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Showing papers on "Laves phase published in 2016"


Journal ArticleDOI
TL;DR: Based on the existing binary phase diagrams with eutectic points, a strategy of designing EHEAs with desired high strength and ductility is proposed in this article, which is composed of a ductile face centered cubic (FCC) phase and a hard Laves phase with fine laminar structures.

318 citations


Journal ArticleDOI
TL;DR: The AlCoCrFeNiZr x alloys are produced by electric arc melting and their microstructure and mechanical properties were analyzed in this article, where the compressive test showed that minor Zr addition can significantly improve the mechanical properties.

139 citations


Journal ArticleDOI
TL;DR: In this article, the microstructure characteristics of the as-deposited IN718 have been analyzed, and the mechanical properties of it have been tested, aiming to solve these problems the methods in order to improve material performance have been studies.

117 citations


Journal ArticleDOI
12 Feb 2016-JOM
TL;DR: In this article, a microstructure gradient and associated tensile property gradient are characterized for all EBM Inconel 718 builds, the extent of which is dependent on build geometry and the specifics of a build's processing history.
Abstract: During the electron beam melting (EBM) process, builds occur at temperatures in excess of 800°C for nickel-base superalloys such as Inconel 718. When coupled with the temporal differences between the start and end of a build, a top-to-bottom microstructure gradient forms. Characterized in this study is a microstructure gradient and associated tensile property gradient common to all EBM Inconel 718 builds, the extent of which is dependent on build geometry and the specifics of a build’s processing history. From the characteristic microstructure elements observed in EBM Inconel 718 material, the microstructure gradient can be classified into three distinct regions. Region 1 (top of a build) is comprised of a cored dendritic structure that includes carbides and Laves phase within the interdendritic regions. Region 2 is an intermediate transition zone characterized by a diffuse dendritic structure, dissolution of the Laves phase, and precipitation of $$\delta $$ needle networks within the interdendritic regions. The bulk structure (Region 3) is comprised of a columnar grain structure lacking dendritic characteristics with $$\delta $$ networks having precipitated within the grain interiors. Mechanically, at both 20°C and 650°C, the yield strength, ultimate tensile strength, and elongation at failure exhibit the general trend of increasing with increasing build height.

98 citations


Journal ArticleDOI
TL;DR: In this paper, the structure and mechanical properties of high-entropy alloys after arc melting and annealing at 1200°C for 24-h are investigated, and the experimental phase composition of the alloys is compared with predicted equilibrium phases and the factors governing the transformation of C15 to C14 Laves phases due to Al addition to the CrNbTiVZr alloy analyzed.

96 citations


Journal ArticleDOI
TL;DR: In this paper, a multicomponent Co 20 Cu 20 Fe 20 Ni 20 Ti 20 eutectic high entropy alloy (HEA), processed by vacuum arc melting cum suction casting technique was studied.
Abstract: Multicomponent Co 20 Cu 20 Fe 20 Ni 20 Ti 20 eutectic high entropy alloy (HEA), processed by vacuum arc melting cum suction casting technique was studied. The microstructure of this eutectic HEA consists bcc (β) and fcc (α 2 ) solid solution dendritic phases and eutectics (fcc (α 1 ) plus Ti 2 (Ni, Co)-type Laves phase). Serrations in the flow behaviour are attributed to multi substitutional solutes in the multi-phase microstructure. Based on the detailed analysis of mechanical data together with deformed microstructural characterization, the optimum thermo-mechanical processing conditions for hot working are identified as T=930–990 °C (1203–1263 K) and strain rate range of 10 −3 s −1 –10 −1 s −1 .

90 citations


Journal ArticleDOI
TL;DR: The eutectic microstructure and mechanical properties of the samples were investigated by scanning electron microscopy, X-ray diffraction, compressive and hardness tests as mentioned in this paper.

