Doped Alloys Research Articles

The formation mechanism of micro-nano secondary phase in solid-liquid doped TZM alloy

Among the various secondary phases distributed in the TZM (Titanium-Zirconium-Molybdenum) alloy matrix, the ones that can play a strengthening role are often those with a particle size smaller than 1 μm. In this study, titanium sulfate, zirconium nitrate, and fructose were used as raw materials. The TZM alloy with uniform distribution and an average secondary phase particle size of 940 nm (hereinafter referred to as MN-TZM alloy) was prepared through a solid-liquid doping preparation process. The thermodynamic calculation reveals the formation mechanism of the micro-nano-level secondary phase in the MN-TZM alloy. Thermogravimetric analysis (TG-DSC, TG-MS) and transmission electron microscope (TEM) confirmed the calculation results. The generation process of the micro-nano secondary phase evolution can be divided into four parts. The first stage is the process of solute dissolution at room temperature. In the second stage, doping and drying process take place below 100 °C. Third, reduction and secondary phase precursor incubation processes occur from 100 to 700 °C. Fructose decomposes (100 °C) to obtain organic carbon and water. The decomposition of zirconium nitrate (100 °C) yields NH 3 , H 2 O, ZrO 2 and Zr, while the titanium sulfate decomposes directly at 200– 242 °C to obtain SO 2 , H 2 O, TiO 2 and Ti. In the last stage, the secondary phase nucleates and grows up (700– 1800 °C). A large variety of micro-nano-scale and even nano-scale secondary phase particles have been discovered, including TiO 2 , ZrO 2 , ZrC and TiC. These observations provide necessary information for tracing back the secondary phase precipitation mechanism in the manufacturing process of high-performance molybdenum alloys. • The average grain size of MN-TZM alloy is 940 nm. • The micro-nano secondary phase reduces the average grain size of TZM alloy by 26%. • TZM alloy was prepared from titanium sulfate, zirconium nitrate, fructose and molybdenum powder for the first time. • The formation mechanism of micro-nano secondary phase in TZM alloy was clarified.

Cd-doping effects in Ni–Mn–Sn: experiment and ab-initio study

Martensitic transformation (MT), magnetic properties, and magnetocaloric effect (MCE) in Heusler-type Ni47Mn40Sn13−x Cd x (x= 0, 0.75, 1, 1.25 at. %) metamagnetic shape memory alloys (MetaMSMAs) are investigated, both experimentally and theoretically, as a function of doping with Cd. Ab-initio computations reveal that the ferromagnetic (FM) configuration is energetically more favorable in the cubic phase than the antiferromagnetic (AFM) state in undoped and doped alloys as well. Moreover, it is revealed that the alloys in the ground state exhibit a tetragonal structure confirming the existence of MT, in agreement with the experiments. It was indicated, both in theory and practice, that a reduction of the unit cell volume and an increase of the MT temperature as a function of the Cd doping. Indirect estimations of MCE in the vicinity of MT were carried out by using thermomagnetization curves measured under different magnetic fields up to 5 T. The results demonstrated that the doped alloys exhibit enhanced values of the inverse MCE comparable with those of Ni-Mn-based MetaMSMAs. Maximum magnetic entropy change in a field change of 2 T increases from 3.0 for the undoped alloy to 3.4 and 5.0 for the alloys doped with 0.75 and 1 at.% of Cd, respectively. The inverse and conventional MCE were explored by direct measurements of the adiabatic temperature change under the magnetic field change of 1.96 T. The Cd doping increased the maximum of inverse MCE by nearly 78% from 0.9 K to 1.6 K for the undoped and doped alloys, respectively. The results depicted that Cd doping can effectively tailor the structural, magnetic, and MCE properties of the Ni–Mn–Sn MetaMSMAs.

