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Rudi Kulenovic - One of the best experts on this subject based on the ideXlab platform.
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measurement of thermochemical properties of some Metal hydrides titanium ti Misch Metal mm and lanthanum la based alloys
International Journal of Hydrogen Energy, 2013Co-Authors: Karthick P Selvam, P. Muthukumar, Marc Linder, Rainer Mertz, Rudi KulenovicAbstract:Abstract In this manuscript, the estimation of thermochemical properties such as enthalpy of formation (ΔH) and entropy of formation (ΔS) during hydriding and dehydriding reactions of three titanium (Ti), five Misch Metal (Mm) and eight lanthanum (La) based Metal hydride alloys are presented. van't Hoff plots of the selected Metal hydride alloys are constructed using the Pressure–Concentration–Temperature (PCT) characteristics measured at different operating temperatures. Reaction enthalpies during hydriding and dehydriding processes are expressed as a function of hydrogen storage capacity by a polynomial equation of order three. The average enthalpy of formation during dehydriding process of the investigated titanium and lanthanum based alloys are about 3–18% higher than their respective hydriding enthalpies. While, dehydriding enthalpies of LmNi4.49Al0.205Mn0.205Co0.1 and MmNi4.85Al0.15 are about 26.5% and 40% higher than their respective hydriding enthalpies. The variation in reaction enthalpies during the initial and final stages of hydriding process of titanium based alloys is in the range of 7–9%, while the respective ranges for Misch Metal and lanthanum based alloys are about 3–7.5% and 2.1–8.5%, respectively.
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Measurement of thermochemical properties of some Metal hydrides – Titanium (Ti), Misch Metal (Mm) and lanthanum (La) based alloys
International Journal of Hydrogen Energy, 2013Co-Authors: P. Karthick Selvam, P. Muthukumar, Marc Linder, Rainer Mertz, Rudi KulenovicAbstract:Abstract In this manuscript, the estimation of thermochemical properties such as enthalpy of formation (ΔH) and entropy of formation (ΔS) during hydriding and dehydriding reactions of three titanium (Ti), five Misch Metal (Mm) and eight lanthanum (La) based Metal hydride alloys are presented. van't Hoff plots of the selected Metal hydride alloys are constructed using the Pressure–Concentration–Temperature (PCT) characteristics measured at different operating temperatures. Reaction enthalpies during hydriding and dehydriding processes are expressed as a function of hydrogen storage capacity by a polynomial equation of order three. The average enthalpy of formation during dehydriding process of the investigated titanium and lanthanum based alloys are about 3–18% higher than their respective hydriding enthalpies. While, dehydriding enthalpies of LmNi4.49Al0.205Mn0.205Co0.1 and MmNi4.85Al0.15 are about 26.5% and 40% higher than their respective hydriding enthalpies. The variation in reaction enthalpies during the initial and final stages of hydriding process of titanium based alloys is in the range of 7–9%, while the respective ranges for Misch Metal and lanthanum based alloys are about 3–7.5% and 2.1–8.5%, respectively.
C.h. Koo - One of the best experts on this subject based on the ideXlab platform.
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improving the microstructure and high temperature properties of the ti 40al 16nb alloy by the addition of a minor sc or la rich Misch Metal
Intermetallics, 2004Co-Authors: C.t. Yang, C.h. KooAbstract:Abstract This work investigated the effect of a slight increase in Nb content of approximately 1 at.% and the effect of adding a minor Sc or La-rich Misch Metal (Mm) on the microstructure, phases and high temperature properties of Ti–40Al–15Nb alloy. Microstructural analysis and phase characterizations of the Ti–40Al–16Nb alloy with 0.39 wt.% Sc or La-rich Misch Metal additions are summarized as follows. (i) The as-cast Ti–40Al–16Nb–0.39 wt.% M (M=Sc or Mm) alloys have an α 2 matrix and contain α-Ti and B2 phase precipitates but few γ phase precipitates. The Sc 2 O 3 or La 2 O 3 oxide dispersoids, formed by internal oxidation, are observed in this work; but Ti 3 (Al,Sc) presented in the dual phases of γ-TiAl were not found. (ii) Adding Sc and La-rich Misch Metal decreases the α-transus temperatures of the TiAl–Nb alloys, possibly stabilizing the α 2 phase and inhibiting the B2 or γ phase formation. (iii) After homogenization, the σ phase and γ phase precipitates in the α 2 phase matrix and the B2 phase are absent. The distributed morphology of the oxide dispersoids in the TiAl–Nb alloy with added La-rich Mm is more uniform and discontinuous than that in the TiAl–Nb alloy with added Sc, after the homogenization. The compressive peak flow stress increment measured from high temperature compression testing at 900 °C is around 450 MPa and the high temperature strength at temperatures above 900 °C is also enhanced. The significant improvement in high-temperature mechanical properties is attributed to the precipitation of fine oxide particles with high thermal stability in the alloys. Furthermore, adding either a minor Sc or Mm to the alloy increases the strength of adhesion between the oxide layers and the alloys and changes the morphology of the oxide particles formed in the TiAl alloy with a high niobium content.
