Influence of Powder Morphology and Microstructure on the Cold Spray and Mechanical Properties of Ti6Al4V Coatings

The powder microstructure and morphology has significant influence on the cold sprayability of Ti6Al4V coatings. Here, we compare the cold sprayability and properties of coatings obtained from Ti6Al4V powders of spherical morphology (SM) manufactured using plasma gas atomization and irregular morphology (IM) manufactured using the Armstrong process. Coatings deposited using IM powders had negligible porosity and better properties compared to coatings deposited using SM powders due to higher particle impact velocities, porous surface morphology and more deformable microstructure. To evaluate the cohesive strength, multi-scale indentation was performed and hardness loss parameter was calculated. Coatings deposited using SM powders exhibited poor cohesive strength compared to coatings deposited using IM powders. Images of the residual indents showed de-bonding and sliding of adjacent splats in the coatings deposited using SM powders irrespective of the load. Coatings deposited using IM powders showed no evidence of de-bonding at low loads. At high loads, splat de-bonding was observed resulting in hardness loss despite negligible porosity. Thus, while the powders from Armstrong process lead to a significant improvement in sprayability and coating properties, further optimization of powder and cold spray process will be required as well as consideration of post-annealing treatments to obtain acceptable cohesive strength.     

Mechanical and Tribological Properties of Cold-Sprayed Ti Coatings on Ti-6Al-4V Substrates

A cold spray process was used to deposit titanium (Ti) coatings of different thicknesses on commercial Ti-6Al-4V (Ti64) substrates. The hardness of the Ti coatings was measured using a Vickers micro-indenter. It was found that the thicker Ti coatings had higher hardness probably due to the better uniformity and higher density of the coatings. The tribological results showed that the friction and wear of the Ti coatings tested against a steel ball under dry condition became lower with higher thickness probably due to the higher wear resistance of the thicker coatings associated with their higher hardness. The specific wear rates of all the Ti coatings were significantly lower than that of the Ti64 substrate as a result of the higher wear resistance of the Ti coatings associated with their cold-worked microstructures and the formation of high wear resistant oxide layers on their wear tracks during the wear testing.     

电弧喷涂Ti6Al4V涂层组织与耐磨损性能

采用ZPGD-400型电弧喷涂机在Q235钢基体上喷涂Ti6Al4V涂层,并借助扫描电镜(SEM)、X射线衍射仪(XRD)、显微硬度计及滑动磨损试验机对喷涂涂层的显微组织、结合状态、硬度以及磨损表面进行分析.结果表明,Ti6Al4V涂层组织呈典型的层状特征,孔隙少,涂层与基体结合紧密,涂层平均显微硬度1013 HV0.2其耐磨损性能为Q235钢的20倍,磨损机制主要为剥层磨损和粘着磨损.     

激光修复TC4钛合金显微组织与力学性能

本文以低氧TC4粉末为熔覆材料,采用激光修复技术制备了TC4钛合金面修复试样,对比研究了锻件和修复试样(沉积态)的显微组织和力学性能。结果显示修复试样的组织宏观上分为锻件基材区,热影响区和激光沉积区,三个区域中热影响区的显微硬度最高,沉积区和锻件基材的显微硬度相当。锻件试样的强度及塑性均略高于修复试样,同时发现40%修复试样(即拉伸试样承受载荷部位横截面上沉积区所占的面积分数为40%)的强度略低于50%修复试样,塑性则高于后者。表明采用低氧TC4粉末为熔覆材料时,有利于修复试样沉积区和基材区强度和塑性的匹配,从而提高修复试样的综合性能。对拉伸断口进行扫描电镜观察发现,锻件试样拉伸失效后断口呈现出典型的韧性断裂特征,而修复试样的断口则表现复杂,从沉积区到锻件基材区呈现出解理台阶到韧窝的连续变化特征,同时断口形貌与显微组织呈现出很好的对应关系。     

Effects of Spray Parameters and Post-spray Heat Treatment on Microstructure and Mechanical Properties of Warm-Sprayed Ti-6Al-4V Coatings

