改性平面流铸粉末化过程的数值模拟

在传统平面流铸技术的上,研究出一种新的粉末制取技术－－改性平面流铸粉末化技术。将改性平面流铸粉末化工艺过程分为平面液流的形成、平面液流的破碎和金属粉末的形成3个主要阶段,对这3个阶段建立了完整的数学模型,并对Sn60Pb40合金粉末化过程进行了数值计算。计算了平面液流形成过程动态熔潭中熔融金属液的温度场和流场,以及所得金属粉末的尺寸,计算结果与实验结果相吻合。考察了喷嘴几何尺寸、雾化气氛气体密度等主要工艺参数对改性平面流铸粉末化工艺的影响。     

平面流铸技术的数值模拟与实验研究进展

平面流铸是生产微晶或非晶薄带的一种快速凝固方法。文中介绍了平面流铸的工艺装置、工艺过程和工艺参数对薄带产品厚度的影响,重点分析了平面流铸技术的数值模拟研究工作;叙述了用红外线测温装置和高速摄影技术对平面流铸熔潭形成过程进行的实验研究     

快速凝固制取金属粉末技术的发展状况

分别从工艺原理、工艺过程和工艺适用范围等方面对国内外采用快速凝固技术制取金属粉末的方法进行了分析，并着重比较了不同方法间的技术特点和所获得粉末的特性。     

电子封装材料过共晶硅-铝合金的组织特征和热性能(英文)

采用快速凝固制粉技术和粉末热压烧结技术制备55%Si-Al,70%Si-Al和90%Si-Al3种过共晶含量的硅铝合金。结果表明:雾化沉积是制备过共晶硅铝合金的有效的快速凝固工艺,采用该工艺获得的快速凝固硅铝合金粉末的尺寸小于50μm。快速凝固的硅铝合金粉末经过550°C和700MPa热压后,获得3种不同成分合金试样的相对密度分别为99.4%,99.2%和94.4%。作为电子封装材料,3种试样的热导率、热膨胀系数和电导率都可以满足应用要求。55%Si-Al合金的热膨胀系数随温度的变化最剧烈,但是该合金具有较好的热导率。90%Si-Al合金的热膨胀系数较小,但是其热导率最差,小于100W/(m·K)。70%Si-Al合金具备热沉材料所应具备的优良的热导率和热膨胀系数的综合性能。     

制取快速凝固微细金属粉末的装置和原理

在研究和分析了多种快速冷凝制粉装置的工作原理后,提出了金属熔体的多级快速凝固过程的成粉理论,井以此理论为基础研制出一系列制取微细金属粉末的新型快速冷凝装置。这类装置能够生产多种非晶、准晶、微晶和微细金属粉末,制粉装置的冷凝速度为10~5~10~6k/s,粉末平均粒度最细可达5~15μm,生产量为2~5kg/min,可连续生产,生产成本和普通气体雾化方法相当。对装置的工作特性进行了详细介绍,其结果表明,由著者发明的多级快速凝固装置既是制取非晶、准晶、和微晶粉末的理想装置,又是制取微细金属粉末的高效装置。     

快速凝固制造贵金属微细粉末

研究了快速凝固高压气体雾化和离心雾化组合制粉设备和技术及其在贵金属微细粉末、电工合金、电子浆料、钎料中的应用,与传统的电解法化学共沉淀法生产银粉和银基电工材料比较,结果表明快速凝固粉末微细有效地扩大了合金元素的固溶度,并具有优异的综合性能。加工工艺中贵金属损耗小、效率高、生产成本低、无环境污染等。因此,利用该技术不仅开发出新材料,而且在改善传统材料性能的同时为规模化生产开辟新途径。     

急冷凝固铝合金粉制造技术简介

简介了急冷凝固粉末铝合金的优点,着重介绍了国外三种急冷凝固制粉法及其基本原理,以及国外研究出的几种快速凝固粉末铝合金的强度和耐应力腐蚀性能,介绍了国内急冷凝固粉末铝合金的发展动态。     

超细金属粉的制法及其特性

一、超细金属粉及其形成过去制取金属粉,采用机械粉碎法或物理、化学等各种方法。由于所生产的份末得到了应用,粉末冶金法作为一种金属加工技术已被重视起来,并在工业上已确定了各种制粉技术及生产各种材料的工艺。在粉末冶金方面使用的粉末一般平均粒度为数十到数百微米,所生产的粉末部具有上述那种范围     

