Microstructure and mechanical properties of large size Ti-43Al-9V-0.2Y alloy pancake produced by pack-forging

A pancake of Ti-43Al-9V-0.2Y (at.%) alloy with dimensions of ϕ480 mm × 46 mm was fabricated by pack-forging with a thick reduction of 80%. The as-forged Ti-43Al-9V-0.2Y alloy pancake has a duplex (DP) microstructure, which is composed of B2/α₂/γ lamellar colonies and massive B2 and γ phase regions distributed along the boundaries between the lamellar colonies. Different microstructures were obtained by heat treatment of samples cut from the as-forged Ti-43Al-9V-0.2Y alloy pancake. A fully lamellar (FL) structure consisting of B2/α₂/γ lamellar colonies was obtained after the heat treatment of 1350 °C/8 h. Tensile test results exhibited that the yield strength (YS) and ultimate tensile strength (UTS) of the alloy with DP microstructure were decreased from 680.7 MPa to 834.3 MPa at room temperature to 589.5 MPa and 693.1 MPa at 700 °C, respectively, and the elongation (δ) of the alloy with DP microstructure was increased from 1.99% at room temperature to 12.12% at 700 °C; the elongation (δ) of the alloy with FL microstructure was increased from 1.52% at room temperature to 85.84% at 800 °C.     

Microstructure and mechanical properties of low- and heavy-alloyed intermetallic alloys based on γ-TiAl + α2-Ti3Al

The microstructure and mechanical properties of the Ti-43.7Al-3.2(Nb,Cr,Mo)-0.2B alloy in the as-cast state (after gasostatistic processing) and of the Ti-45Al-8Nb-0.2C alloy after hot extrusion at temperatures corresponding to the ?? + ?? phase field followed by heat treatment have been studied. The extruded heavy-alloyed alloy has demonstrated significantly higher plastic/mechanical properties at room temperature with close values of the plasticity/tensile strength and long-term strength at elevated temperatures. A comparison of the results with literature data has shown the properties of the as-cast Ti-43.7Al-3.2(Nb,Cr,Mo)-0.2B to be similar to or superior to those of the best-known casting ?? (TiAl) + ??₂ (Ti₃Al) alloys.     

固溶时效温度对Ti-6Al-4V-0.5Si合金组织性能的影响

分析了不同固溶时效温度对Ti-6Al-4V-0.5Si合金抗拉强度、伸长率及显微组织的影响。结果表明,固溶处理后Ti-6Al-4V-0.5Si合金中存在较多的六方α′和斜方α″两种马氏体相和亚稳定相。时效处理后,马氏体相和亚稳定相分解再结晶得到分散的α+β相。综合分析表明,固溶时效工艺为950℃×30min(水冷,WQ)+480℃×4h(空冷,AQ),合金的综合性能最好,此时合金的抗拉强度和伸长率分别为745.6MPa和8.3%,比铸态合金分别提高了24.8%和36.0%。     

Microstructure and mechanical properties of Ti-6Al-4V/Ti-22Al-25Nb joint formed by diffusion bonding

Ti-6Al-4V (wt.%) and Ti-22Al-25Nb (at.%) were joined by diffusion bonding at 950 °C and 15 MPa for 100 min, and the microstructure and mechanical properties of the resulting joints were investigated. The composition of the diffusion layer is B2/discontinuous α/α₂ layer/necklace-shaped β+α′ layer, where the content of any element at a given point mainly depends on the distance of the point from the interface and the phase type at the point. The tensile strength of the joint is 894 MPa, which is almost the same as that of the Ti-22Al-25Nb base alloy. The fracture surfaces on both sides of the joint are composed of two main regions. One region displays a relatively flat surface and fractures along the bonding interface. The other is composed of a moderate number of irregularly-shaped cavities on the Ti-6Al-4V side and many irregularly-shaped bulges on the Ti-22Al-25Nb side. Both regions result from fracture along the boundaries between β+α′ layers and α_p grains or from the transcrystalline fracture of α_p grains.     

