元素Cr对粉末冶金Ti-6Al-4V合金组织与性能的影响

采用冷等静压、真空烧结的方法制备不同Cr含量的Ti-6Al-4V合金,通过金相观察、力学性能测试及SEM分析等方法研究Cr元素对Ti-6Al-4V合金显微组织与力学性能的影响。结果表明:添加Cr元素后,合金中并未出现化合物Ti Cr2,其组织是由(α+β)相组成的魏氏组织。Cr的添加降低了合金的致密度,提高了其抗压强度,当Cr质量分数为4%时,合金的抗压强度达到1 855 MPa。Cr质量分数为1%、2%时,合金断裂形式为韧性断裂;Cr含量为3%、4%时,合金断裂形式为解理断裂。     

注射成形Ti-6Al-4V合金的显微组织和力学性能

采用金属注射成形方法制备Ti-6Al-4V合金坯体,然后利用溶剂脱脂和热脱脂工艺脱除坯中粘结剂,研究了合金在真空烧结和热等静压烧结条件下的显微组织和力学性能.结果表明:真空烧结Ti-6Al-4V合金具有典型的魏氏体组织,其初始的β晶粒粗大,β晶粒内为次生片状α和薄β相片,空隙较多,合金的强度和塑性较低;合金经热等静压处理后,组织明显细化且均匀,空隙很少或几乎没有,从而强度和塑性都有所提高.     

Process window for electron beam melting of Ti-6Al-4V

Selective electron beam melting (EBM) is a powder-bed based additive manufacturing technique for the fabrication of dense metallic parts. As a free-form deposition process EBM offers a high degree of freedom in design and a highly efficient utilization of material. For a widespread industrial application the achievable build rate is a critical factor. In this paper the process window for Ti-6Al-4V is explored by varying beam current and scan speed in a wide range. The EBM specimens were characterized by their density, porosity size and distribution, chemical composition, microstructure, hardness and tensile strength. Key findings include: (1) the minimum line energy necessary to achieve full density, (2) parameter sets for increased build rates at full density, and (3) formation of α'-martensite at high scan rates.     

置氢Ti-6Al-4V合金组织与室温变形行为的相关性

应用压缩实验研究置氢Ti-6Al-4V合金的室温力学行为,采用OM、SEM分析了氢对钛合金组织的影响和断口形貌特征,探讨了置氢钛合金组织和室温变形行为之间的相关性.结果表明:氢的固溶强化作用使置氢Ti-6Al-4V合金硬化效应增加,但适量的氢可以显著降低其压缩屈服强度和弹性模量,且断裂时发生的变形量增加,此时合金组织为α+β的双态组织,当合金中产生粗大的β晶粒时,断裂时发生的变形量显著降低;氢的加入促进了合金中斜方马氏体α″的生成;置氢Ti-6Al-4V合金的室温压缩断口为延性沿晶断裂或脆性沿晶断裂和解理型穿晶断裂两种断裂方式的混合断口.     

Effect of cerium on microstructure,mechanical properties and corrosion properties of Al-Zn-Mg alloy

The effects of trace Ce on the microstructure,mechanical properties and corrosion resistance of Al-Zn-Mg alloy were studied by means of metallographic analysis,scanning electron microscopy(SEM),mechanical tensile test,slow strain rate tensile test,cyclic polarization curve test,electrochemical impedance spectroscopy test and anodic oxidation test.The results show that the addition of trace Ce has little effect on the strength of Al-Zn-Mg alloy,but can significantly improve the corrosion resistance of the alloy;The mechanical properties and corrosion resistance of the alloys decrease significantly with the addition of excessive Ce;the addition of 0.04 wt%Ce can reduce significantly the self-corrosive current density of AlZn-Mg alloy and increase obviously passivation film resistance of the alloy.The stress corrosion sensitivity index decreases from 0.612 to 0.219,which improves the corrosion resistance properties significantly.     

