激光选区熔化成形S136模具钢的成形性能研究

采用激光选区熔化(SLM)技术成形了S136模具钢,对其相组成、微观组织、磨损性能、硬度及腐蚀行为等进行了研究.研究结果表明:水平成形方向上(正面),裂纹易于在熔化道附近产生并垂直于熔化道,因较大冷却速度产生了大量细小的针状马氏体组织,从而有较高的显微硬度(688.20 HV3),在滑动摩擦过程中形成了黏附层,磨损率较低(5 590?m3/(N·m)),在Fe Cl3溶液中发生了均匀腐蚀;而在垂直成形方向上(侧面),裂纹则垂直于SLM层-层堆积方向,显微硬度较低(649.04 HV3),磨损率为25 840?m3/(N·m),在腐蚀液中发生了层间腐蚀.上述结果进一步证实了SLM成形试样存在各向异性.最后,SLM成形了具有复杂的随形冷却流道的模具镶块,注塑应用表明采用该镶块可提升注塑冷却效率25%,降低注塑生产周期20%.     

Anisotropy of nickel-based superalloy K418 fabricated by selective laser melting

Selective laser melting (SLM) is a promising additive manufacturing (AM) technology for fabricating the near net-shaped parts by selectively melting and solidifying a thin powder layer with a high-intensity laser beam according to the CAD data for arbitrary components. In this work, Ni-based superalloy K418 samples were fabricated by selective laser melting (SLM). To evaluate the anisotropic mechanical behavior of the SLM processed K418 samples with layer-by-layer melting, the samples were manufactured parallel (transverse specimens) and vertical (longitudinal specimens) to the building direction on the substrate. The microstructural anisotropy analysis was performed by optical microscopy (OM) and scanning electron microscopy (SEM). Electron backscatter diffraction (EBSD) analysis was used to identify their crystallographic preferred orientation (texture) and to correlate the anisotropy of the mechanical strength with the texture of the material. The results showed that the transverse specimens had slightly higher yield strength, but much significantly higher ductility than that of the transverse specimens with the elongated columnar grains along the building direction.     

激光选区熔化AlMgScZr/AlSi10Mg工艺及性能

开展了含钪铝合金/铝合金多材料激光选区熔化(selective laser melting,SLM)成形研究,分析工艺参数对微观结构和宏观性能的影响.采用HK125型激光选区熔化成形设备,优化激光功率和扫描速率正交窗口,获得多材料样件界面结合最优的体能量密度为117.6 J/mm3.通过光镜观察和能谱仪(energy ...     

Ti-Si-Al合金的显微组织与滑动摩擦学行为研究

研究了Al元素对Ti-Si共晶合金显微组织和滑动摩擦学行为的影响.结果表明,添加7.3%的Al改善了铸态合金的微观组织,形成了由近等轴状Ti5Si3颗粒增强α-Ti(Al,Si)固溶相的有利形态.Al的加入可同时提高合金的强度、硬度和塑性,从而有效抑制了磨损亚表层裂纹的生长,在磨损表面产生了具有保护作用的机械混合层,从而显著地提高了合金的耐磨性和摩擦稳定性.     

选区激光熔化直接成型零件工艺研究

为了提高选区激光熔化成型金属零件致密性与精度,首先对激光扫描单道熔池形成特性进行研究,讨论扫描速度、激光功率对熔池宽度影响,观察到熔池附近无粉区宽度 与熔池宽度 的关系为： = ×（1.5~2）。根据单道熔池成型特性,采用层间错开扫描策略提高零件致密性到近乎100%,显微观察层间与层内熔池搭接紧密。接着成型包括圆柱圆孔等几何单元讨论热影响、原始尺寸对尺寸精度的影响,当光斑补偿 与聚焦光斑直径 满足 时,尺寸精度达到（0.04~0.06）mm。对SLM成型件拉伸强度、延伸率、显微硬度测试分别为636Mpa、15%~20%与HV0. 3 250~285。结果表明,层间错开扫描策略与优化的光斑补偿值对SLM直接成型金属零件的致密性与精度具有较好效果。     

Anisotropy in mechanical properties and corrosion resistance of 316L stainless steel fabricated by selective laser melting

The corrosion behavior and mechanical properties of 316 L stainless steel(SS) fabricated via selective laser melting(SLM) were clarified by potentiodynamic polarization measurements, immersion tests, and tensile experiments. The microstructural anisotropy of SLMed 316 L SS was also investigated by electron back-scattered diffraction and transmission electron microscopy. The grain sizes of the SLMed 316 L SS in the XOZ plane were smaller than those of the SLMed 316 L SS in the XOY plane, and a greater number of low-angle boundaries were present in the XOY plane, resulting in lower elongation for the XOY plane than for the XOZ plane. The SLMed 316 L was expected to exhibit higher strength but lower ductility than the wrought 316 L, which was attributed to the high density of dislocations. The pitting potentials of the SLMed 316 L samples were universally higher than those of the wrought sample in chloride solutions because of the annihilation of MnS or(Ca,Al)-oxides during the rapid solidification. However, the molten pool boundaries preferentially dissolved in aggressive solutions and the damage of the SLMed 316 L in FeCl3 solution was more serious after long-term service, indicating poor durability.     

