线间距对SLM成形钛合金Ti–6Al–4V力学性能的影响研究

目的 探究选区激光熔化技术工艺参数线间距对钛合金Ti–6Al–4V增材试件力学性能的影响。方法 通过SLM成形技术,以钛合金粉末为原材料、以线间距为变量制备增材成形试件,通过拉伸试验、断口形貌分析以及表面硬度测量获取不同线间距工艺参数条件下钛合金成形试件力学性能表现较好的较优解。结果不同线间距条件下成形试件拉伸曲线差异较大,线间距为0.05mm和0.10mm时,成形试件拉伸曲线表现较好,成形试件断口组织撕裂均具有连续性,韧窝结构明显,具有一定塑性。试件成形过程受氧化影响,其拉伸性能与硬度性能表现不一致。结论 试验最终工艺参数如下：曝光时间为80μs、点间距为40μm、线间距为0.05mm,SLM成形试件获得了较高的表面硬度,试件断口组织撕裂连续性较为明显,韧窝结构较大,断口界面缺陷较少,力学性能较优。     

Static coarsening behaviour of lamellar microstructure in selective laser melted Ti–6Al–4V

Static coarsening mechanism of selective laser melted (SLMed) Ti–6Al–4V with a lamellar microstructure was established at temperatures from 700 °C to 950 °C. Microstructure evolution revealed that high heat treatment temperature facilitated martensite decomposition and promoted lamellae growth. At each temperature, the growth rate decreased with increasing holding time. The static coarsening behaviour of SLMed Ti–6Al–4V can be interpreted by Lifshitz, Slyozov, and Wagner (LSW) theory. The coarsening coefficient were 0.33, 0.33–0.4, 0.4–0.5 for 700–800 °C, 900 °C and 950 °C, respectively. This indicated the coarsening mechanism was bulk diffusion at 700–800 °C, and a combination of bulk diffusion and interface reaction at 900 °C and 950 °C conditions.     

Microstructure developed in the surface layer of Ti-6Al-4V alloy after sliding wear in vacuum

Microstructural changes in the surface layer of Ti-6Al-4V alloy after sliding wear in vacuum have been studied by means of scanning and transmission electron microscopy (SEM and TEM). The wear rates of Ti-6Al-4V alloy in vacuum were measured under different sliding velocities and loads. The experimental results showed that a severely deformed layer with a grain size of 50–100 nm and thickness about 70 μm was formed underneath the worn surface. Under the slower sliding velocities, the substructure of the layer had a high dislocation density, while under higher sliding velocities, twins were found to exist in the substructure. A process by which the deformed layer formed has been proposed and the deformation of materials at the contacting spots of the Ti-6Al-4V sample is discussed.     

Rapid prototyping with high power fiber lasers

Laser rapid prototyping technologies comprise a set of technologies used in a wide range of materials to produce prototypes or small batches of complex shaped components. This paper presents a research work on rapid prototyping technology with laser additive manufacture of wire based alloy Ti-6Al-4V with an 8 kW fiber laser for the production of components with cylindrical geometry. For this, an engineering system was developed, a demonstration part produced and the deposition process was characterized. Two processing parameters were investigated: and these were the relative position between the wire feeding system and the substrate and the laser beam to wire width ratio. The former affects the molten metal transfer mode and the pressure exerted by the wire tip on the molten pool, while the laser beam to wire width ratio affects the process efficiency, since this is a compromise of process stability and process speed. Both parameters control surface finishing and the smoothness of the part. The melting efficiency of the process is low when compared to alternative processes involving powder pre deposition, but the density of the part is improved with homogeneous structural characteristics.     