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Improving the microstructure and high temperature properties of the Ti–40Al–16Nb alloy by the addition of a minor Sc or La-rich Misch Metal
Intermetallics, 2004Co-Authors: C.t. Yang, C.h. KooAbstract:Abstract This work investigated the effect of a slight increase in Nb content of approximately 1 at.% and the effect of adding a minor Sc or La-rich Misch Metal (Mm) on the microstructure, phases and high temperature properties of Ti–40Al–15Nb alloy. Microstructural analysis and phase characterizations of the Ti–40Al–16Nb alloy with 0.39 wt.% Sc or La-rich Misch Metal additions are summarized as follows. (i) The as-cast Ti–40Al–16Nb–0.39 wt.% M (M=Sc or Mm) alloys have an α 2 matrix and contain α-Ti and B2 phase precipitates but few γ phase precipitates. The Sc 2 O 3 or La 2 O 3 oxide dispersoids, formed by internal oxidation, are observed in this work; but Ti 3 (Al,Sc) presented in the dual phases of γ-TiAl were not found. (ii) Adding Sc and La-rich Misch Metal decreases the α-transus temperatures of the TiAl–Nb alloys, possibly stabilizing the α 2 phase and inhibiting the B2 or γ phase formation. (iii) After homogenization, the σ phase and γ phase precipitates in the α 2 phase matrix and the B2 phase are absent. The distributed morphology of the oxide dispersoids in the TiAl–Nb alloy with added La-rich Mm is more uniform and discontinuous than that in the TiAl–Nb alloy with added Sc, after the homogenization. The compressive peak flow stress increment measured from high temperature compression testing at 900 °C is around 450 MPa and the high temperature strength at temperatures above 900 °C is also enhanced. The significant improvement in high-temperature mechanical properties is attributed to the precipitation of fine oxide particles with high thermal stability in the alloys. Furthermore, adding either a minor Sc or Mm to the alloy increases the strength of adhesion between the oxide layers and the alloys and changes the morphology of the oxide particles formed in the TiAl alloy with a high niobium content.
Bao-gen Shen - One of the best experts on this subject based on the ideXlab platform.
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Hydrogen Decrepitation Behaviors of Novel RE–Fe–B Strip-Casting Alloys Based on Misch Metal
IEEE Transactions on Magnetics, 2020Co-Authors: Liu Yanli, Fei Liu, Tongyun Zhao, Jirong Sun, Jian-jun Zhou, Xin Wang, Bao-gen ShenAbstract:To reduce the Nd–Fe–B material cost and balance the utilization of rare earth sources, the Misch Metal (MM) substitution for Nd in the sintered magnet attracts interest. Under the processing of fabricating Nd–Fe–B magnet, hydrogen decrepitation (HD) is widely used to obtain magnetic powder; however, the HD behaviors of RE–Fe–B strips based on MM may be complex. The HD behaviors of the [(Pr, Nd)1– x MM x ]30.8FebalCo1.4 B0.97 ( $x $ = 0–1) strips were studied under 0.2 MPa pressure. We find that it is similar to the Nd–Fe–B, 2:14:1 tetragonal structure of RE–Fe–B strips based on MM which is not broken during hydrogen decrepitating. But the REFe2 phase in MM30.8FebalCo1.4B0.97 disappears dramatically as a result of hydrogenation. For the samples with MM, the HD process is quicker and the particle size gets smaller than that for free MM, especially for samples with 35 wt.% MM, which may be attributed to La and Ce elements.
