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Showing papers on "Laves phase published in 2015"


Journal ArticleDOI
TL;DR: A series of five-component CoCrFeNiNbx high entropy alloys were synthesized to investigate alloying effects of the large atom Nb on the structure and tensile properties as discussed by the authors.

300 citations


Journal ArticleDOI
TL;DR: In this paper, phase composition of high entropy alloys is compared with results of thermodynamical modeling of equilibrium phases in the alloys, and possibilities for properties optimization of the AlCrxNbTiV and AlCr15NbV alloys are suggested.

185 citations


Journal ArticleDOI
TL;DR: In this article, the nucleation of Mo-rich Laves phase particles during aging and creep of 12.5% Cr tempered martensite ferritic steels (TMFS) was investigated.

134 citations


Journal ArticleDOI
TL;DR: In this article, the microstructural evolution of the IN718 samples and the effects of energy input (Ev) on micro-structural architectures, dendritic morphology, precipitated phases and thus microhardness were investigated in detail.

110 citations


Journal ArticleDOI
TL;DR: In this paper, the crystal structure, microstructure, microhardness and compression mechanical properties of AlxNbTiVZr (x = 0, 05, 1, 15) high entropy alloy were examined.
Abstract: The crystal structure, microstructure, microhardness and compression mechanical properties of AlxNbTiVZr (x = 0, 05, 1, 15) high entropy alloy were examined In the as solidified conditions, the alloys consisted from bcc matrix and C14 Laves phase After homogenisation, the NbTiVZr alloy was bcc solid solution, whereas in Al containing alloys, C14 Laves phase and Zr2Al particles were found in the bcc matrix Volume fraction of second phase increased with Al concentration Increase in Al content results in gradual decrease in density of the alloys from 649 g cm− 3 of the NbTiVZr to 555 g cm− 3 of the Al15NbTiVZr alloy The microhardness of the alloys was higher in the alloys with higher Al content and was generally proportional to the volume fraction of second phase particles The compression yield strength of the alloys was of 960–1320 MPa, and NbTiVZr alloy was stronger than Al containing alloys The ductility of the alloys gradually decreased with increase in Al content The factors determi

95 citations


Journal ArticleDOI
TL;DR: A series of CoFeNi2V0.5Nbx high-entropy alloys were synthesized to investigate the alloying effect of the Nb element on the microstructures and properties.
Abstract: A series of CoFeNi2V0.5Nbx (x = 0–1) high-entropy alloys (HEAs) were synthesized to investigate the alloying effect of the Nb element on the microstructures and properties. It was found that the microstructures change from initial single-phase FCC solid solutions (x = 0), to a hypoeutectic microstructure (0 < x < 0.75), then to a fully eutectic microstructure (x = 0.75), and finally to a hypereutectic microstructure (0.75 < x < 1). The eutectic microstructure consists of the FCC solid solution phase and the Fe2Nb-type Laves phase. Nb0 (x = 0) and Nb02 (x = 0.2) alloys exhibit excellent ductility, the compressive plastic elongation of which can reach up to 80 % without fracture. With increasing Nb content, increased brittle Laves phase leads to the decrease of the plastic strain and the increase of the yield strength, and the Vickers hardness shows an approximately linear increase from HV 133.4 to HV 687.7. Besides, the CoFeNi2V0.5Nbx HEAs exhibit excellent soft magnetic behavior, in which the Nb0 alloy shows the maximum saturation magnetization (M s) of 70.33 emu/g, and minimum coercivity (H c) of 1.62 Oe.

80 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of partial substitution of Ti by Zr, and of Cr by Mo and W, on the hydrogen storage properties of Ti-Cr-Mn-based alloys have been systematically investigated.

78 citations


Journal ArticleDOI
TL;DR: In this paper, the microstructure of direct laser deposited (DLD) IN718 has been investigated in detail using scanning electron microscopy (SEM) and TEM, and the results confirm that the dendrite core micro-structure can be linked to the cooling rate experienced during the deposition.

68 citations


Journal ArticleDOI
TL;DR: In this paper, a microstructural characterization of alloy 718 fusion zone welded with both solid solution and age hardenable filler metal has been done by employing three levels of weld cooling rate.

