Oxidation behavior of MnCuNiFeZnAl damping alloy under varied high temperatures

Abstract

High-entropy Mn-based damping alloys, such as MnCuNiFeZnAl with a mixing entropy of 9.39 Jmol⁻¹K⁻¹, are promising for high-temperature use. In-situ XRD shows oxidation starts at 673 K, forming MnO, ZnO, and CuO, followed by Mn₃O₄ and Mn₂O₃. The alloy demonstrates enhanced antioxidation performance due to a continuous Al₂O₃ film near the oxidation film/matrix interface but is prone to oxide scale detachment at high temperatures. Splitting of MnO diffraction peaks arises from Mn₂O₃/Mn₃O₄ redox reactions or replacement of MeO (Zn, Cu, Ni, Fe) by Mn.

Keywords

high-entropy Mn-based alloy in-situ XRD analysis isothermal oxidation ion transportation

Introduction

Mn-Cu based damping alloys have attracted much attention because of their excellent vibration and noise reduction performance. It has been pointed out that the damping capacity of the alloys mainly comes from the migration of {101} twin boundary or phase interface movement during the process of face-centered cubic (fcc) to face-centered tetragonal (fct) phase transformation,¹ and the service temperature can be tuned to keep high damping in a wide temperature range from 150 K to 380 K by adjusting the microstructure through varied heat treatment.² Traditional vibration and noise reduction methods include system damping and structural damping, such as sound absorption, sound insulation treatment, vibration isolation, and damping vibration reduction. However, these methods make the entire system cumbersome and bulky, and sometimes, they fail to provide a solution under high-temperature conditions. In order to cater for the demand for vibration and noise control of mechanical parts at high-temperature service conditions in the fast-developing modern industry, high-entropy Mn-based MnCuNiFe damping alloy with doping of Zn has been developed with excellent damping performance at temperatures higher than 673 K,³ in which experiment of the in-situ X-ray diffraction (XRD), however, it is found the alloy is susceptible to oxidation.

Mn-based alloys are easily oxidized at high temperatures,⁴ as Mn is a special 3d-series element with large atomic radius and varied oxidation valence of +2, + 3, + 4, + 6, and +7, and the diameter of manganese ions decreases with the increase of valence after oxidation in comparison with the metal atoms.⁵ It has been found that in the oxidation process of MnCuNiFe alloy at temperatures from 800 °C∼1000 °C,⁶ the alloying elements react with oxygen in the order of Mn, Fe, Ni and Cu, and MnO is formed preferentially to Mn₃O₄, FeO, NiO and Cu₂O from the point of thermodynamics. Furthermore, the displacement reactions of the oxides Cu₂O, NiO and FeO with Mn element has been verified to occur by thermodynamic calculations, and interestingly, once Mn₃O₄ is formed in the outer layer, it can be reduced to MnO by the Mn atom diffused from the metal matrix. Of these oxides, at ambient conditions MnO is of fcc structure,⁷ while Mn₃O₄ is a unique mixed-valence oxide that shows a tetragonal distorted spinel structure.⁸ The complex oxidation behaviour will seriously affect the service life of damping alloy parts at high temperature environments.

It is known that the entropy of mixing dependence of a solid solution containing n elements follows⁹:

Δ S_{m i x} = - R \sum_{i = 1}^{n} c_{i} l n c_{i}

(1)

where: R = 8. 314 J/(K·mol);

c_{i}

is the molarity of element i,

\sum_{i = 1}^{n} c_{i} = 1

Materials with multi-principal elements, unlike traditional alloys featuring one or two key alloying elements, are also called high entropy alloys (HEAs) for higher mixed entropy.¹⁰ The damping capacity has been explored in HEAs prepared by casting method,^11–13 or by mechanical alloying and spark plasma sintering.^14,15 It has been found the peak of internal friction (IF) of Fe_65−xMn₂₀Cr₁₅Co_x (x = 0, 5, 10, 15) HEAs increased monotonously as the configurational entropy was increased from 0.88R to 1.23R^.¹⁵ As for AlxCrFeNi (x = 0.3, 0.35, 0.37, 0.4, 0.5) alloy system, it is revealed that the phase constituent changes gradually from fcc dominated structure to a single body-centered cubic (bcc) structure when x increases from 0.3 to 0.5 while the Al_0.37CrFeNi shows the maximum damping capacity of 0.07093 at the strain amplitude of 1.5 × 10^−4.¹¹ For all the AlxCoCrFeNi (x = 0, 0.25, 0.5, 0.75, and 1) alloy investigated, the IF value increases very gradually at lower temperatures, and then starts to increase very rapidly at temperatures higher than 698 K, which is attributed by the structural relaxations under the applied periodic stress.¹²