89 citations


Journal ArticleDOI
TL;DR: In this paper, modified P92 steel specimens were examined after creep tests under applied stresses ranging from 200 to 100 MPa at T=650°C, and the final dimensions of these particles were independent of further aging time.
Abstract: Microstructure and hardness in the grip and gage sections of ruptured 3%Со modified P92 steel specimens were examined after creep tests under applied stresses ranging from 200 to 100 MPa at T=650 °C. Under long-term aging, the depletion of W from solid solution leads to precipitation of the Laves phase. In addition, coarsening of MX carbonitrides occurs after 34 h of aging. The final dimensions of these particles are independent of further aging time. A breakdown of applied stress vs time to rupture dependence takes place at a stress of 140 MPa or a rupture time of 1828 h at which the W content in the ferritic matrix almost attains a thermodynamical equilibrium level. Under long-term creep conditions, the strain-induced coarsening of M23C6 carbides and the Laves phase takes place. No strain-induced coarsening of MX carbonitrides was found. However, V-rich MX carbonitrides transform to Z-phase in the gage section. Zener drag force restraining migration of grain/subgrain boundaries decreases, and with long-term creep, the transformation of the tempered martensite lath structure (TMLS) to subgrain structure occurs, whereas short-term creep conditions and long-term aging result in the retained lath structure.

79 citations


Journal ArticleDOI
TL;DR: A comparative study on the metallurgical properties and material microstructures of Inconel 718 (IN718) deposited by High Deposition Rate Laser Metal Deposition (HDR-LMD) using Gas Atomization (GA) and Plasma-rotating Electrode Process (PREP) powders has been carried out.

76 citations


Journal ArticleDOI
05 Jul 2016
TL;DR: In this paper, a microstructure suited for high-temperature applications by employing high-power selective laser melting was adjusted by applying a post-process heat treatment to examine if the desired microstructural features can be preserved.
Abstract: Optimising the microstructure and mechanical performance of Ni-base alloys is vital to achieve higher efficiencies in many high-temperature applications. With the recent emergence of the additive manufacturing technologies, new possibilities with respect to freedom of design and microstructure manipulation are opened up. This study aims at adjusting a microstructure suited for high-temperature applications by employing high-power selective laser melting. The parts are subjected to diverse post-process heat treatments to examine if the desired microstructural features can be preserved and proper precipitations can be formed. Results obtained by electron backscatter diffraction show a high resistance against recrystallization in the temperature range contemplated. Still, process-induced formation of undesired brittle Laves phase particles was observed via transmission electron microscopy and backscattered electron imaging. Mechanical tests in the form of hardness measurements, tensile tests, and high-temperature compression creep tests proved a high dependency of the performance on the post-processing treatment conducted. Hardness, yield strength and elongation at failure at room temperature are adequate in comparison with conventionally processed materials. High-temperature compression creep tests emphasised the importance of solution annealing to enable for proper precipitation of strengthening phases during subsequent ageing.

72 citations


Journal ArticleDOI
TL;DR: In this article, a significant partitioning of Gd into Zn-rich precipitates was observed, which is considered to be responsible for improving the thermal stability of Zn rich precipitates and enhancing precipitation hardening of the alloy.

Journal ArticleDOI
TL;DR: In this article, the microstructural stability and consequent phase decomposition of tungsten-free gamma-gamma' alloys of base composition Co-10Al-5Mo-2Nb with or without the addition of Ni and Ti were reported.
Abstract: This article reports the microstructural stability and consequent phase decomposition including the appearance of topologically close-packed (TCP) phases at high temperature of recently discovered tungsten-free gamma-gamma' alloys of base composition Co-10Al-5Mo-2Nb with or without the addition of Ni and Ti. On prolonged aging at 800 degrees C of the Co-10Al-5Mo-2Nb alloy, needle-shaped DO19-ordered precipitates with stoichiometry of Co-3(Mo, Nb) start appearing in the microstructure. In addition, growth of cellular domains from the grain boundaries featuring a three-phase composite lamellar structure could be observed. These phases are fcc gamma-Co with composition different from the original matrix, CoAl with B2 ordering and Co-3(Mo, Nb) with DO19 ordering. All the phases exhibit well-defined crystallographic orientation relationships. The decomposition of the alloys depends on the solvus temperature of the gamma' phase. The Ni-containing alloy exhibits no phase decomposition until 100 h of aging at 800 degrees C without any significant effect on gamma' volume fraction (76 %). However, at 950 degrees C, the alloy decomposes leading to the appearance of four different phases including TCP phases: a Cr3Si-type cubic phase, a hexagonal Laves phase, rhombohedral mu phase, and solid solution of Co phase. The gamma-gamma' microstructure in the Co-10Al-5Mo-2Nb and Co-30Ni-10Al-5Mo-2Ta alloys is not stable at 800 and 950 degrees C, respectively, on long-term aging. This shows that the measured solvus temperatures (i.e., 866 and 990 degrees C) are metastable solvus temperatures. We also report that the Ti-containing alloy exhibits superior stability with no evidence of either TCP phase formation or any other decomposition of gamma' precipitates, even after aging at 950 degrees C for 100 h.

