TNM Alloy Research Articles

Strengthening the {0001} basal texture of α phases for extruded TNM alloy by high magnetic field heat treatment at 1290 ℃

The effect of the magnetic field heat treatment on the high-temperature α phase orientation for extruded TNM alloy was studied. Results show that the strength of {0001} basal texture ({0001} crystal plane is parallel to the extrusion direction) increased after holding for 30 min at 1290 ℃ under the 10T magnetic field. The main reason is due to the preferred growth of α phases with <11-20> orientation (<11-20> crystal orientation is normal to the extrusion direction) during the holding time and the growth behavior of α phases with <11-20> orientation is related to the magnetic field direction. Preferred growth of α phases with <11-20> orientation is mainly by consuming adjacent α phases with <10-10> orientation during holding time at 1290 ℃ under the 10T magnetic field. If the magnetic field direction is parallel to the extrusion direction, the preferred growth of α phases with <11-20> orientation is attributed to the magnetic field inducing the increasing of grain boundary mobility. If the magnetic field direction is normal to the extrusion direction, the preferred growth of α phases with <11-20> orientation is caused by the magnetic driving force generated in grain boundaries under the 10T magnetic field.

In-situ observation of solidification process in β-solidifying γ-TiAl-based alloy

The solidification process of Ti-40Al alloy, a representative β-solidifying γ-TiAl-based alloy, is investigated in-situ using high-temperature laser scanning confocal microscopy (HTLSCM). During the heating process, Ti-40Al alloy exhibits a complete β phase microstructure; however, peritectic α phase is observed during solidification. The occurrence of peritectic α phase is discussed and attributed to the segregation of Al under certain solidification conditions. This finding is further confirmed in the directional solidification of another β-solidifying γ-TiAl-based alloy, TNM alloy, and it provides valuable guidance for controlling the microstructure of β-solidifying γ-TiAl-based alloys.

Twins and β0 precipitation effects on the lamellar degradation in TNM alloy during creep

In this paper, the microstructure instability of the TNM alloy during creep at 800 °C under 150 MPa and 250 MPa was investigated. The results indicate that, both β0 precipitation (inside lamellae) and primary γ twins formation are initiated during the second stage of creep. Compared to low creep stress conditions (150 MPa), high creep stress conditions (250 MPa) accelerate the initiation of the third stage of creep, inducing the precipitation of ω0 phase and secondary twins. The nanoscale ω0 particles formed inside β0 or at the interface of the β0/β0. The intersection of secondary γ twins and α2 lamellae leads to stress concentration and dislocation accumulation, providing nucleation points for β0 phase and promoting the precipitation of β0 within α2 lamellae. The precipitation of the secondary γ twin introduces a unit dislocation of 1/3 [111]γ in the (111) atomic planes, promoting the movement of adjacent atomic planes within the (111) atomic planes. The 1/3 [111]γ dislocations will dissociate into two partial dislocations via 1/3 [111]γ→1/4 [11 1‾]γT +1/9 [0 1‾1]γM. The adjacent atomic planes of the γ matrix and secondary γ twin can transformation to β0 through shear along 1/9 [0 1‾1]γM and 1/4 [11 1‾]γT, respectively. The size and content of β0 phase significantly increase in the third stage of high creep stress, accelerating the decomposition and fragmentation of the α2 lamellae, leading to rapid creep failure.

Detrimental Effects of βo-Phase on Practical Properties of TiAl Alloys

The TNM alloy, a βo-phase-containing TiAl alloy, has been withdrawn from use as a last-stage turbine blade in commercial jet engines as it suffered frequent impact fractures in service, raising doubts regarding the necessity of the βo-phase in practical TiAl alloys. Here, we evaluate the practical properties required for jet engine blades for various TiAl alloys and investigate the effects of the βo-phase thereupon. First, we explore the influence of the βo-phase content on the impact resistance and machinability for forged Ti–43.5Al–xCr and cast Ti–46.0Al–xCr alloys; the properties deteriorate significantly at increasing βo-phase contents. Subsequently, two practical TiAl alloys—TNM alloy and TiAl4822—were prepared with and without the βo-phase by varying the heat treatment temperature for the former and the Cr concentration for the latter. In addition to impact resistance and machinability, the creep strength is significantly reduced by the presence of the βo-phase. Overall, these findings suggest that the βo-phase is an undesirable phase in practical TiAl alloys, especially those used for jet engine blades, because, although the disordered β-phase is soft at high temperatures, it changes to significantly more brittle and harder βo-phase after cooling.