Synergistically optimizing carrier and phonon transport properties in n-type PbTe through I doping and SnSe alloying

PbTe is a promising thermoelectric material, but the properties in n-type PbTe need further improvement to match its advanced p-type material. In this work, the thermoelectric performance in n-type PbTe is synergistically enhanced with iodine (I) doping and SnSe alloying. The experiments show that I element is a good donor dopant to tune the carrier density and SnSe alloying can effectively balance the triple-relations between carrier mobility, carrier effective mass, and lattice thermal conductivity. Thus, high carrier mobility of ∼755 cm2V−1s−1 results in an optimum power factor (PF) of ∼27.0 μWcm−1K−2 in PbTe–2%SnSe at 573 K. Microstructure observation reveals the dispersively embedded Sn-rich nanoprecipitates in PbTe–2%SnSe, which largely suppresses lattice thermal conductivity at room temperature, from ∼3.41 Wm−1K−1 in PbTe to ∼1.01 Wm−1K−1 in PbTe–2%SnSe. Combined the optimized PF and decreased thermal conductivity, the peak ZT value of ∼1.5 can be obtained at 773 K in PbTe–2%SnSe. The obtained high thermoelectric performance in our work is comparable with other advanced n-type PbTe thermoelectrics and has great application potential.

Decoupling of thermoelectric transport performance of Ag doped and Se alloyed tellurium induced by carrier mobility compensation

• Ag doping and Se alloying optimize the thermoelectric performance of Te. • Se alloying effectively reduces lattice thermal conductivity of Te by refining grain of Te and introducing high density-defects. • Ag doping regulates the micro morphology and increases the grain size of Te-Se solid solution. • Ag doping successfully compensates the lost carrier mobility due to Se alloying while retains the ability of Te-based matrix to scatter high-frequency (ω) and medium-frequency phonons. • Sb doping effectively optimizes the carrier concentration of Te. Alloying with Se is proved to be feasible to suppress the lattice thermal conductivity ( κ L ) of tellurium by introducing multidimensional lattice defects. However, extra ionization impurity centers induced by Se alloying are harmful to the electric transport properties of the matrix. In this paper, we propose that the incorporation of Ag could successfully compensate the lost carrier mobility ( μ H ) due to Se alloying through the regulation of microstructure, resulting in the higher power factor (PF) than that of samples without Ag. After composition optimization, the κ L decreased from 1.29 W m −1 K −1 of Te 0.99 Sb 0.01 to 1.05 W m −1 K −1 of Te 0.94 Ag 0.02 Se 0.03 Sb 0.01 at 350 K, while the PF remained unchanged or even slightly increased. Benefit from the synergistic effect of carrier mobility compensation and phonon scattering, a maximum zT of 0.91 at 573 K and an average zT of 0.57 (between 298 and 573 K) are achieved in Te 0.94 Ag 0.02 Se 0.03 Sb 0.01 . This work presents a new strategy for decoupling the thermal and electric parameters of Te-based thermoelectric materials.

Effects of Fe, Mn Individual Doping and (Fe, Mn) Co-Doping on Ferromagnetic Properties of Co2Si Powders.

Magnetic materials are crucial energy materials that are widely used in day-to-day life. Therefore, the development and study of high-performance magnetic materials are of great significance. In this study, the magnetic materials CoSi, CoXSi (X = Fe, Mn), and CoFeMnSi were prepared via the ball milling and sintering processes. Their crystal structures, electrical conductivity, and magnetic properties were investigated via the X-ray diffraction analysis and by using a resistivity tester, vibrating sample magnetometer, and vector network analyser. The X-ray diffraction analysis revealed that a single phase of CoSi and its doped alloy powders were successfully obtained. The electrical conductivities of MnCoSi and FeMnCoSi were measured using a resistivity tester. The results indicate that Mn doping and Fe and Mn Co-doping enhanced the electrical conductivity of CoSi. The magnetic properties of CoSi were determined using a vibrating sample magnetometer. We observed that the magnetic properties were enhanced after doping. CoFeMnSi exhibited excellent magnetic properties. Further, its permeability was determined using a vector network analyser. At a low frequency, the u’ and u” values of CoFeSi and CoFeMnSi were enhanced; whereas, at a high frequency, after doping, the u’ and u” values changed only slightly. This study can be used as a basis for future studies on magnetic functional materials.

