It is well-known that grain refiners can tailor the microstructure and enhance the mechanical properties of titanium alloys fabricated by additive manufacturing (AM). However, the intrinsic mechanisms of Ni addition on AM-built Ti–6Al–4V alloy is not well established. This limits its industrial applications. This work systematically investigated the influence of Ni additive on Ti–6Al–4V alloy fabricated by laser aided additive manufacturing (LAAM). The results showed that Ni addition yields three key effects on the microstructural evolution of LAAM-built Ti–6Al–4V alloy. (a) Ni additive remarkably refines the prior-β grains, which is due to the widened solidification range. As the Ni addition increased from 0 to 2.5 wt. %, the major-axis length and aspect ratio of the prior-β grains reduced from over 1500 μm and 7 to 97.7 μm and 1.46, respectively. (b) Ni additive can discernibly induce the formation of globular α phase, which is attributed to the enhanced concentration gradient between the β and α phases. This is the driving force of globularization according to the termination mass transfer theory. The aspect ratio of the α laths decreased from 4.14 to 2.79 as the Ni addition increased from 0 to 2.5 wt. %. (c) Ni as a well-known β-stabilizer and it can remarkably increase the volume fraction of β phase. Room-temperature tensile results demonstrated an increase in mechanical strength and an almost linearly decreasing elongation with increasing Ni addition. A modified mathematical model was used to quantitatively analyze the strengthening mechanism. It was evident from the results that the α lath phase and the solid solutes contribute the most to the overall yield strength of the LAAM-built Ti–6Al–4V–xNi alloys in this work. Furthermore, the decrease in elongation with increasing Ni addition is due to the deterioration in deformability of the β phase caused by a large amount of solid-solution Ni atoms. These findings can accelerate the development of additively manufactured titanium alloys.

以SrCO3和ZrO2为原料、二者摩尔比为2:1，在1 400 ℃通过高温固相合成法制备了锆酸锶质氧化物耐火材料，并在1 750 ℃烧成制备坩埚，将其用于富钛含量Ti2Ni合金的感应熔炼，并与锆酸钡坩埚在合金熔炼的稳定性表现进行了对比研究。通过X射线衍射仪，扫描电子显微镜和光学显微镜，分析研究了锆酸锶质氧化物耐火材料的相组成及微结构，耐火材料与钛合金熔体的界面反应层及熔体受耐火材料的污染程度。结果表明：锆酸锶质氧化物耐火材料主要由Sr3Zr2O7、Sr2ZrO4和SrO三相共存，动力学反应时间不足是导致Sr2ZrO4单相无法生成的主要原因。锆酸锶质氧化物和锆酸钡坩埚熔炼Ti2Ni合金后的坩埚受侵蚀层分别为1 250 μm和2 120 μm，而合金中氧含量平均值分别为0.332%(质量分数)和0.566%。说明锆酸锶质氧化物耐火材料对Ti2Ni合金熔体稳定性优于锆酸钡耐火材料。

Several detailed studies have comprehensively investigated the benefits and limitations of laser-assisted machining (LAM) of titanium alloys. These studies have highlighted the positive impact of the application of laser preheating on reducing cutting forces and improving productivity but have also identified the detrimental effect of LAM on tool life. This paper seeks to evaluate a series of the most common cutting tools with different coating types used in the machining of titanium alloys to identify whether coating type has a dramatic effect on the dominant tool wear mechanisms active during the process. The findings provide a clear illustration that the challenges facing the application of LAM are associated with the development of new types of cutting tools which are not subjected to the diffusion-controlled wear processes that dominate the performance of current cutting tools.

Complex thin-walled titanium alloy components play a key role in the aircraft, aerospace and marine industries, offering the advantages of reduced weight and increased thermal resistance. The geometrical complexity, dimensional accuracy and in-service properties are essential to fulfill the high-performance standards required in new transportation systems, which brings new challenges to titanium alloy forming technologies. Traditional forming processes, such as superplastic forming or hot pressing, cannot meet all demands of modern applications due to their limited properties, low productivity and high cost. This has encouraged industry and research groups to develop novel high-efficiency forming processes. Hot gas pressure forming and hot stamping-quenching technologies have been developed for the manufacture of tubular and panel components, and are believed to be the cut-edge processes guaranteeing dimensional accuracy, microstructure and mechanical properties. This article intends to provide a critical review of high-efficiency titanium alloy forming processes, concentrating on latest investigations of controlling dimensional accuracy, microstructure and properties. The advantages and limitations of individual forming process are comprehensively analyzed, through which, future research trends of high-efficiency forming are identified including trends in process integration, processing window design, full cycle and multi-objective optimization. This review aims to provide a guide for researchers and process designers on the manufacture of thin-walled titanium alloy components whilst achieving high dimensional accuracy and satisfying performance properties with high efficiency and low cost.