烧结温度与混粉比例对双尺度钛合金组织与性能的影响

采用高能球磨-放电等离子烧结技术制备具有双尺度显微组织的Ti-6Al-4V合金,并研究烧结温度和加入未球磨粉末的比例对烧结试样显微组织及力学性能的影响。实验结果表明:当球磨时间为6 h时,由于球磨粉末内部的应变量不均匀,球磨粉末烧结试样的显微组织均由粗晶网篮组织和细晶等轴组织组成。随烧结温度升高,烧结试样的密度逐渐提高,细晶区的晶粒尺寸逐渐增大,材料强度呈先上升后下降的趋势。在球磨粉末中加入一定比例的未球磨粉末可显著提高烧结材料的塑性,并且保持较高的强度。当球磨粉末与未球磨粉末按质量比4:1混合、SPS烧结温度为850℃、保温时间为4min时,烧结材料相对密度达到99.0%,细晶区晶粒尺寸为1~2μm,烧结试样获得最佳强度-塑性组合,其拉伸屈服强度为1012 MPa,断裂强度为1056 MPa,伸长率为10%。     

粉末粒度对热压Ti-6Al-4V合金微观组织和力学性能的影响

以4种不同粒径的球形Ti-6Al-4V粉末为原料,采用真空热压法进行成形固结。利用X射线衍射仪(XRD)、金相显微镜、扫描电镜、万能材料试验机分别分析粉末Ti-6Al-4V合金的物相组成、微观组织、断口形貌以及力学性能,研究粉末粒度及其组成对烧结体微观组织和力学性能的影响。研究结果表明:热压烧结Ti-6Al-4V样品致密度均可达到98%以上。不同粒度粉末烧结后的合金均为网篮排列层片状组织。合金塑性主要受原始粉末粒度影响,随原始粉末粒度增大,烧结样品的晶粒尺寸增大,从而导致合金的塑性降低。粉末粗细搭配相比于原始粗粉,有助于提高合金的塑性,从而有效降低粉末钛合金的成本。     

置氢Ti-6Al-4V合金组织演变与超塑性能

应用高温拉伸实验研究了氢对Ti-6Al-4V合金超塑变形行为的影响,借助于OM、SEM、TEM和XRD等分析手段,分析了氢对钛合金组织演变的影响.结果表明:氢可促进合金中β相数量的增加,氢质量分数达到0.2%时合金出现马氏体组织,并随着氢含量的增加而逐渐粗化;适量的氢可以改善钛合金超塑变形行为,如降低流动应力和超塑变形温度、提高应变速率敏感指数m值;Ti-6Al-4V合金加入质量分数0.1%的氢,其峰值流动应力降低53%,变形温度降低约60℃,且由于氢的加入,使得超塑变形后的位错密度减少,说明氢促进了位错的运动.     

Effect of copper on magnetostriction and mechanical properties of TbDyFe alloys

The intrinsic brittleness of the TbDyFe alloy significantly decreases its mach inability and applications.This paper aims to improve the toughness of TbDyFe alloy by adding Cu. Various alloys of the type(Tb_(0.3)Dy_(0.7))_(0.37)Fe_(0.63-χ)Cu_χ(χ=0, 0,01.0.03, 0.05, 0.08, 0.1) were fabricated by an arc melting furnace under a high purity argon atmosphere. The microstructure, magnetostrictive properties and mechanical performance were studied systematically. The results show that the (Tb,Dy)Cu phase forms in these alloys upon the addition of Cu. Correspondingly, their toughness improves, attributed to the formation of a (Tb,Dy)Cu phase. Compared to the Cu-free alloy, the fracture toughness (Kic) increases 2-3 times with increasing Cu content. However, the magnetostriction performance of these alloys declines with Cu addition, due to the low-magnetic performance of the (Tb,Dy)Cu phase at room temperature. Compared with other alloys, the alloy with the addition of 1at%Cu shows the best compromise between the saturation magnetostriction and fracture toughness.     

热处理温度对Ti-6Al-4V耐腐蚀性及力学性能的影响

为了改善Ti-6Al-4V合金的性能,将Ti-6Al-4V合金在90％氮气和10％氧气组成的气氛中进行化学热处理以达到表面强化的目的.试验通过扫描电子显微镜(SEM)对涂层形貌进行表征、X射线衍射(XRD)确定涂层的化学组成、利用极化曲线(Tafel)和显微硬度(HV)测试涂层的耐腐蚀性能和力学性能.测试结果显示涂层和基体结合良好,涂层由TiO2和TiN构成,在800℃处理时具有最高的硬度和最强的耐腐蚀性能.     