Hydrophilic/Aerophobic Tunning of Zn Doped Nicoox-1 Alloys Nanorods Nanoarray for High-Efficiency Hydrogen Production Via Overall Hydrazine Splitting in Alkaline Electrolyte

Hydrophilic/Aerophobic Tunning of Zn Doped Nicoox-1 Alloys Nanorods Nanoarray for High-Efficiency Hydrogen Production Via Overall Hydrazine Splitting in Alkaline Electrolyte

Enhancement of thermoelectric performance for n-type PbS via synergy of CuSbS2 alloying and Cl doping

Lead sulfide has attracted extensive attention as an outstanding thermoelectric material with practical energy conversion applications at intermediate temperature scope due to its cost-effectiveness and earth-abundant constituent elements. However, the naturally low carrier concentration and high thermal conductivity greatly restrict the thermoelectric performance of PbS-based materials. Herein, we present a significantly promoted thermoelectric performance in n-type PbS through synergistically promoting the electrical conductivity and suppressing lattice thermal conductivity with Cl doping and CuSbS2 alloying. The alloying with CuSbS2 lowers lattice thermal conductivity of PbS, which is essentially ascribed to point defect scattering. While the substitution of Cl for S in lattice significantly increases the Hall carrier concentration and carrier mobility, which prominently boosts electrical conductivity and thus results in high power factor of ~1.38 mW/mK2 at 723 K. Finally, compound with the nominal composition of (PbS0.98Cl0.02)0.95(CuSbS2)0.05 reaches a peak zT of ~0.76 at 773 K.

Boosting the water gas shift reaction on Pt/CeO2-based nanocatalysts by compositional modification: Support doping versus bimetallic alloying

The water gas shift reaction is of vital significance for the generation and transition of energy due to the application in hydrogen production and industries such as ammonia synthesis and fuel cells. The influence of support doping and bimetallic alloying on the catalytic performance of Pt/CeO2-based nanocatalysts in water gas shift reaction was reported in this work. Various lanthanide ions and 3d transition metals were respectively introduced into the CeO2 support or Pt to form Pt/CeO2:Ln (Ln = La, Nd, Gd, Tb, Yb) and PtM/CeO2 (M = Fe, Co, Ni) nanocatalysts. The sample of Pt/CeO2:Tb showed the highest activity (TOF at 200 °C = 0.051 s−1) among the Pt/CeO2:Ln and the undoped Pt/CeO2 catalysts. Besides, the sample of PtFe/CeO2 exhibited the highest activity (TOF at 200 °C = 0.12 s−1) among PtM/CeO2 catalysts. The results of the multiple characterizations indicated that the catalytic activity of Pt/CeO2:Ln catalysts was closely correlated with the amount of oxygen vacancies in doped ceria support. However, the different activity of PtM/CeO2 bimetallic catalysts was owing to the various Pt oxidation states of the bimetals dispersed on ceria. The study of the reaction pathway indicated that both the samples of Pt/CeO2 and Pt/CeO2:Tb catalyzed the reaction through the formate pathway, and the enhanced activity of the latter derived from the increased concentration of oxygen vacancies along with promoted water dissociation. As for the sample of PtFe/CeO2, its catalytic mechanism was the carboxyl route with a higher reaction rate due to the moderate valence of Pt along with improved CO activation.

Synergistically enhanced thermoelectric properties of Bi2S3 bulk materials via Cu interstitial doping and BiCl3 alloying

Synergistically enhanced thermoelectric properties of Bi2S3 bulk materials via Cu interstitial doping and BiCl3 alloying

Dislocations Stabilized by Point Defects Increase Brittleness in PbTe

AbstractDislocations and the residual strain they produce are instrumental for the high thermoelectric figure of merit, zT ≈ 2, in lead chalcogenides. However, these materials tend to be brittle, barring them from practical green energy and deep space applications. Nonetheless, the bulk of thermoelectrics research focuses on increasing zT without considering mechanical performance. Optimized thermoelectric materials always involve high point defect concentrations for doping and solid solution alloying. Brittle materials show limited plasticity (dislocation motion), yet clear links between crystallographic defects and embrittlement are hitherto unestablished in PbTe. This study identifies connections between dislocations, point defects, and the brittleness (correlated with Vickers hardness) in single crystal and polycrystalline PbTe with various n‐ and p‐type dopants. Speed of sound measurements show a lack of electronic bond stiffening in p‐type PbTe, contrary to the previous speculation. Instead, varied routes of point defect–dislocation interaction restrict dislocation motion and drive embrittlement: dopants with low doping efficiency cause high defect concentrations, interstitial n‐type dopants (Ag and Cu) create highly strained obstacles to dislocation motion, and highly mobile dopants can distribute inhomogeneously or segregate to dislocations. These results illustrate the consequences of excessive defect engineering and the necessity to consider both mechanical and thermoelectric performance when researching thermoelectric materials for practical applications.