Al is an economical alloying element in HEAs with the specific characteristic of the atomic diameter of 2.86 Å and valence electron concentration (VEC) of 3. Most importantly, alloying Al in metals might improve the antioxidation performance because of formation of Al₂O₃ under oxidation atmosphere.¹⁶ Accordingly, the MnCuNiFeZnAl alloy was prepared by doping Al in MnCuNiFeZn alloy, and the entropy of mixing was elevated to 9.39 Jmol⁻¹K⁻¹ from 8.62 Jmol⁻¹K⁻¹ with the consideration of keeping high-temperature damping capacity as well as structural stability. It can be seen MnCuNiFeZnAl alloy show much higher configurational entropy than that commonly used M2052 alloy with the value of 6.48 Jmol⁻¹K⁻¹.

In order to clarify the high-temperature oxidation behaviour of high-entropy MnCuNiFeZnAl damping alloys, oxidation experiments were carried out to study the growth characteristic of the oxide film and to reveal the oxidation mechanism of the damping alloy at high temperatures.

Experimental procedure

The Mn-based alloy ingot with the composition of Mn-15Cu-10Ni-4Fe-5Zn-1Al wt% was prepared by induction melting of manganese (99.9 wt%), copper (99.9 wt%), industrial pure iron and nickel under argon atmosphere, according to Equation 1, the entropy of mixing is 9.39 Jmol⁻¹K⁻¹. The ingot with the diameter of 90 mm was forged and then rolled into a plate of 20 mm thickness. The specimens for oxidation with the dimension of 10 × 10 × 10 mm was spark cut from the plate, and then ground up to 1200 grit SiC abrasive paper followed by ultrasonically cleaning in ethanol and acetone. Since the oxide scale of the Mn-based alloy is prone to fall off at high temperatures after holding even for 10 min,⁶ the specimens were put into corundum crucible for oxidation in order to prevent the measurement error caused by the drop of oxide from the specimens. After recording the weight of individual specimen and the corresponding crucible, the specimens were subjected to high-temperature oxidation tests at temperatures from 873 K to 1273 K with the holding time from 0.5 h to 6 h by using a muffle furnace, and then the mass change after oxidation was determined for each crucible containing the specimen. Bruker^TM D8 Discover X-ray diffraction (XRD) was used to identify the phase constituents of the oxide film by using Cu Kα with a scanning speed of 3 °/min, operated at tube voltage of 40 kV and a current of 40 mA. Due to severe detachment of the oxide scale at 1273 K, the phase structure of the test was also determined by taking the detached oxide and the substrate with residual oxide film, respectively. The in-situ XRD was performed by employing the Rigaku Smart Lab X-ray diffractometer without gas protection during the experiment. The scanning rate for high-temperature phase analysis was 10°/min, and a finely focused 9 kW rotating target X-ray generator was used. A Quanta450 scanning electron microscope (SEM) equipped with an energy spectrometer (EDS) was used to observe the surface morphology of the specimens and to analyze the composition distribution of the matrix and the oxide layer.

Results and discussions

Oxidation kinetics

Figure 1 shows the relationship between mass gain and holding time at different oxidation temperatures. With the increase of holding time, the mass gain dependence of square root of holding time all show a linear growth trend for all the specimens under different oxidation temperatures. Oxidation at lower temperatures (873K、1073 K), the mass gain of the oxidized specimen is very low, and the value at 873 K holding for 6 h is only 4.15 g/m², while that at 1073 K holding for 6 h is 37.64 g/m², respectively. The mass gains are much faster for specimens oxidized at higher temperatures of 1173 K to 1273 K. The mass gain significantly increases to 147.75 g/m² for specimen holding at 1173 K for 6 h, and further elevates to 187.44 g/m² for that at 1273 K for 6 h. It can be seen that the corresponding fitting equation is $y = 2.07 \sqrt{t} - 0.23$ (R²= 0.98) at 873 K, $y = 14.17 \sqrt{t} + 3.52$ (R²= 0.95) at1073 K, $y = 63.29 \sqrt{t} - 16.37$ (R²= 0.956) at 1173 K, and $y = 70.67 \sqrt{t} + 8.79$ (R²= 0.93) at 1273 K with satisfied accuracy, respectively. Compared with the mass gain of M2052 alloy oxidation at 900 °C for 2 h,² the antioxidation performance of this alloy is improved by 4 times that of M2052.

