This study investigates the structural properties, wear resistance and corrosion behavior of a CoCuFeNiMo equiatomic high-entropy alloy. The alloy was prepared using a vacuum arc melting device, and ...its structural properties were analyzed through X-ray diffraction (XRD) and scanning electron microscopy (SEM). Wear tests were conducted using a pin-on-disc machine against 4140 stainless steel at different loads. Corrosion behavior was evaluated through potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in a 3.5 wt% NaCl solution. The results indicated the presence of a major face-centered cubic (FCC) phase and a minor (µ) phase. The alloy exhibited segregation of Cu, attributed to positive mixing enthalpy. The coefficient of friction exhibited stability under lower loads but fluctuated under higher loads, possibly due to inhomogeneity in the microstructure caused by Cu segregation. Wear rates increased linearly with applied loads, indicating a direct relationship between load and wear properties. The worn surfaces displayed characteristics of mild abrasive wear, with delaminations, plowing, and abrasive wear tracks. Pitting corrosion was observed, and the corrosion process was explained as the attack of Cl- ions leading to galvanic corrosion between different phases. In the corrosion analysis, the Ecorr value was −0.616 V, and the icorr value was found to be 2.22 × 10−5 A/cm2.
•The produced CoCuFeNiMo HEA composed of major FCC and minor µ phases.•The microstructure of HEA has a segregation of Cu.•HEA slightly improved wear resistance and friction coefficient and caused to fluctuation in friction coefficient at 50 N.•The corrosion potential and the corrosion current value of HEA was −0.616 V, 2.22×10−5 A/cm2, respectively.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this study, the effect of Ti addition on microstructure and corrosion properties of high entropy CoCuFeNiMnTix (x = 0.0–0.5) produced by the vacuum arc melting method was investigated. According ...to X-ray diffraction analysis, it has been found that Ti-free CoCuFeNiMn and CoCuFeNiMnTix HEAs had FCC crystal structures. It was understood from the SEM images that the CoCuFeNiMn and CoCuFeNiMnTix alloys were dendritically solidified. While the CoCuFeNiMn alloy had a homogeneous chemical composition in dendritic and interdendritic regions, Ti-rich regions were formed in the interdendritic regions with the Ti addition to the CoCuFeNiMn. The ratio of the Ti-rich region formed in the interdendritic region increased with the increase of Ti in the CoCuFeNiMnTix alloy. The corrosion resistance of the CoCuFeNiMnTix alloy decreased with the increase of Ti addition. The Ecorr and icorr values for CoCuFeNiMn alloy were found to be as −0.322 V (vs. Ag/AgCl) and 6.30 × 10−7 A.cm−2, and these values were measured as −0.982 V and 1.16 × 10−3 A.cm−2 for CoCuFeNiMnTi0.5 alloy, respectively. From the Nyquist and phase angle plots, it was understood that the 0.3% Ti ratio was the critical value for the formation of the passive TiO2 layer on the alloy surface. Ti addition's most important effect on the CoCuFeNiMn alloy's corrosion properties was determined as the transformation of pitting corrosion type to galvanic corrosion.
•The Ti-dopped CoCuFeMnNiTix high entropy alloys were successfully produced by vacuum arc melting in the FCC structure.•Additional Ti in CoCuFeMnNiTix caused micro-level segregation in the interdendritic regions in the microstructure.•Pitting corrosion in the titanium-free alloy turned into galvanic corrosion in the titanium-free HEAs.•The corrosion resistance of the Ti-free high entropy alloy was equal to Cantor alloy.•The additional Ti decreased the corrosion resistance of the CoCuFeMnNiTix.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study aims to investigate the effect of Sn content on the structural, mechanical, wear, and electrochemical properties of Ti-6Al-xSn (x = 3.5–17.5, wt%) alloys fabricated by powder metallurgy ...method. The results showed that the microhardness generally decreased with increasing Sn content, although there was an unusual increase in microhardness in the alloy with 10.5 wt% Sn. Depending on the Sn content, various phases such as α-Ti, Ti3Sn, and Ti3Al indicated complex phase formations. The flexural and tensile strengths increased up to 10.5 wt% Sn content, but the strengths reduced above this level. The maximum values for flexural and tensile strengths were obtained as 270 MPa and 125.8 MPa, respectively. With increasing Sn content, the fracture surfaces shifted from cleavage mode to mixed brittle and ductile failure modes. The wear tests were conducted in two different environments: dry and wet conditions. Considering dry sliding conditions, the lowest specific wear rate was obtained as 0.85 × 10−6 mm3/N·m in the alloy coded 3.5Sn at a sliding distance of 1500 m. On the other hand, the highest wear was measured as 2.89 × 10−6 mm3/N·m in the 17.5Sn coded sample at a sliding distance of 6000 m in wet conditions. The wear results demonstrated a relationship between mechanical properties and wear resistance, which was influenced by the existence of porosity. The Ti-6Al-7Sn alloy exhibited the best corrosion resistance with a 2.22 × 10−7 icorr value, while the one with Ti-6Al-17.5Sn alloy showed the worst performance with a 9.71 × 10−6 icorr value.