真空高温退火对锻态Ti-6Al-4V合金显微组织与超塑性性能的影响

退火处理是改善钛合金显微组织,提高力学性能及超塑成形性能的一种重要工艺。使用真空退火炉在850℃-950℃温度区间内对锻态Ti-6Al-4V合金的进行了高温退火处理,研究了退火态Ti-6Al-4V合金微观组织演变及其在温度为900℃,应变速率为0.01 s^-1时的超塑拉伸性能。结果表明,锻态Ti-6Al-4V合金的初生α晶粒尺寸随真空退火温度的升高而减小,β相比例随真空退火温度升高而增大。当真空退火温度为910℃时,Ti-6Al-4V合金的晶粒尺寸和α相与β相分布较为均匀,其超塑拉伸试验结果表明,该合金表现出最佳的超塑拉伸性能,其拉伸延伸率达到785%,峰值应力仅为26.8 MPa。     

Laser Surface Modification of Ti-6Al-4V with Addition of Pr

The behaviour of oxidation at elevated tem-peratures and fretting in the laser-alloyed layer ofTi-6Al-4V with the addition of Pr was studied.The results show that the addition of Pr changes thestructure of oxide scale of Ti-6Al-4V,controls theshort-range diffusion of oxygen to thescale/substrate interface and increases the adhe-sion and ductility of the scale,thus changing theoxidation kinetics and considerably reducingoxidation rate.The analysis of fretting test showsthat the existence of high hardness layer in the al-loyed zone,fine dendrites perpendicular to the sur-face of the high hardness layer and the oxide scaleproduced during fretting at elevated temperaturesare all beneficial to the improvement of wear resist-ance.     

Ti3Al基合金与Ti-6Al-4V合金TLP连接接头的组织转变

采用TiZrNiCu合金作为中间层材料研究了Ti3Al基合金与Ti-6Al-4V合金的瞬间液相(TLP)扩散连接接头成分、组织转变及显微硬度.研究结果表明,连接温度和连接时间对接头成分和组织有较大的影响.随着连接温度的提高和连接时间的延长,接头中元素分布趋于均匀,连接区宽度增大.连接温度为850℃和900℃时,液相的残留使得接头中存在Ti-Cu金属间化合物.当连接温度为950℃,连接时间为30min时,等温凝固的完成使Ti-Cu金属间化合物从接头中消失.随着连接温度的提高和连接时间的延长,接头连接区硬度降低.当连接温度为950℃,连接时间为30min时,接头硬度分布较均匀.     

真空感应凝壳熔炼TC4合金的显微组织和力学性能

针对在航空航天等领域有重要应用背景的TC4合金 ,运用水冷铜坩埚真空感应熔炼炉制备了合金铸锭 ,研究了合金在铸态、热处理和热等静压条件下的显微组织和力学性能 .结果表明 ,铸态TC4合金的晶粒粗大 ,基体为大片状α+ β相组织 ,合金的强度较高 ,塑性低 ;合金经热处理 ,尤其经热等静压处理后 ,组织明显细化 ,塑性提高 .     

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.     

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...     

Friction-stir welding and processing of Ti-6Al-4V titanium alloy: A review

In this work, the current understanding and development of friction-stir welding and processing of Ti-6Al-4V alloy are briefly reviewed. The critical issues of these processes are addressed, including welding tool materials and design, tool wear, processing temperature, material flow, processing window and residual stresses. A particular emphasis is given to microstructural aspects and microstructure-properties relationship. Potential engineering applications are highlighted.     

Microstructure,mechanical properties and multiphase synergistic strengthening mechanisms of a novel laser additive manufactured AlNi6TiZr alloy