钴基非晶合金粉末压粉铁心的磁性能

日本Epson Atmix公司2004年开发成功的一种新型制粉工艺“SWAP”法，即金属熔体旋淬雾化法，是利用高速旋转水流以高达10^5K／s的冷速实现高速获取金属粉末的方法。此次则研究了几乎为零磁致伸缩成分的Co基非晶合金粉末的制取、粉末和压粉铁心制作条件与其磁特性之间的关系。本研究中所采用的SWAP装置与传统的熔体水雾化制粉法不同之点，在于利用在高速旋转水流中将金属熔滴气体雾化获取粒径达数百μm的粉末。快冷凝固的粉末的合金成分为了进一步降低其铁损，     

氧化锆粉体的制备及其在热障涂层中的应用

分别描述了纳米氧化锆粉体与空心球氧化锆粉体的制备工艺，分析了不同工艺影响氧化锆产物形态、结构、粒度等方面的因素，并将2种粉末制备的涂层分别与传统微结构涂层进行性能对比。在分析由不同氧化锆粉末制备而成的涂层性能时，除了工艺参数外，更多的是考虑初始氧化锆粉末对涂层性能所带来的影响。期待在未来的研究中，能够优化现有或者探索出更优异的制粉工艺，研究出性能更加优良的新型粉末，以期能够提高热障涂层的性能，满足高精尖领域在未来的使用需求。最后，针对不同制粉工艺及不同粉末制备涂层的发展方向进行了展望。     

Sn60Pb40 solder powders produced by the planar flow casting atomization process

Conventional planar flow casting (PFC) is one of rapid solidification processes for the fabrication of microcrystalline or amorphous ribbons. Based on the conventional PFC process, the planar flow casting atomization (PFCA) process has been developed, which is a new rapid solidification process for the production of metal powder directly from alloy melts. A prototype experimental apparatus was designed and manufactured.With the apparatus, Sn60Pb40 alloy solder powders were prepared, and the effects of the main technological parameters on the powder size distribution and morphology were experimentally studied. The experimental investigations indicate that the metal powders produced by the PFCA process can be classified by velocity; and fine spherical tin-lead alloy solder powders can be fabricated by adjusting the technical parameters. The new PFCA process has such features as high productivity and efficiency, low energy consumption, simple operation,short technological process, and large gross yield.     

Effect of particle size variations of gypsum bonded investment powders on metallurgical quality of investment castings

Abstract

In the present work, the effect of particle size distribution parameters of investment powder on the metallurgical characteristics of castings produced by flask mould investment casting process was investigated. The main aim of this study is to establish the relationships between the casting quality and investment powder characteristics. For this purpose, models for tensile, density and surface roughness specimens were prepared in accordance with the standards and these models were moulded by gypsum bonded investment powders. Specimens of sterling silver (92·5Ag–7·5Cu alloy) were subsequently cast into these moulds by centrifugal casting process. After the completion of solidification process, the specimens were tested and results were analysed. The preliminary results illustrate that fineness of investment powders play an important role in determining the metallurgical quality of castings produced by investment casting process.     

镍基高温合金快速凝固粉末颗粒中MC型碳化物相的研究

对等离子旋转电极雾化（PREP）法制备的FGH95镍基高温合金粉末中碳化物的形态、结构、成分及其稳定性进行了实验研究,分析了粉末颗粒凝固过程中的热学参数和非平衡溶质分配对碳化物形成过程的影响．结果表明：快速凝固FGH95合金粉末中亚稳MC型碳化物形态的几何完整度随粉末颗粒尺寸减小由规则形态向复杂形态变化,不同尺寸粉末颗粒中碳化物的形态和数量决定于凝固过程中热学参数的变化和非平衡溶质分配系数的不同．亚稳MC型碳化物在加热作用下发生分解及合金元素再分配,其形态由复杂形状为主转变为规则形态的稳定MC型碳化物．     

Solidification of metal foams

Expansion and contraction phenomena during solidification of liquid metal foams were studied. Such foams were processed by mixing metal powders with TiH₂ powder and compacting the resulting blends, after which the compacted powders were melted. The subsequent foaming process was monitored in situ by X-ray radioscopy. An intermediate expansion stage during solidification was observed. This solidification expansion (SE) could be linked to phase transformations in the alloy. SE was found to depend mainly on the time spent at the foaming temperature before cooling (holding time), the cooling rate and the alloy composition. The interplay between gas shrinkage, solidification shrinkage, gas production by the blowing agent and gas losses due to out-diffusion was identified as the main reason for SE. While the blowing agent had a major influence on SE, gas dissolved in the metal also played a role, since some SE was observed in foams blown without TiH₂ by pure pressure manipulation.     

