脉冲电流对0.27%置氢Ti-6Al-4V合金变形行为的影响

对0.27%(质量分数)置氢Ti-6Al-4V合金进行压缩试验,对断口进行观察与分析,研究了脉冲电流对其变形行为的影响。结果表明,脉冲电流使0.27%置氢和未置氢Ti-6Al-4V合金的变形抗力降低和压缩延伸率提高。脉冲电流产生的焦耳热效应,是影响0.27%置氢Ti-6Al-4V合金力学性能变化的主要原因。由于电致塑性效应的影响,Ti-6Al-4V合金的断裂形式由延性脆性沿晶断裂向准解理穿晶断裂转变,但是对于0.27%置氢Ti-6Al-4V合金,由于在低温条件下氢脆的影响其准解理断裂特征不如未置氢Ti-6Al-4V合金的明显。     

TI-6Al-4V合金置氢-除氢组织与力学性能

为研究除氢处理对置氢钛合金组织与性能的影响,对Ti-6Al-4V合金在不同参数条件下进行了置氢与除氢处理,采用光学显微镜分析了置氢-除氢处理过程中Ti-6Al-4V合金微观组织的演化规律,通过室温拉伸试验研究了置氢-除氢处理后Ti-6Al-4V合金的力学性能,探讨了Ti-6Al-4V合金置氢-除氢组织与力学性能之间的相...     

基于α'组织设计适于激光立体成形的新型高塑性Ti-4.13Al-9.36V合金

为了提高Ti-6Al-4V合金的加工硬化率和塑性,基于其团簇成分式12[Al-Ti₁₂](AlTi₂)+5[Al-Ti₁₄](V₂Ti)设计成分式为4[Al-Ti₁₂](AlTi₂)+12[Al-Ti₁₄](V₂Ti)的(Ti-4.13Al-9.36V, %)合金,采用激光立体成形工艺制备Ti-4.13Al-9.36V和Ti-6.05Al-3.94V(对比合金),研究了沉积态和固溶温度对其显微组织和力学性能的影响。结果表明,沉积态Ti-4.13Al-9.36V和Ti-6.05Al-3.94V合金的显微组织均由基体外延生长的初生β柱状晶和晶内细小的网篮α板条组成。Ti-6.05Al-3.94V合金的初生β柱状晶的宽度约为770 μm,α板条的宽度约为0.71 μm;而Ti-4.13Al-9.36V合金的初生β柱状晶的宽度显著减小到606 μm,α板条的宽度约为0.48 μm。经920℃固溶-淬火处理后Ti-6.05Al-3.94V样品的显微组织为α'+α相,其室温拉伸屈服强度约为893 MPa,抗拉强度约为1071 MPa,延伸率约为3%。经750℃固溶-淬火处理后Ti-4.13Al-9.36V样品的显微组织为α'+α相,与α'马氏体相比,应力诱发的α'马氏体能显著地提高合金的加工硬化能力,其室温拉伸屈服强度约为383 MPa,抗拉强度约为 989 MPa,延伸率达到了17%。这表明,根据团簇理论模型调控α'+α的显微组织能有效提高激光立体成形Ti合金的加工硬化能力和塑性。     

置氢对Ti6Al4V合金室温组织的影响

通过在钛合金中引入临时元素氢,可以改变钛合金的相组成,进而改变钛合金的力学性能和加工性能.利用OP、XRD和TEM研究了固态置氢后Ti6Al4V合金的微观组织变化.研究表明:随氢含量的增加,合金中的β相含量增加,在置氢0.302%及0.490%(质量分数)的试样中发现面心立方(fcc)的氢化物δ,及大量的斜方结构的马氏体α",未发现亚稳态的氢化物γ.提出了一种基于扩散的由βH共析转变生成α及fcc结构的片状氢化物δ的机制,并指出氢的引入可能诱发马氏体转变.     