66 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of partial substitution of Cr with Fe on the hydrogen storage properties of (Ti0.85Zr0.15)1.1CrMn have been systematically investigated.

63 citations


Journal ArticleDOI
TL;DR: In this article, the transformation of C15 Laves phase interstitial clusters to prismatic loops in body-centered cubic iron was reported, showing that within a certain size range, C15 clusters are more stable than loops, but the relative stabilities are reversed beyond this range.

Journal ArticleDOI
TL;DR: In this paper, the effect of Si in the range of 0.05-0.77 wt.% on the microstructure, tensile properties and impact toughness of reduced activation ferritic/martensitic (RAFM) steels has been investigated.

Journal ArticleDOI
TL;DR: In this article, the Co-Al-Nb ternary system and its two binary subsystems CoNB and AlNB were thermodynamically modeled by the Calphad method based on own experimental results and critically assessed literature data.

Journal ArticleDOI
TL;DR: In this paper, a 12%Cr reduced activation ferrite/martensite (RAFM) steel with good corrosion resistance and irradiation performance was developed, where V and Ta were added to form fine MX type carbonitrides and enhance the high temperature creep rupture strength.

Journal ArticleDOI
Xu Yuantao1, Mingjia Wang1, Yan Wang1, Gu Tao1, Lei Chen1, Xuan Zhou1, Ma Qian1, Liu Yuming1, Huang Jing1 
TL;DR: In this article, the nucleation and growth of Laves phase in a 10% Cr martensite ferritic steel after long-term aging was investigated, and it was found that Laves phases prefer to locate at prior austenite grain boundaries and martensites lath boundaries, especially, most of them precipitate at grain boundaries with a misorientation angle of 40-60°.

Journal ArticleDOI
TL;DR: In this article, chemical composition modifications of a Laves phase-related BCC solid solution base alloy, Ti15.6Zr2.1V44Cr11.2Mn6.9Fe2.7Co1.4Ni15.7Al0.3, were investigated in order to study the function of each constituent element on the structural, gaseous phase and electrochemical hydrogen storage properties of these alloys.

Journal ArticleDOI
TL;DR: In this paper, the effect of cooling rate on the microsegregation and Laves phase in INCONEL718 superalloy castings was studied by high-temperature-laser confocal scanning microscopy and quantitative metallography.
Abstract: Cooling rate is an important and controllable variable in casting processing. The effect of cooling rate on the microsegregation and Laves phase in INCONEL718 superalloy castings was studied by high-temperature–laser confocal scanning microscopy and quantitative metallography in this study. The transformation rate of solid phase with a feature of Gaussian distribution in the solidifications at the cooling rates of 0.10 to 14 K/s is acquired. The solidification time and secondary dendrite arm spacing (SDAS) as a function of cooling rate are analyzed. The amount of Laves phase presents a maximum value at a threshold cooling rate of 3 K/s owing to the opposite effects of cooling rate on the solidification time and SDAS. A modified dimensionless microsegregation index criterion was used for the scaling of solute segregation and Laves phase depending on cooling rates. The prediction of maximal microsegregation and the amount of Laves phase by MSI and experiments provide a guide for cooling rate control in the casting applications.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the mechanical and thermodynamics properties of C 14-type Laves phases AMg 2 (A = Ca, Sr and Ba) using first principles total energy calculations within the generalized gradient approximation (GGA).

Journal ArticleDOI
TL;DR: In this paper, the structure of a series AB2 metal hydride alloys, in which La substitutes for Zr (Ti12Zr22.8−xV10Cr7.5Mn8.1Co7.0Ni32.2LaxAl0.4, x = 0 to 5), is studied and correlated to various hydrogen storage properties in both gaseous phase and electrochemical systems.