采用脉冲激光偏移镁侧并添加铜中间层的方法对镁合金和钛合金进行激光对接焊接,研究了界面元素扩散和反应特点,分析了铜中间层厚度对接头组织和力学性能的影响及接头断裂的主要原因。结果表明:铜中间层的加入改善了焊缝/钛合金界面的组织,增大了界面附近Ti-Cu化合物的含量;随着铜中间层厚度增大,界面处Ti2Cu反应层的厚度逐渐增大并变得连续,且接头的断裂位置从界面反应层转变到焊缝区;当铜中间层的厚度达到30 μm时,接头的抗拉强度达到了121 MPa。

通过激光熔化沉积技术,在Ti-6Al-4V(TC4)基材表面原位合成了NiTi基金属间化合物涂层,并研究了其微结构特征、显微硬度和电化学腐蚀性能。研究结果表明,涂层主要由NiTi、Ni₃Ti、NiTi₂和Ni₄Ti₃等金属间化合物组成;涂层的显微硬度达到800 HV,比TC4基材的提高了约1.3倍;涂层表面生成了不均匀钝化膜,出现大量点蚀,故该涂层的耐蚀性能与TC4基材的相比略有下降。

激光选区熔化(SLM)作为一种直接制造金属构件的增材制造技术,可实现复杂结构件的高精度制造。介绍了SLM技术的发展现状及原理,从材料体系、成形工艺、显微组织及力学性能方面论述了国内外钛及钛合金SLM技术的研究及应用现状,总结了SLM技术加工钛及钛合金过程中存在的问题,及对其未来的发展趋势进行了展望。

利用高功率、短脉冲Nd∶YAG激光对TC17钛合金进行了激光喷丸(LP)处理, 并在400 ℃温度下进行了恒温氧化增重试验, 分析了LP对钛合金恒温氧化性能的影响。研究结果表明, 相较于LP前, LP后TC17钛合金在400 ℃下的恒温氧化增重减小了64.9%; 材料表面的氧化膜更加致密, 能更有效阻挡氧的扩散。表面能谱分析结果显示, LP后氧化试样表面的Cr比未喷丸处理的多。大量的Cr能改善氧化层与基体间的附着力, 因此LP可以改善钛合金的恒温抗氧化性能。

镁/钛(Mg/Ti)异种金属既不反应也不互溶的特性制约着两者之间的冶金结合和可靠连接。为解决这一问题并拓宽Mg、Ti的应用，采用富铝镁基焊丝对Mg/Ti实施激光填丝搭接焊，实现了Mg/Ti之间的连接。在此基础上，利用扫描电镜对界面进行观察分析，并利用Miedema二元热力学模型和Toop三元热力学模型对调控元素Al在界面处的扩散及连接机理进行研究。结果表明，在焊丝中调控元素Al的参与下，Mg/Ti界面处形成超薄的反应层，元素线扫描结果显示Al在靠近Ti一侧界面处富集，实现了界面的冶金结合。热力学计算结果显示，在界面处Al-Ti化合物具有更大的析出驱动力，而且Al在富Ti一侧的化学势较低，且Al的界面偏聚导致Al的化学势进一步下降，表明Al的扩散方式为上坡扩散。

钛合金由于比强度高和耐蚀性好而在航空航天、石油化工等领域得到广泛的应用。但其表面不耐磨而限制了其更为广泛的应用。将经过激光处理和未经激光处理的TB5合金放置在一种特殊固体介质进行渗氧处理, 通过研究炉的加热条件和前处理过程, 分析其对TB5合金的显微组织和硬度的影响。此外, 在相同实验条件下与TA4合金进行了比较。实验结果表明, 经激光处理和未经激光处理的钛合金在相同温度和氧化时间下进行渗氧处理均获得了一层强化层, 且经激光处理后的试样在进行渗氧处理后渗氧层的厚度和表面硬度值明显要高于未经激光处理的试样。在相同实验条件下, TA4合金比TB5合金更容易渗氧。