In this work,selective laser melting(SLM)process is used to prepare the AlNi6TiZr alloy.By analyzing the printing quality and mechanical properties of the printed specimens with different process parameters,the SLM forming window of AlNi6TiZr is obtained.The relative density of the sample printed with 270 W-1100 mm/s(laser energy density:82 J/mm3)reaches 99.7％,exhibiting excellent mechanical properties(yield strength(YS):421.7 MPa;ultimate tensile strength(UTS):480.4 MPa).After an aging treatment of 325 ℃-12 h,the YS and UTS of the sample increased to 494 MPa and 550.7 MPa,respectively.Adding Ni,Ti,and Zr components promoted the generation of multi-phase precipitates in the Al alloy and improved the synergistic strengthening effect of multi-phases.The hard-shell structure(HSS)formed by the Al3Ni phase at the grain boundary significantly strengthened the grain boundary strength.The precipitated Al3(Ti,Zr)phases at the grain boundaries prevent grain growth and dislocation movement.The Al3Ni and Al3(Ti,Zr)phases have good thermal stability that can still maintain excellent enhancement effects at high temperature.AlNi6TiZr alloy has great application prospects in medium and high-temperature environments.     

A review of selective laser melting of aluminum alloys: Processing,microstructure, property and developing trends

Selective laser melting (SLM) is an attractive rapid prototyping technology for the fabrication of metallic components with complex structure and high performance. Aluminum alloy, one of the most pervasive structural materials, is well known for high specific strength and good corrosion resistance. But the poor laser formability of aluminum alloy restricts its application. There are problems such as limited processable materials, immature process conditions and metallurgical defects on SLM processing aluminum alloys. Some efforts have been made to solve the above problems. This paper discusses the current research status both related to the scientific understanding and technology applications. The paper begins with a brief introduction of basic concepts of aluminum alloys and technology characterization of laser selective melting. In addition, solidification theory of SLM process and formation mechanism of metallurgical defects are discussed. Then, the current research status of microstructure, properties and heat treatment of SLM processing aluminum alloys is systematically reviewed respectively. Lastly, a future outlook is given at the end of this review paper.     

Study on the flow properties of Ti-6Al-4V powders prepared by radio-frequency plasma spheroidization

Spherical Ti-6Al-4V powders were prepared using radio-frequency plasma spheroidization. A laser particle size analyser, a scanning electron microscope, an X-ray diffractometer and a Freeman FT4 powder rheometer were used to analyse the granulometric parameters, micro-morphologies, phase constitutions and flow properties of the raw and the spheroidized powders, respectively. The spheroidized powders exhibited an almost 100% degree of sphericity, smooth surfaces, favourable dispersion and narrow particle size distribution under appropriate plasma technological parameters. The average particle size of the spheroidized powders increased slightly as compared with that of the raw powders. In addition, the spheroidized powders exhibited higher conditioned bulk density and improved flow properties (including the dynamic flow properties, aeration, compressibility, permeability and shear properties) as compared with those of the raw powders.     

Antibacterial Properties of Ti-6Al-4V-xCu Alloys

Surgical implant-associated bacterial infection is becoming a serious clinical problem.A series of copper-bearing titanium alloy,Ti—6AI—4V—xCu(x = 1,3,5 wt%),were fabricated in the present study in order to reduce the hazard of the bacterial infection problem by means of the strong antibacterial ability of Cu element.The metallography,X-ray diffraction,antibacterial ability,corrosion resistance and cytotoxicity of Ti—6AI—4V—xCu alloys were preliminarily studied with comparison to the commercial medical Ti—6AI—4V alloy.The Ti—6AI—4V—xCu alloys showed obvious antibacterial abilities with good corrosion resistance and cytocompatibility,and the antibacterial role was enhanced with increasing Cu content,which has significant potential for clinical applications as surgical implant materials.     

超塑性变形Ti-6Al-4V合金中接近重位点阵取向α晶界滑动机制的TEM研究

用 TEM 研究了超塑性变形 Ti_(-6)Al_(-4)V 合金中接近重位点阵取向(near-CSL)的α晶界,发现在部分晶界上晶界位错(GBD:)的衍衬象变得漫散,但仍然保持线状特征;某些 GBD 有局部的分解和束集反应;在α晶界与晶内亚结构的交界处,GBS 通过束集反应形成新的组态;构成晶界坎的各个界面上,GBD 排列的位向各不相同,晶界坎可向晶内发射点阵位错。