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cerium based rco5 r ce la0 35ce0 65 and Misch Metal type nanocrystalline hard magnetic materials with high coercivity
APL Materials, 2019Co-Authors: Jeotikanta Mohapatra, Xuefeng Zhang, Tongyun Zhao, Fengxia Hu, Yongfeng Li, Bao-gen ShenAbstract:Nanocrystalline RCo5 (R = Ce, La0.35Ce0.65, and Misch-Metal noted as MM) ribbons with hexagonal crystal structure and an average grain size of 5 nm have been prepared via a one-step melt-spinning technique. Coercivity as high as 13.0, 13.8, and 10.9 kOe has been obtained at 300 K for the CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. High thermal stability is also achieved as shown by the high coercivity of 9.3 kOe, 10.2 kOe, and 8.8 kOe at 400 K for CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. The coercivity mechanism is studied by magnetization analysis and microstructural observations. The nanocrystalline grains promote a strong exchange interaction, as indicated by the positive δM and the relatively high remanence ratio (∼0.8). In addition, the temperature dependence of coercivity of RCo5 ribbons shows the low coercivity temperature coefficient of −0.2% to −0.25%/K.Nanocrystalline RCo5 (R = Ce, La0.35Ce0.65, and Misch-Metal noted as MM) ribbons with hexagonal crystal structure and an average grain size of 5 nm have been prepared via a one-step melt-spinning technique. Coercivity as high as 13.0, 13.8, and 10.9 kOe has been obtained at 300 K for the CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. High thermal stability is also achieved as shown by the high coercivity of 9.3 kOe, 10.2 kOe, and 8.8 kOe at 400 K for CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. The coercivity mechanism is studied by magnetization analysis and microstructural observations. The nanocrystalline grains promote a strong exchange interaction, as indicated by the positive δM and the relatively high remanence ratio (∼0.8). In addition, the temperature dependence of coercivity of RCo5 ribbons shows the low coercivity temperature coefficient of −0.2% to −0.25%/K.
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cerium based rco5 r ce la0 35ce0 65 and Misch Metal type nanocrystalline hard magnetic materials with high coercivity
APL Materials, 2019Co-Authors: Xuefeng Zhang, Wen-liang Zuo, Tongyun Zhao, Jirong Sun, Jeotikanta Mohapatra, Ping J Liu, Bao-gen ShenAbstract:Nanocrystalline RCo5 (R = Ce, La0.35Ce0.65, and Misch-Metal noted as MM) ribbons with hexagonal crystal structure and an average grain size of 5 nm have been prepared via a one-step melt-spinning technique. Coercivity as high as 13.0, 13.8, and 10.9 kOe has been obtained at 300 K for the CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. High thermal stability is also achieved as shown by the high coercivity of 9.3 kOe, 10.2 kOe, and 8.8 kOe at 400 K for CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. The coercivity mechanism is studied by magnetization analysis and microstructural observations. The nanocrystalline grains promote a strong exchange interaction, as indicated by the positive δM and the relatively high remanence ratio (∼0.8). In addition, the temperature dependence of coercivity of RCo5 ribbons shows the low coercivity temperature coefficient of −0.2% to −0.25%/K.
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Cerium-based RCo5 (R = Ce, La0.35Ce0.65, and Misch-Metal) type nanocrystalline hard magnetic materials with high coercivity
APL Materials, 2019Co-Authors: Wen-liang Zuo, Xuefeng Zhang, Tongyun Zhao, Jirong Sun, J. Ping Liu, Jeotikanta Mohapatra, Bao-gen ShenAbstract:Nanocrystalline RCo5 (R = Ce, La0.35Ce0.65, and Misch-Metal noted as MM) ribbons with hexagonal crystal structure and an average grain size of 5 nm have been prepared via a one-step melt-spinning technique. Coercivity as high as 13.0, 13.8, and 10.9 kOe has been obtained at 300 K for the CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. High thermal stability is also achieved as shown by the high coercivity of 9.3 kOe, 10.2 kOe, and 8.8 kOe at 400 K for CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. The coercivity mechanism is studied by magnetization analysis and microstructural observations. The nanocrystalline grains promote a strong exchange interaction, as indicated by the positive δM and the relatively high remanence ratio (∼0.8). In addition, the temperature dependence of coercivity of RCo5 ribbons shows the low coercivity temperature coefficient of −0.2% to −0.25%/K.