Lamellar orientation control of TiAl-based alloy by uniaxial compressive deformation at high-temperature in (α+β) two-phase region

In this study, the orientation of (α+γ) lamellar structure in the TNM alloy (Ti-43.7Al-4 Nb-1Mo-0.1B) is controlled by high-temperature uniaxial compression conducted in the (α+β) two-phase region. The control of the lamellar orientation is focused on a control of α phase orientation because of being decisive for lamellar γ orientation. All true stress-true strain curves indicated the work softening due to dynamic recrystallization. The stress-strain curve behaviors were consistent with microstructure observation. The peak stress increased with a decrease in lamellar colony size. After deformation in the (α + β) two-phase region at 1543 K and 1573 K, where the content of α phase was dominant, a fiber texture with the (0001)α2 plane tilted 35° away from the compression plane was formed by the deformation mechanism of α phase. On the other hand, at 1623 K where the content of β phase was dominant, a double (0001)α2 fiber texture tilted at 35°- 45° and 80°- 90° away from the compression plane was observed. The double (0001)α2 fiber texture is considered to be caused by β→α phase transformation during cooling according to Burgers orientation relationship. Single-step uniaxial compressions conducted at the (α + β) two-phase region at different temperature (1543 K−1623 K) led to an inclination of (0001)α2to compression plane and subsequently lamellar interfaces of one colony unparallel to those of other colonies.

Origin of surface oxidation induced the nucleation and propagation of microcracks in TNM alloy

This study investigated the impact of surface degradation caused by oxygen (O) and nitrogen (N) elements in the environmental atmosphere on the service failure of nearly lamellar TNM alloy. The results show that oxidation-induced phase transformations at the surface and subsurface regions strongly affect the alloy's tensile properties at high temperatures. The precipitation of Al2O3, which disrupts the integrity of the Ti2AlN layer, has a weaker deformation resistance capacity compared to the Z-phase. Under stress conditions, numerous dislocations concentrate at the Al2O3 phase, causing Al2O3 particles to easily detach and initiating crack nucleation at the Z-phase/Al2O3 interface. This is the origin of oxidation failure. Cracks nucleate at the Al2O3 detachment region, propagate, and connect with surface microcracks induced by the rough and loose outer oxide layer structure. This leads to the rapid propagation of cracks into the subsurface. The consumption of β-stabilizing elements at the surface, along with the internal diffusion of O and N elements into the subsurface region, results in the formation of the hard brittle Z-phase at the subsurface lamellar structure and a transition from β0 to α2 at the lamellar colony boundaries. The precipitation of α2 and Z-phase also accelerates crack propagation. In summary, the failure mode shifts from toughness fracture to brittle fracture.

Identifying low-cost, machinable, impact-resistant TiAl alloys suitable for last-stage turbine blades of jet engines

Existing TiAl alloys used for fabricating last-stage turbine blades of jet engines are relatively cost-prohibitive and unreliable, particularly for use in next-generation engines. The present study was conducted to address these issues by uncovering new TiAl alloy compositions with a focus on improving machinability and impact resistance. Ternary alloys integrated with V or Cr were examined and compared with two commercial TiAl alloys (TiAl4822 and TNM alloy). V and Cr were selected because they are significantly cheaper than the Nb added to existing commercial TiAl alloys and can improve impact resistance (results of previous research). A comparison of the commercial alloys revealed no significant differences in impact resistance; however, TiAl4822 was notably superior to TNM alloy in terms of machinability. Moreover, the V-containing ternary alloys demonstrated significantly higher impact resistance than that of TiAl4822, yet they exhibited inferior machinability. Notably, numerous Cr-doped ternary alloys (such as 48.0Al-2.0Cr/2.5Cr) were superior to TiAl4822 in both machinability and impact resistance. Overall, the study findings indicate that a new TiAl alloy for fabricating jet engine turbine blades with significantly reduced cost and improved reliability can be obtained simply by removing Nb from the existing TiAl4822.

