To improve the heat resistance of titanium alloys, the effects of Y content on the precipitation behavior, oxidation resistance and high-temperature mechanical properties of as-cast ...Ti-5Al-2.75Sn-3Zr-1.5Mo-0.45Si-1W-2Nb-xY (x = 0.1, 0.2, 0.4) alloys were systematically investigated. The microstructures, phase evolution and oxidation scales were characterized by XRD, Laser Raman, XPS, SEM and TEM. The properties were studied by cyclic oxidation as well as room- and high-temperature tensile testing. The results show that the microstructures of the alloys are of the widmanstätten structure with typical basket weave features, and the prior β grain size and α lamellar spacing are refined with the increase of Y content. The precipitates in the alloys mainly include Y
O
and (TiZr)
Si
silicide phases. The Y
O
phase has specific orientation relationships with the α-Ti phase: (002)
// (1¯1¯20)
, 110
// 4¯401
. (TiZr)
Si
has an orientation relationship with the β-Ti phase: (022¯1¯)
// (011)
, 1¯21¯6
// 044¯
. The 0.1 wt.% Y composition alloy has the best high-temperature oxidation resistance at different temperatures. The oxidation behaviors of the alloys follow the linear-parabolic law, and the oxidation products of the alloys are composed of rutile-TiO
, anatase-TiO
, Y
O
and Al
O
. The room-temperature and 700 °C UTS of the alloys decreases first and then increases with the increase of Y content; the 0.1 wt.% Y composition alloy has the best room-temperature mechanical properties with a UTS of 1012 MPa and elongation of 1.0%. The 700 °C UTS and elongation of the alloy with 0.1 wt.% Y is 694 MPa and 9.8%, showing an optimal comprehensive performance. The UTS and elongation of the alloys at 750 °C increase first and then decrease with the increase of Y content. The optimal UTS and elongation of the alloy is 556 MPa and 10.1% obtained in 0.2 wt.% Y composition alloy. The cleavage and dimples fractures are the primary fracture mode for the room- and high-temperature tensile fracture, respectively.
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Ti-Cu alloys have broad application prospects in the biomedical field due to their excellent properties. The properties of Ti-Cu alloys are strongly dependent on Cu content, microstructures, its ...Ti2Cu phase and its preparation process. The aim of this work is to investigate the effect of Cu content on the precipitation behaviors, mechanical and corrosion properties of the as-cast Ti-Cu alloys. The microstructures and phase evolution were characterized by SEM and TEM, and the properties were studied by tensile and electrochemical test. The results show that the volume fraction of Ti2Cu phase increases with the increase of Cu content. The Ti2Cu phase presents a variety of microscopic morphologies with different Cu content, such as rod, granular, lath and block shaped. The crystal orientation relationships between the Ti2Cu and α-Ti matrix in Ti-4Cu and Ti-10Cu alloys are (103)Ti2Cu//(011¯11)α-Ti, 3¯01Ti2Cu//21¯1¯0α-Ti, and (103)Ti2Cu//(0002)α-Ti, 3¯31Ti2Cu//12¯10α-Ti, respectively. The tensile strength, Vickers hardness and Young’s modulus of the Ti-Cu alloys increase with the increase of Cu content, whereas the elongation decreases. The fracture morphologies of these alloys reveal ductile, ductile-brittle hybrid, and cleavage brittle mode, respectively. The corrosion resistance of the Ti-Cu alloys in SBF solution can be described as: Ti-4Cu alloy > Ti-10Cu alloy > Ti-7Cu alloy. The volume fraction of Ti2Cu phases and the “protective barrier” provided by the fine lath Ti2Cu phases strongly affected the electrochemical performances of the alloys.