Journal ArticleDOI
TL;DR: In this paper, the influence of solidification conditions on the segregation of niobium and the resultant formation of Nb-rich Laves phase was studied using the microstructure observation and EDS analysis.

Journal ArticleDOI
TL;DR: The same structural motifs for the metallic glass and intermetallic compounds of Cu-Zr system are suggested and explains the drastic increase of the abundances of these clusters observed at γmin.
Abstract: Using molecular dynamics simulations with embedded atom model potential, we study structural evolution of Cu64.5Zr35.5 alloy during the cooling in a wide range of cooling rates γ ∈ (1.5 ⋅ 10(9), 10(13)) K/s. Investigating short- and medium-range orders, we show that the structure of Cu64.5Zr35.5 metallic glass essentially depends on cooling rate. In particular, a decrease of the cooling rate leads to an increase of abundances of both the icosahedral-like clusters and Frank-Kasper Z16 polyhedra. The amounts of these clusters in the glassy state drastically increase at the γmin = 1.5 ⋅ 10(9) K/s. Analysing the structure of the glass at γmin, we observe the formation of nano-sized crystalline grain of Cu2Zr intermetallic compound with the structure of Cu2Mg Laves phase. The structure of this compound is isomorphous with that for Cu5Zr intermetallic compound. Both crystal lattices consist of two types of clusters: Cu-centered 13-atom icosahedral-like cluster and Zr-centered 17-atom Frank-Kasper polyhedron Z16. That suggests the same structural motifs for the metallic glass and intermetallic compounds of Cu-Zr system and explains the drastic increase of the abundances of these clusters observed at γmin.

Journal ArticleDOI
01 Oct 2016-Carbon
TL;DR: In this article, the survivability of MWCNTs, susceptibility to heat affected zone (HAZ) liquation cracking and tensile mechanical properties of the coatings were studied.

Journal ArticleDOI
Li Jiang1, Wei Wu1, Zhiqiang Cao1, Dewei Deng1, Tingju Li1 
TL;DR: In this paper, the CoFeNi2V0.5Nb0.75 and CoFeNb 0.5nb 0.5n b HEAs were laser cladded on 304 stainless steel substrate with laser power of 1400, 1600, and 1800 W. Results show that the HEA coatings are composed of the FCC solid solution phase and the Fe2Nb-type Laves phase.
Abstract: The high-entropy alloy (HEA) coatings have received considerable attentions owing to their unique structures and properties caused by the quick solidification. In this work, the CoFeNi2V0.5Nb0.75 and CoFeNi2V0.5Nb HEAs which show fully eutectic and hypereutectic microstructures in their casting samples were laser cladded on 304 stainless steel substrate with laser power of 1400, 1600, and 1800 W. Results show that the HEA coatings are composed of the FCC solid solution phase and the Fe2Nb-type Laves phase. The cladding zones of the CoFeNi2V0.5Nb0.75 and CoFeNi2V0.5Nb coatings show cellular dendritic crystals, while the bonding zones show directional columnar crystals. Compared to the 304 stainless steel substrate, the HEA coatings show better wear resistance because of the combination of the hard Fe2Nb-type Laves phase and the ductile FCC solid solution matrix. Moreover, the HEA coatings with power of 1600 W show the best wear resistance attributing to the maximum volume fraction of the hard Fe2Nb-type Laves phase.