Identification of the features of structural-phase transformations in the processing of waste from the production of high-alloy steels

This paper reports a study into the peculiarities of the structural-phase composition of the alloy obtained by using anthropogenic waste from the production of high-alloy steels involving reduction melting. That is necessary for determining the technological parameters that could help decrease the loss of alloying elements in the process of obtaining and using a doped alloy. This study has shown that at an O:C ratio in the charge of 1.84, the alloy consisted mainly of the solid solution of carbon and alloying elements in α-Fe. The manifestation of Fe3C C carbide with alloying elements as substitution atoms was of relatively weak intensity. At the O:C ratios in the charge of 1.42 and 1.17, there was an increase in the intensity of the Fe3C carbide manifestation. At the same time, the emergence of the carbide compounds W2C·Mo2C and WC was identified. Several phases with different content of alloying elements were present in the microstructure images. Cr content in the examined areas changed in the range of 0.64–33.86 % by weight; W content reached 41.58 % by weight; Mo –19.53 % by weight; V – 18.55 % by weight; Co – 3.95 % by weight. The carbon content was in the range of 0.28–2.43 % by weight. Analysis of the study results reveals that the most favorable ratio of O:C in the charge was 1.42. At the same time, the phase composition was dominated by a solid solution of the alloying elements and carbon in α-Fe. The share of the residual carbon concentrated in the carbide component was in the range of 0.52–2.11 % by weight, thereby ensuring the required reduction capability of the alloy when used. The study reported here has made it possible to identify new technological aspects of obtaining an alloy by utilizing anthropogenic waste, and whose indicators provide for the possibility of replacing part of standard ferroalloys when smelting steels without strict restrictions on carbon content.

Engineering the Thermal Conductivity of Doped SiGe by Mass Variance: A First-Principles Proof of Concept

Thermal conductivity of bulk Si0.5 Ge0.5 at room temperature has been calculated using density functional perturbation theory and the phonon Boltzmann transport equation. Within the virtual crystal approximation, second- and third-order interatomic force constants have been calculated to obtain anharmonic phonon scattering terms. An additional scattering term is introduced to account for mass disorder in the alloy. In the same way, mass disorder resulting from n- and p-type dopants with different concentrations has been included, considering doping with III-group elements (p-type) such as B, Al, and Ga, and with V-group elements (n-type) such as N, P, and As. Little effect on the thermal conductivity is observed for all dopants with a concentration below 1021 cm−3. At higher concentration, reduction by up to 50% is instead observed with B-doping in agreement with the highest mass variance. Interestingly, the thermal conductivity even increases with respect to the pristine value for dopants Ga and As. This results from a decrease in the mass variance in the doped alloy, which can be considered a ternary system. Results are compared to the analogous effect on the thermal conductivity in doped Si.

Bandgap widening and behavior of Raman-active phonon modes of cubic single-crystalline (In,Ga)2O3 alloy films

The influence of Ga incorporation into cubic In2O3 on the electronic and vibrational properties is discussed for (In1−x,Gax)2O3 alloy films grown by molecular beam epitaxy. Using spectroscopic ellipsometry, a linear dependence of the absorption onset on the Ga content x is found with a blueshift of up to 150 meV for x = 0.1. Consistently, the fundamental bandgap exhibits a blueshift as determined by hard x-ray photoelectron spectroscopy. The dependence of the absorption onset and the effective electron mass on the electron concentration is derived from the infrared dielectric functions for a Sn doped alloy film. The influence of alloying on phonon modes is analyzed on the basis of Raman spectroscopic measurements. The frequencies of several phonon modes are identified as sensitive measures for the spectroscopic determination of the Ga content.

Effect of boron addition on the microstructure and mechanical properties of refractory Al0.1CrNbVMo high-entropy alloy

The effect of boron (B) addition on the microstructure and mechanical properties of a refractory high-entropy alloy (RHEA) was investigated. The Al0.1CrNbVMo RHEA was doped with 0.015 at.% of B by the powder metallurgical process, and its mechanical properties were compared with undoped RHEA. The microstructures of the undoped and doped RHEAs consisted of a single body-centered cubic matrix phase with homogeneously distributed Al2O3 inclusions. The doped B atoms segregated along grain boundaries and did not form any boride phases. Boron segregation at the grain boundaries was characterized by atom-probe tomography. Compared with the undoped RHEA, the B-doped RHEA showed improved yield strength of 2933 MPa (15% improvement) and ductility of 25.9% (26% improvement). Adding B transformed the fracture surface from intergranular to transgranular due to enhanced grain boundary cohesion induced by B segregation, which resulted in improved ductility. Quantitative analysis was conducted on the undoped and doped alloys to investigate the effect of B on yield strength. The improved yield strength resulting from B doping was attributed to the combined effects of Orowan, dislocation, and B interstitial strengthening. This work demonstrates that B doping of RHEAs is a promising way to overcome their limited room temperature ductility, while maintaining excellent strength.

