盘,柱状喷射沉积毛坯的形状控制及组织分析

喷射沉积工艺作为一种新兴的快速凝固技术,已经被广泛地应用于研制和开发各种高性能的快速凝固材料,近年来发展非常迅速。通过对喷射沉积工艺参数的分析和调整,制备了不同形状的ＡｌＣｕＦｅＮｉＣｅＺｒ合金沉积毛坯,实现了对喷射沉积毛坯的形状和尺寸的初步控制;同时研究了过喷粉末的粒度分布规律以及沉积毛坯的致密度和显微组织。结果发现,倾斜喷射（θ≠０）,沉积器抽拉（Ｖ≠０）和自旋（ω≠０）条件下,可以有效地改善沉积坯的几何外形,获得形状较好的盘、柱状沉积坯,其致密度大于９６％,沉积坯组织细小、均匀,晶粒的平均尺寸为５μｍ左右,过喷粉末的平均粒度为３０μｍ。     

喷射成形圆柱坯的计算机模拟与工艺设计

建立了描述喷射成形圆柱坯形状演化过程的数学模型，找到了一种较为简便的计算屏蔽系数的方法，研究了圆柱坯的生长规律．模拟结果表明，雾化参数、沉积盘的下拉速率和起始偏心距等是影响沉积坯形状演化的重要因素；喷射角主要影响上部过渡区的形状；而沉积盘转速在一定范围内变化时，对沉积坯形状演化几乎没有影响．喷射成形开始一段时间后，沉积坯顶点的生长速率将等于沉积器的下拉速率．在其它参数一定的情况下，通过适当选取起始偏心距，可以缩短沉积坯进入稳态生长的时间．模型结果与实验结果吻合较好．提出了喷射成形圆柱坯工艺的设计思路．     

3D形状模型辅助喷射成形工艺的优化

喷射盛开有工艺能够以较少的工序生产整体致密、成分均匀、晶粒细化、力学性能优良的坯件，但控制喷射成形过程的独立工艺参数却较多，给工艺优化带来困难。结合所建立的３Ｄ形状模型，针对两处不同运动的沉积器，探讨了喷射滴所质量流率沿雾化锥的轴向及径向的空间分布，研究了雾化压力、沉积距离、沉积器下降速度、偏心及倾斜角对高温合金沉积坯形状及致密度的影响，研究结果表明，通过计算机辅助优化工艺参数后，可以获得所需形状     

速度等高线法优化喷射成形棒坯的形状控制参数

提出并建立了喷射成形棒坯的沉积速度等高线模型,利用计算机数值模拟技术计算了喷射成形空间质量流率分布,找到了沉积器的最佳位置zm与最佳回缩速度v的关系,分析了不同空间位置对沉积坯端面的影响.采用二维坐标跟踪计算了沉积坯的形貌,计算的结果与实际喷射成形铝硅合金棒坯进行了比较,实验结果与预测得到了较好的吻合.     

管状喷射沉积坯成形过程数值模拟

喷射成形是一种近终形材料加工技术,针对管状沉积坯的成形过程进行了模拟。首先建立了管状沉积坯成形过程的数学模型,然后模拟了沉积坯厚度变化过程。结果表明：沉积器平移速度、沉积器半径、喷射距离对沉积层厚度均产生影响;而沉积器旋转速度超过30r/min时,该参数对沉积层厚度影响可以忽略。     

高强韧镁合金的制备方法

一种高强韧镁合金的制备方法，涉及喷射沉积制备工艺，提出采用保护气氛中的喷射成形技术，解决镁合金挥发、氧化及安全等难点问题，制备形状完整、低偏析、高致密度和成分合格的镁合金沉积坯件，使Mg-Al-Zn系合金宏观力学性能和塑性变形能力得到同步提高。     

喷射成形过程模拟研究

喷射成形将快速凝固技术与金属材料的直接成形技术有机地结合起来，是一种先进的材料制备技术，可用于制备晶粒细小、成分均匀、合金元素过饱和度高的管坯、板坯或圆柱坯等。为了认识喷射成形过程，优化设计喷射成形工艺，近年来人们对喷射成形过程开展了大量的模拟研究工作。介绍了雾化液滴冷却凝固过程模型和喷射成形沉积坯形状演变过程模型。     

