Ar气流量对电动机用SLM制备Ti6Al4V合金性能的影响

为了提高电动机用激光选区熔融(SLM)制备Ti6Al4V合金的拉伸力学综合性能,通过控制变量的方式研究Ar气流量对其微观组织和拉伸力学性能的影响。研究结果表明:所有Ti6Al4V合金都形成了α’白色组织,控制Ar气流量为6 L/min有助于马氏体发生原位分解。此时形成了大量的α’组织以及部分α与β相,所有组织的宽度都接近0.5μm。在Ti6Al4V合金中形成了具有密排六方晶格的α组织,在SLM成形阶段存在大量α’组织转变成(α+β)结构的情况。Ar气流量为6 L/min下合金达到了更高延伸率。当能量密度增大到6 L/min之后,靠近撕裂棱区域产生了数量更多的韧窝,表明提高能量密度能够优化合金韧性,此时断口组织上产生韧窝没有出现解离面。该研究对优化SLM制备钛合金的工艺参数具有一定的理论意义。     

Ti6Al4V高速干滑动摩擦磨损特性研究

对Ti6Al4V合金在高速干滑动摩擦条件下进行了系统的磨损性能测试,研究了载荷和速度对Ti6Al4V合金的摩擦磨损机制的影响,对Ti6Al4V合金的磨损表面、纵剖面进行了显微分析及X-衍射分析,实验结果表明,Ti6Al4V合金的磨损率和摩擦表面温度随着载荷和速度的升高而增加,摩擦表面的温度最高达到1044℃,磨损表面出现"蘑菇头"的磨损现象,表面出现裂纹及剥落坑,表层及次表层出现裂纹,组织变得粗大,磨损纵剖面析出Ti3O,Ti6O,VO0.53,VN等化合物.     

Ti6A14V合金的低温超塑性拉伸变形行为

在700℃-850℃的温度范围内对Ti-6%Al-4%V(质量分数)合金板材进行超塑性拉伸试验,研究了应变速率为3×10-4-5×10-38-1条件下的拉伸变形行为.结果表明:Ti6A14V合金在空气中表现出良好的低温超塑性变形能力.在800℃初始应变速率ε=5×10-4s-1条件下,延伸率达到536%.在较低的700℃下变形(ε=5×10-4s-1),延伸率仍然超过了300%.在整个变形温度区间内,应变速率敏感性指数m均为0.3左右,最大值为0.63.在850℃变形激活能与晶界自扩散激活能十分相近,表明晶界扩散控制的晶界滑动是超塑性变形的主要机制.在700-750℃,变形激活能远大于晶界自扩散激活能,位错运动是激活能升高的原因.在800℃变形的激活能介于两者之间,表明随着温度的降低变形机制逐渐发生改变.     

Ti6Al4V合金SIM熔炼过程中氧元素的溶解与控制

建立了氧元素溶解到Ｔｉ６Ａｌ４Ｖ合金中的热力学模型,并以此计算了ＩＳＭ熔炼过程中氧元素在ＴｉＡｌ４Ｖ合金熔体中熔解度,分析了影响氧元素在ＴｉＡｌ４Ｖ合金中溶解度的几个因素。结果表明,熔化室内氧气分压是决定Ｔｉ６Ａｌ４Ｖ合金氧含量的主要因素,需要合理控制,同时提出了利用多次抽真空反充氩气以降低熔化室内氧气分压的方法,该方法在降低Ｔｉ６Ａｌ４Ｖ合金中的氧含量方面取得明显效果。     

激光冲击处理对Ti6Al4V力学性能的影响

通过对钛合金Ti6Al4V的激光冲击处理,研究了激光冲击处理工艺对钛合金Ti6Al4V力学性能的影响.实验表明:激光冲击处理能有效提升Ti6Al4V的力学性能,在激光功率密度由1.15GW/cm2增加到2.31GW/cm2过程中,其冲击波峰值压力线性增加,表面最大残余压应力也相应增大,最高达-264MPa,表面硬化层的显微硬度高达510Hv,硬化层深度约为0.25mm,经过激光冲击处理后硬度相对于原始钛板提高了64%,随着激光能量的增加,冲击区域的抗拉强度极大增强,塑性降低.     