Influence of environment on thermoelectric properties of n-type silicon-germanium alloy

Environmental stability of material properties is an important factor for its utilization for electronic devices. Gases in air such as oxygen can react chemically with material and cause degradation of its properties. This work reports on effect of air on thermoelectric properties of nanostructured n-type silicon-germanium (SiGe) alloy: a well-known high temperature thermoelectric material with superior properties. Phosphorous doped SiGe alloy was synthesized via mechanical alloying followed by hot-press and characterized by powder X-ray diffraction, scanning electron microscopy, and thermoelectric measurements. The average grain size of alloyed powder was in the range 50 - 400 nm. The reduction in grain size caused decrease in thermal conductivity of SiGe alloy (2.044 W/mK at ~ 900K). To study the effect of air on the transport properties of alloy measurements were carried out in presence of air and in inert (argon) atmosphere. Interesting results have been obtained and discussed with the available literature.

Alloying and magnetic disordering effects on the martensitic transformation and elastic property of Co2VGa Heusler alloy: A first-principles study

Using the first-principles exact muffin-tin orbital method in combination with the coherent potential approximation, the alloying and magnetic disordering effects on the phase stability and elastic property of L21- and D022-Co2VGa Heusler alloy are systematically investigated. It is shown that at the ground ferromagnetic (FM) state, Co2VGa alloy possesses the L21 structure and correspondingly, its shear modulus, Young modulus, and Debye temperature of the phase are all larger than those of the D022 phase. When the FM state transiting to the paramagnetic (PM) one, both C′(=(C11-C12)/2) and C44 of the L21 phase decrease whereas the elastic anisotropy increases, and they do so as well with increasing the number of valence electrons per atom (e/a) in the off-stoichiometric ternary and doped quarternary alloys with the FM ordering. As a result, at 0 K the magnetic disordered Co2VGa alloy with the disordering degree (y) larger than 0.2 can show the martensitic transformation (MT) from L21 to D022, and the MT is also obtained in the FM Co2V(Ga1-xZx) alloys with Z = Co (x⩾0.2), V and Ge (x⩾0.4), Si (x⩾0.5), and Sb (x⩾0.3). Accompanying the MT, their volume tends to decrease, and these L21 alloys possessing a bigger volume than those with the same e/a ratios are also relatively more prone to the MT. In the Z = V alloys, both greater magnetocaloric and magnetostrain effects may be expected during the MT as well. Both the minority Co d and V d states around the Fermi level should be responsible for the composition and magnetic ordering dependence of the phase stability of Co2VGa alloy.

Identification of patterns in the structural and phase composition of the doping alloy derived from metallurgical waste processing

This paper reports a study into the structural-phase composition of the doping alloy made by processing metallurgical anthropogenic waste involving reduction smelting. This is required for determining the technological parameters that ensure an increase in the level of extraction of target elements during the processing of anthropogenic waste and for the further use of the doping alloy. It was revealed that the phase composition of the doping alloy manifested a solid solution of the doping elements and carbon in α-Fe. Cementite Fe3C and silicides Fe5Si3, FeSi, and FeSi2 were also identified. In this case, the doping elements were more likely to act as substitution atoms. It has been determined that the microstructure of the alloy consisted of several phases of different shapes and contents of the basic doping elements. Sites with an elevated iron level of up to 95.87 % by weight in the composition could be represented by the solid solution phase of the doping elements and carbon in α-Fe. The sites with a relatively high (% by weight) content of carbon (0.83‒2.17) and doping elements ‒ W, up to 39.41; Mo, up to 26.17; V, to 31.42; Cr, to 9.15 ‒ were apparently of a carbide nature. The sites with a silicon content of 0.43‒0.76 % by weight likely included silicide compounds. The alloy's characteristics make it possible to smelt steel grades without strict carbon restrictions, replacing some of the standard ferroalloys. Neither phases nor compounds with a relatively high propensity for sublimation were identified in the material produced. Therefore, there is no need to provide conditions to prevent evaporation and loss in the gas phase of the doping elements. That could increase the degree of extraction of the doping elements

