电子束粉末床熔融增材制造装备发展综述

电子束粉末床熔融(EB-PBF)增材制造技术具备成形效率高、成形零件应力低等优势,适用于高温合金、高熔点金属的成形,在航空航天、生物医疗等领域具有广阔的应用前景。对电子束粉末床熔融装备的研究情况进行了概述,回顾了EB-PBF装备的发展历程,汇总分析了国内外主要厂商的装备特点及研发进展,综述了抗吹粉、多材料、多束流复合3个方面装备的关键改进与创新方法。在此基础上,着重介绍了离子中和、机械装置屏蔽、近红外预热等新型成形舱改进方案,及其对工艺过程稳定性的提升效果;介绍了新型铺送粉装置改进方案对多材料成形的潜力,即该方案可有效满足多材料成形、成形效率提高等需求;此外提出并实现了多电子枪同幅加热成形、电子束-激光复合成形等突破传统单电子枪加工思路的新型成形技术。最后,总结了该方向的研究进展并对其发展前景和主要发展方向进行了展望。     

GB/T 37463-2019《增材制造塑料材料粉末床熔融工艺规范》国家标准解读

国家标准GB/T 37463-2019《增材制造塑料材料粉末床熔融工艺规范》已于2019年12月1日起正式实施,对进一步提升我国增材制造产业的整体技术水平、质量可靠性和市场竞争力具有重要的现实意义。本文通过对该标准的编制背景、主要内容及国际化等方面进行解读,帮助使用者理解标准原意,并能够准确、熟练运用标准。     

电子束粉末床熔融制备钛铝基金属间化合物研究进展

钛铝基金属间化合物是一种理想的高温结构材料,但因存在室温塑性差、加工困难等不足而限制了其发展与应用。电子束粉末床熔融(Electron Beam Powder Bed Fusion, EB?PBF)技术能够实现近净成形,其加工中的低热应力特点适宜脆性材料的制备,是近年来广受关注的新型钛铝基金属间化合物成形方法。对用电子束粉末床熔融制备的钛铝基金属间化合物进行了介绍,并对近年来发表的以EB?PBF钛铝材料为研究对象的相关文献进行了综述。从工艺、后处理和性能表征等角度对目前的研究现状进行了分析总结,并对未来的研究工作提出了展望。     

聚醚醚酮及其复合材料激光粉末床熔融成形的研究现状与展望

聚醚醚酮(PEEK)及其复合材料因具有优异的力学性能、耐化学腐蚀性及生物相容性而受到广泛关注,然而随着对复杂结构以及个性化PEEK零件的需求日益增加,传统的注塑成形工艺显然已经难以满足高度复杂化与个性化制造的需求。激光粉末床熔融(LPBF)技术为PEEK及其复合材料的成形制造提供了一种新的方法。介绍了激光粉末床熔融工艺的基本原理与PEEK及其复合材料的激光粉末床熔融制备工艺的特点和应用,总结归纳了PEEK及其复合材料的激光粉末床熔融成形装备的发展状况与性能特点,目前的成形装备在预热温度和激光功率等参数方面已经有了很大的提升,可以保证一定的成形精度,但要形成一套成熟的高精密和大尺寸复杂成形系统仍需进一步的研究。基于已有研究,重点阐述了PEEK及其复合材料激光粉末床熔融成形工艺的研究现状,虽然通过温度场和激光参数等成形参数的优化,成形件的性能有了一定的提升,但仍然存在翘曲变形、成形力学性能较低的问题。最后对未来高性能PEEK及其复合材料激光粉末床熔融成形工艺的发展进行了展望。     

高性能聚芳醚酮及其复合材料粉末床熔融成形的现状与挑战

粉末床熔融成形是增材制造技术中的一种,以聚合物及其复合粉末为原材料,可用于特种工程塑料聚芳醚酮及其复合材料的增材制造,无需任何工装和模具即可完成复杂结构制件的直接成形,为航空航天、汽车工业领域内对制件结构优化和快速开发提供了一种解决方案。介绍了粉末床熔融成形聚芳醚酮及其复合材料的国内外研究现状,从成形系统、原材料、成形工艺以及碳纤维增强聚芳醚酮复合材料增强机理与性能等几个方面展开了论述,并对粉末床熔融成形聚芳醚酮及其复合材料面临的挑战进行了分析。     

基于DSP的声发射在线监测系统的研制

声发射信号频率范围宽,要求采样频率高,对其进行在线监测要处理的数据量相当大,对监测系统的信号处理速度和传输速度要求相当高.利用DSP的高速处理能力,把信号的声发射参数提取等初步处理都放在硬件内完成以减少向上位机传输的数据量,从而减少数据传输的时间.论文研究了整个系统的软、硬件设计中的关键问题,并给出了解决方案.     