Figure 1.

Mass gain dependence of holding time at different temperatures.

XRD analysis

Figure 2 shows the in-situ XRD patterns of specimens heated to different temperatures. It can be seen that the alloy at room temperature consists of a single γ-Mn phase. When the specimen is heated to 673 K, oxidation starts with the appearance of the diffraction peaks of fcc structured MnO, wurtzite structured ZnO and monoclinic tenorite structured CuO.

Figure 2.

In-situ XRD spectra of MnCuNiFeZnAl alloy specimens heated to elevated temperatures.

As the temperature is increased to 773 K, the spinel Mn₃O₄ phase begins to appear on the surface of the specimen accompanied by obviously heightening of the MnO peak and gradually weakening of γ-Mn matrix phase peak, indicating the growth of oxide film and the formation of the mainly MnO oxidation substance. As the temperature increases to 873 K, the MnO diffraction peak becomes the predominant one, and the Mn₃O₄ peak is also relatively strengthened. Meanwhile, the CuO peak disappears while the Mn₂O₃ phase appears in the first time. It is obvious that the main constituents of the oxide are of the MnO phase with a certain amount of Mn₃O₄, ZnO and some Mn₂O₃ phase at this temperature. As the temperature comes to 973 K, the diffraction peaks for MnO and Mn₃O₄ are comparably strong, indicating that the Mn₃O₄ film begins to form in the outer oxide layer. Then, the surface of the specimen has been completely covered by a layer of oxide film, and the matrix phase cannot be detected any more.

Figure 3 shows the XRD spectra of MnCuNiFeZnAl specimens holding at 873 K and 1273 K for 6 h, respectively. It can be seen that after isothermal oxidation at 873 K for 6 h, the surface oxide of the specimen is mainly composed of MnO, and some Mn₃O₄ and CuO. The detached oxide scale from the specimen isothermal oxidation at 1273 K for 6 h also consists of MnO and Mn₃O₄, while the constituents of the residual oxide chiefly contain MnO, Mn₃O₄, as well as Mn₂O₃ phase remaining on the substrate.

Figure 3.

XRD spectra of MnCuNiFeZnAl specimen isothermal oxidation at 600 °C and 1000 °C for 6 h.

Surface morphology observation

Figure 4 shows the surface morphology of the specimens oxidized at different temperatures. As seen in Figure 4(a), the scratches originated from the polishing process by sandpaper can be clearly seen on the surface of the specimen held at 873 K for 0.5 h, indicating that the oxide film formed is very thin, and the enlarged morphology shown by the inset figure reveals that the oxide film consists of flocs and needles, which may be one-dimensional nanowire ZnO crystal exhibiting as an asymmetric wurtzite structure^.^17,18 As the oxidation time increases to 6 h, scratches still exist while the oxide on the surface of the sample has grown into granular and cubic shape (Figure 4(b)), which corresponds to fcc MnO and spinel Mn₃O₄ according to Figure 3, respectively. Figure 4(c) shows the surface morphology of specimen isothermal oxidation at 1073 K for 6 h, it can be seen that the surface of the specimen has formed a relatively dense oxide film, of which make up by bulk particles with varied sizes under high magnification. However, multilayered oxide film already exists on the surface of specimen oxidized at 1273 K only for 0.5 h, indicating that severe oxidation has occurred, and the oxide scale has been partially detached from the substrate.

Figure 4.

Surface morphology of the samples oxidized at different temperatures, (a) 600 °C for 0.5 h, (b) 600 °C for 6 h, (c) 800 °C for 6 h, (d) 1000 °C for 0.5 h, where the inset is enlarged morphology.

Figure 5 gives the compositional map scan of the oxide film oxidation at 873 K for 0.5 h. It can be seen that the distribution of Mn and O in the surface oxide is relatively uniform, indicating that the surface oxide is mainly of MnO. According to the height variation on the morphology combined with the Zn distribution, it is inferred that the needle like substance on the specimen surface is surely ZnO. It is noted that the enrichment of Cu and Ni also appear on the surface oxide of the specimen, as the CuO and NiO phases are also identified in Figure 2, it is indicated that these oxides may be also generated at the early stage of oxidation.