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•Ti-6Al-10.5Sn alloy showed the best mechanical properties among Ti-6Al-xSn alloys.•There was no significant difference in the wear rates under dry or wet conditions.•The lowest specific wear rates were observed in Ti-6Al-3.5Sn alloy.•Ti-6Al-7Sn alloy exhibited the best corrosion resistance among all samples.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this study, Ti–6Al–xNb alloys with different Nb percentages (x = 3.5–21 wt%) were produced by the conventional powder metallurgy technique. After mixing and pressing the alloy powders in ...appropriate proportions, the green samples were sintered in a tube furnace under a vacuum atmosphere at 1200 °C for 2 h. The X-ray diffraction analysis (XRD) showed that all the alloys consist of α–Ti, TiNb (β–Ti) and AlNb2 phases. The results showed that the Ti–6Al–14Nb alloy among all alloys has the best mechanical properties, and the microhardness, tensile and flexural strength are 276.4 Vickers hardness (Hv0.2), 453 MPa and 1682 MPa, respectively. Tribological tests were carried out in both dry and wet conditions with Hanks' Balanced Salt Solution. While generally, the specific wear rates of the samples increased with Nb content up to 17.5 wt% under dry conditions, on the other hand, they increased with increasing Nb content under wet conditions. On the other hand, the specific wear rate increased with increasing the sliding distance. The best corrosion resistance alloy among all the samples was Ti–6Al–7Nb with −0.0968 V corrosion potential (Ecorr), 0.015 μA/cm2 corrosion current density (Icorr) values.
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•Ti-6Al-14Nb alloy showed the best mechanical properties among Ti-6Al-xNb alloys.•The wear rates of Ti-6Al-xNb alloys generally increased as the Nb amount increased.•The lowest specific wear rates were observed in Ti-6Al-3.5Nb alloy.•Ti-6Al-7Nb alloy exhibited the best corrosion resistance among all samples.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In the present study, we have produced CuAl10Ni5Fe4 alloy powders by using the planar flow casting method. The microstructure, wear response, and corrosion properties of as-cast and P/M parts were ...systematically investigated, and the improvements by P/M production method were presented. While the as-cast microstructure contained α, β, κıı and κııı phases, the rapidly solidified powders had α, and β’ martensite phases. On the other hand, the lower friction coefficient values were obtained in the case of the P/M production technique in comparison to the as-cast state. Also, an improvement in specific wear rate performances of P/M parts compared with the as-cast alloy was observed. It was observed that the P/M parts exhibited better corrosion properties than the as-cast samples.
•Nickel-aluminum bronze (NAB) powders are produced by planar flow casting method.•The rapidly solidified powders consist of α and β′ martensite phases.•The lower friction coefficient values obtain in the P/M part.•The P/M parts exhibit better corrosion properties than the as-cast NAB alloy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZRSKP
The aim of this study is to enhance the magnetic and thermal properties of strontium hexaferrites by substituted with Al, Cr, and Mn ions instead of Fe, and to elucidate the changes in their ...structural, morphological, and thermal characteristics, in detail. SrFe12-xMxO19 (M: Al, Cr, Mn; x = 0.1, 0.3, and 0.5) powders were produced by the mechanochemical synthesis method from mill scale, which is a solid waste in steel production. While the Al3+ substitution did not cause any change in the phase structure, the Cr3+ and Mn3+ caused the formation of nanosized α-Fe2O3 and MnδFe2-δO4 phases in the structure, respectively. Increasing the Al substitution ratio led to a decrease in crystal size, from 176 nm to 32 nm. Similarly, the substitution of Cr resulted in a decrease in crystal size to 78 nm. However, Mn substitution had the opposite effect, increasing the crystal size of the powders. Al3+, Cr3+, and Mn3+ substitutions led to various effects on magnetic properties due to their placement in different lattice sites in the SrFe12O19 hexagonal crystal. The residual or remanent magnetization (Mr) and saturation magnetization (Ms) were lower than the initial values of Mr = 41.76 and Ms = 69.94 emu/g depending on the type and ratio of substitution ions. The highest coercivity was observed as 7116 Oe for SrFe11.5Al0.5O19. The Curie temperature increased to 515 °C with Cr3+ substitution but decreased to 431 °C and 426 °C with Al3+ and Mn3+, respectively.