On thermoplastic shear instability in the machining of a titanium alloy (Ti-6Al-4V)

A thermal model for the thermoplastic shear instability in the machining of a titanium alloy (Ti-6Al-4V) is developed. It is based on the analysis of the shear-localized chip formation process and the temperature generated in the shear band due to various heat sources (primary, preheating, and image) in machining. The temperature in the shear band was determined analytically using the Jeager’s classical stationary- and moving-heat-source methods. Using Recht’s classical model of catastrophic shear instability (thermal softening vs strain hardening), the onset of shear localization was determined. The shear stress in the shear band is calculated at the shear-band temperature and compared with the value of the shear strength of the bulk material at the preheating temperature. If the shear stress in the shear band is less than or equal to the shear strength of the bulk material, then shear localization is imminent. The cutting speed at which this occurs is taken as the critical speed for the onset of shear localization, which continues at all speeds above this value. In the case of titanium alloys, this speed is rather low, indicating shear localization practically at all conventional cutting speeds. The effect of the depth of the cut on the onset of shear localization was also considered, as it may affect the heat transfer from the shear-localized region, i.e., between the segments in the chip, to the rest of the chip and preheating of the segment. For example, there can be a significant difference in the thermal aspects of shear localization in ultraprecision machining (where the depths of cuts are a few micrometers or less) compared to conventional machining (where the depths of cuts are several hundred micrometers). This is because of the differences in the distances between the segments as well as the energy inputs in each case.     

还原铁粉对Fe-1.1Ni-0.5Mo-0.5Cr合金组织与性能的影响

在惰性气体雾化法制备的Fe-1.1Ni-0.5Mo-0.5Cr预合金粉末中添加1.5％的Cu粉和0.6％的C粉(均为质量分数)以及还原铁粉(添加量分别为0、10％、20％和30％),混合均匀后在600 MPa压力下模压,在1 180℃烧结1h.烧结合金经180℃/1h回火处理后,进行密度、硬度、拉伸力学性能检测以及显微...     

轧制变形量对Ti-45Al-7Nb-0.3W合金组织与性能的影响

利用X衍射分析(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、室温拉伸试验等手段,研究粉末冶金Ti-45Al-7Nb-0.3W(原子分数,%)合金包套轧制过程中的显微组织和力学性能的变化规律。结果表明:热等静压法态的Ti-45Al-7Nb-0.3W合金组织为近γ组织,主要由块状的γ相组成,同时包括少量的α2相及极少量的B2相。轧制后Ti Al合金板材为双态组织,B2相消失。随轧制变形量增加,合金板材强度增加,变形量为40%时,板材抗拉强度最大,达到955 MPa。继续增加变形量合金板材的力学性能有所降低。当变形量较小时,合金的塑性变形主要通过位错滑移和攀移来实现。随变形量增加,孪生和动态再结晶机制发挥作用。     

Study on microstructure and mechanical properties of spark plasma sintered Alumix 431 powder

Spark plasma sintering (SPS) has been used to successfully densify a 7075 aluminium alloy obtained from Alumix 431 powder. Sintering experiments were conducted at the temperature of 450 and 500°C for 2.5, 5 and 10?min. All the presented results confirm the excellent sinterability of Alumix 431 powder in vacuum during the SPS process and clearly show the effect of sintering temperatures and holding times on the densification, microstructure and mechanical properties of the obtained sintered compacts. The best results of hardness (1412?±?39?MPa), tensile strength (345?±?15?MPa) and compressive strength (618?±?4?MPa) were obtained by the compacts sintered at 500°C for 5 min.     

固溶温度对挤压态Mg-13Al-6Zn-4Cu合金组织与性能的影响

采用不同的固溶温度对挤压态Mg-13Al-6Zn-4Cu(质量分数,%)合金进行热处理,然后在(150℃/10 h)条件下进行时效处理,通过金相显微镜、扫描电镜及能谱分析、维氏硬度与极化曲线测试,研究固溶温度对挤压态合金显微组织、硬度与腐蚀性能的影响。结果表明:固溶处理促进晶界处的β-Mg_(17)Al_(12)相充分溶入α-Mg基体中。提高固溶温度使基体晶粒再结晶长大,逐渐缩小T-MgAlCuZn相心部的Cu元素富集区,改变β析出相的形态和分布,促进层片状β相在α-Mg晶界析出,从而提高时效态合金的硬度。但固溶温度超过420℃时,合金晶粒粗化并发生过烧。固溶温度升高导致合金腐蚀电位负移,腐蚀电流增大,腐蚀速率加快。     

