低成本高性能钛基3D打印粉体材料开发及其SLM成形研究

THE STUDY OF LOW-COST, HIGH_x005fPERFORMANCE TITANIUM-BASED3D PRINTING POWDER MATERIAL AND ITS SLM PROCESSING

侯羽航

11649150

硕士

材料工程

严明

2018-05-27

2018-07-02

哈尔滨工业大学

深圳

钛及钛合金作为一种先进的结构材料，由于其具有优异的比强度、耐蚀性和生物相容性而被广泛应用于航天航空、深海探测和生物医疗等领域。近年来，选区激光熔化技术，作为增材制造 3D 打印中非常重要的一项技术逐渐发展起来。其通过高能激光束来熔化金属粉末，以逐层累积的方式，最终制备形成目标零件，使结构复杂的零件制备加工更加灵活方便。因此，钛及钛合金的选区激光熔化加工也成为了目前研究应用的重点。然而，纯钛（CP-Ti）粉末价格昂贵，制约了钛合金 3D 打印成型的进一步发展和应用。为了降低 3D 打印钛合金的原料成本，本研究以制备流程简单、价格低廉的氢化脱氢（HDH）钛粉作为实验对象，通过高能球磨的手段，对原始 HDH 钛粉体进行了形貌改性，制备出了能够应用于选区激光熔化金属打印机上的新型改性钛基粉体材料。实验探究了高能球磨过程中，各项参数对粉体整形效果的影响，确定了适用于 HDH 钛粉的最佳球磨参数。同时，通过一系列实验设备对改性钛粉的球形度、粉体粒径大小和分布、元素含量以及物相组成等进行了表征。研究发现，在高能球磨过程中，磨球和球磨罐内壁不可避免存在磨损，从而向改性粉末中引入了 Fe、Cr、O 等杂质元素。这些微量元素以合金化元素的形式进入粉体中，在粉体成型加工过程中，影响马氏体相变和组织形貌，从而改变了材料的力学性能。同时，本研究通过 SLM125HL 金属 3D 打印机，对改性粉体进行了选区激光熔化成型，制备出了成型件，确定了最优打印参数，并对成型件的机械性能进行了测试。实验结果表明，改性纯钛粉体成型件具有出色的力学性能，在不损失延伸率的情况下，其布氏硬度较 CP-Ti 成型件增大了约 30 HB，最大抗拉强度提高了约 200 MPa。随后，研究通过 SEM、TEM 和 XRD 等设备，对改性纯钛粉体成型件的组织形貌和物相组成进行了表征，确定了改性纯钛成型件中的马氏体组织为 α′相，并对改性纯钛成型件机械性能的提高做出了解释。最后，研究考察了去应力热处理对改性纯钛粉体成型件的影响。改性纯钛粉体成型件在经过去应力热处理后，加工硬化效果削弱，硬度和抗拉强度降低，而塑性得到了较大的提升。

As advanced structural materials, titanium and titanium-based alloys are widely used in aerospace, offshore drilling, biomedical treatment and other fields, due to their good corrosion resistance, high specific strength, and excellent biocompatibility. In recent years, as a newly three-dimensional additive manufacturing (AM) process, selective laser melting builds up metal via high-energy laser beam in a layer-by-layer manner, increasing design freedom and manufacturing flexibility. Therefore, various studies on SLM of titanium-based alloys have been carried out. However, expensive production costs of commercial titanium powder limit the development of the industry.In order to reduce the raw material costs of titanium alloys fabricated by 3D printing, we choosed HDH Ti powder as the research object, which has a simple preparationprocess and low price. And the morphology of the HDH Ti powder was improved through ball milling treatment, so that the modified HDH Ti powder can be used in SLM 3D printing machine. The research explored the influence of various parameters on the powder shaping effect in high-energy ball milling process and determined the best ball milling parameters for HDH titanium powder. At the same time, a series of experiments were carried out to characterize the sphericity, powder size and distribution, element content and phases composition of the modified HDH Ti powder.It was found that in the process of high-energy ball milling, the abrasion of the the grinding pot’s inner wall and the grinding balls was unavoidable, so the Fe, Cr, O and other impurity elements were introduced into the modified powder. These trace elements entered the HDH Ti powder in the form of alloying elements. During the powder molding process, they will affect the transformation and morphology of the martensitic microstructure to improve the mechanical properties of the Ti alloys. What’ s more, the modified HDH Ti powder was fabricated by SLM ways in a SLM125HL 3D printer and the modified HDH Ti parts were prepared successfully. At the same time, we determined the optimal printing parameters of the modified HDH Tipowder and tested the mechanical properties of the molded parts. The experimental results showed that the modified pure titanium powder molded parts had excellent mechanical properties. The Brinell hardness was increased by about 30 HB and the maximum tensile strength was improved by about 200 MPa compared with the CP-Ti molded parts without any loss of elongation. The microstructure and phase composition of the modified pure titanium molded parts were characterized by SEM, TEM and XRD. It was confirmed that the martensite microstructure in the modified pure titanium molded parts was α′ phase.And the improvement of the mechanical properties of modified pure titanium molded parts were explained.Finally, the influence of destressed heat treatment on the as-cast microstructure of modified titanium molded parts was investigated. After the destressed heat treatment, the work hardening effect was weakened, the hardness and the tensile strength of the modified titanium molded parts were reduced, however, the plasticity was improved.

选区激光熔化 钛及钛合金 粉体改性 球磨 马氏体相变 热处理

Selective laser melting Titanium and titanium alloys Powder modification Ball milling Martensitic transformation Heat treatment

中文

联合培养

南方科技大学

侯羽航. 低成本高性能钛基3D打印粉体材料开发及其SLM成形研究[D]. 深圳. 哈尔滨工业大学,2018.