Heat-treated microstructure and mechanical properties of laser solid forming Ti-6Al-4V alloy

The effects of heat treatment on the microstructure and mechanical properties of laser solid forming (LSF) Ti-6Al-4V alloy were investigated. The influences of the temperature and time of solution treatment and aging treatment were analyzed. The results show that the microstructure of LSFed samples consists of Widmanstätten α laths and a little acicular in columnar prior β grains with an average grain width of 300 µm, which grow epitaxially from the substrate along the deposition direction (Z). Solution treatment had an important effect on the width, aspect ratio, and volume fraction of primary and secondary α laths, and aging treatment mainly affects the aspect ratio and volume fraction of primary α laths and the width and volume fraction of secondary α laths. Globular α phase was first observed in LSFed samples when the samples were heat treated with solution treatment (950°C, 8 h/air cooling (AC)) or with solution treatment (950°C, 1 h/AC) and aging treatment (550°C, above 8 h/AC), respectively. The coarsening and globularization mechanisms of α phase in LSFed Ti-6Al-4V alloy during heat treatment were presented. To obtain good integrated mechanical properties for LSFed Ti-6Al-4V alloys, an optimized heat treatment regimen was suggested.     

Effects of yttrium on microstructures and properties of Ti- 17Al-27Nb alloy

1 Introduction With the rapid development in aerospace technology, the aero engine components have to endure larger force and higher temperature due to speed increase of aero-craft. Therefore, more requisitions have to be presented when selecting material…     

添加晶粒细化剂硅对Ti-6Al-4V合金组织和性能的影响(英文)

采用真空感应凝壳熔炼工艺在石墨模中制备Ti-6Al-4V和Ti6Al4V0.5Si两种钛合金。将硅作为一种晶粒细化剂加入到Ti-6Al-4V合金中,考察添加硅对铸态和模锻态Ti-6Al-4V合金组织和性能的影响。铸态合金先在900°C下进行热模锻处理,然后分别进行两种不同的热处理。一种是将模锻样品在1050°C下保温30min,然后水淬以获得细小的层片状组织;另一种是将模锻件在1050°C下保温30min,然后再在800°C下保温30min,以获得粗大的层片状组织。Ti6-Al-4V合金中添加0.5%Si后,铸态合金的晶粒尺寸从627μm减小到337μm,其极限抗拉强度增加约25MPa。具有细小、层片状组织的Ti-6Al-4V0.5Si合金的最大极限抗拉强度为1380MPa,在Hank溶液和NaCl溶液中的腐蚀速度分别为1.35×106和5.78×104mm/a。Ti-6Al-4V合金中添加0.5%Si后,在低滑动速度下的磨损率降低50%,在高滑动速度下的磨损率降低约73%。     

Design for Ti-Al-V-Mo-Nb alloys for laser additive manufacturing based on a cluster model and on their microstructure and properties

In this study, α+β Ti-Al-V-Mo-Nb alloys with the addition of multiple elements that are suitable for laser additive manufacturing (LAM) were designed according to a Ti-6Al-4V cluster formula. This formula can be expressed as 12[Al-Ti₁₂](AlTi₂)+5[Al-Ti₁₄]((Mo, V, Nb)₂Ti), in which Mo and Nb were added into the alloys partially instead of V to give alloys with nominal compositions of Ti-6.01Al-3.13V-1.43Nb, Ti-5.97Al-2.33V-2.93Mo, and Ti-5.97Al-2.33V-2.20Mo-0.71Nb (wt.%). The microstructures and mechanical properties of the as-deposited and heat-treated samples prepared via LAM were examined. The sizes of the β columnar grains and α laths in the Nb-containing samples are found to be larger than those of the Ti-6Al-4V alloy, whereas Mo- or Mo/Nb-added alloys contain finer grains. It indicates that Nb gives rise to coarsened β columnar grains and α laths, while Mo significantly refines them. Furthermore, the single addition of Nb improves the elongation, whereas the single addition of Mo enhances the strength of the alloys. The simultaneous addition of Mo/Nb significantly improves the comprehensive mechanical properties of the alloys, leading to the best properties with an ultimate tensile strength of 1,070 MPa, a yield strength of 1,004 MPa, an elongation of 9%, and micro-hardness of 355 HV. The fracture modes of all the alloys are ductile-brittle mixed fracture.     