通过等离子渗碳/CrN覆层改性处理提高Ti-6Al-4V合金的耐磨性和抗疲劳特性

In this study, a newly developed duplex coating method incorporating plasma carhurization and CrN coating was applied to Ti-6AI-4V and its effects on the wear resistance and fatigue life were investigated. The carburized layer with approximately150μm in depth and CrN coating film with 7. 5 μm in thickness were fomled after duplex coating. Hard carbide particles such as TiC And V4C3 were formed in the carburized layer. XRD diffraction pattern analysis revealed that CrN film had predominant [111] and [200] textures. The hardness (Hv) was significantly improved up to ahout 1960 after duplex coating while the hardness value of original Ti-6Al-4V was 402. The threshold load for the modification and/or failure of CrN coating was measured to be 32 N using the acoustic emission technique. The wear resistance and fatigue life of duplex coated Ti-6Al-4V improved significantly compared to those of un-treated specimen. The enhanced wear resistance can be attributed to the excellent adhesion and improved hardness of CrN coating film for the duplex coated Ti-6Al-4V. The initiation of fatigue cracks is likely to be retarded by the presence of hard and strong layers on the surface, resulting in the enhanced fatigue life.     

Relationship between fracture toughness and crack extension resistance curves (R curves) for Ti-6Al-4V alloys

The effects of microstructure, impurity content, and testing temperature on the fracture toughness (as measured by the crack tip opening displacement (CTOD)) and microcrack extension resistance curves (R curves) of Ti-6Al-4V alloys were examined. At 0 °C, microstructure is the most influential factor in the toughness-strength relationship. Acicular microstructure specimens have a higher CTOD than specimens with equiaxed microstructures, regardless of strength (0.2 pct proof stress) and impurity content. At −196 °C, impurity content becomes a controlling factor in the toughness-strength relationship. Extra-low impurity (ELI) specimens, which have a lower impurity content, show a higher CTOD, irrespective of microstructure. Microcracks extended from the notch tip before the maximum load was reached during testing were investigated, and crack initiation (δ _i) and extension-resistance properties were evaluated by obtaining exact R curves of the microcracks. At 0 °C, specimens with different microstructures and different impurity contents have almost the same δ _i. But acicular-microstructure specimens with a higher CTOD at a given strength show a greater crack extension resistance. At −196 °C, ELI specimens, which have a higher CTOD, show a larger crack extension resistance. It is concluded that the crack extension-resistance property of the microcracks extended from the notch tip before the maximum load is a controlling factor for the fracture toughness of Ti-6Al-4V alloys.     

热挤压工艺对Ti-6Al-4V钛合金组织与性能的影响

研究了挤压温度和挤压比对Ti-6Al-4V钛合金挤压型材显微组织、织构及力学性能的影响.挤压温度在相变点T_β以上150~350℃、挤压比λ为25~85范围内时,型材动态再结晶均已完成,形成均匀的魏氏组织.型材的晶粒随挤压温度的降低和挤压比的提高而细化.型材织构在挤压比较低(λ=25)时强度较弱且为随机分布;当挤压比增加时,织构增强并有形成(相似文献   

Mg含量对Al-4.8Cu-xMg-1.0Ag合金组织与力学性能的影响

通过对显微硬度与疲劳裂纹扩展速率的测试以及扫描电镜和透射电镜观察等实验手段,研究Mg含量对Al-Cu-Mg-Ag合金时效析出过程与力学性能的影响.结果表明:随着Mg含量的上升,合金的时效响应速率加快,而硬度则先上升后下降,在Cu/Mg质量比接近6时,合金硬度最高;Mg含量的提高可为主要析出相Ω相提供更多的形核位置,使得...     

锻造方式对Ti-6Al-4V合金组织及取向分布的影响

在快锻液压机上对Ti-6Al-4V合金进行了锻造变形,采用扫描电镜、背散射电子衍射技术以及X射线衍射技术研究了不同锻造方式下合金组织及晶粒取向的变化规律.在单向镦拔和换向镦拔两种不同锻造方式下,难变形区、小变形区及大变形区中α相及β相的分布差别不大,组织均匀性基本一致,两种变形方式下锻坯不同区域的应变稍有差别.进一步对不同变形区域形变织构的定量分析可知:在应变较小的边缘区域,变形主要以{0001}基面滑移为主,形成基面织构;在应变较大的内部区域,织构明显转向{11相似文献