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High performance Misch-Metal (MM)-Fe-B magnets prepared by melt spinning
Journal of Alloys and Compounds, 2017Co-Authors: Wen-liang Zuo, Xuefeng Zhang, Shulan Zuo, Tongyun Zhao, Jirong Sun, J. Ping Liu, Bao-gen ShenAbstract:Abstract A series of Misch-Metal (MM = 28.27 wt % La, 50.46 wt % Ce, 5.22 wt % Pr, 15.66 wt % Nd)-iron-boron isotropic ribbons with atomic formula (MM)12+xFe82-x-yB6+y (x = 0, 1, 2, 3, 4, y = 0, 0.5, 1, 1.5, 2) are prepared by melt spinning technique. A large energy product (BH)max of 12 MGOe is obtained with the composition of MM13Fe81B6 at optimized processing. The ribbons with both coercivity larger than 10 kOe and (BH)max larger than 10 MGOe are achieved in a wide composition range. All the samples exhibit the tetragonal crystal structure. The magnetization and Henkel plot (δM) measurements indicate that the ribbons have a relatively homogeneous microstructure and strong exchange-coupling interactions. The average grain size of the ribbons is around 30 nm determined via Scherrer's formula. Meanwhile, the transmission electron microscope (TEM) image also verifies that the ribbons have a homogeneous nanoscale microstructure. In addition, the spin reorientation temperature Tsr is investigated by ac susceptibility χac measurement.
Wen-liang Zuo - One of the best experts on this subject based on the ideXlab platform.
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cerium based rco5 r ce la0 35ce0 65 and Misch Metal type nanocrystalline hard magnetic materials with high coercivity
APL Materials, 2019Co-Authors: Xuefeng Zhang, Wen-liang Zuo, Tongyun Zhao, Jirong Sun, Jeotikanta Mohapatra, Ping J Liu, Bao-gen ShenAbstract:Nanocrystalline RCo5 (R = Ce, La0.35Ce0.65, and Misch-Metal noted as MM) ribbons with hexagonal crystal structure and an average grain size of 5 nm have been prepared via a one-step melt-spinning technique. Coercivity as high as 13.0, 13.8, and 10.9 kOe has been obtained at 300 K for the CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. High thermal stability is also achieved as shown by the high coercivity of 9.3 kOe, 10.2 kOe, and 8.8 kOe at 400 K for CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. The coercivity mechanism is studied by magnetization analysis and microstructural observations. The nanocrystalline grains promote a strong exchange interaction, as indicated by the positive δM and the relatively high remanence ratio (∼0.8). In addition, the temperature dependence of coercivity of RCo5 ribbons shows the low coercivity temperature coefficient of −0.2% to −0.25%/K.
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Cerium-based RCo5 (R = Ce, La0.35Ce0.65, and Misch-Metal) type nanocrystalline hard magnetic materials with high coercivity
APL Materials, 2019Co-Authors: Wen-liang Zuo, Xuefeng Zhang, Tongyun Zhao, Jirong Sun, J. Ping Liu, Jeotikanta Mohapatra, Bao-gen ShenAbstract:Nanocrystalline RCo5 (R = Ce, La0.35Ce0.65, and Misch-Metal noted as MM) ribbons with hexagonal crystal structure and an average grain size of 5 nm have been prepared via a one-step melt-spinning technique. Coercivity as high as 13.0, 13.8, and 10.9 kOe has been obtained at 300 K for the CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. High thermal stability is also achieved as shown by the high coercivity of 9.3 kOe, 10.2 kOe, and 8.8 kOe at 400 K for CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. The coercivity mechanism is studied by magnetization analysis and microstructural observations. The nanocrystalline grains promote a strong exchange interaction, as indicated by the positive δM and the relatively high remanence ratio (∼0.8). In addition, the temperature dependence of coercivity of RCo5 ribbons shows the low coercivity temperature coefficient of −0.2% to −0.25%/K.