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X2CrNi12 ferritic stainless steel has a wide range of application prospects in the railway transportation, construction, and automobile fields due to its excellent properties. The properties of ...X2CrNi12 ferritic stainless steel can be further improved by cold-rolling and subsequent annealing treatment. The purpose of this work is to investigate the effect of cold-rolling reduction on the microstructure, texture and corrosion properties of the recrystallized X2CrNi12 ferritic stainless steel by using SEM, TEM, EBSD and electrochemical testing technology. The results show that the crystal orientation characteristics of the cold-rolled sheet could be inherited into the annealed sheet. The higher cold-rolling reduction could promote the deformed grains rotating into the {111} orientation, increasing storage energy and driving force for recrystallization, which could reduce the recrystallized grain size. The orientation densities of α-fiber and γ-fiber were low at 50% cold-rolling reduction. After recrystallization annealing, a large number of grains with random orientation could be produced, and the texture strength was weakened. When the cold-rolling reduction rose to 90%, the γ-fiber texture at {111} was strengthened and the α-fibers, particularly the {112} component, were weakened after recrystallisation annealing, which could improve the formability of the steels. The proportions of special boundaries, i.e., low-angle grain boundaries and low-Σ CSL boundaries, among the grain boundary distribution of the recrystallized X2CrNi12 stainless steel were higher when the reduction was 90%, especially when the annealing temperature was 770 °C. Additionally, the proportion of LAGBs and low-Σ CSL boundaries were 53% and 7.43%, respectively, which improves the corrosion resistance of the matrix, showing the best corrosion resistance.
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The cyclic oxidation behaviors of the as-cast Ti-1100-xNb (x = 0.5, 1.0, 1.5, 2.0) alloys exposed at 650 °C for up to 100 h were systematically investigated. The aim of this work is to explore the ...in-depth oxidation mechanism by using the oxidation kinetics and the structure of the oxide products. The oxidation kinetics were determined by thermogravimetrically, and the microstructure and composition of the oxidation scale were studied by using XRD and SEM. The results demonstrate that Nb can significantly improve the oxidation resistance. However, the average weight gains of the alloys decrease firstly and then increase with the increase of Nb content. The oxidation kinetics obeys a parabolic model. The Ti-1100-1.0Nb alloy has the lowest k
value, which is 5.7 10
g
cm
s
. The surface oxidation products are mainly composed of massive or acicular rutile-TiO
, Ti
O (x = 3, 6), NbO
and Al
O
. Besides, Al
(MoO
)
oxide is also presented on the oxidation surface of the Ti-1100-1.5Nb alloys. Ti-1100-1.0Nb alloy shows the best oxidation resistance property revealed by combining weight gains and EDS-SEM element content profiles analysis. The interaction of Nb, O, Ti, and other elements retarded the diffusion of O atoms into the alloys, which improves the oxidation resistance.
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The Ti/SiC gradient material with Mg2Si additive was designed and fabricated by reaction sintering. The structure, microstructure and properties were investigated systematically. The result indicated ...that the Ti/SiC gradient material contained six layers with Ti-rich and Si-rich regions. The relative density decreased from 98.32% to 88.73%, and it increased to 97.28%. Besides, the harness increased from 532.97 HV to 571.32 HV and reduced to 228.14 HV with the increase of Ti content. The fracture toughness of the SiC layer was 6.74 MPa m1/2, and it decreased to 4.91–5.39 MPa m1/2 at the layers containing Ti. The shrinkage rates increased during heating, and it slowed down at the holding stage. The densification primarily occurred at the heating and holding stages. The densification mechanism is the pore displacement controlled by lattice diffusion. Ti5Si3 synthesized by the reaction between Ti and SiC shows the incoherent interface to the Ti grain.