Effect of compositional minor adjustment on localized lamellar structure coarsening of TiAl alloys with different solidification modes

Possible lamellar coarsening in the as-cast microstructure of TiAl alloys significantly affects the subsequent processing of ingot metallurgy, and a systematic study of it is necessary. In this paper, two TiAl alloys with different solidification modes (TNM-45Al alloy and TNM-0.3Si-0.7 C alloy) were obtained by compositional minor adjustment basing on TNM alloy. The effect of different adjustment routes on the localized lamellar structure coarseing behaviour and the resulting differences in the uniformity of the nanohardness distribution were investigated by comparing with TNM alloy. It is found that increasing the Al content of the TNM alloy while keeping the solidification mode as β-solidification unchanged leads to severe localised lamellar coarsening in the S-segregation zone of TNM-45Al alloy, including continuous coarsening (CC) and discontinuous coarsening (DC). In contrast, the solidification mode of the TNM-0.3Si-0.7 C alloy with the addition of the strong α stabilizer elements Si and C is transformed into hypoperitectic solidification with severe peritectic segregation, but the lamellar structure exhibits surprising full-domain stability. The results show that the thermodynamic tendency caused by high Al content and the absence of net-like β-segregation leads to severe localised lamellar coarsening in TNM-45Al alloy. CC can be accomplished through the migration of interface defects. DC is formed by the nucleation and expansion of γ-phase Shockley incomplete dislocations, and the interfaces consist of the α2 /γ interface and the first discovered γ /γ twin interface. The lamellar coarsening of TNM-0.3Si-0.7 C alloy can be effectively suppressed by the solid solution of Si/C atoms and the near net-like β-segregation in the primary β-phase region. As a result, the distribution uniformity of the nanohardness of the lamellar structure in TNM-0.3Si-0.7 C alloy is excellent, with the variance decreasing from ±0.24 of TNM alloy to ±0.20, while it increases to ±0.37 for the TNM-45Al alloy.

Characteristics of lamellar evolution and softening behavior of Powder-HIPed TNM alloy during hot compression

The TNM alloy with full lamellar microstructure and extremely less content of βo/β phase was prepared by powder hot isostatic pressing technology, and the lamellar evolution during hot compressions at temperature of 1200 ℃ and strain rate of 0.01 s−1 were studied in depth. The results show that massive lamellar colonies kink and bend at the initial stage of compression, called geometric softening, leading to the appearance of shaper stress peak in flow curve. The kinked and bent lamellar colonies result from the continuous rotation of lamellae with the lattice rotation axis of 112̅0α//11̅0γ, which gradually transfer the angle of the interfaces of lamellar with respect to the loading axis from 0° to 45°. And then recrystallized grains form at kink bands and the boundaries of deformed lamellar colonies, which is responsible for the slow softening kinetics and the persistent softening stage. The absence of β phase transfers the softening mechanism at the initial deformation stage and weakens the effect of softening at the strain of 0.9.

Cyclic Oxidation Kinetics and Thermal Stress Evolution of TiAl Alloys at High Temperature

The oxidation resistance of TiAl alloys is crucial for their commercial application. In this paper, a cyclic oxidation test with stable air circulation was designed to investigate the cyclic oxidation behavior of the TNM alloy and 4822 alloy at 800 °C and to analyze the phase, morphology, and thermal stress evolution of the oxide layer. The oxidation weight gain curves of both alloys are found to be in parabolic form, and the oxidation reaction orders of the TNM alloy and 4822 alloy are 2.374 and 1.838, respectively. The Nb and Mo elements enhance the antioxidant performance of the TNM alloy by inhibiting the dissolution and diffusion of oxygen, Ti, and Al atoms in the TiAl alloy. The thermal stress evolution of the two alloys during the heating and cooling phases of the cyclic oxidation process are calculated separately, and it is found that the thermal stresses in the TNM alloy are smaller than those in the 4822 alloy, while the maximum thermal stresses appear at the oxide/substrate interface rather than inside the oxide scale, which quantitatively explains the oxidation peeling resistance of the two alloys.