Ti-6Al-4V合金的吸氢行为和氢化过程中的相变

本文研究了 Ti-6Al-4V 合金在氢压为一个大气压下的吸氢行为和氢化过程中的相变,结果发现:合金在570℃有一个吸氢峰;氢化过程中氢固溶于β相,使 d_(200)面间距增大;氢化物(γ)在α相内析出,为 fcc 结构(α=440.1pm),与基体的取向关系为{(?)}_α//{(?)}γ,<(?)>α//<110>γ;充氢使α,β相明暗衬度和充氢前比较正好相反;充氢后合金出现 Ti_3Al 有序结构。     

氢辅助气体捕捉法制备泡沫Ti-6Al-4V及其机理研究

对气体捕捉法制备泡沫Ti-6Al-4V过程中未发泡的坯料进行置氢处理,然后再进行等温发泡。运用阿基米德原理对发泡后坯料孔隙率进行测量。通过OM和SEM对坯料内部微观特征进行观察。研究氢对坯料等温发泡过程的影响规律及作用机制。结果表明:质量分数为0.15%的氢能将坯料最佳发泡温度降低60℃,即在890℃下孔隙率可达到32.88%(体积分数),孔径达到160μm,孔洞分布弥散的泡沫Ti-6Al-4V。主要机理:氢以降低坯料(α+β)/β相转变温度的方式,提高基体内塑性较好的β相比例,并能在一定程度上软化α相,降低坯料高温流变应力,进而降低最佳发泡温度。     

钛材晶粒超细化的氢处理法

晶粒超细化是金属材料不牺牲延性和韧性而达到高强化的唯一有效方法.氢处理法即是这种方法之一.此方法的主要工艺路线为:吸氢→固溶(马氏体化)→热轧→脱氢.Ti-6Al-4V合金经过各种氢化处理,晶粒可细化到0.3～0.5μm,屈服强度大大提高,且呈现出极佳的超塑性性能.     

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.     

Ti-6Al-4V合金表面超声振动滚压强化研究

采用超声振动滚压加工技术对Ti-6Al-4V合金表面进行处理,探究该项技术对Ti-6Al-4V合金表面质量的影响。通过对该工艺加工前后的Ti-6Al-4V合金进行表面粗糙度参数、XRD图谱、截面微观形貌、表层残余应力及显微硬度的对比分析,结果表明:经该工艺处理后的合金表面各项粗糙度参数皆有明显降低;加工后的合金表面XRD图谱的衍射峰减弱且宽化,衍射角向高角度方向偏移;加工后的合金表层β相组织相较加工前明显细化,且随着深度增加β相组织逐渐增大;在距离表面约50μm位置的残余应力值最大可达到-967 MPa;加工后的合金表面显微硬度可达到421HV,且在0~140μm的深度范围内,显微硬度随着深度的增加逐渐减小至与基体硬度一致。经超声振动滚压加工后的Ti-6Al-4V合金表面质量显著提高,有利于提高其零部件的使用性能。     

航空用钛合金紧固件选材分析

分析了三类钛合金紧固件材料的应用概况、材料特性和紧固件制造技术特点.结果表明BT16钛合金制造冷变形强化紧固件的工作量和成本最低;采用热镦和真空固溶时效制造的Ti-6Al-4V紧固件的密度最低,强度和疲劳性能最好;采用β合金制造的螺栓综合水平要比BT16和Ti-6Al-4V紧固件低,但可用其冷镦铆钉在需要的场合使用.     

Effects of hydrogenation temperature on room-temperature compressive properties of CMHT-treated Ti6Al4V alloy

Compression tests were performed at room temperature to investigate the effects of hydrogenation temperature on compressive properties of Ti6Al4V alloy treated by continuous multistep hydrogenation treatment (CMHT).Pressure-composition isotherms and microstructures were also studied.Results showed that the equilibrium hydrogen pressure increased,and the hydrogen absorption rate decreased with the increase of hydrogenation temperature.The amounts of β phase and α'martensite increased first and then decreased when Ti6Al4V alloy was treated by four times CMHT with the increase of hydrogenation temperature.Hydrogenation temperature played a different role on the compressive properties of CMHT-treated Ti6Al4V alloy.The ultimate compression of Ti6Al4V alloy treated by 11 times CMHT at 850 ℃ increased by 83.3 ％ as compared to the as-received Ti6Al4V alloy.The compressive properties of Ti6Al4V alloy were dependent on the amounts of different phases and microstructures when Ti6Al4V alloy was treated by CMHT at different temperatures.     