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Influence of Misch Metal content on microstructure and magnetic properties of R-Fe-B magnets sintered by dual alloy method
Chinese Physics B, 2017Co-Authors: Rong-xiang Shang, Renjie Chen, Jie-fu Xiong, Dan Liu, Shulan Zuo, Xin Zhao, Wen-liang Zuo, Tongyun Zhao, Jirong SunAbstract:MM14Fe79.9B6.1/Nd13.5Fe80.5B6 magnets were fabricated by dual alloy method (MM, Misch Metal). Some magnets have two Curie temperatures. Curie temperatures T-c1 corresponds to the main phase which contains more LaCe, and Tc1 decreases from 276.5 degrees C to 256.6 degrees C with the content of MM increasing from 30.3 at.% to 50.6 at.%. The variation of Br with the increase ofMMindicates the existence of inter-grain exchange coupling in the magnets. When MM/R = 7.11 kOe and the maximum energy product (BH)(max) >= 41 MGOe. Compared with Nd, La and Ce are easier to diffuse to the grain boundaries in the sintering process, and this will cause the decrease of H-cj. Due to the diffusion between the grains, the atomic ratio of La, Ce, Pr, and Nd in each grain is different and the percentage of Nd in all grains is higher than that in Misch Metal.
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Magnetic properties of (Misch Metal, Nd)-Fe-B melt-spun magnets
AIP Advances, 2017Co-Authors: Rong-xiang Shang, Jie-fu Xiong, Wen-liang Zuo, Tongyun Zhao, Dongyuan Liu, Hao Kuang, J. R. Sun, B. G. ShenAbstract:The effect of replacing Nd with Misch Metal (MM) on magnetic properties and thermal stability has been investigated on melt-spun (Nd1-xMMx)13.5Fe79.5B7 ribbons by varying x from 0 to 1. All of the alloys studied crystallize in the tetragonal 2:14:1 structure with single hard magnetic phase. Curie temperature (Tc), coercivity (Hcj), remanence magnetization (Br) and maximum energy product ((BH)max) all decrease with MM content. The melt-spun MM13.5Fe79.5B ribbons with high ratio of La and Ce exhibit high magnetic properties of Hcj = 8.2 kOe and (BH)max= 10.3 MGOe at room temperature. MM substitution also significantly strengthens the temperature stability of coercivity. The coercivities of the samples with x = 0.2 and even 0.4 exhibit large values close to that of Nd13.5Fe79.5B7 ribbons above 400 K.
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High performance Misch-Metal (MM)-Fe-B magnets prepared by melt spinning
Journal of Alloys and Compounds, 2017Co-Authors: Wen-liang Zuo, Xuefeng Zhang, Shulan Zuo, Tongyun Zhao, Jirong Sun, J. Ping Liu, Bao-gen ShenAbstract:Abstract A series of Misch-Metal (MM = 28.27 wt % La, 50.46 wt % Ce, 5.22 wt % Pr, 15.66 wt % Nd)-iron-boron isotropic ribbons with atomic formula (MM)12+xFe82-x-yB6+y (x = 0, 1, 2, 3, 4, y = 0, 0.5, 1, 1.5, 2) are prepared by melt spinning technique. A large energy product (BH)max of 12 MGOe is obtained with the composition of MM13Fe81B6 at optimized processing. The ribbons with both coercivity larger than 10 kOe and (BH)max larger than 10 MGOe are achieved in a wide composition range. All the samples exhibit the tetragonal crystal structure. The magnetization and Henkel plot (δM) measurements indicate that the ribbons have a relatively homogeneous microstructure and strong exchange-coupling interactions. The average grain size of the ribbons is around 30 nm determined via Scherrer's formula. Meanwhile, the transmission electron microscope (TEM) image also verifies that the ribbons have a homogeneous nanoscale microstructure. In addition, the spin reorientation temperature Tsr is investigated by ac susceptibility χac measurement.
