

通过金属熔体过热与氯盐熔剂净化相结合，使Ａｌ－４．５％Ｃｕ合金在金属型锭模中获得了６２℃的形核过冷度．用形核理论对大体积Ａｌ－４．５％Ｃｕ合金极限热力学过冷度进行计算后发现其范围在７４Ｋ到１０７Ｋ之间．     

液固界面滞后对凝固初始过渡区溶质再分配的影响

实际定向凝固过程中,当改变外加速度或凝固刚开始时,液固界面并不是立即跟上外加速度,而是存在一种滞后效应。本文在采用一些近似假设的基础上,研究了这种滞后效应对定向凝固过程初始过渡区溶质再分配的影响,得到一个新的初始过渡区溶质分布公式,证明Tiller的经典结果只是本文结果当△T_0/G→0时的极限情况。理论计算结果还表明,液固界面实际速度对外部控制速度的滞后效应将使凝固初始过渡区溶质分布趋于稳态所需时间和距离增长;不仅外部控制速度V_0和分配系数k,而且温度梯度G,合金平均成分C_0和液相线斜率m都会影响初始过渡区溶质再分配过程,其影响以V_0最大,k、D_L次之,G,C_0,m最小。     

Nucleation and undercooling of metal melt

The effects of thermodynamic and dynamic factors on nucleation process have been integrated in a theoretical formula representing the dependence of undercooling on parameters concerned. Moreover, a method to determine the kind and amount of the most effective catalyst in an undercooled melt has been acquired. The results show that the undercooling increases with the decreasing surface area of the most effective catalyst and the increasing cooling rate as the kind of the most effective catalyst is constant. It increases to a maximum value when the ratio of the surface area of catalyst ( Sv V) to the cooling rate of melt ( Rc) decreases to a critical value. The maximum undecooling not only depends on the ratio of non-dimensional factor of activation energy for an atom to diffuse (φ) to non-dimensional factor of driving force for nucleus to form (ψ), but also depends on the contact angle of the most effective catalyst; the smaller the ratio of φ to ψ, the higher the maximum undercooling, but it does not     

铝熔体中夹杂物形状与取向对其电磁分离的影响

采用有限元方法,对电磁场作用下铝熔体中任意形状与取向夹杂的受力进行数值计算。结果表明：不同形状与取向的夹杂均仅受到一个与熔体所受电磁力方向相反的斥力作用;电磁斥力的大小不仅与夹杂的形状有关,还受其取向的影响;当夹杂的形状奇异程度愈大时,取向对电磁斥力的影响也愈大;当夹杂在磁场方向的主轴长度较大,并且在电磁力方向的主轴长度较小时,夹杂所受电磁斥力不显著。     

Effect of Ca and Y additions on oxidation behavior of AZ91 alloy at elevated temperatures

In order to develop the ignition-proof magnesium alloy, the effect of alloying elements, Ca and Y, on the oxidation behavior of AZ91 magnesium alloy at elevated temperatures was investigated. The ignition-proof performance, oxide products and oxidation kinetics of Ca- and Y-containing AZ91 alloys were studied. The results indicate that the proper addition of Ca can increase the ignition point of AZ91 alloy greatly. However, the oxide film of Ca-bearing AZ91 alloy formed at elevated temperature is thick and brittle, which is prone to crack in melting and cooling process. In addition, the oxide film of AZ91-xCa alloy is incompact and cannot inhibit the diffusion of reaction particles. The oxide film of AZ91-xCa alloy turns to thin and plastic one after Y is added, and the density of the oxide film increases greatly due to the formation of composite oxide film composed of MgO, CaO and Y2O3.     

快淬Al15Mg50Zn35三元合金中的二十面体准晶相

采用激冷铜模快淬的方法,在靠近Bergman线附近的富Mg区域的成分中获得了单相二十面体准晶相.利用X射线衍射仪、扫描电镜、场发射高分辨扫描电镜及透射电镜,分析了二十面体准晶相的微观组织、成分及原子簇结构.结果表明:快淬Al15Mg50Zn35合金中可以获得几乎单相的二十面体准晶相,能谱分析结果表明,其成分为39.76 at%Mg, 18.34 at%Al, 和41.90 at%Zn;二十面体准晶相从熔体中直接形核并长大,呈现出典型的棱面枝晶形貌,其最快生长沿3次轴方向;同时,准晶晶粒还呈现出规则的六边形状,其尺寸约为0.2 μm.二十面体准晶相的原子簇结构为具有二十面体对称性的五角十二面体,在每个五角面上可以看到微小的"凸起".     

THE PURIFICATION AND HYPERCOOLING OF Fe-B EUTECTIC ALLOY

通过真空熔炼和气体保护, 采用熔融玻璃与循环过热相结合的深过冷快速凝固技术,研究了影响富Fe端Fe-B共晶合金熔体净化效果的主要因素, 确定了该合金熔体获得超过冷的净化方法, 并使Fe83B17共晶合金熔体稳定获得了300-460 K的超过冷度, 使Fe80B20过共晶合 金熔体的过冷度达到了485 K, 从而使Fe-B共晶系合金熔体开始形核前的初始过冷度达到了0.3m-0.4m的水平. 通过对冷却曲线的分析, 讨论了表征超过冷快速凝固的热力学特征.