Warm spray is a novel thermal spray technique that allows the formation of dense and relatively pure Ti-6Al-4V coatings due to its capability to control the temperature of the propellant gas by diluting the combustion flame with an inert gas such as nitrogen. Recently, its combustion pressure has been increased from 1 to 4 MPa aiming to further increase particle velocity to over 1000 m/s. Two series of coatings with combustion pressure of 1 and 4 MPa and various nitrogen flow rates were prepared in this study. Effects of combustion pressure and nitrogen flow rate on the microstructure and mechanical properties of the Ti-6Al-4V coatings were systematically studied. Miniature tensile specimens with a total length of about 9 mm were used for static tensile tests. It was found that the spray parameters affect both the porosity and oxygen content of the coatings significantly and had remarkable effects on their mechanical properties. High level of porosity in the Ti-6Al-4V coatings reduced the effective cross-sectional area of the mini-specimens and caused a drop in their tensile strength and Young’s modulus. Subsequent heat treatments were found effective in significantly recovering the mechanical properties of the as-sprayed coatings.     

Processing,Microstructure and Mechanical Properties of Ti6Al4V Particles-Reinforced Mg Matrix Composites

Novel Ti6Al4V particles-reinforced AZ91 Mg matrix composites were successfully fabricated by stir casting method. The stirring time in semisolid condition directly affected the particle distribution and the quality of the ingots.Furthermore, the optimal speed of the heating and the liquid stirring could overcome particle settlement caused by the density difference between the matrix and the particles. Ti6Al4V particles distributed uniformly in the composites with different particle contents. The average grain size decreased with the increase in the particle contents. The Ti6Al4V particles bonded pretty well with the alloy matrix. In addition, there were some interfacial reactions in the composites.There were rod-like Al_3Ti phases at the interface. The precipitates extended from the particle surface to the matrix, and they might improve the interfacial bonding strength. The ultimate tensile strength, yield strength and elastic modulus were enhanced as the particle contents increased, and the elongation was much better than that of the same matrix material reinforced with SiC particles. Thus, the novel composites exhibit better comprehensive mechanical properties.     

Ti6Al4V表面火焰喷焊Ni基WC涂层的组织和性能研究

在Ti6Al4V表面采用火焰喷焊技术制备硬质Ni基WC涂层,利用扫描电镜、显微硬度计、成分分析仪、X射线衍射仪进行组织形貌、显微硬度HV、EDS成分及相组成分析。分析结果表明:喷焊涂层由强化层、过渡层组成,涂层与基体结合紧密,与基体之间无分层、开裂等现象,涂层总厚度达到2400μm,涂层的表面硬度为11070MPa。涂层主要元素呈梯度变化,涂层硬度也呈相应的梯度变化。强化层中W原子配比大于C的原子配比,分子组合为WxC,WxC弥散分布于Ni基材料中,形成典型的韧Ni基体+硬质WxC的组织;WxC的出现是由于少量WC热分解为W2C;微量的氧化物存在于喷焊层表面,未在强化层整层中出现,其是喷焊层在放置冷却过程中出现的;强化层与过渡层之间无气孔等缺陷,两者有良好过渡。过渡层为Ni基材料与基体的互熔,形成良好的冶金层,过渡层与基体为冶金结合。     

Zr添加对TiC/Ti6Al4V复合材料组织和性能的影响

用熔铸法制备原位自生TiC/Ti6Al4V复合材料,研究Zr元素的添加对TiC/Ti6Al4V复合材料显微组织、压缩性能和耐磨性能的影响。结果表明：当Zr添加量在1%~4%（质量分数,下同）范围内变化时,初生TiC呈枝晶状,在初生TiC周围伴有花瓣状、片状或须状共晶TiC生成;且随着Zr含量的增加,初生TiC的尺寸减小,共晶TiC的数量增加,复合材料的耐磨性能和压缩性能增强。当Zr添加量在6%~10%内时,枝晶状TiC又变得发达,但在此范围内随着Zr含量的增加,复合材料的耐磨性和压缩性能呈下降趋势。当Zr量为4.0%时,复合材料的抗压强度达到峰值。     

不同热处理工艺对Ti6Al4V钛合金微观结构和力学性能影响

通过对Ti6Al4V钛合金进行不同工艺的热处理,分析了不同工艺处理后的显微组织,进行了拉伸试验、示波冲击试验测试。研究固溶时效处理对Ti6Al4V钛合金显微组织、力学性能和冲击韧性的影响。利用金相显微镜、环境扫描电镜（ESEM）进一步分析了钛合金的组织、冲击断口特征与力学性能间的关系。结果表明随固溶温度增加,钛合金屈服强度和抗拉强度得到显著提高,塑韧性先增加后降低。优化热处理工艺后,Ti6Al4V钛合金经960 ℃ WQ和500℃ × 4 h AC处理,获得优良综合性能,σ0.2为1050MPa,σb为1120 MPa,Ak为46.22 J。钛合金固溶时效后的组织由β基体和析出的α相组成,片层状β相和小针丛状α相组织提高合金综合性能。     