Journal ArticleDOI
TL;DR: In this article, a density functional theory (DFT) based first-principles investigation has been performed to study the cohesive, elastic and electronic properties of Fe-Zr binary intermetallics across the composition range.

Journal ArticleDOI
TL;DR: In this article, the microstructures and the cryogenic mechanical properties of electron beam welds between cast and forged Inconel 718 superalloys with a thickness of 10 mm were investigated in comparison with gas tungsten arc (GTA) welds.
Abstract: The microstructures and the cryogenic mechanical properties of electron beam (EB) welds between cast and forged Inconel 718 superalloys with a thickness of 10 mm were investigated in comparison with gas tungsten arc (GTA) welds. EB welding with a heat input lower than 250 J/mm caused the formation of liquation microfissuring in the cast-side heat-affected-zone (HAZ) of the EB welds. HAZ liquation microfissuring appeared to be associated with the constitutional liquation of primary NbC carbides at the grain boundaries. Compared with the GTA welding process, the EB welding produced welds with superior microstructure, exhibiting fine dendritic structure associated with the reduction in size and fraction of the Laves phase due to the rapid cooling rate. This result was responsible for the superior mechanical properties of the EB welds at 77 K (−196 °C). Laves particles in both welds were found to provide the preferential site for the crack initiation and propagation, leading to a significant decrease in the Charpy impact toughness at 77 K (−196 °C). Crack initiation and propagation induced by Charpy impact testing were discussed in terms of the dendrite arm spacing, the Laves size and the dislocation structure ahead of the crack arisen from the fractured Laves phase in the two welds.

Journal ArticleDOI
TL;DR: In this article, the effect of tempering temperature in the range of 740-780°C on the creep rupture life was investigated, and the results varied from 100 to 3000h, and creep rate by one order of magnitude.
Abstract: Stress rupture tests of normalized and tempered P92 (9Cr–0.5Mo–1.8 W) steel were performed in the range of 135–215 MPa at 650 °C. Effect of tempering temperature in the range of 740–780 °C on the creep rupture life was investigated. Resulting rupture times varied from 100 to 3000 h, and creep rate by one order of magnitude. In the high stress regime, lower tempering temperature resulted in the highest rupture time due to initial high dislocation density and fine laths. However, at lower stresses, highest rupture time was observed for highest tempering temperature. Formation of Laves phase (Fe 2 Mo, Fe 2 W) adjacent to M 23 C 6 carbides was responsible for increase in rupture time. Back scattered electron imaging (BSE) in scanning electron microscopy (SEM) was used to identify Laves phases, and study their distribution. Reduction in dislocation density and coarsening of laves phase precipitates result in decrease in stress exponent value ‘n’ at higher test temperatures of 650 °C.

Journal ArticleDOI
TL;DR: The hardness, elastic modulus and contact stiffness of the NiCoCrAlYTa coating were determined by nano-indentation test as discussed by the authors, which indicated that the coating exhibits good corrosion resistance, which was ascribed to the formation of Al and Cr oxide protective film.

Journal ArticleDOI
TL;DR: Toughness of G115 martensitic heat resistant steel after heat treatment and aging for different time at 650 ÂC was tested at room temperature as mentioned in this paper, and the results showed that the absorbed energy of G 115 steel can reach 115 ÂJ after a heat treatment, and then keeps almost stable with further increasing aging time to 8000 Â
Abstract: Toughness of G115 martensitic heat resistant steel after heat treatment and aging for different time at 650 °C was tested at room temperature. The corresponding microstructure was also experimentally obtained by field emission scanning electron microscope (FESEM), field emission transmission electron microscope (FETEM), X-Ray diffraction (XRD), electron back-scattered diffraction (EBSD) characterization and phase analysis. The results show that the absorbed energy of G115 steel can reach 115 J after heat treatment. After the first 300 h aging, the absorbed energy decreases drastically to just 36 J and then keeps almost stable with further increasing aging time to 8000 h. The hardness of base metal and the amount of large angle (LA) boundaries (>15°) are not the main factors dominating the toughness of G115 steel during aging process. The main reason for the change of toughness can be attributed to the precipitation of Laves phase. Since Laves phase particles are large, angular and hard, it is difficult for them to harmonize with the matrix during deformation, resulting that the crack initiation and propagation become easy and then the toughness of the steel sharply decreases. The reason why the toughness keeps nearly stable from 300 h to 8000 h can be attributed to that the negative effect of the precipitation of Laves phase and the decrease of LA boundaries is counteracted by the positive effect of the softening of metal matrix.