Figure 5.

Compositional map scan of specimen oxidation at 600 °C for 0.5 h.

Figure 6 shows the enlarged morphology of specimen oxidation at 1273 K for 0.5 h. It can be seen that massive particles are also formed inside the detachment pit of oxide film (Figure 6(a)), and the rapidly developed massive oxides on the surface mostly have a layered structure, as shown in Figure 6(b). The composition analysis is carried out on typical points, of which results are shown in Table 1. It can be seen that all of them contain a certain amount of Zn, as well as a small amount of Cu or Fe. The bulk oxide contains higher content of Mn in point 1, while the Zn content is much higher in small particles of the oxide in point 2, however, according to the XRD in Figure 3, the oxide should be of Mn₃O₄ and MnO phases, which suggests that the element Zn occupies the lattice of the two oxides. The white material of point 3 possesses a higher content of O and Al, indicating the domination of Al₂O₃.

Figure 6.

Oxide surface morphology of specimen at 1273 K for 0.5 h, （a） scaling-off pit （b） chemical composition analysis points in the enlarged morphology.

Table 1.

Chemical composition analysis of points in Figure 6 (at.%).

	C	O	Mn	Zn	Cu	Fe	Al
1	18.01	39.98	11.58	29.18	1.26
2	13.82	47.67	29.62	7.75		0.41
3	10.74	52.25	12.18	3.47	0.56		20.8

Cross-sectional characterization

The mass gain of the specimens oxidized at 873 K and 1073 K is much lower, and the cross-sectional morphology of the specimen oxidized at 1073 K is shown in Figure 7. It can be seen that although the outermost oxide film has displayed the evidence of delamination and sign of detachment, the surface oxide film is relatively intact. Oxidation has proceeded along the grain boundary near the interface of the oxide film / matrix, as shown by the arrow in Figure 7(a). Figure 7(b) represents the result of the compositional line scan along the dashed line in Figure 7(a). Obvious two layers are characterized by the element distribution of the oxide film, of which outer layer is mainly Mn and O, while the distribution in the inner layer is more complex. From the matrix outward, the content of Mn and O gradually increases, while the distribution of Cu, Ni, Fe, and Zn shows a downward trend. Correspondingly, the trend of alloying elements distribution in the matrix from inside out is just the opposite, Mn content gradually decreases while the contents of Cu, Ni, Fe, and Zn gradually increase to the concentration reaching its maximum at the interface.

Figure 7.

Cross-sectional analysis of specimen oxidation at 1073 K for 6h， (a) cross-sectional microstructure morphology, and (b) line scan of dashed line in (a).

Figure 8 shows the cross-section morphology and the corresponding compositional map scan of the specimen oxidized at 1273 K. It can be seen that the concentration of Mn is higher in the oxide film and lower in the substrate, which has undergone serious internal oxidation. Speculation from the compositional distribution characteristics of Al, the main product of inner oxidation is Al₂O₃ particles, and has formed a continuous Al₂O₃ film in the substrate near the interface of the oxidation film / matrix, which will effectively improve the antioxidant performance of the alloy. Interestingly it is found that the distribution characteristics of Cu, Ni, Zn and Fe are the same, and enriched in a band just beyond the Al₂O₃ layer, as shown in Figure 8 by the dotted line belt, where Mn and O are poor, indicating the occurrence of replacement reactions of CuO, NiO, ZnO, FeO with Mn to produce MnO, as well as the precipitation of Zn, Cu, Ni and Fe in the matrix. The distribution characteristics of Fe are opposite to that of Mn, and it is also distributed in the oxide film, but the concentration in the matrix is relatively high.

Figure 8.

Cross-sectional map scan of specimen oxidation at 1000 °C for 6 h.

Ion transportation and thermodynamics during oxidation

According to the thermodynamic principle,¹⁹ the formation and growth of the oxide layer on the alloy surface is closely related to the Gibbs free energy of the oxide. At certain temperature, the more negative the Gibbs free energy, the greater the affinity of the element with oxygen and the easier the occurrence of oxidation reaction.²⁰ The standard Gibbs free energies ( $Δ_{γ} G_{T}^{θ}$ ) corresponding to the oxides of different elements at 873K–1273 K are listed in Table 2. It can be seen that. Since the value for Al is the most negative in the alloy system at all the calculated temperatures, which is account for the phenomenon of inner oxidation of Al. MnO is preferentially formed in comparison with ZnO，FeO，NiO and CuO, and the reactivity of these elements with oxygen in sequence is Mn-Zn-Fe-Ni-Cu. However, at the initial stage of the oxidation, all the elements in the matrix can react with oxygen to form the corresponding oxides MeO (Me = Mn, Cu, Ni, Fe, Zn) as soon as they are exposed to oxygen. Because of the abundance of Mn elements in the alloy the initial oxide film is formed with the main content of MnO.²¹

Table 2.