Corrosion of indium doped E-AlMgSi aluminum conductor alloy (Aldrey)

The effect of impurities on the electrical conductivity of aluminum has been studied in detail. The electrical conductivity of aluminum is 65.45% of that of copper. The tensile strength of aluminum wire is 150–170 MPa which, at equal conductivity, is about 65% of the strength of copper wire. This strength of aluminum wire is sufficient for bearing the wire’s own weight but may be too low in case of snow, ice or wind overloads. One way to improve the strength of aluminum wire is to use aluminum alloys having higher strength combined with sufficiently high electrical conductivity, e.g. the E-AlMgSi alloy (Aldrey). The key strengthening agent of the E-AlMgSi alloy (Aldrey) is the Mg2Si phase which imparts high mechanical strength to aluminum. In this work we present experimental data on the kinetics of high-temperature oxidation and electrochemical corrosion of indium doped E-AlMgSi aluminum conductor alloy (Aldrey). Thermal gravimetric study has shown that indium doping and high temperature exposure increase the oxidation rate of E-AlMgSi alloy (Aldrey), with the apparent alloy oxidation activation energy decreasing from 120.5 to 91.8 kJ/mole. Alloy oxidation rate data determined using a potentiostatic technique in NaCl electrolyte media have shown that the corrosion resistance of the indium doped alloy is 20–30% superior to that of the initial alloy. With an increase in NaCl electrolyte concentration the electrochemical potentials of the alloys decrease whereas the corrosion rate increases regardless of alloy composition.

Martensitic transition assisted modification of the antiferromagnetic ordering in Ge-site doped MnNiGe alloys

The magnetic equiatomic alloys of the nominal compositions ${\mathrm{MnNiGe}}_{0.9}{\mathrm{Al}}_{0.1}$ and ${\mathrm{MnNiGe}}_{0.928}{\mathrm{Ga}}_{0.072}$ have been investigated through the neutron powder diffraction (NPD) technique. Both these alloys undergo a martensitic phase transition from the high-temperature hexagonal (${\mathrm{Ni}}_{2}\mathrm{In}$ type, with space group $P{6}_{3}/mmc$) austenite phase to the low-temperature orthorhombic (TiNiSi type, with space group $Pnma$) martensite phase. Our NPD analysis confirmed an incommensurate antiferromagnetic ordering of the low-temperature martensitic phase with helical modulation. The incommensurate propagation vector $\mathbf{k}$ is found to be (0.2065(1),0,0) and (0.2088(4),0,0) for Al and Ga doped alloys, respectively, at 1.5 K and shows a monotonic increase with increasing sample temperature. On the other hand, a commensurate antiferromagnetic ordering was observed for the high-temperature austenite phase. The incomplete martensitic transition allowed both these incommensurate and commensurate antiferromagnetic structures to coexist down to the lowest temperature of measurement (1.5 K).

Enhanced creep properties of Y2O3-bearing Ti-48Al-2Cr-2Nb alloys

Abstract This study examined the influence of Y2O3 addition on the creep behavior of Ti-48Al-2Cr-2Nb alloy. Creep tests of Ti-48Al-2Cr-2Nb and Ti-48Al-2Cr-2Nb-0.05Y2O3 alloys were performed under 275–325 MPa at 800 °C. The results show Y2O3 can significantly enhance the creep properties of the titanium aluminide (TiAl) alloys. Under applied stress, the creep rupture life can be increased three-fold with the addition of Y2O3 and the minimum creep rate drops by around one-third. Stress exponents of the TiAl alloy matrix and Y2O3-bearing alloy were found to be 6.77 and 4.49, respectively, suggesting creep is controlled by the dislocation climb mechanism. The excellent creep properties of the doped alloy can be attributed to the thin lamellar structures and dispersed second phases. The fine Y2O3 particles can impede dislocation climb and prevent sub-boundary formation. Microstructure instabilities occur in both alloys during creep exposure. Y2O3 particles accelerate recrystallization of γ phases and precipitation of B2 phases. The combination of fine grains, increasing massive γ phases and more precipitates in the Y2O3-bearing alloy may promote the development of cracks and cavities, leading to the low fracture strain.