Journal ArticleDOI
TL;DR: In this paper, the effects of addition elements on phase composition, microstructure and mechanical behaviors of the HEA were studied, which showed that the selection and addition of supplementary elements based on the formation rule for HEAs play an important role on the evolution of phase, microstructural morphology and mechanical properties of Ti20Zr20Hf20Ni20Cu20 HEA.
Abstract: In this study, alloys with composition of equi-atomic substituted TiZrHfNiCu, TiZrHfNiCuCo, and TiZrHfNiCuNb high-entropy alloys (HEAs) were produced by suction casting method. The effects of addition elements on phase composition, microstructure and mechanical behaviors of the HEA were studied. The suction casted Ti20Zr20Hf20Ni20Cu20 HEA exhibits single C14 Laves phase (MgZn2-type) with fine homogeneous microstructure. When Co or Nb elements are added, morphologies are slightly modulated toward well-developed dendritic microstructure, phase constitutions are significantly changed from single Laves phase to mixed multi-phases as well as mechanical properties are also altered with increased plasticity and high strength. It is believed that modulated mechanical properties are mainly ascribed to the change of phase constitution and crystalline structure, together with the microstructural characteristics. This clearly reveals that the selection and addition of supplementary elements based on the formation rule for HEAs play an important role on the evolution of phase, microstructural morphology and mechanical properties of Ti20Zr20Hf20Ni20Cu20 HEA.

Journal ArticleDOI
TL;DR: In this article, the microstructures and tensile properties of Inconel 718 (IN718) formed by high deposition-rate laser metal deposition (LMD), and furthermore verify that the properties of the material are equivalent to those obtained by conventional manufacturing processes, such as casting and forging, and therefore satisfy the specifications for industrial applications.
Abstract: The aim of this study is to characterize microstructures and tensile properties of Inconel 718 (IN718) formed by high deposition-rate laser metal deposition (LMD), and furthermore to verify that the properties of the material are equivalent to those obtained by conventional manufacturing processes, such as casting and forging, and therefore satisfy the specifications for industrial applications. Initially, the powdery additive was characterized in terms of chemical composition, morphology, and porosity. Afterward, blocks for producing tensile specimens were deposited by applying the newly developed high deposition-rate LMD process that has a deposition rate of approximately 2 kg/h. Finally, microstructures and tensile properties of directly deposited and heat-treated material were analyzed, respectively. From the results, precipitation of an irregular shaped phase, which is believed to be Laves phase, and segregation of Nb and Mo were found at interdendritic regions of the directly deposited material. The...

Journal ArticleDOI
TL;DR: In this paper, the microstructural evolution and the dispersion of secondary phases were studied in a low-nitrogen 10%Cr martensitic steel with 3% Co and 0.008% B additives at 650°C under an applied stress of 140MPa.
Abstract: The microstructural evolution and the dispersion of secondary phases were studied in a low-nitrogen 10%Cr martensitic steel with 3% Co and 0.008% B additives at 650 °C under an applied stress of 140 MPa. It was demonstrated that the superior creep strength of this steel can be attributed to the high resistance of M23C6-type carbides and Nb-rich MX carbonitrides against coarsening, resulting in a stable of the tempered martensite lath structure (TMLS) under short-term creep conditions. The TMLS remains slightly changed under creep: lath coarsening occurs with a two-fold decrease in the lattice dislocation density. M23C6-type carbides were found to give the main contribution in hindering the transformation of interlath boundaries to subgrain boundaries, impeding the migration of low-angle boundaries by exerting a large pinning pressure. A high Zener drag pressure is maintained up to rupture. The precipitation of a Laves phase under creep conditions results in a minor contribution to the overall pinning pressure. V-rich MX carbonitrides tend to dissolve with increasing time. No formation of a Z-phase was detected. M23C6 carbides retain their orientation relationship with ferritic matrix up to rupture. No significant strain-induced coarsening of M23C6 carbides, Laves phase, or MX carbonitrides was observed.