激光粉末床熔融增材制造高导热银-铜异种金属界面的微观组织和显微硬度研究

银和铜由于其优异的高导电和导热(HETC)特性,被广泛应用于智能电子、可穿戴设备、医疗等关键领域。激光粉末床熔融(LPBF)技术是一种高精度制造异种金属部件的创新技术,拓展了银-铜在新兴高科技领域的应用。本研究采用LPBF技术成功制备无宏观缺陷的Ag7.5Cu/Cu10Sn/Ag7.5Cu银-铜异种金属样件,探究了Ag7.5Cu/Cu10Sn(A/C)和Cu10Sn/Ag7.5Cu(C/A)界面的微观组织对显微硬度的影响。研究发现,高导热基底增强了A/C和C/A界面结合区的熔池流动,减少了孔隙与裂纹缺陷,提高了界面结合强度。界面结合区的梯度晶粒阻碍了微裂纹的扩展,有利于减少裂纹缺陷,晶粒的各向同性使两个界面都具有良好的宏观力学性能。A/C界面更强烈的马兰戈尼对流形成了更宽的结合区,促进了元素的广泛迁移,减少了宏观偏析,使结合区的平均硬度(183.34HV)高于C/A界面的(134.27HV)。本研究为LPBF制备HETC异种金属提供了理论指导和工艺参考。     

基于声发射信号时频图深度学习的桥梁钢桁架焊接节点损伤程度识别

针对桥梁钢桁架疲劳损伤识别难度大、精度低的现状,提出基于声发射信号时频分析与深度学习的钢桁架焊接节点损伤程度识别方法。对桁架节点在桥梁运营状态下产生的声发射信号进行小波变换,表征不同损伤程度信号的时频能量分布模式,然后建立卷积神经网络(convolutional neural network, CNN)模型对时频图进行损伤特征提取,并通过迁移学习思想提升模型的训练效率和学习能力,从而实现桁架焊接节点严重损伤、轻微损伤和噪声工况的准确识别。进一步对模型各卷积层激活区域进行可视化分析,解剖模型的损伤特征学习过程及分类逻辑。某悬索桥中央纵向腹板钢桁架焊接节点现场试验结果表明：相较于利用时域波形进行特征学习的一维卷积神经网络模型,时频图包含了更丰富的损伤信息,所建立的二维卷积神经网络模型对钢桁架焊接节点三种损伤程度的识别准确率超过94%,具有更强鲁棒性和实际应用价值。     

Soft-Magnetic Behavior of Fe-Based Nanocrystalline Alloys Produced Using Laser Powder Bed Fusion

Herein, an extensive experimental study is presented on the influence of the major process parameters of the laser powder bed fusion (LPBF) technique on the bulk density and soft-magnetic properties of Fe-based bulk metallic glasses (BMGs). For this purpose, 81 samples are manufactured using the combinations of different process parameters, that is, layer thickness (t: 50–70 μm), laser power (P: 70–130 W), laser scan speed (v: 900–1100 mm s⁻¹), and hatch spacing (h: 20–40 μm). High bulk density (≥99%) is achieved utilizing low P and v combined with low h and t in order to decrease energy input to the powder, preventing cracks associated with the brittle nature of BMGs. Furthermore, it is indicated that h = 30 μm and v = 1000 mm s⁻¹ play a determining role in acquiring high saturation magnetization (≥200 Am² kg⁻¹). Due to the laser scanning nature of the process, two distinct microstructures evolve, melt-pool (MP) and heat-affected zone (HAZ). According to thermal modeling performed in this study, laser power has the major effect on the thermal development in the microstructure (thermal gradient evolved between the two hatches and the cooling rate from MP through HAZ).     

Evolution of Creep Damage of 316L Produced by Laser Powder Bed Fusion

The damage mechanisms of metallic components produced by process laser powder bed fusion differ significantly from those typically observed in conventionally manufactured variants of the same alloy. This is due to the unique microstructures of additively manufactured materials. Herein, the focus is on the study of the evolution of creep damage in stainless steel 316L specimens produced by laser powder bed fusion. X-ray computed tomography is used to unravel the influence of the process-specific microstructure from the influence of the initial void distribution on creep damage mechanisms. The void distribution of two specimens tested at 600 °C and 650 °C is analyzed before a creep test, after an interruption, and after fracture. The results indicate that the formation of damage is not connected to the initial void distribution. Instead, damage accumulation at grain boundaries resulting from intergranular cracking is observed.     

High-Entropy Alloy-Induced Metallic Glass Transformation: Challenges Posed by in situ Alloying via Additive Manufacturing

In situ alloying and fabricating glassy structures through a layer-by-layer fashion approach are challenging but have high potential to develop novel-graded materials. For the first time, this cost-effective approach is applied to additive manufacturing (AM) of a Zr-based bulk metallic glass (BMG) from high-entropy alloys (HEAs). A newly developed composition of Zr₄₀Al₂₀Cu₂₀Ti₂₀ is fabricated through laser powder bed fusion (LPBF). Process parameters are optimized within a wide range of laser power (50–200 W) as well as scanning speed (50–800 mm s⁻¹). In all printed samples, microscopic and compositional examinations reveal no glass formation, but very fine grains and CuTi and AlTi nanocrystals. Some glassy transitions at the interfaces may be encouraged to occur with proper melting and mixing. However, the main reason for not obtaining a glassy matrix is the substantial proportion of unmelted Zr raw powder throughout the structure as spherical particles. Consequently, glass formation can be hindered by a considerable amount of compositional deviation. During LPBF, in situ alloying poses significant challenges to developing BMGs. Hence, the various stages of the process, including raw material specifications, laser settings, and process parameters, should be investigated further.