置氢Ti6Al4V合金的微观组织演变规律

为研究置氢Ti6Al4V合金的高温加工改性机理,从微观组织的角度对合金进行了对比分析.利用OM、SEM、XRD等研究了置氢对Ti6Al4V合金变形前后微观组织演变的影响.研究结果表明:氢的加入不仅使置氢Ti6Al4V合金中β相比例明显增大,而且改变了α相与β相之间的电势差,在氢含量为0.3%~0.5%两相颜色将发生互换,氢含量增加到0.50%以上时,合金中将出现面心立方结构的δ氢化物;随氢含量的增加,合金超塑拉伸变形后的组织由α+β两相等轴晶粒变为粗大的β晶粒,造成α与β界面的协调能力下降,并改变了合金的变形机制.     

Ti6Al4V磁控溅射沉积Ti-Ag-(N)薄膜及其抗菌性的研究

利用磁控溅射法在医用钛合金Ti6Al4V表面制备Ti-Ag、Ti-Ag-N薄膜。采用扫描电子显微镜、X射线衍射、X射线能量色散谱、X射线光电子能谱分析薄膜的表面形貌、微观结构、化学成分和化学价态。采用平板计数法测试薄膜对大肠杆菌的抗菌性。研究结果表明:薄膜主要由Ti、Ag、(N)组成,且Ag是以Ag~0形式存在;与基材相比,两种薄膜对大肠杆菌(E.coli)均有抗菌性,且Ti-Ag-N薄膜表现出更优越的抗菌性能。     

超疏水Ti6Al4V表面的制备及其润湿性

为了使Ti6Al4V合金具有超疏水特性,采用激光技术加工规则点阵状纹理,然后采用自组装技术在试样表面制备自组装分子膜,得到了超疏水Ti6Al4V表面.激光加工构造的微米级点阵结构规整,形成了具有一定高度的类似锥台或柱状的凸起.通过激光加工和沉积自组装分子膜,Ti6Al4V试样表面的水接触角显著增大,最大可达到151°.将测得的接触角与分别用Wenzel模型和Cassie模型计算的理论值进行比较,实测结果更接近Cassie模型的结果.通过改变激光加工表面微结构的参数,可以控制表面接触角的大小.随着表面粗糙度值的增大,接触角呈增大趋势.当表面粗糙度大于4μm时,接触角均大于150°,形成超疏水表面.     

Ti6Al4V表面纹理制备及其润湿性

采用激光加工技术在Ti6Al4V表面分别加工直线、网格和具有规则点阵状结构的表面纹理,采用自组装技术制备自组装分子膜。采用扫描电镜、形貌分析仪和接触角测量仪对成膜后的钛合金表面进行形貌和接触角的表征与测量。结果表明,通过激光加工和沉积自组装分子膜,可显著增大Ti6Al4V的水接触角。其中直线纹理的试样表面水接触角可达124.8°,网格纹理的试样表面接触角可达126.1°,点阵状纹理的试样表面接触角可达151.6°。表面接触角与表面粗糙度相关,随着表面粗糙度值的增大,接触角呈增大趋势,当表面粗糙度>4μm时,接触角均>150°,形成超疏水表面。     

Effect of calcium-ion implantation on the corrosion resistance and bioactivity of the Ti6Al4V alloy

The corrosion resistance and bioactivity of Ti6Al4V alloy after calcium-ion implantation were examined. Polished samples were implanted with a dose of 10¹⁷ Na⁺/cm² at a beam energy of 25 keV. The chemical composition of the surface layer formed during the implantation was determined by XPS and SIMS. The bioactivity of the samples was evaluated by soaking them in a simulated body fluid (SBF) at 37 °C for 168 and 720 h. The corrosion resistance in SBF at 37 °C was determined by electrochemical methods after exposure in SBF for various times. The surfaces of the samples before and after examinations were observed by optical microscopy, SEM-EDS and AFM.The results of the corrosion examinations indicated that under stationary conditions and after short-term exposures, the calcium-ion implanted titanium alloy had an increased corrosion resistance, but during the anodic polarization, calcium-implanted samples underwent pitting corrosion. The microscopic observations show that the precipitations of calcium phosphates are present on the surface, but they do not form a continuous layer.     