Journal ArticleDOI
TL;DR: In this article, the effect of aging on the microstructure and mechanical behavior of an alumina-forming austenitic stainless steel, Fe-20Cr-30Ni-2Nb-5Al (at%) has been investigated.
Abstract: The effect of aging on the microstructure and mechanical behavior of an alumina-forming austenitic stainless steel, Fe–20Cr–30Ni–2Nb–5Al (at%) has been investigated. The alloy was fully solutionized after a 1250 °C, 24 h heat treatment, and the precipitation of B2 and Laves phases was studied after aging at 800 °C for up to 1325 h. While after 24 h the Laves phase precipitates in the matrix were 205 nm in diameter, they showed a further increase in diameter of only 50 nm even after aging for 1325 h. In contrast, the B2 precipitates in the matrix grew at a faster rate: after first being observed after aging for 24 h at an average diameter of 194 nm, they more than doubled in size from 330 to 734 nm as the aging time increased from 240 h to 1325 h. Both the Laves and B2 precipitates in the grain boundaries grew at a faster rate and were larger than matrix precipitates. The grain boundary coverage at 2.4 h (Laves 192 nm, NiAl 126 nm) was 56% with Laves phase initially making up the bulk of the precipitates, but after 2.4 h Laves phase and B2 precipitates alternated on the grain boundaries and total coverage reached 93% after 1325 h. An increase in the volume fraction of precipitates in the alloy was accompanied by an increase in the yield strength from 205 MPa after the solutionizing treatment up to 383 MPa after aging at 800 °C for 1325 h. After aging for 1325 h, even with extensive intermetallic grain boundary coverage, the alloy showed a room temperature elongation of 19%.

Journal ArticleDOI
TL;DR: In this paper, a CoCrFeMnNbNi HEA coating was produced on AISI 304 steel by tungsten inert gas cladding and the microstructure and wear behavior of the cladding coating were studied by X-ray diffraction, scanning electron microscopy, energy dispersive spectrometer, microhardness tester, pin-on-ring wear tester and 3D confocal laser scanning microscope.
Abstract: Alloy cladding coatings are widely prepared on the surface of tools and machines. High-entropy alloys are potential replacements of nickel-, iron-, and cobalt-base alloys in machining due to their excellent strength and toughness. In this work, CoCrFeMnNbNi HEA coating was produced on AISI 304 steel by tungsten inert gas cladding. The microstructure and wear behavior of the cladding coating were studied by X-ray diffraction, scanning electron microscopy, energy dispersive spectrometer, microhardness tester, pin-on-ring wear tester, and 3D confocal laser scanning microscope. The microstructure showed up as a nanoscale lamellar structure matrix which is a face-centered-cubic solid solution and niobium-rich Laves phase. The microhardness of the cladding coating is greater than the structure. The cladding coating has excellent wear resistance under the condition of dry sliding wear, and the microploughing in the worn cladding coating is shallower and finer than the worn structure, which is related to composition changes caused by forming the nanoscale lamellar structure of Laves phase.

Journal ArticleDOI
TL;DR: In this paper, the long term precipitation and coarsening of Laves-phase in tungsten strengthened 9% Cr steel under thermal aging at 923 K was investigated and reported.

Journal ArticleDOI
TL;DR: In this article, the effect of Nd-addition to the AB2-based alloy Ti12Zr22.8−xV10Cr7.5Mn8.1Co7.0Ni32.2Al0.4Ndx is studied for its effects on the structure, gaseous-phase hydrogen storage, and electrochemical properties.

Journal ArticleDOI
TL;DR: The structural evolution towards Cu2Zr is accompanied by an increase in the fraction of Cu-centered icosahedra, which demonstrates that a large icosahedral fraction does not just indicate structural relaxation.
Abstract: Indications of the Cu2Zr Laves phase are observed in MD simulations of amorphous Cu64Zr36 upon isothermal holding just above the glass transition temperature. The structural evolution towards Cu2Zr is accompanied by an increase in the fraction of Cu-centered icosahedra, which demonstrates that a large icosahedral fraction does not just indicate structural relaxation. The crystal-like regions generate an increase in strength and Young's modulus, and a stronger localized shear band. A universal relation between the fraction of full icosahedra and their interconnectivity is found, and both can be modified simultaneously via changes of temperature or strain.