超声处理对Ti6Al4V合金微弧氧化涂层结构和性能的影响

目的提高钛合金植入体的生物活性。方法采用Ti6Al4V合金在0.18 mol/L的Ca(CH_3COO)_2·H_2ONH_4H_2PO_4电解液体系中进行微弧氧化处理,并同时采用40 kHz和70 kHz的超声波分别对电解液进行超声振动处理。采用SEM、EDS、XRD技术分析超声辅助微弧氧化涂层的Ca/P比、相组成、表面形态和抗腐蚀性能。结果超声处理可降低微弧氧化起弧电压,处理时间5 min时降低了涂层的生长速度,而处理时间5 min时促进了涂层的生长。超声处理促进了阳极氧化速度,增加了等离子放电通道,降低了放电微孔直径,从而提高了疏松层的密度,促使疏松层和致密层界面处产生大量孔穴,涂层发生震碎和裂纹,并且增加了微弧氧化涂层的Ca/P比,促进了金红石相的生成,但对提高涂层耐蚀性效果不明显。结论超声处理改变了涂层成分、相含量及表面结构,且保持了涂层较好的耐蚀性,有利于提高涂层的生物活性。     

热氧化时间对Ti6Al4V表层组织和性能的影响

在973 K和保温10,20,30,40,50 h条件下对Ti6Al4V进行热氧化处理。采用X射线衍射仪、辉光光谱分析仪和扫描电镜分析热氧化层的特征。借助显微硬度计,摩擦磨损试验机和电化学工作站研究热氧化时间对Ti6Al4V的表面硬度、耐磨性和耐蚀性的影响。结果表明:Ti6Al4V表面制备的热氧化层均匀、连续;延长热氧化时间可促进氧化层的增厚。热氧化处理显著提高了Ti6Al4V的表面硬度、改善了其耐磨性和耐蚀性,但没有呈现线性增长特征。结合氧化层的厚度、表面硬度、耐磨性和耐蚀性等结果,973 K/30 h工艺下获得的氧化层具有较好的综合特征。     

电弧喷涂Ti6Al4V涂层的组织与耐蚀性能研究

采用电弧喷涂技术在Q235钢基体上喷涂Ti6Al4V涂层,并对涂层进行封孔处理.表征了涂层的物相组成和微观形貌,通过盐水浸泡实验和极化曲线测试对比分析了Q235钢基体、未封孔涂层和封孔涂层的耐腐蚀性能.结果表明:涂层呈典型的层状特征,物相组成为TiN,TiO和少量的Ti;未封孔涂层与封孔涂层均具有较宽的钝化电位区间,封...     

Ti—6Al—4V合金表面化学镀Ni—P层的显微组织及性能研究

为了改善钛合金的耐磨性及抗微动损伤能力,对Ｔｉ－６Ａｌ－４Ｖ合金的化学镀Ｎｉ－Ｐ工艺进行了研究,发现应用一种由化学除油－化学浸蚀－表面活性－化学镀Ｎｉ－Ｐ的新工艺路线,可获得高质量的Ｎｉ－Ｐ镀层。通过扫描电镜,Ｘ射线衍射及硬度测量,对镀层在稳定化处理过程中的显微组织及硬化效应进行了测定与分析。     