Standard Gibbs free energy ( $Δ_{r} G_{T}^{θ}$ , 1 mol O₂) of the oxides for Mn, Zn, Fe, Ni, Cu and Al (J /mol).

	Mn→MnO	Zn→ZnO	Fe→FeO	Ni→NiO	Cu→CuO	Al→Al₂O₃
873K	−639786	−579927	−422210	−320624	−158943	−702104
1073K	−609332	−539192	−391734	−284664	−130805	−673037
1173K	−594657	−529627	−395973	−266625	−118273	−658466
1273K	−580083	−499527	−384558	−248818	−106089	−644013

As oxidation proceeds, O diffuses inward through the oxide film, and then further oxidation produces the high valent oxides of Mn₂O₃ and Mn₃O₄, and eventually a two-layer structured oxide develops with the outer layer of Mn₂O₃ and Mn₃O₄ and the inner layer of MnO. As shown in Figure 8, the ion transport behavior of Fe is similar to that of Mn in the oxide scale. Table 3 list the $Δ_{r} G_{T}^{θ}$ of the high valent oxides for Mn and Fe, other than pure Fe₃O₄ at 1273 K, it can be seen that complex oxides of the two element Me₂O₃ (Me = Mn, Fe) can be formed, as well as Me₃O₄ may, which is in accordance with the XRD identification in Figures 2 and 3.

Table 3.

Standard gibbs free energy ( $Δ_{r} G_{T}^{θ}$ , 1 mol O₂) of the high valent oxides for Mn and Fe(J /mol).

	Mn→ Mn₂O₃	MnO→ Mn₃O₄	Fe→Fe₂O₃	FeO→ Fe₃O₄
873K	−538526	−229498	−198525	−29809
1073K	−504342	−186367	−175912	−11898
1173K	−486811	−160151	−172606	−2500
1273K	−469280	−134034	−163974	7223

Meanwhile, Mn diffuses outward in the matrix, and further redox reactions may take place, as shown in Table 4, MnO film can be thickened by the redox reactions of Mn₂O₃ and Mn₃O₄ with Mn. Moreover, Mn can replace the metal element in CuO, NiO, ZnO, and FeO to produce MnO, and simultaneously lead to the enrichment belt beneath the inner oxide layer (Figure 8). It is clear that MnO not only originates from the oxidation of Mn, but also comes from either the redox reaction or the replacement reaction.

Table 4.

Standard formation Gibbs free energy ( $Δ_{r} G_{T}^{θ}$ , 1 mol MnO) (J /mol).

	Mn + Mn₂O₃→MnO	Mn + Mn₃O₄ →MnO	Mn + CuO →MnO + Cu	Mn + NiO →MnO + Ni	Mn + ZnO→MnO + Zn	Mn + FeO→MnO + Fe
873K	−75632	−49261	−240421	−156581	−58059	−108788
1073K	−76510	−50847	−239262	−162334	−61370	−108799
1173K	−76768	−51497	−238326	−164016	−55340	−99342
1273K	−76843	−52002	−236997	−165632	−55483	−97762

Susceptibility to detachment of oxide scale

It is known that the spinel Mn₃O₄ is easily scaled off, in addition, the oxidation reaction process can be reflected by the change of XRD profiles. Take the (200) diffraction peak in Figure 2 for an example, Figure 9 shows the enlarged MnO peak dependence of heating temperature. As seen in Figure 9(a), the peak gradually shifts to the left and gets closer to the MnO standard peak position of 40.226° with the increase of temperature. It is known that internal stresses in the oxygen film are the main cause of oxide cracking and peeling off. For cubic crystal systems, the internal stress $σ$ has the form²²:

σ = - \frac{Δ d}{d} \frac{E}{2 v} = \frac{E}{4 v} \cdot \cot θ \cdot Δ 2 θ

(2)

where d is the crystal plane spacing, E is the average Young's modulus, v is the Poisson's ratio, and 2θ is the angle of diffraction peak. It is can be seen that with the increase of heating temperature, the increase of crystal plane spacing leads to enough lattice distortion, and thus can generates large internal stress to peel the oxide film off.