•A novel Ti/SiC gradient material was fabricated.•The structure, microstructure and properties were investigated systematically.•The reaction mechanism was clarified.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Herein, an FeCrBSi coating was fabricated via plasma spray on AISI1045 steel, and subsequently, a gas tungsten arc welding (GTA) process was employed to remelt the coating. The microstructure, ...microhardness, fracture toughness and surface roughness of the coating before and after remelting were investigated, as well as the wear resistance was tested by a UMT-3-type sliding wear apparatus. The results showed that, upon remelting, most defects in the as-sprayed coating were effectively eliminated, the surface roughness decreased by 43%, and the coating–substrate interface bonding changed from mechanical to metallurgical. The phase composition of the as-sprayed coating was primarily α-Fe and a small amount of hard Fe
3
B phase, while the remelted coating consisted of α-Fe and (Fe,Cr)
23
C
6
and a small quantity of CrB. In addition, remelting the coating was found to induce a 287.6% increase in the fracture toughness, a 33.4% increase in the average microhardness, and a 47.5% decrease in the wear volume, while the failure mechanism changed from abrasive wear to fatigue wear upon remelting. Therefore, GTA remelting of plasma-sprayed coating was found to be a feasible method to obtain a coating with good wear resistance.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Ni based coatings were prepared on steel substrate by means of plasma spraying, and were remelted by TIG (tungsten inert gas arc) method subsequently. The microstructure, microhardness, ...electrochemical corrosion and corrosive wear resistance under PH = 4, PH = 7 and PH = 10 conditions of the coatings before and after remelting were investigated. The results showed that the TIG remelting obviously reduced the defects and dramatically decreased the coating's porosity from 7.2% to 0.4%. Metallurgical bonding between the remelted coating and substrate was achieved. Meanwhile, the phase compositions of as-sprayed coating were γ-Ni, Mn5Si2 and Cr2B, while the phase compositions of the remelting coating were Fe3Ni, Cr23C6, Cr2B and Mn5Si2. The microhardness of the coating decreased from 724 HV to 608 HV, but the fracture toughness enhanced from 2.80 MPa m1/2 to 197.3 MPa m1/2 after remelting. After corrosive wear test, the average wear weight loss and 3D morphology of wear scar of two coatings indicated that the wear resistance of the remelted coating was remarkably higher than that of as-sprayed coating. Therefore, TIG remelting treatment was a feasible method to improve the coating's microstructure and enhance its corrosive wear resistance.
NiCr–Cr
3
C
2
coating was fabricated using supersonic plasma spraying technology. Subsequently, rolling/sliding contact fatigue (R/SCF) testing was carried out, using acoustic emission (AE) ...technology to monitor the failure process. The results showed that R/SCF consists of three failure modes, namely abrasion, spalling, and delamination. Abrasion is the main failure mode, but delamination is the most severe. The AE monitoring results indicated that the R/SCF failure process is composed of normal contact, crack initiation, crack propagation, and material removal stages. The frequency of each stage was analyzed by fast Fourier transform, revealing a peak frequency for each stage mainly distributed from 200 to 250 kHz.
For improving the wear resistance of Al-30Si-5Cu coating, in this study, the composite coating in-situ synthesized TiC-TiN-TiN0.8C0.2/Al-30Si-5Cu (TiCN/Al-30Si-5Cu) was prepared used TiH2-graphite ...aggregates as raw materials and plasma spraying technology. The effect of in-situ synthesized ceramic reinforcements on the coating was researched in detail. The results showed that during the plasma spraying process, TiH2 decomposed and chemically reacted with graphite to form TiC. Additionally, some Ti also reacted with N2 and O2 in the air to form TiN and TiO2. The phases composition of TiCN/Al-30Si-5Cu composite coating were α-Al, β-Si, θ-Al2Cu, β-Ti, TiC, TiN, TiN0.8C0.2, TiO2, as well as amorphous CNX and residual graphite. The TiC-dominated ceramic phases and β-Si were uniformly distributed in the coating, which were tightly bound to the α-Al matrix. Because of the exceptionally rapid cooling rate during the coating preparation, a minor amount of submicron Si particles were also generated. The microhardness, elasticity modulus, and fracture toughness of TiCN/Al-30Si-5Cu composite coating appeared improvements compared to those of Al-30Si-5Cu coating. The TiCN/Al-30Si-5Cu composite coating exhibited smoother friction coefficient curve, along with lower friction coefficient and wear volume in comparison to the Al-30Si-5Cu coating. This suggested that the ceramic reinforcing phases in-situ synthesized led to a notable advancement in the wear resistance of the TiCN/Al-30Si-5Cu composite coating. The wear resistance of TiCN/Al-30Si-5Cu composite coating demonstrated an increasement of 78.3 % over the substrate and 28.2 % over the Al-30Si-5Cu coating. Under the dry friction test conditions outlined in this study, the wear mechanism of the TiCN/Al-30Si-5Cu composite coating included abrasive wear and fatigue wear, coupling with a minimal amount of oxidative wear.
•In-situ synthesized TiC-TiN-TiN0.8C0.2 were achieved using TiH2-graphite agglomerates.•The TiC-dominated reinforcements were evenly distributed and tightly bonded with α-Al.•TCN/Al-30Si-5Cu coating had better mechanical and wear resistance properties.
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