Ti6Al4V基体及其改性试样的冲击磨损行为分析

在Ti6Al4V合金基表面制备了N＋注入与氮化层、TiN膜及DLC膜,进行小载荷反复冲击,分析不同冲击周次下磨痕形貌及磨坑深度,比较磨损性能。结果表明疲劳磨损是反复冲击条件下实验试样的共同失效机制,主要表现为疲劳剥落。改性后试样的抗冲击磨损能力较基体材料均有提高,其中N＋注入与氮化的＂长程强化效应＂使试样在较高冲击周次保持良好的抗磨性能;晶态结构TiN膜层由于较高的表层硬度,提高了试样的耐磨性,尤其是较低的冲击周次下;DLC膜的特殊非晶态结构,使其在整个冲击过程中具有小的磨损深度,高的失效周次。     

钛合金微弧氧化膜成分特性分析

钛合金微弧氧化膜层硬度大、耐蚀性好、电绝缘性好,可用于耐磨、耐蚀零件的处理.介绍了钛合金微弧氧化技术现状,采用引进设备,通过控制电压、电流密度、电解液浓度等参数在Ti6Al4V表面生成了膜层;测试了膜层的厚度、粗糙度、显微硬度及绝缘电阻值;采用X射线衍射及扫描电镜并结合能谱仪研究了膜层的结构、形貌及元素;分析了膜层的形成机理.结果表明,膜层厚度为22 μm,粗糙度Ra为2.0 μm,显微硬度为HV 2 200,绝缘电阻值为5 MΩ,包含非晶相和晶相-钛组织,是由膜层基体和大量的直径只有几微米的孔洞组成,主要包含O,Si,Ti和Al元素.     

Ultrasonic Assisted Electrical Discharge Machining of Ti–6Al–4V Alloy

In this research, an attempt was made to investigate the influence of copper tool vibration with ultrasonic frequency on output parameters in the electrical discharge machining of Ti–6Al–4V. The selected input parameters for the experiment comprise of ultrasonic vibrations of tool, current and pulse duration and the outputs are tool wear ratio (TWR), material removal rate (MRR), and stability of machining process and surface integrity of a workpiece, including surface roughness, thickness of recast layer, and formation of micro cracks. Scanning electron microscope and X-Ray diffraction were employed to examine the surface integrity of the workpiece. The results revealed that tool vibration with ultrasonic frequency enhances MRR via increasing normal discharges and decreasing arc discharges and open circuit pulses. Also, by using ultrasonic vibrations in finishing regimes, the density of cracks and TWR decrease while in roughing regimes, the thickness of recast layer, density of cracks, and TWR increase.     

Customised titanium implant fabricated in additive manufacturing for craniomaxillofacial surgery

Customised implants manufacture has always presented difficulties which result in high cost and complex fabrication, mainly due to patients' anatomical differences. The solution has been to produce prostheses with different sizes and use the one that best suits each patient. Additive manufacturing (AM) as a technology from engineering has been providing several advancements in the medical field, particularly as far as fabrication of implants is concerned. The use of additive manufacturing in medicine has added, in an era of development of so many new technologies, the possibility of performing the surgical planning and simulation by using a three-dimensional (3D) physical model, very faithful to the patient's anatomy. AM is a technology that enables the production of models and implants directly from the 3D virtual model (obtained by a Computer-Aided Design (CAD) system, computed tomography or magnetic resonance) facilitating surgical procedures and reducing risks. Furthermore, additive manufacturing has been used to produce implants especially designed for a particular patient, with sizes, shapes and mechanical properties optimised, for areas of medicine such as craniomaxillofacial surgery. This work presents how AM technologies were applied to design and fabricate a biomodel and customised implant for the surgical reconstruction of a large cranial defect. A series of computed tomography data was obtained and software was used to extract the cranial geometry. The protocol presented was used for creation of an anatomic biomodel of the bone defect for the surgical planning and, finally, the design and manufacture of the patient-specific implant.     

选区激光熔化Ti6Al4V合金的各向异性

采用金相分析和拉伸测试等方法,分析了激光熔化成形Ti6Al4V试样在不同沉积高度、不同方向截面的组织和性能。结果表明,平行于沉积方向的截面其组织类似柱状晶,具有较弱的织构特征;垂直于沉积方向的截面其组织为块状结构,具有较强的织构特征。选区激光熔化成形Ti6Al4V合金在沉积高度方向上的力学性能受柱状晶尺寸的影响,随着沉积高度的增大其抗拉强度和屈服强度先降低后升高而延伸率先提高后降低。织构和熔合不良等缺陷,使试样垂直于沉积方向上的强度和塑性都比平行于沉积方向的试样高。