Figure 9.

The (200)_MnO diffraction characteristics under different heating temperatures, (a) the enlarged peaks, (b) separation of the peak at 973K.

Other more, the peak gradually splits from a flat-sloped one into overlapping double peaks, which can be well fitted by the peak separation, shown in Figure 9(b), which indicates that the MnO phase exhibits varied lattice distances. During the in-situ oxidation process, the oxidation process becomes fast while the oxide film gets thicker with the increase of heating temperature and holding time. It is supposed that the peak splitting should be attributed by the replacement reaction of the former formed MeO (Me = Cu, Ni, Fe, Zn) with the outward diffused Mn, and then the right peak corresponds to the direct oxidation of metals probably with other elements occupation the lattice position leading to a higher crystal spacing, while the left one with smaller spacing is the MnO peak from replacement reaction. The different origins of MnO formation provide the detachment nature of the developed oxide scale.

The oxide formation under isothermal oxidation also reflects the ion transport and reaction by a certain degree. Figure 10 shows the enlarged (100)_MnO diffraction, exhibiting a smooth-sloped peak at 873 K, which means that the splitting peaks have merged again with the growth of oxide film. Surely as shown in Figure 4(b), the surface oxide has developed into granular or cubic crystals after isothermal holding at 873 K for 6 h. As for oxidation at 1273 K, the diffusion rate is so fast that that both the redox reaction and the replacement reaction happen rapidly. If we assume that the splitting peak of MnO in the outer scale layer is owing to the redox reaction of Mn₂O₃ and Mn₃O₄, while that in the inner layer is contributed by the replacement reaction, it can be seen that high internal stress will be generated in the inner layer in comparison with the previously formed outer layer during the oxide growing process, which is the reason why the high-temperature oxide scale be prone to peel off.

Figure 10.

The (100)_MnO diffraction characteristic of the isothermal oxidation specimens, (a) at 873 K for 6 h, (b) 1273 K for 6 h.

Conclusions

The oxidation behaviour of MnCuNiFeZnAl alloy were studied under different temperatures, the main conclusions are as follows:

The mass gains dependence of square root of holding time show a linear relationship under different oxidation temperature, and the fitting equation follows $y = 2.07 \sqrt{t} - 0.23$ (R²= 0.98) at 873 K, $y = 14.17 \sqrt{t} + 3.52$ (R²= 0.95) at1073 K, $y = 63.29 \sqrt{t} - 16.37$ (R²= 0.956) at 1173 K, and $y = 70.67 \sqrt{t} + 8.79$ (R²= 0.93) at 1273 K, respectively, displaying better antioxidation performance of MnCuNiFeZnAl alloy than that of M2052.

The in-situ XRD analysis of MnCuNiFeZnAl alloy reveals that oxidation begins at 673 K with the formation of MnO, ZnO, and CuO. As the temperature increases, MnO phase dominates and then Mn₃O₄ and Mn₂O₃ appears in the outer oxide layer. After isothermal oxidation at 873 K for 6 h, the surface oxide consists mainly of MnO, with some Mn₃O₄ and CuO. Oxidation at 1273 K for 6 h results in the formation of MnO and Mn₃O₄, and the residual oxide on the substrate also contains Mn₂O₃ phase.

In the early stages of oxidation at 873 K, there forms needle-like ZnO, flocs like MnO, CuO and NiO phases, as oxidation time extends and holding temperature increases, the oxide film grows denser, forming granular and cubic shapes of MnO and spinel Mn₃O₄. Severe oxidation occurs at 1273 K, but continuous Al₂O₃ film has formed in the substrate near the interface of the oxidation film / matrix, effectively improving the antioxidant performance of the alloy.

There exists obvious two layers of oxide scale for the specimen oxidized at 1073 K. The element distributions in the oxide film and the matrix reflect the redox reactions of Mn₂O₃ and Mn₃O₄ with Mn, as well as the replacement reaction of MeO (Zn, Cu, Ni, Fe) with Mn to produce MnO. The process of ion transport and chemical reaction are reflected by the shift and split of MnO diffraction peak, disclosing the nature of manganese oxide scale susceptibility to detachment.