快速凝固Al-Fe-V-Si合金喷射沉积坯的显微组织与力学性能

用喷射沉积法制备快凝Al-8.5Fe-1.3V-1.7Si合金沉积坯,通过金相、X射线衍射、透射电镜、扫描电镜、拉伸力学性能测试等分析手段研究快凝Al-Fe-V-Si合金喷射沉积坯的显微组织与力学性能。结果表明,喷射沉积Al-Fe-V-Si合金坯是由形状大小不同的雾化液滴沉积凝固微区(粉末)构成,也存在大量的孔隙和原始粉末界面。沉积坯主要由α(Al) Al12(Fe,V)3Si(bcc,a≈1.260nm)的两相混合组织构成,细小的Al12(Fe,V)3Si球形颗粒均匀分布在α(Al)基体上,但不同粉末内部组织形态存在差异,使沉积坯表现出组织微观不均匀性。喷射沉积坯的力学性能与坯体致密度存在强烈的依赖关系,大量孔隙和原始粉末界面的存在使得坯体强度和塑性都处于较低的水平。     

喷射成型制备的Al23Si5Fe合金圆锭的凝固组织

根据喷射成型的工艺过程特点, 研究了喷射成型制备的高硅铝合金圆锭凝固组织。结果表明： 喷射成型过程中, 在沉积坯件的上表面存在一个有一定尺寸的液态金属熔池; 沉积坯件的凝固组织与粉末凝固组织有明显差别： 沉积坯件整体上呈逐层凝固, 但不同部位的微观组织随凝固速度的不同而有明显区别     

H13钢喷射成形热锻模坯组织分析

对喷射成形H13热锻模沉积坯进行了金相分析、SEM组织形貌观察和能谱分析、硬度宏观分布测试。结果表明:喷射沉积H13钢的凝固晶粒为细小等轴晶,晶粒大小分布不均匀;喷射态的微观组织主要由贝氏体、马氏体、残留奥氏体组成,并有少量碳化物及夹杂物;喷射沉积坯的宏观组织存在明显层状特征,层与层之间存在不同程度的孔隙,沉积坯的底部及顶部区域的孔隙率高;孔隙率高、组织不均匀是沉积坯硬度分布不均的原因;造成沉积坯组织不均匀的原因是金属液流温度和速度在整个喷射过程不均匀。     

Preparation of large size aluminium alloy cylindrical preforms by multi-layer spray deposition

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雾化喷射沉积成型凝固过程模拟Ⅱ.Al-Cu合金的计算结果

根据本文作者提出的喷射沉积成型沉积体内的凝固模型,对典型的Al-Cu合金进行了计算分析结果表明,工艺参数（如沉积速率和沉积时雾化锥的温度）和材料的热物性（如界面换热系数）对沉积体内的凝固过程有明显影响在沉积热力学条件（沉积前雾化锥的热力学状态）相同的情况下,沉积表面的温度随工艺参数和材料热物性发生显著变化所以,必须以沉积表面温度的变化作为工艺控制的参考、以往提出的以沉积前雾化锥热力学状态作为工艺控制标准的原则需要重新加以考虑     

SIMULATION OF SOLIDIFICAFION BEHAVIOR IN SPRAY DEPOSITED PREFORM Ⅱ.Calculation Results For Al-Cu Alloy

根据本文作者提出的喷射沉积成型沉积体内的凝固模型,对典型的Ａｌ－Ｃｕ合金进行了计算分析。结果表明,工艺参数和材料的热物性对沉积体内的凝固过程有明显影响。     

挤压铸造制备Cf/ZL109复合材料及其组织观察

采用挤压铸造制备碳纤维增强ZL109复合材料．SEM观察预处理前后的碳纤维以及碳纤维顶制件的形貌．金相显激镜观察纤维在复合材料中的分布结果表明：预处理使碳纤维长径比满足制备合格预制件的要求，并有利于纤维在预制件中的均匀分散及预制件的成型；模压预制件纤维分布均匀．表面无团聚．碳纤维无氧化；挤压铸造制备的Cf／ZL109复合材料中纤维在基体中分市均匀，并具有方向性。     

The effects of binders and heating temperatures on the properties of preforms

The use of binders in fabricating ceramic fiber preforms is essential when producing metal-matrix com-posites via squeeze casting or liquid metal infiltration. The binder is not only used to stabilize the shape of the preform, but also to increase its strength. A strong preform is needed to make a net shape or near-net shape casting so that many post-machining processes can be reduced or eliminated. However, very lit-tle attention has been paid to preform fabrication, subsequent processing, and its characterization. This work focuses on the relation between preform processing (selection of binder, heat treatment of the pre-form, etc.) and the properties of the resulting preforms. Silica and phosphate binders were used to make short alumina fiber preforms. The use of binders and the heat treatments used were correlated to the properties of the resulting preforms. The results showed that the heat treating temperature, as well as the amount of binder, is relevant to the resulting properties of the preform. Correlations among the use of binders, heat treatment condition, composition of the binders, and the properties of the preforms were investigated.     