Tailoring lamellar orientation and tensile properties of TNM alloy via extrusion

The rectangular billet of TNM alloy with oriented lamellar microstructure was obtained by extrusion above its α transus temperature. The as-extruded TNM alloy exhibits a nearly lamellar microstructure with an average colony size of approximately 60 μm, and the proportion of lamellar colonies with an angle between the interface and the extrusion direction less than 30° exceeds 70 %. EBSD results show that strong basal texture of α phase with basal planes parallel to the extrusion direction was formed during the extrusion process in the (α+β) two-phase field. During the subsequent cooling process, the γ lamellae precipitates along the (0001) plane of α phase according to the Blackburn orientation relationship, allowing the lamellar structure to inherit the orientation of the parent phase. Tensile test results indicate that the strength and fracture elongation of the as-extruded TNM alloy along the extrusion direction (ED) increased simultaneously, which were 1100 MPa and 1.26 %, respectively. The hindrance effect of interfaces on dislocations and stacking faults in lamellar colonies parallel to the extrusion direction helps to improve strength, while the activation of the prismatic slip and pyramidal slip systems in the α2 lamellae is beneficial to the plasticity. This study shows that it is feasible to control the lamellar orientation and improve the mechanical properties of TNM alloy by extrusion above its α transus temperature.

Emissivity measurements conducted on intermetallic γ-TiAl-based alloys for aeronautical applications

The directional spectral emissivity of a Ti–48Al–2Nb–2Cr alloy (in at.%), 4822 alloy, and a Ti-43.5Al–4Nb–1Mo-0.1B alloy (in at.%),TNM alloy, used in the aeronautical industry, are measured between 150 and 850 °C. The differences in the emissivity values between both alloys at the lowest temperatures, indicates that the βo phase, only present in TNM, exhibit higher emissivity values. By numerical integration of the measured data, the total directional and hemispherical emissivity have been calculated. At 850 °C the total hemispherical emissivity in vacuum are nearly identical with 0.274 ± 0.006 for the 4822 alloy and 0.273 ± 0.007 for the TNM alloy. The lower emissivity change with temperature measured in TNM alloys is related with the deconvolution of βo phase by diffusion processes. Afterwards, near-normal spectral emissivity measurements are performed in both alloys during isothermal oxidation treatments at 750 °C and 850 °C for 120 h. The emissivity data reveal that the TNM alloy exhibits higher oxidation resistance especially at 750 °C. In parallel, microstructural characterization has been performed before the measurements, after the directional emissivity measurements prior to oxidation and after isothermal oxidations. The formed oxide scale is composed of four layers that coincide with those reported in the literature: an outer layer of TiO2 contiguous with a layer of Al2O3, followed by a TiO2/Al2O3 mixed layer and finally a thin layer of Nb-rich nitride. This mixed layer governs the interferential part of the alloys’ emissivity spectra, which, in combination with the background, determines the overall radiative behavior of the alloys under service conditions.

Improvement in compressive creep resistance of Ti-43.5Al–4Nb–1Mo-0.1B alloy via micro-alloying with C and Si

In the present work, the effects of the addition of C and Si on the compressive creep behavior of Ti-43.5Al–4Nb–1Mo-0.1B (TNM) alloy at 850 °C and 900 °C under 260 MPa were investigated. The results show that micro-alloying with C and Si can significantly strengthen the compressive creep resistance of TNM alloy. During compressive creep, obvious dynamic recrystallization occurs in TNM alloy, including major discontinuous dynamic recrystallization and minor continuous dynamic recrystallization. The development of dynamic recrystallization greatly softens the alloy, which leads to large creep deformation. Meanwhile, with the increase of creep strain, the bearing area increases and the actual stress decreases, which eventually results in the secondary creep behavior. In addition, the content of α2 phase increases during compressive creep, which can be attributed to two phase transformations. After adding C and Si, the B2 phase content is decreased and the lamellar colony size is increased, which contributes to the improvement of creep resistance. In addition, fine and dispersed Ti3AlC and Ti5Si3 particles precipitate in α2 lamellae during compressive creep, and maintain definite orientation relationships with α2 and γ phases. This will delay the decomposition of α2 lamellae and greatly improve the lamellar stability. Then, the excellent lamellar stability will inhibit the development of dynamic recrystallization, thus effectively reducing the creep rate.

A refined fully lamellar TiAl alloy extruded at α-phase region: Microstructure and mechanical properties

Multiphase TiAl alloys with refined fully lamellar (RFL) microstructure can balance their mechanical properties at room temperature (RT) and high temperatures, which is vital for their applications. A new cost-effective and compact processing method is needed to reduce the processing cost and widen the extent of applications. In this work, Ti–44.5Al–4Nb–0.5Mo–0.1B (at.%) alloy with RFL microstructure was fabricated using a one-step hot-pack extrusion process at 1280 °C with an extrusion ratio of 4. The microstructure and mechanical properties of the extruded rod were uniform except in a thin layer near the surface. The RFL microstructure exhibited a deformation texture with <11 2‾ 0> α2 parallel to the extrusion direction and (0001) α2 parallel to the radial direction of the rod. The yield strength, ultimate tensile strength and ductility of the rod were simultaneously improved after extrusion due to elimination of βo phase, decrease in the sizes of the lamellar colony and spacing, and the presence of texture. The fundamental reason why RFL microstructure can be obtained by extrusion is that the higher Al and lower Mo contents in the alloy expand α phase region and decrease βo content of the alloy compared with TNM alloy.