激光选区熔化颗粒增强钛基复合材料的抗压性能EI北大核心CSCD

采用激光选区熔化(selective laser melting,SLM)制备LaB_(6)颗粒增强钛基复合材料,研究不同激光能量密度下试样的致密化行为、显微组织、物相及其在准静态和动态冲击条件下的力学性能。结果表明:LaB_(6)颗粒的加入在一定程度上改变了材料的致密化行为,过高或者过低的激光能量密度均会降低试样的致密度。而增强颗粒的加入细化了基体材料的晶粒,钛合金的初始β晶粒及针状α晶粒的晶界有一定程度的弱化,从而导致复合材料的屈服强度和极限强度增加,但延展性降低,同时复合材料表现出明显的应变率强化效应。与SLM成型Ti-6Al-4V合金相比,复合材料在塑性段的应变硬化效应和失稳阶段的脆性断裂特征更显著,为激光增材制造高性能颗粒增强钛基复合材料的动态抗压性能优化提供理论基础。     

Hydrogen Treatment of Cast Ti-6Al-4V Alloy

This paper presents the results of an investiga-tion of the effect of hydrogen treatment onmicrostructures and tensile and low cycle fatigueproperties of a Ti-6Al-4V cast alloy.The phasetransformation and the refining mechanism of thecast microstructure during the process of hydrogentreatment were studied.It was found that afterhydrogen treatment,the coarse Widmanstttenstructure of the as-cast Ti alloy was transformedinto a very fine and equiaxed α+β microstructurewithout any GBα phase.The tensile strength andductility and the low cycle fatigue life of thehydrogen treated specimens were significantly im-proved.     

Microstructure and properties of Ti-6Al-4V fabricated by low-power pulsed laser directed energy deposition

Thin-wall structures of Ti-6Al-4V were fabricated by low-power pulsed laser directed energy deposition. During deposition, consistent with prior reports, columnar grains were observed which grew from the bottom toward the top of melt pool tail. This resulted in a microstructure mainly composed of long and thin prior epitaxial β columnar grains (average width ≈200 μm). A periodic pattern in epitaxial growth of grains was observed, which was shown to depend upon laser traverse direction. Utilizing this, a novel means was proposed to determine accurately the fusion boundary of each deposited layer by inspection of the periodic wave patterns. As a result it was applied to investigate the influence of thermal cycling on microstructure evolution. Results showed that acicular martensite, α' phase, and a small amount of Widmanstätten, α laths, gradually converted to elongated acicular α and a large fraction of Widmanstätten α laths under layer-wise thermal cycling. Tensile tests showed that the yield strength, ultimate tensile strength and elongation of Ti-6Al-4V thin wall in the build direction were 9.1%, 17.3% and 42% higher respectively than those typically observed in forged solids of the same alloy. It also showed the yield strength and ultimate tensile strength of the transverse tensile samples both were ˜13.3% higher than those from the build direction due to the strengthening effect of a large number of vertical β grain boundaries, but the elongation was 69.7% lower than that of the build direction due to the uneven grain deformation of β grains.     

Fibroblast Adhesion and Proliferation on a New β Type Ti-39Nb-13Ta-4.6Zr Alloy for Biomedical Application

Cell attachment and spreading on Ti-based alloy surfaces is a major parameter in implant technology. Ti-39Nb-13Ta-4.6Zr alloy is a new β type Ti alloy developed for biomedical application. This alloy has low modulus and high strength, which indicates that it can be used for medical purposes such as surgical implants. To evaluate the biocompatibility and effects of the surface morphology of Ti-39Nb-13Ta-4.6Zr on the cellular behaviour, the adhesion and proliferation of rat gingival fibroblasts were studied with substrates having different surface roughness and the results were also compared with commercial pure titanium and Ti-6Al-4V. The results indicate that fibroblast shows similar adhesion and proliferation on the smooth surfaces of commercial pure titanium （Cp Ti）, Ti-39Nb-13Ta-4.6Zr, and Ti-6Al-4V, suggesting that Ti-39Nb-13Ta-4.6Zr has similar biocompatibility to Cp Ti and Ti-6Al-4V. The fibroblast adhesion and spreading was lower on rough surfaces of Cp Ti, Ti-39Nb-13Ta-4.6Zr and Ti-6Al-4V than on smooth ones. Surface roughness appeared to be a dominant factor that determines the fibroblast adhesion and proliferation.     