粉末冶金碳化物强化铌合金组织演变及其力学行为

采用机械球磨与热压烧结相结合的粉末冶金法对不同球磨时间Nb-35Ti-6Al-5Cr-8V-5C合金的粉末变形行为,微观组织结构和力学行为进行研究。结果表明:随着球磨时间的增加,Nb-35Ti-6Al-5Cr-8V-5C复合粉末中的块状金属颗粒首先变形为片状后在碰撞挤压作用下破碎成絮状,TiC粉末均匀的分布于片状金属粉末表面;Nb-35Ti-6Al-5Cr-8V-5C合金由Nbss和(Nb,Ti)C两相构成,各合金碳化物体积分数均为11%左右,Ti元素主要分布于Nbss晶界和碳化物内,Al、Cr、V元素主要分布于Nbss晶粒内,Nbss和(Nb,Ti)C相尺寸均随球磨时间增加而尺寸减小;Nbss晶粒细化及强化相碳化物弥散化导致合金的室温压缩力学性能和塑性变形能力显著提高,压缩变形后合金Nbss与碳化物具有良好的界面结合能力,但是碳化物内部存在明显的近似平行分布的裂纹;数据对比表明,粉末冶金法制备Nb-35Ti-6Al-5Cr-8V-5C合金的力学性能优于电弧熔炼法。     

Isothermal compression behavior and constitutive modeling of Ti-5Al-5Mo-5V-1Cr-1Fe alloy

Hot compression behavior of Ti-5Al-5Mo-5V-1Cr-1Fe alloy with an equiaxed (α+β) starting microstructure was investigated by isothermal compression test and optical microscopy. Based on the true strain–stress data with temperature correction, constitutive models with a high accuracy were developed and processing maps were established. Strain inhomogeneity at different locations in the compressed sample is reduced by raising temperature, leading to a uniform distribution of α phases. For the temperature range of 800–840 °C with a strain rate of 10 s^?1, the transformed volume fraction of α phase increases and the average grain size of α phase decreases slightly with increasing the temperature, indicating co-existence of dynamic recovery and dynamic recrystallization. Flow localization and faint β grain boundaries are observed at the strain rate of 10 s^?1 in the temperature range of 860–900 °C. The processing map analysis shows that hot working of Ti-5Al-5Mo-5V-1Cr-1Fe alloy should be conducted with the strain rate lower than 0.01 s^?1 to extend its workability.     

Ti-6Al-4V合金的轧制与组织性能

采用光学显微镜、透射电镜和拉伸试验等手段,研究了多道次两向轧制和单向轧制对不同原始状态(热轧态、水淬态和空冷态)Ti-6Al-4V合金显微组织和力学性能的影响。结果表明,热轧态Ti-6Al-4V合金的组织为片状α相+β相+少量等轴α相,水淬态Ti-6Al-4V合金形成了针状马氏体组织,空冷态Ti-6Al-4V合金形成了网状组织。Ti-6Al-4V合金适宜的两向轧制温度为700 ℃,此时合金中可见颗粒状β相弥散分布在α基体上。两向轧制Ti-6Al-4V合金的抗拉强度和屈服强度从高至低顺序为:水淬态>热轧态>空冷态,且轧向强度要高于横向;相较于单向轧制,两向轧制明显降低了Ti-6Al-4V合金板材拉伸性能的各向异性,且水淬态Ti-6Al-4V合金的轧向和横向强度差异最小,700 ℃轧制Ti-6Al-4V合金的主要细化机制为位错细化。     