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•Strontium hexaferrite powders are successfully produced using a mill scale wastes.•Mn3+ substation was caused to fomed MnδFe2-δO4 phase.•Powder shape and crystal properties of strontium hexaferrite powders was change depending on substutition rate.•The Curie temperature was cgange with substitution ion type and rate.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this study, the production of strontium carbonate (SrCO3) from concentrated celestite ore (SrSO4) by mechanochemical synthesis process was investigated. Different proportions of ammonium carbonate ...((NH4)2CO3) were used to convert the celestite ore to strontium carbonate. The effects of SrSO4: (NH4)2CO3 stoichiometric ratio and synthesis time on the purity of the produced strontium carbonate were examined. In the mechanochemical synthesis experiments, the stoichiometric ratios of 1:1, 1:1.5 and, 1:2 between SrSO4 and (NH4)2CO3, and synthesis times of 10, 100, and 200 min were applied. Impurities and contaminations in concentrated celestite ore were removed by acid leaching and calcination processes. DTA, TGA, XRD, SEM, EDX, TEM, and FT-IR analyzes were performed throughout the strontium carbonate production process. Experimental studies have revealed that the 1:2 stoichiometric ratio between SrSO4 and (NH4)2CO3 and 200 min synthesis time are the most suitable process parameters for the production of high purity strontium carbonate.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Today, waste management and recycling have critical importance given the dwindling natural resources and to create powerful technologies for a green future. One of these strontium hexaferrite powders ...were produced by mechanochemical process using mill-scale and strontium carbonate from obtained celestite ore. The strontium carbonate and the mill scale were prepared in stoichiometric ratio, and mechanochemical process was applied for 16 h to produce hard-ferrite powders. Following the mechanochemical synthesis process, powder mixture was annealed at 850–1000 °C temperatures. The morphology, crystal structure and phase composition of strontium hexaferrite powders caused the magnetic properties to change according to the annealing temperature. As a result of the studies, the most suitable annealing temperature was determined as 975 °C. The Hc, Br and (BH)max of produced powders correspond to 5505Oe, 347 mT and 5.77MGOe at 975 °C, respectively. The Curie temperature of the annealed powders was determined as 474 °C.
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•Strontium hexaferrite powders are successfully produced using a mill scale wastes.•The phase ratios and types in the strontium hexaferrite structure changed with the annealing temperature.•The powder shape of the strontium hexaferrite turned into a hexagonal structure with the increase in annealing temperature.•The best magnetic performance of strontium hexaferrite powders was obtained in annealed at 975 °C.•(BH)max. of annealed strontium hexaferrite powders was increased up to 5.77 MGO.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this study, we have produced strontium hexaferrite (SrFe12O19) magnets by mechanochemically synthesizing the mill scale which is the waste material from the hot rolling process of steel slabs and ...strontium carbonate (SrCO3) powders. The mechanochemical synthesis process was conducted via high energy ball milling process. The stoichiometric ratio (SrCO3/Fe2O3) was changed from 1:5.5 to 1:6.6 by 0.1 increments, and the influence of stoichiometric ratio was investigated with regards to phase structure and magnetic properties. The relationship between the magnetic performances and structures was well established through Vibrating Sample Magnetometry (VSM) measurements and Rietveld refinement analysis of powder X-ray diffraction data. The primary phase formed in powder structures for all the stoichiometric ratios was SrFe12O19 and the other phases of α-Fe2O3, SrO, and SrFe2O4 with varying amount, depending on the stoichiometric ratios, were also obtained. The maximum magnetic properties were obtained with 1:6.0 SrCO3/Fe2O3 stoichiometric ratio. The coercivity (Hc), the saturated magnetic flux density (Bs), the residual magnetic flux density (Br), and maximum energy product (BH)max values for 1:6.0 stoichiometric ratio were obtained as 3682 Oe, 506 mT, 311 mT, and 3.11 MGOe, respectively.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Strontium hexaferrite powders are successfully produced using a recycled mill scale.•The mechanochemical synthesis time of 16 h is crucial process parameter to produce high performance strontium ...hexaferrite.•The coercivity value of the hexaferrite powders increased up to 5.5 kOe.•The change in the phase ratio of the SrFe12O19 and lattice parameters affected the magnetic properties.•After annealing at, all of C─O bonds in SrCO3 were not visible and Sr─O and Fe─O bonds in SrFe12O19 were strengthened.
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In the present study, the strontium hexaferrite (SrFe12O19) has been successfully produced from recycled mill scale and strontium carbonate (SrCO3) powders with stoichiometric ratio (SrCO3/Fe2O3) of 1:6 by mechanochemical synthesis process, followed by annealing at 975 °C temperature. As the mechanochemical synthesis time increased, the phase ratio of hard magnetically SrFe12O19 in the structure increased after the annealing, according to the XRD analysis. The SrFe12O19 phase formation temperature decreased from 851 °C to 762 °C with increasing mechanochemical synthesis time. Also, FTIR analysis showed that The C═O bond peaks are only visible for a 2 h synthesis time at 854 cm−1 wavenumbers. Magnetic properties have changed according to particle size, activation energy, and phase ratios. The best magnetic properties were obtained with the application of 16 h of synthesis time. The coercivity values of 3.3, 3.6, 4.6, 5.5, 5,4, and 3.7 kOe were obtained for 2, 4, 8, 16, 32, and 64 h of mechanochemical synthesis times, respectively. The residual magnetization density (Br) values under 1 T magnetic field for the same synthesis times were obtained as 168, 221, 292, 347, 314, 258 mT, respectively.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