选择性激光烧结复合粉末法制造合金零件

通过混合Fe,Ni,C单质和粘接剂粉末配制了选择性激光烧结(SLS)用复合粉末,并利用间接SLS方法制备了复合粉末毛坯.经过脱脂、高温烧结和渗铜处理,制造了致密的渗铜Fe-Ni-C合金材料.对零件毛坯的成型与后处理工艺及合金的微观组织和机械性能进行了研究.结果表明:高温烧结中Ni和C能够通过固态扩散固溶到-γFe中,且合金元素分布均匀;合金经900℃固溶并在330℃等温处理1 h后,室温下由下贝氏体组织、沉淀析出的-αCu和Fe-Ni构成;合金材料的极限拉伸强度超过350 MPa,延伸率小于4%.     

Reduction and melting behavior of carbon composite lateritic bauxite pellets

Direct reduction of low-grade lateritic bauxite was studied at high temperature to recover Fe and beneficiate Al₂O₃ slag. The results show that a metallization rate of 97.9% and a nugget recovery rate of 85.1% can be achieved when the reducing and melting temperatures are 1350 and 1480℃, respectively. Moreover, a higher-grade calcium aluminate slag (Al₂O₃=50.52wt%) can also be obtained, which is mainly composed of α-Al₂O₃, hercynite (FeAl₂O₄), and gehlenite (Ca₂Al₂SiO₇). In addition, high-quality iron nuggets have been produced from low-grade lateritic bauxite. The nugget is mainly composed of iron (93.82wt%) and carbon (3.86wt%), with almost no gangue (slag).     

激光熔化沉积成形Cu-Al-Mn-Ti形状记忆合金组织与性能研究

采用激光熔化沉积（laser melting deposition, LMD）成形Cu-Al-Mn-Ti形状记忆合金,研究其组织、冶金缺陷与性能特点。研究表明,LMD成形Cu-Al-Mn-Ti合金的显微组织具有各向异性特征：建造面为柱状晶组织,扫描面为等轴晶组织。这是由于LMD成形过程沉积方向存在较大的温度梯度导致的。LMD成形Cu-Al-Mn-Ti合金的基体组织为β相板条马氏体,并存在大量Cu₂AlMn颗粒状析出相。孔隙缺陷是LMD成形Cu-Al-Mn-Ti合金中主要的冶金缺陷,严重影响了合金的力学性能。热处理可提高LMD成形Cu-Al-Mn-Ti合金的力学性能及形状记忆性能。固溶、时效处理后,LMD成形Cu-Al-Mn-Ti合金的抗拉强度可由453.6 MPa提高至519.5 MPa,形状回复率可由68%提高至97%;当时效温度为500 ℃时,在晶界上开始析出网状α相导致Cu基体中的Al含量增加,使合金的力学性能和形状回复率下降。     

铸造方法对巴氏合金组织及性能的影响

铸造方法对巴氏合金的力学及磨损性能有显著的影响。通过对合金的金相组织观察、相成分的分析，结合磨损试验以及磨损表面形貌分析，研究铸造方法对合金的组织及性能的影响。分析发现离心浇注能明显的细化晶粒，提高合金的耐磨性与减磨性，与静置浇注的合金相比，其磨损量下降了9．6％。     

基于激光选区熔化成型螺杆转子工艺仿真分析

为探究螺杆转子的增材制造方法可行性,以螺杆转子为研究对象,采用正交试验法,通过热力耦合数值模拟,利用Inspire软件对螺杆转子进行了激光选区熔化(SLM)成型仿真模拟,并分析出了一种工艺参数使SLM成型的螺杆转子变形较小且质量较优,模拟验证了方案的可行性。仿真结果表明,在激光功率200 W、扫描速度1.8 m/s、堆积层厚0.09 mm时SLM成型的螺杆转子质量较优,最大变形量为0.596 6 mm,发生在螺杆转子螺旋齿下部外凸齿上,符合形变累积效应;最大等效应力为2.085×10~2 MPa,同样发生在螺旋齿下端面,与实际符合。     