Microstructure and mechanical properties of the intermetallic alloy Ti-45Al-6(Nb, Mo)-0.2B

The microstructure and tensile properties of the intermetallic γ-TiAl + α₂-Ti₃Al alloy Ti-45Al-6(Nb, Mo)-0.2B are studied after various heat and thermomechanical treatments. Its cast state is found to be characterized by a homogeneous, relatively fine-grained structure in the cases of both a model 30-g ingot and a bulk laboratory ?120 × 180-mm ingot. The cast material subjected to heat treatment with furnace cooling and aging at T = 1100°C exhibits strength properties at T = 20–900°C that are relatively high for cast γ + α₂ alloys. Due to the rational choice of the alloy, its thermomechanical treatment is facilitated, a fine-grained structure can easily be formed upon hot deformation, and a superplastic state with elongations in the test-temperature range T = 900–1000°C that are very large for γ + α₂ alloys is reached. However, the high contents of niobium and molybdenum in the Ti-45Al-6(Nb, Mo)-0.2B alloy hinder the formation of an equilibrium lamellar structure upon heat treatment, and an increase in the aging temperature to T = 1100°C leads to the development of the α₂ → ß(B2) phase transformation, which makes it impossible to reach a high level of the mechanical properties in the temperature range of the potential application of γ + α₂ alloys. Our study has revealed that the compositions of the γ + α₂ alloys need further optimization of the way of refining the niobium and molybdenum contents.     

Precision casting of Ti-15V-3Cr-3AI-3Sn alloy setting

In this research, Ti-15V-3Cr-3Al-3Sn alloy ingots were prepared using ceramic mold and centrifugal casting. The Ti-15V-3Cr-3Al-3Sn setting casting, for aeronautic engine, with 1.5 mm in thickness was manufactured.The alloy melting process, precision casting process, and problems in casting application were discussed. Effects of Hot Isostatic Pressing and heat treatment on the mechanical properties and microstructure of the Ti-15V-3Cr-3Al-3Sn alloy were studied.     

不同SPS烧结温度Ti-45Al-5.5(Cr,Nb,B,Ta)合金的显微组织及力学性能(英文)

采用高能球磨和放电等离子烧结(SPS)技术,制备成分为Ti-45Al-5.5(Cr,Nb,B,Ta)的TiAl合金块体,随后对TiAl合金进行热处理。研究在不同SPS烧结温度下制备的TiAl合金经过热处理后的显微组织和力学性能。结果表明:高能球磨后的合金粉末形状不规则,粉末颗粒尺寸大约为几十微米。XRD分析表明,机械球磨后的粉末由TiAl和Ti3Al两相组成;烧结后的Ti-45Al-5.5(Cr,Nb,B,Ta)合金块体主要是TiAl相,以及少量的Ti3Al和TiB2相。当烧结温度为900°C和1000°C时,合金的显微组织为双相结构,并伴随有一些细小的等轴γ晶粒和细小的针状TiB2相。当烧结温度从900°C上升到1000°C时,Ti-45Al-5.5(Cr,Nb,B,Ta)合金的显微硬度变化不大,抗压强度从1812MPa提高到2275MPa,压缩率从22.66%增加到25.59%,合金的断裂方式为穿晶断裂。     

Precision casting of Ti-15V-3Cr-3Al-3Sn alloy setting

In this research, Ti-15V-3Cr-3Al-3Sn alloy ingots were prepared using ceramic mold and centrifugal casting. The Ti-15V-3Cr-3Al-3Sn setting casting, for aeronautic engine, with 1.5 mm in thickness was manufactured. The alloy melting process, precision casting process, and problems in casting application were discussed. Effects of Hot Isostatic Pressing and heat treatment on the mechanical properties and microstructure of the Ti-15V-3Cr-3Al- 3Sn alloy were studied.     