Footnotes

Author contribution(s)

Ling Mei: Data curation; Formal analysis; Investigation; Methodology; Writing – original draft; Writing – review & editing.

Pengbo Duan: Data curation; Investigation.

Guoxiang Cheng: Data curation; Investigation.

Qingchao Tian: Conceptualization; Formal analysis; Methodology; Resources; Supervision; Validation; Writing – original draft; Writing – review & editing.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

References

Tian

Yin

Sakaguchi

, et al. Internal friction behavior of the reverse martensitic transformation in deformed MnCu alloy. Mater Sci Eng A 2006; 438–440: 374–378.

Zhang

Tian

, et al. Tuning ultra-high damping capacity of Mn-Cu alloy to fit wide-range service temperature. Mater Sci Technol 2022; 38: 299–307.

Mei

Niu

Ding

, et al. High temperature damping behavior and phase transition characteristics of high-entropy MnCuNiFeZn damping alloy. J Mater Eng 2024; 52: 193–199.

Nanni

Viani

Elliott

, et al. High-temperature oxidation of copper-manganese alloys. Oxid Met 1979; 13: 181–195.

Tsakiropoulos

. On Nb silicide based alloys: alloy design and selection. Materials 2018; 11: 44.

Jiang

Zheng

Tian

. Oxidation characteristics of a MnCuNiFe damping alloy. Mater Res Express 2019; 6: 126590.

Klotz

Komatsu

Polian

, et al. Crystal structure and magnetism of MnO under pressure. Phys Rev B 2020; 101: 1.

Sagar

. Structural and electrical studies of nanocrystalline Mn₃O₄. Ferroelectr Lett Sect 2018; 45: 94–98.

Yeh

Chen

Lin

, et al. Nanostructured high-entropy alloys with multiple principal elements: novel alloy design concepts and outcomes. Adva Eng Mater 2004; 6: 299–303.

10.

Miracle

Senkov

. A critical review of high entropy alloys and related concepts. Acta Mater 2017; 122: 448–511.

11.

Wang

Zhang

Gao

, et al. Alxcrfeni medium entropy alloys with high damping capacity. J Alloys Compd 2021; 876: 159991.

12.

Liaw

Gao

, et al. Damping behavior of Al_xCoCrFeNi high-entropy alloys by a dynamic mechanical analyzer. J Alloys Compd 2014; 604: 331–339.

13.

Peltier

Lohmuller

Meraghni

, et al. Damping behavior in a wide temperature range of femn-like high entropy shape memory alloys. Shape Mem Superelasticity 2022; 8: 335–348.

14.

Chen

Zhang

Zhou

, et al. A novel high-entropy alloy with excellent damping property toward a large strain amplitude environment. J Alloys Compd 2019; 802: 493–501.

15.

Wang

Chen

Liu

, et al. Synergistic damping effect mechanism of magneto-mechanical hysteresis and dislocations energy dissipation in FeMnCrCo high entropy alloys. Mater Sci Eng A 2021; 818: 141412.

16.

Lees

. The effects of surface-applied oxide films containing varying amounts of yttria, chromia, or alumina on the high-temperature oxidation behavior of chromia-forming and alumina-forming alloys. Oxid Met 2000; 53: 507–527.

17.

Jeong

Kim

Y-R

, et al. Crystal-Structure-Dependent piezotronic and piezo-phototronic effects of ZnO/ZnS core/shell nanowires for enhanced electrical transport and photosensing performance. ACS Appl Mater Interfaces 2018; 10: 28736–28744.

18.

Liu

Yang

Zhang

, et al. Nanowire piezo-phototronic photodetector: theory and experimental design. Adv Mater 2012; 24: 1410–1417.

19.

. Metallurgy and materials physical chemistry. Beijing, China: Metallurgical Industry Press, 2001, pp.514–517.

20.

Tian

Guo

. Structure and oxidation behavior of Si-Y co-deposition coatings on an Nb silicide based ultrahigh temperature alloy prepared by pack cementation technique. Surf Coat Technol 2009; 204: 313–318.

21.

Geng

Zhao

Wang

, et al. Initial oxidation behavior of ferritic stainless steel with sputtered Mn-Cu coating. Oxid Met 2017; 88: 203–210.

22.

Yang

. Study of X-ray stress analysis of thin films. J Shanghai Jiao Tong Univ 1994; 28: 52–58.