锻造粉末冶金Ti6Al4V合金的性能和组织研究

摘 要: 本文对粉末冶金Ti6Al4V合金进行不同方式的锻造,并对锻造前后的性能和组织进行分析。研究表明,锻造是提高粉末冶金钛合金致密度、提高力学性能的有效手段。一方面,对粉末冶金Ti6Al4V合金在不同温度下进行一次锻造变形,发现960℃锻造后合金塑性最高,延伸率达到15.44%;随着锻造温度升高,组织中等轴α不断减少,逐渐向网篮组织转变,塑性有所降低,但是由于粉末的原始颗粒边界对晶粒长大的阻碍作用,在1150℃锻造后粉末冶金Ti6Al4V合金的晶粒没有明显长大,小于20μm的晶粒约占71%。晶粒尺寸小,有利于材料的塑性,其延伸率仍达到14.30%。因此,粉末冶金Ti6Al4V合金比传统熔铸钛合金具有更宽的锻造温度窗口。另一方面,对粉末冶金Ti6Al4V合金在不同温度下进行二次锻造变形,首先在高温锻造,利用小变形量的高温锻造来提高粉末钛合金的致密度,然后在低温进行二次锻造,获取需要的组织。经过两次锻造变形的Ti6Al4V合金的延伸率均大于17%,抗拉强度大于990MPa,屈服强度大于960MPa。     

TC4（Ti—6Al—4V）钛板超塑性成形后的力学性能研究

通过对 Ｔ Ｃ４（ Ｔｉ６ Ａｌ４ Ｖ）钛板超塑性成形后的试件进行常温双向拉伸和定量金相分析，并采用一元线性回归的数理统计方法进行数据处理，得出了 Ｔ Ｃ４ 钛板超塑成形后σ０．２、σｂ 与晶粒平均直径的定量关系。并简要分析了超塑性成形后材料力学性能变化的规律和原因。本文的试验结果可作为其它类型超塑性材料超塑成形后力学性能分析的参考。     

Microstructural Influence on Mechanical Properties in Plasma Microwelding of Ti6Al4V Alloy

The complexity of joining Ti6Al4V alloy enhances with reduction in sheet thickness. The present work puts emphasis on microplasma arc welding (MPAW) of 500-μm-thick Ti6Al4V alloy in butt joint configuration. Using controlled and regulated arc current, the MPAW process is specifically designed to use in joining of thin sheet components over a wide range of process parameters. The weld quality is assessed by carefully controlling the process parameters and by reducing the formation of oxides. The combined effect of welding speed and current on the weld joint properties is evaluated for joining of Ti6Al4V alloy. The macro- and microstructural characterizations of the weldment by optical microscopy as well as the analysis of mechanical properties by microtensile and microhardness test have been performed. The weld joint quality is affected by specifically designed fixture that controls the oxidation of the joint and introduces high cooling rate. Hence, the solidified microstructure of welded specimen influences the mechanical properties of the joint. The butt joint of titanium alloy by MPAW at optimal process parameters is of very high quality, without any internal defects and with minimum residual distortion.     

结构尺寸对Ti6Al4V多孔结构力学性能的影响

采用激光选区熔化技术制造了不同单元结构尺寸（1~6 mm）、孔隙率（40~80%）的拓扑优化多孔阵列结构,研究了单元结构尺寸对其压缩形变规律和弹性性能的影响。结果表明,多孔阵列结构的抗压强度、弹性模量均与单元结构尺寸成反比,抗压强度在126~199 MPa,弹性模量在3.5~55.47 GPa;压缩应力-应变曲线与单元结构尺寸有关,分别遵循弹性、弹脆性和脆性多孔材料三种应力应变规律;通过数值模拟多孔阵列结构的压缩形变过程,解释了两种45°断裂带的成因,力学性能与实验结果基本吻合;利用Gibson-Ashby模型评价多孔结构的稳定性,稳定性参数C与单元结构尺寸成反比;给出Gibson-Ashby拟合方程,特征参数n随单元结构尺寸增加而增大;建立了单元结构尺寸、相对密度和相对弹性模量的三维曲面数学模型,提出骨植入体的设计区域。     

直接激光沉积Ti6Al4V/Inconel 718复合材料微观组织与力学性能分析

Ti6A14V和Inconel 718合金被广泛用于航空航天.但TC4或Inconel 718难以同时满足轻量化和耐高温的需求.因此采用直接激光沉积制备了不同比例Ti6A14V/Inconel718复合材料.分别通过X射线衍射,扫描电子显微镜和能谱仪分析相组成,微观结构和元素分布.同时,研究了显微硬度和摩擦磨损性能.结...     

Ti6Al4V合金表面微弧氧化涂层的微观组织和摩擦性能研究

在不同电解液中采用微弧氧化法在Ti6Al4V钛合金表面制备复合涂层,研究其微观组织和摩擦性能。结果表明,在微弧氧化电解液中添加石墨可以有效地降低复合涂层的摩擦系数,摩擦系数为0.55左右,提高耐磨性能。