Journal ArticleDOI
TL;DR: In this article, the structural, elastic, mechanical, electronic, thermal and superconducting properties of a new Laves phase superconductor NbBe 2, prototype with MgCu 2, having maximum T c ∼2.6 K has been systematically studied.

Journal ArticleDOI
TL;DR: In this article, high-temperature cyclic oxidation of ferritic stainless steel (FSS) with minor addition of Nb and Ti elements has been carried out at 800°C in air for 70 cycles.

Journal ArticleDOI
TL;DR: In this paper, the thermal annealing of a Laves phase-related body-centered-cubic (BCC) alloy, Ti15.6Zr2.1V40.0Cr11.2Mn6.9Co1.4Ni22.5Al0.3, was studied.

Journal ArticleDOI
Shao Yang1, Fei Yang1, Chaoling Wu1, Yungui Chen1, Yuan Mao1, Linshan Luo1 
TL;DR: In this article, the cyclic properties of (VFe) 60 (TiCrCo) 40-x Zr x (0, 1, 2) alloys were investigated systematically.

Journal ArticleDOI
TL;DR: In this paper, the microstructural evolution of DAFA26, an alumina-forming austenitic (AFA) stainless steel, was investigated during aging, and the effect of aging at 750 and 800°C on the growth of spherical γ’-Ni3(Al, Ti) particles present in the as-processed state was studied extensively using X-ray diffraction, microhardness testing, scanning electron microscopy, transmission electron microscope, and atom probe tomography.
Abstract: The microstructural evolution of DAFA26, an alumina-forming austenitic (AFA) stainless steel, was investigated during aging. The effect of aging at 750 °C and 800 °C on the growth of spherical γ’-Ni3(Al, Ti) particles present in the as-processed state was studied extensively using X-ray diffraction, microhardness testing, scanning electron microscopy, transmission electron microscopy, and atom probe tomography. The γ’ particles had a cube-on-cube orientation relationship with the matrix (i.e. ( ( 010 ) m// ( 010 ) p, [ 100 ] m// [ 10 0 ] p)). The coarsening kinetics of γ’-Ni3Al particles were in agreement with the Lifshitz, Slyozof-Wagner theory. Coarse Laves phase particles were also present in the as-processed state, and during the aging process both smaller Laves phase precipitates and B2-NiAl precipitates formed on both the grain boundaries and in the matrix. The γ’ precipitates were determined to have the most impact on the room temperature hardness.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the autonomous repair of creep damage by site-selective precipitation in a binary Fe-Mo alloy (6.2 ¼wt/pct Mo) during constant-stress creep tests at temperatures of 813 K, 823 K, and 838 K (540,°C, 550 °C and 565   c).
Abstract: We have investigated the autonomous repair of creep damage by site-selective precipitation in a binary Fe-Mo alloy (6.2 wt pct Mo) during constant-stress creep tests at temperatures of 813 K, 823 K, and 838 K (540 °C, 550 °C, and 565 °C). Scanning electron microscopy studies on the morphology of the creep-failed samples reveal irregularly formed deposits that show a close spatial correlation with the creep cavities, indicating the filling of creep cavities at grain boundaries by precipitation of the Fe2Mo Laves phase. Complementary transmission electron microscopy and atom probe tomography have been used to characterize the precipitation mechanism and the segregation at grain boundaries in detail.