Metallographic problems of the production of parts from continuously cast high-speed steels

It has been assumed until recently that high-speed steels cannot be produced by the method of continuous casting. Numerous attempts to use this highly efficient technology for manufacturing such steels have failed because of breakage of the cast preforms. A solution was sought in improving the design of the continuous-casting machines (CCM), increasing the level of their automation, and using rational compositions of slag-forming mixtures (SFM). The idea was that a high-speed steel can be cast only in vertical CCM. The present work concerns regimes of secondary cooling under which the structures formed in high-speed steels provide a ductility sufficient for bending the continuously cast preform without failure. Steel R6M5 cast continuously in such a machine can easily be machined into hot-rolled preforms for sheets, wire, silver-steel rods, and other final products without a forging stage. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 9, pp. 6–13, September, 1998.     

Computer-aided preform design in forging of an airfoil section blade

This study attempts to establish systematic procedures for the preform design in forging of an airfoil section blade as a two-dimensional plane-strain problem. Forward loading and backward tracing simulations by the finite element method are used. A circular shape is selected as an original stock, and a side-pressed preform of the circular shape is adopted in view of preliminary simulations using rectangular preforms. The optimal slope angle of the die parting line and the position of the preform within the die, which satisfy the final design condition of flashless forging, are determined from the results of the simulations.     

Developing intelligent control for spray forming processes

A program to implement real-time sensing and control of spray-formed preform conditions is underway at the David Taylor Research Center. The objective of the program is to develop sensor and control technologies that can be used to monitor critical process conditions and modify operational parameters during the spray forming of components. This task has been divided into two phases. The first entails developing sensors and controls to monitor and correct simulated process conditions. In the second phase, the selected sensors and controls will be combined with actuators, thereby integrating research center equipment and enabling the production of nonsymmetric preforms.     

Modeling and experimental verification of tubular product formation during spray forming

A mathematical model is formulated to predict the shape evolution and the final geometry of a tubular product prepared by spray forming. The effects of several important processing parameters on the shape evolution of the tube are investigated. The model is validated against experiments of spray formed large diameter tubes. The experimental and the modeling results show that there are three distinct regions in the preform, i.e., the left transition region, the middle uniform diameter region and the right transition region. The results show that the atomization parameters as and bs, traversing speed v of the substrate, the outer diameter D0 of the substrate, and the initial deposition distance d0 play important roles in the contour and the wall thickness of the spray formed tube. But the angular velocity ω of the substrate has little effect on the buildup of the deposit. After a certain time from the beginning of the process, the deposit will come into a steady growth state. In addition, an equation is provided to estimate the wall thickness of the deposit under the steady growth state based on the mass conservation.     

C／C坯体对RMI C／C—SiC复合材料组织的影响

以PAN基炭纤维（Cf）针刺整体毡为预制体，用化学气相渗透（CVI）、浸渍炭化（IC）方法制备了不同炭纤维增强炭基体的多孔C／C坯体，采用反应熔渗（RMI）法制备C／C—SiC复合材料，研究了渗Si前后坯体的密度和组织结构。结果表明：不同C／C坯体反应溶渗硅后复合材料的物相组成为SiC相、C相及单质Si相；密度低的坯体熔融渗硅后密度增加较多；密度的增加与开口孔隙度并不是单调增加的关系，IC处理的坯体开口孔隙度低，但渗硅后复合材料的密度增加较多；IC坯体中分布分散的树脂C易与熔渗Si反应，CVI坯体中的热解C仅表层与熔渗Si反应，在Cf和SiC之间有热解C存在；坯体密度相同时，IC处理的坯体中SiC量较多，单质Si相含量少且分散较好，而CVI坯体中SiC量较少，单质Si相的量较多；制备方法相同时，高密度的C／C坯体，渗硅后C相较多。