Precipitation behavior of hexagonal carbides in a C containing intermetallic γ-TiAl based alloy

Intermetallic γ-TiAl based alloys are currently used as structural materials in high-temperature applications such as turbocharger wheels, valves and turbine blades. Adding C yields solid solution and precipitation hardening of the TiAl alloys, which raises their service temperature. Within this work, the effect of C on the TNM alloying system is analyzed by complementary differential scanning calorimetry measurements and selected heat treatments in conjunction with detailed electron microscopy analysis. This allowed the determination of the transition temperatures and revealed the precipitation onset of hexagonal Ti2AlC carbides between 1450 °C and 1475 °C. The precipitation kinetics of the carbides were further investigated by laser scanning confocal microscopy and revealed a preferred and steady growth in the length direction. Further, orientation relationships between the TiAl phases and the carbides from Blackburn and Burgers type could be determined by electron back-scatter diffraction. The results of this study provide a better understanding of the effect of C addition on the TNM alloy and thus enable further improvement of the alloying design process.

Oxidation protection of TNM alloys with Al-rich γ-TiAl-based coatings

The request to reduce carbon emissions as well as fuel consumptions of modern aerospace and aviation mobility, heavily motivated the development of lighter and more durable high temperature materials. γ-TiAl bulk materials meet many of these requirements due to their unique properties, such as low density, high strength or excellent creep resistance. However, improving their oxidation resistance above 750 °C is still challenging, especially without deteriorating other material properties. Recently, we showed that magnetron sputtered Al-rich γ-TiAl coatings are ideal candidates for well-established TNM bulk alloys (Ti-43.5Al-4Nb-1Mo-0.1B, in at%) to increase their oxidation resistance and to block oxygen inward diffusion. Within this study, we present detailed microstructural investigations of the appearing phase transformations and morphological changes in the coating due to ambient-air-exposure at 850 °C for up to 1000 h. These show that only a 4-µm-thin, well-adhering α-Al2O3-based thermally grown oxide (TGO) forms on top of an initial 16.5-µm-thick coating. Cross-sectional nanobeam diffraction in conjunction with high resolution chemical as well as structural analysis during transmission electron microscopy after these exposures highlight that the Al-rich γ-TiAl coating is perfectly intermixed with the TNM substrate material. Already after 100 h oxidation at 850 °C, no interface between the Al-rich γ-TiAl coating and the TNM alloy can be identified chemically or structurally. The structural homogenization is governed by the transformation of all Al-rich phases (i.e., TiAl3 or Ti2Al5) – also present in the as-deposited state – towards γ-TiAl. After 1000 h at 850 °C, the predominant phase within the original coating region is γ-TiAl, next to the highly dense and well-adherent α-Al2O3-based scale.

Enhanced strength-ductility synergy of β-solidifying TiAl alloy with preferred lamellar orientation by texturing high-temperature α phase through hot extrusion

A preferentially-aligned lamellar structure in TNM alloy with enhanced strength-ductility synergy is successfully obtained by texturing the high-temperature α phase through hot extrusion. The lamellar orientations of the resultant lamellar colonies inherit the texture feature of the extruded high-temperature α phase ({0001} basal fiber texture), exhibiting a preferential distribution with 60% of the lamellar traces {0001}α/{111}γ nearly parallel to the extrusion direction (ED). The influence of the microstructural variables on the deformation mechanisms and fracture mechanisms are elucidated by microstructural characterization and crystallographic analysis. Results show that when the lamellar trace is parallel to the tensile direction (TD//ED), twinning and stacking faults in the γ laths are favorable to be activated. The origin of the enhanced strength-ductility synergy is attributed to the combined effects of twinning, stacking faults and its induced dislocation slip, as well as the extra interaction stresses introduced by the multiple deformation mechanisms and the α2/γ interfaces. This study can provide a novel strategy for microstructural regulation and design of high-performance β-solidifying TiAl alloys.