不同载荷下C/C复合材料往返式滑动摩擦行为

以GCr钢球为对偶,在UMT-3微摩擦试验机上测试2种具有不同基体炭结构的C/C复合材料长时间往返式滑动摩擦磨损行为。研究结果表明:在相同载荷下,具有粗糙层热解炭基体的材料A的平均摩擦因数高于具有光滑层/树脂炭基体的材料B平均摩擦因数;在60N时,材料A的平均摩擦因数出现最大值,为0.193;而材料B的平均摩擦因数出现最低值,为0.120;随着载荷的增加,2种材料的平均摩擦因数均出现较大的波动,其中:材料A的平均摩擦因数变化趋势为先升后降,材料B的平均摩擦因数先降后升,但二者的差值随载荷增加先增后减;随着时间的延长,所有试样的摩擦因数均逐渐趋于稳定;材料A的摩擦表面膜较完整、致密,但存在大块摩擦膜剥落或交替堆叠;材料B的摩擦表面较粗糙,形成纤维与基体炭分开堆积成膜形貌。     

铜基复合发光涂层组织及其摩擦磨损性能

利用真空热压烧结技术以铜粉、铜铝混合粉、高铝青铜合金粉和磷光粉体SrAl2O4∶Eu2+,Dy3+、Ba Al2O4∶Eu2+,Dy3+为原料分别制备纯铜、铜铝和高铝青铜系列的铜基复合发光涂层,采用MMW-1A型摩擦磨损试验机测试磷光颗粒掺杂的不同铜基复合涂层的摩擦磨损性能;采用扫描电子显微镜分析摩擦前后复合涂层磨损表面形貌.结果表明:磷光颗粒在3种复合涂层中都是均匀分布于涂层中,与各基体之间形成机械结合;硬质磷光颗粒可以显著增强铜铝基复合发光涂层和高铝青铜基复合发光涂层的耐磨性,其中高铝青铜基复合发光涂层摩擦磨损性能、磨损表面组织均优于铜铝基复合发光涂层,高铝青铜基复合发光涂层的磨损机制主要为磨粒磨损.     

激光选区熔化技术在钴基高温合金制备中的应用进展

钴基高温合金是一种具有较高强度以及良好的耐热腐蚀性能的材料,在生物医疗、航空航天等领域有着广泛的应用。近年来以激光选区熔化技术(selective laser melting, SLM)为代表的增材制造技术快速发展。介绍了SLM技术在钴基高温合金制备中的应用,综述了在SLM过程中不同工艺参数对样品致密度、粗糙度等力学性能的影响,探讨了成形样品是否需要后处理以及后处理所带来的影响等。     

选区激光熔化成型镁合金构件关键技术综述

选区激光熔化成型镁合金构件性能优异且个性化程度高,在工业生产、生物医疗等多个领域具有重要应用意义。首先,对选区激光熔化成型镁合金技术的基本原理与技术特点进行了简要阐释;其次,基于选区激光熔化成型镁合金技术的国内外研究现状,将目前已有研究成果与尚未解决的技术问题进行归纳与总结;再次,对选区激光熔化成型镁合金关键技术进行分析,对主要技术难点及其解决方案进行综述;最后,对选区激光熔化成型镁合金发展趋势进行探讨,指出今后可在以下方面进行深入研究:1)优化现有工艺参数与成型仓风道等机械除尘结构,通过主动抑尘与被动抑尘相结合的方法提高成型质量;2)通过工艺调控减少成型缺陷,制备高性能镁合金构件;3)优化粉末筛分结构,提高成型安全性。     

选区激光熔化TC4生物腐蚀和生物相容性分析

选区激光熔化(SLM)为降低TC4钛合金医用植入体的弹性模量、减小应力屏蔽效应提供了一种有效的解决方案,但这种材料在投入实际应用前尚需有充分的生物安全性评价。采用SLM技术制备出致密度为99.5%的TC4合金,通过电化学实验、溶血实验和细胞毒性实验测试了SLM成形TC4的生物腐蚀性能和生物相容性,并与传统铸轧工艺制备的合金进行了对比。实验结果表明:前者相比于后者有着更好的耐蚀性能,并且SLM成形TC4还具有优良的生物相容性,在生物医用植入物方面展现出很好的应用前景。     

Microstructure and mechanical properties of nickel-based superalloy fabricated by laser powder-bed fusion using recycled powders

Evaluating the recyclability of powders in additive manufacturing has been a long-term challenge. In this study, the microstructure and mechanical properties of a nickel-based superalloy fabricated by laser powder-bed fusion(LPBF) using recycled powders were investigated. Re-melted powder surfaces, satellite particles, and deformed powders were found in the recycled powders, combined with a high-oxygencontent surface layer. The increasing oxygen content led to the formation of high-density oxide inclusions; moreover, printing-induced cracks widely occurred and mainly formed along the grain boundaries in the as-built LPBF nickel-based superalloys fabricated using recycled powders. A little change in the Si or Mn content did not increase the hot cracking susceptibility(HCS) of the printed parts. The changing aspect ratio and the surface damage of the recycled powders might contribute to increasing the crack density. Moreover, the configuration of cracks in the as-built parts led to anisotropic mechanical properties, mainly resulting in extremely low ductility vertical to the building direction, and the cracks mainly propagated along the cellular boundary owing to the existence of a brittle precipitation phase.