Micromodel of Simulation on Twin-Roll Continuous Casting Thin Strip Solidification Structure

在研究双辊连铸铝合金薄带工艺凝固过程的基础上,基于金属凝固的基本原理,建立双辊连铸铝合金薄带凝固的异质形核、枝晶尖端的生长动力学(KGT)、柱状晶向等轴晶生长的转变(CET)的解析模型,同时建立基于元胞自动机(CA)的双辊连铸铝合金薄带凝固组织的仿真模型,为双辊连铸薄带凝固组织形成的仿真模拟奠定基础,从而为双辊薄带连铸工艺提供一定的理论指导。同时利用铝合金双辊薄带连续铸轧组织凝固过程验证了数学模拟的可行性。     

Microstructure and mechanical properties of rapidly solidified Mg alloy powders compacted by magnetic pulsed compaction (MPC) method

Gas atomized Mg–Zn_4.3Y_0.7 (at%) alloy powders were consolidated by using a magnetic pulsed compaction (MPC) process, and obtained by rapid solidification not to lose the fine microstructure during the generally conducted thermal consolidation process. MPC is known as one of the most rapid pressing process with the GPa range. The effects of the discharging voltage and thermal pressure on the microstructure, hardness, density and compressive strength were investigated. The experimental results showed that the density increased with increasing the voltage although the sample MPCed still consists of pores especially between the powder boundaries even at the maximum pressure of this investigation. The density was improved further up to 96% to the cast value by the MPC at the maximum voltage. Uniform and fine microstructure formed in the alloy powders as atomized was almost maintained even after the thermal MPC.     

铝合金石膏型精密铸件凝固过程数值模拟与实验验证

应用自行开发的铸件充型及凝固模拟系统,对铝合金石膏型精密铸件的凝固过程进行了数值模拟。采用自行设计制备的多通道自动测温装置,对所模拟的铸件进行现场测温。为了提高模拟精度,对铸件铸型热物性参数进行了实测,并采用最小二乘法进行拟合。通过计算机模拟预测了铸件的缩孔区,分析了铸件缺陷产生的原因,提出了合理的工艺方案,消除了铸件内缩孔的发生。实验验证的结果表明,数值模拟结果与测试值拟合较好     

熔体快淬铜磷合金对ZL109变质效果的影响

采用金属熔融铸造法,用熔体快淬Cu-P中间合金对ZL109活塞合金进行了变质处理,随后对变质后的合金试样进行了金相组织观察和性能检测,并对晶粒细化的机理进行了研究。结果表明:与加入传统Cu-P变质剂相比,在ZL109合金中加入熔体快淬Cu-P变质剂,使组织中的初晶硅和共晶硅得到了更好的细化,增加了界面能,减少了铸造缺陷,使其综合性能得到了进一步的提高。因此,熔体快淬处理是提高Cu-P变质剂变质效果的一种有效方法。     

基于同步辐射CT技术表征3D打印用气雾化TC4粉末的研究

本研究利用气雾化技术制备球形TC4合金粉末,作者利用SEM、同步辐射CT扫描-三维重建等分析手段对异常颗粒粉体以及不同粒径的TC4合金粉末表面和内部的孔缺陷进行了表征。实验结果表明,本研究制备的TC4合金粉末随着粉末粒径减小,粉体表面由凸凹不平的冷凝收缩痕迹渐变为光滑表面,粉体内部的孔隙逐渐减少,且孔隙尺寸也随之减小;经分析,由于雾化过程中凝固与球化时间的差异及飞行轨迹的不同等原因导致了包裹式、连体式、椭球形、卫星粉等异常粉末颗粒的生成;同步辐射CT扫描-三维重建表明,粉末内部的孔隙率和孔隙尺寸随着粉末粒度的增大而增大;作者认为通过调整雾化工艺,使金属熔滴在未开始冷却凝固前彻底雾化破碎,从而能有效解决粉末内部孔隙缺陷的问题。