Hot salt corrosion behavior of the Ti-44Al-4Nb-1.5Mo-(B,Y) alloy in the temperature range of 750–950 °C

Hot salt corrosion behavior of TNM alloy (Ti-44Al-4Nb-1.5Mo-(B, Y) (at.%)) was investigated in cyclic conditions at 750 °C, 850 °C and 950 °C for 100 h in the 75 wt% Na2SO4 + 25 wt% NaCl salt mixture. The hot salt corrosion resistance of γ、α2 and β phase in the alloy was studied by short-term quasi-in-situ hot corrosion experiments. Results show that the hot salt corrosion resistance of the three phases decreases in the following order: γ、α2、β. The weight changes of TNM alloy after hot salt corrosion at 750 °C, 850 °C and 950 °C for 100 h are 13.8 mg/cm2, -19.6 mg/cm2 and -26.7 mg/cm2. Under the condition of hot salt corrosion at 750 °C, the corrosion scales are mainly composed of a mixed corrosion scale of TiO2 and Al2O3, Al2O3 scale, and Al depletion zone, similar to the morphology of a high-temperature oxidation scale. The corrosion scales are seriously peeled off and destructive transverse cracks are generated inside the corrosion scales under the conditions of hot salt corrosion at 850 °C and 950 °C. The acid-base corrosion dissolution of oxides in the corrosive medium and the formation of volatile chlorides are the main causes of cracks in the TiO2 and Al2O3 scales. In addition, the Nb element in the TNM alloy is mainly enriched beneath the corrosion scales to form a NaNbO3 layer, which can inhibit the decomposition and penetration of the corrosive medium. Mo element reacts with the S element to form MoS2, which anchors the S element to a certain extent.

Electrochemical dissolution behavior of TNM intermetallic in sodium nitrate solution

TNM alloy is a new kind of lightweight and high temperature resistant material. Electrochemical machining (ECM) is an ideal manufacturing method for TNM alloy because of its high machining efficiency and good machining quality. In this work, the dissolution properties and surface passive film of TNM in NaNO3 solution are studied comprehensively. The passivation properties of the samples are tested using potentiodynamic, potentiostatic and CV curves. The results show that there are obvious passive and transpassive areas on the surface of TNM alloy, and the corrosion resistance of the passive film gradually increased with the test time from 0 to 7200 s. XPS and EIS indicate that the passive film mainly consists of Al2O3, TiO2, Nb2O5 and MoO3. Its structure is a bi-layer consisting of an inner layer with few pores and an outer layer with many pores. A corresponding schematic model is also proposed to characterize the interface structure between TNM alloy matrix and passive film. TNM alloy has a very high material removal rate according to the ηω-j curve. The dissolution morphology of TNM alloy is observed at various current densities. It is found that the surface dissolution morphology is very different under low and high current densities. The sample exhibits a loose lamellar microstructure with some isolated lamellar colonies at low current density, while the surface is quite smooth (about Ra 0.55 μm) when current density (j) > 20 A/cm2. Finally, the material dissolution process of TNM alloy at 2 and 25 A/cm2 is also presented.

Microstructural influences on fatigue threshold behavior and fracture toughness of an additively manufactured γ-titanium aluminide

The fracture and fatigue behavior of an additively manufactured γ-TiAl alloy (BMBF3) produced by selective electron beam melting and further subjected to two different heat treatment conditions was investigated. As one of the heat-treatments led to a pronounced layer structure, the experiments were also performed with different specimen orientations to account for possible anisotropy effects. In order to characterize the frequently found peculiarities of the local fracture process in this material class, such as shear ligament bridging, static and cyclic R-curves were recorded. In addition, also fatigue crack growth curves were measured. The results were critically compared with the properties of a selected heat treatment condition of an established TNM alloy manufactured by a conventional processing route. The investigations show that large α2/γ-colonies lead to high fracture toughness, but have almost no positive effect on the long-crack fatigue threshold. On the other hand, duplex microstructures with small α2/γ-colonies and thick lamellae favor high long-crack thresholds, but low fracture toughness. Microstructures with high fractions of globular γ-phase exhibited both, low fracture toughness and low long-crack fatigue threshold values. In comparison to the established TNM reference alloy, the additively manufactured counterparts can compete especially when the evolving anisotropy of the properties is taken into account for component design.