C.t. Yang - One of the best experts on this subject based on the ideXlab platform.
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improving the microstructure and high temperature properties of the ti 40al 16nb alloy by the addition of a minor sc or la rich Misch Metal
Intermetallics, 2004Co-Authors: C.t. Yang, C.h. KooAbstract:Abstract This work investigated the effect of a slight increase in Nb content of approximately 1 at.% and the effect of adding a minor Sc or La-rich Misch Metal (Mm) on the microstructure, phases and high temperature properties of Ti–40Al–15Nb alloy. Microstructural analysis and phase characterizations of the Ti–40Al–16Nb alloy with 0.39 wt.% Sc or La-rich Misch Metal additions are summarized as follows. (i) The as-cast Ti–40Al–16Nb–0.39 wt.% M (M=Sc or Mm) alloys have an α 2 matrix and contain α-Ti and B2 phase precipitates but few γ phase precipitates. The Sc 2 O 3 or La 2 O 3 oxide dispersoids, formed by internal oxidation, are observed in this work; but Ti 3 (Al,Sc) presented in the dual phases of γ-TiAl were not found. (ii) Adding Sc and La-rich Misch Metal decreases the α-transus temperatures of the TiAl–Nb alloys, possibly stabilizing the α 2 phase and inhibiting the B2 or γ phase formation. (iii) After homogenization, the σ phase and γ phase precipitates in the α 2 phase matrix and the B2 phase are absent. The distributed morphology of the oxide dispersoids in the TiAl–Nb alloy with added La-rich Mm is more uniform and discontinuous than that in the TiAl–Nb alloy with added Sc, after the homogenization. The compressive peak flow stress increment measured from high temperature compression testing at 900 °C is around 450 MPa and the high temperature strength at temperatures above 900 °C is also enhanced. The significant improvement in high-temperature mechanical properties is attributed to the precipitation of fine oxide particles with high thermal stability in the alloys. Furthermore, adding either a minor Sc or Mm to the alloy increases the strength of adhesion between the oxide layers and the alloys and changes the morphology of the oxide particles formed in the TiAl alloy with a high niobium content.
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Improving the microstructure and high temperature properties of the Ti–40Al–16Nb alloy by the addition of a minor Sc or La-rich Misch Metal
Intermetallics, 2004Co-Authors: C.t. Yang, C.h. KooAbstract:Abstract This work investigated the effect of a slight increase in Nb content of approximately 1 at.% and the effect of adding a minor Sc or La-rich Misch Metal (Mm) on the microstructure, phases and high temperature properties of Ti–40Al–15Nb alloy. Microstructural analysis and phase characterizations of the Ti–40Al–16Nb alloy with 0.39 wt.% Sc or La-rich Misch Metal additions are summarized as follows. (i) The as-cast Ti–40Al–16Nb–0.39 wt.% M (M=Sc or Mm) alloys have an α 2 matrix and contain α-Ti and B2 phase precipitates but few γ phase precipitates. The Sc 2 O 3 or La 2 O 3 oxide dispersoids, formed by internal oxidation, are observed in this work; but Ti 3 (Al,Sc) presented in the dual phases of γ-TiAl were not found. (ii) Adding Sc and La-rich Misch Metal decreases the α-transus temperatures of the TiAl–Nb alloys, possibly stabilizing the α 2 phase and inhibiting the B2 or γ phase formation. (iii) After homogenization, the σ phase and γ phase precipitates in the α 2 phase matrix and the B2 phase are absent. The distributed morphology of the oxide dispersoids in the TiAl–Nb alloy with added La-rich Mm is more uniform and discontinuous than that in the TiAl–Nb alloy with added Sc, after the homogenization. The compressive peak flow stress increment measured from high temperature compression testing at 900 °C is around 450 MPa and the high temperature strength at temperatures above 900 °C is also enhanced. The significant improvement in high-temperature mechanical properties is attributed to the precipitation of fine oxide particles with high thermal stability in the alloys. Furthermore, adding either a minor Sc or Mm to the alloy increases the strength of adhesion between the oxide layers and the alloys and changes the morphology of the oxide particles formed in the TiAl alloy with a high niobium content.