Fibroblast Adhesion and Proliferation on a New β Type Ti-39Nb-13Ta-4.6Zr Alloy for Biomedical Application

Cell attachment and spreading on Ti-based alloy surfaces is a major parameter in implant technology. Ti39Nb-13Ta-4.6Zr alloy is a new β type Ti alloy developed for biomedical application. This alloy has low modulus and high strength, which indicates that it can be used for medical purposes such as surgical implants.To evaluate the biocompatibility and effects of the surface morphology of Ti-39Nb-13Ta-4.6Zr on the cellular behaviour, the adhesion and proliferation of rat gingival fibroblasts were studied with substrates having different surface roughness and the results were also compared with commercial pure titanium and Ti-6Al-4V. The results indicate that fibroblast shows similar adhesion and proliferation on the smooth surfaces of commercial pure titanium (Cp Ti), Ti-39Nb-13Ta-4.6Zr, and Ti-6Al-4V, suggesting that Ti-39Nb-13Ta-4.6Zr has similar biocompatibility to Cp Ti and Ti-6Al-4V. The fibroblast adhesion and spreading was lower on rough surfaces of Cp Ti, Ti-39Nb-13Ta-4.6Zr and Ti-6Al-4V than on smooth ones. Surface roughness appeared to be a dominant factor that determines the fibroblast adhesion and proliferation.     

增材制造Ti-6Al-4V合金组织调控研究现状

增材制造技术可实现复杂钛合金零件的快速成形,制造的Ti-6Al-4V合金具有较高的强度以及优异的高温性能,被广泛应用于航空、医疗等各大领域。综述了金属增材制造的典型工艺,分析了Ti-6Al-4V合金的相变特征,总结了选区激光熔化制造Ti-6Al-4V的力学性能和组织调控方法,着重分析了热处理温度、冷却速率、变质处理以及超声冲击等对合金组织的影响;展望了增材制造Ti-6Al-4V合金的主要发展方向。     

Influence of alloy element partitioning on strength of primary α phase in Ti-6Al-4V alloy

The partitioning effect of Al(α-phase stabilizer) and V elements(β-phase stabilizer) on strength of the primary α phases in the α/β Ti-6 Al-4 V alloy with the bimodal microstructure was investigated.It was found that partitioning of Al and V elements took place in the Ti-6 Al-4 V alloy during the recrystallization process,leading to the variation of the content of Al and V elements in the primary α phases with changing the volume fraction of the primary α phase.Nanoindentation tests reveal a general trend that the strength of the primary α phases increases with decreasing the volume fraction of the primary α phases,and such trend is independent on the loading direction relative to the c-axis of the α phase.The enhanced strength is attributed to the increase of the content of Al element in the primary α phase,but it is not dominated evidently by the change of the V content.The solid solution strengthening contributed from both the elastic strain introduced by the solute atoms and the variation of the density of states was estimated theoretically.     

Effect of Si3N4 Addition on the Mechanical Properties, Microstructures, and Wear Resistance of Ti-6Al-4V Alloy

In order to improve the wear resistance of Ti-6Al-4V, different amounts of Si3N4 powder were added into the alloy powder and sintered at 1250℃. Porous titanium alloy with higher wear resistance was successfully fabricated. At sintering temperature, reaction took place and a new hard phase of Ti5Si3 formed. The mechanical properties of the fabricated alloys with different amounts of Si3N4 addition were investigated. The hardness of Ti-6Al-4V, which is the index of wear resistance, was increased by the addition of Si3N4. Amounts of Si3N4 addition have very significant influences on hardness and compressive strength. In present study,titanium alloy with 5 wt pct Si3N4 addition has 62% microhardness and 45% overall bulk hardness increase,respectively. In contrast, it has a 16.4% strength reduction. Wear resistance was evaluated by the weight loss during wear test. A new phase of Ti5Si3 was detected by electron probe microanalyzer （EPMA） and X-ray diffraction （XRD） method. The original Si3N4 decomposed during sintering and transformed into titanium silicide. Porous structure was achieved due to the sintering reaction.     

Notch effects on high-cycle fatigue properties of Ti-6Al-4V ELI alloy at cryogenic temperatures

Notch effects on the high-cycle fatigue properties of the forged Ti-6Al-4V ELI alloy at cryogenic temperatures were investigated. Also, the high-cycle fatigue data were compared with the rolled Ti-5Al-2.5Sn ELI alloy. The one million cycles fatigue strength (FS) of the smooth specimen for the forged Ti-6Al-4V ELI alloy increased with a decrease of test temperature. However, the FS of each notched specimen at 4 K were lower than those at 77 K. On the other hand, the FS of the smooth and the notched specimens for the forged Ti-6Al-4V ELI alloy at 4 K were lower than those for the rolled Ti-5Al-2.5Sn ELI alloy. This is considered to be the early initiation of the fatigue crack in the forged Ti-6Al-4V ELI alloy compares with the forged Ti-5Al-2.5Sn ELI.