Microstructural control of Ti-Al-Mo-Nb alloy system with respect to variation of B

In the current study, phase stability of Ti-Al-Mo-Nb alloys was investigated, and the effect of B addition was examined for cast alloys. The fabricated cast alloys were mainly composed of α₂ / γ lamellar with a β phase, when they were heat treated at 1100 °C followed by air cooling, the alloy was composed of α2 / γ lamellar with γ+β necklace phase at the colony boundary for the Ti-45Al-3Mo-2Nb-1B alloy, and the colony size was refined to ~ 20 μm. In order to identify the effect of the microstructures on mechanical strength, compressive tests were performed on the fabricated alloys of Ti-45Al-3Mo-2Nb and Ti-45Al-3Mo-2Nb-1B at room temperature and at 800 °C. The microstructural variations and phase stability were discussed in terms of pseudo-binary phase diagram calculated by Pandat software?.     

Effects of heat treatment on microstructure and mechanical properties of Inconel 625 alloy fabricated by wire arc additive manufacturing process

The microstructure and mechanical properties of Inconel 625 alloy fabricated by wire arc additive manufacturing process were evaluated under as-prepared and heat-treated conditions. A dendritic Ni-based solid solution phase along with (Nb, Ti)C carbide, Laves, and δ-Ni₃Nb secondary phases were developed in the microstructure of the as-prepared alloy. Solution heat treatment led to the dissolution of Laves and Ni₃Nb phases. In addition, dendrites were replaced with large columnar grains. Aging heat treatment resulted in the formation of grain boundary M₂₃C₆ carbide and nanometric γ″ precipitates. Hardness, yield and tensile strengths, as well as elongation of the as-prepared part, were close to those of the cast alloy and its fracture occurred in a transgranular ductile mode. Solution heat treatment improved hardness and yield strength and declined the elongation, but it did not have a considerable impact on the tensile strength. Furthermore, aging heat treatment caused the tensile properties to deteriorate and changed the fracture to a mixture of transgranular ductile and intergranular brittle mode.     

A closely-complete peritectic transformation during directional solidification of a Ti-45Al-8.5Nb alloy

A closely-complete peritectic transformation (PT) was found during directional solidification (DS) of a Ti-45Al-8.5Nb alloy under a low temperature gradient. The closely-complete PT can align the peritectic α phase and control the lamellar orientation. The conditions to obtain a complete PT in primary β TiAl alloys were theoretically evaluated in the dendrite regime.     

Design and preparation of Al-Fe-Ce ternary aluminum alloys with high thermal conductivity

Ce element was introduced to modify Al-2%Fe (mass fraction) binary alloy. The microstructures, crystallization behavior, electrical/thermal conductivities and mechanical properties of these alloys were systematically investigated. The results indicated that the appropriate Ce addition decreased the recalescence temperature and growth temperature of Al-Fe eutectic structure, improved the morphology and distribution of Fe-containing phase, and simultaneously increased the conductivity and mechanical properties. The annealed treatment improved the thermal conductivity of these alloys due to the decreasing concentration of point defects. Rolling process further broke up the coarser Fe-containing phases into finer particles and made the secondary phases uniformly distributed in the α(Al) matrix. After subsequent annealing treatment and rolling deformation, the thermal conductivity, ultimate tensile strength and hardness of the Al-2%Fe-0.3%Ce (mass fraction) alloy reached 226 W/(m·K), (182±1.4) MPa and HBW (49.5±1.7), respectively.     

应用人工神经网络模型预测Ti＋10V-2Fe-3A合金的力学性能

采用人工神经网络方法建立了Ti-10V-2Fe-3Al合金机械性能预测的神经网络模型。模型的输入参数包括变形温度、变形程度、固溶温度、时效温度等热加工工艺参数和热处理制度。模型的输出为钛合金最重要的5个机械性能指标，即抗拉强度、屈服强度、延伸率、断面收缩率和断裂韧性。与传统回归拟合公式相比，该模型具有容错性好、通用性强等优点。该模型可以预测Ti-10V-2Fe-3Al合金在不同热加工工艺参数和热处理制度下的机械性能，也可以用于优化热加工参数和热处理制度。