Journal ArticleDOI
TL;DR: A series of BCC/C14 mixed phase alloys with the chemical composition of Ti13.6+xZr2.1V44Cr13.2−xMn6.9Fe2.7Co1.4Ni15.7Al0.3, x = 0, 2, 4, 6, 8, 10, and 12, was fabricated, and their structural, gaseous phase and electrochemical hydrogen storage properties were studied as mentioned in this paper.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the high-temperature tensile and creep properties of W-added Alumina-Forming austenitic (AFA W ) heat-resistant steel as compared with AFA steel without W.
Abstract: High-temperature tensile and creep properties of W-added Alumina-Forming austenitic (AFA W ) heat-resistant steel were investigated as compared with AFA steel without W. High-temperature tensile properties of two steels were similar to each other, but creep lifetime of AFA W steel was increased. Microstructural examination using SEM and TEM revealed that creep rate rapidly decreased when Laves phase initially precipitated. This indicated that the precipitation of Laves phase played an important role in hardening of AFA steel. It is also found that AFA W steel exhibited finer and denser Laves phase compared with AFA steel, which is due to partial substitution of W for Mo. The finer and denser distribution of Laves phase contributed to improved creep properties of AFA W steel by enhancement in precipitation hardening.

Journal ArticleDOI
TL;DR: In this article, a combination of scanning electron microscopy (SEM), electron probe microanalysis (EPMA), X-ray diffraction (XRD), and differential thermal analysis (DTA) was used to study the Fe-Al-Nb phase diagram.

Journal ArticleDOI
TL;DR: In this paper, the impact toughness of P92 steel aged at 600°C for 2035h was restored to the original level by reheating at 700 ÂC for 1Âh, with Laves phase barely changed.
Abstract: Laves phase has been widely accepted to cause the impact brittleness of 9–12Cr martensitic heat-resistant steels after long time aging at elevated temperatures. However, in the present research, the impact toughness of the already brittle P92 steel aged at 600 °C for 2035 h could be restored to the original level by reheating at 700 °C for 1 h, with Laves phase barely changed. This interesting result strongly indicated that the presence of Laves phase might not be the real reason for the impact brittleness.

Journal ArticleDOI
TL;DR: In this paper, the thermal stability of intermetallic phases in a multi-component Co-base superalloy was investigated under defined heat treatments, and the predicted main transformation temperatures for these phases differ from the experimentally obtained values.
Abstract: The nature and stability of intermetallic phases in a multi-component γ/γ′ Co-base superalloy is investigated. At least three kinds of unwanted intermetallic phases form due to the segregation of Al, Ta, Ti, Si, and Hf during casting in the interdendritic areas in addition to γ and γ′. One of the intermetallic phases that shows a blocky shape, contains high content of Ta, Hf, and Ti and has been identified as a topologically close-packed Laves phase. A B2 phase appears as relatively big pools and in some cases contains needle-shaped precipitates with high content of Al and Ti. The thermal stability of these intermetallic phases is studied in this work under defined heat treatments. The needle-shaped precipitates already dissolve at 1000 °C, whereas the B2 phase is dissolved only at higher temperatures of 1200 °C. Small amounts of Laves phases remained stable during aging at 1200 °C for 25 h. The prediction of phases as well as their stability is also checked by the CALPHAD method. The TCNi5 database, containing the description of Co3(Al,W), predicts the presence of the observed intermetallic phases; however, the predicted main transformation temperatures for these phases differ from the experimentally obtained values.

Proceedings ArticleDOI
08 Jun 2015
TL;DR: In this paper, the microstructures and mechanical properties of Inconel 718 fabricated from the selective laser melting (SLM) process were experimentally investigated using optical microscopy and scanning electron microscope.
Abstract: In this study, the microstructures and mechanical properties of Inconel 718 fabricated from selective laser melting (SLM) process were experimentally investigated. Specimens with different build heights were prepared for microstructural observations by optical microscopy and scanning electron microscope. The texture evolution was also examined using electron backscatter diffraction (EBSD). In general, columnar γ dendrites are found along the build direction from the X-plane (side surface), while the microstructure of Z-plane (scanning surface) is characterized by equiaxed grains. The microstructures vary along the build height: the top layers present coarse columnar dendrites while the bottom layers show much narrower columnar dendrites owing to a higher cooling rate. The top layers also present the combination of a γ matrix and a higher percentage of the Laves phase, while the bottom layers show a much less Laves phase due to, again, a higher cooling rate. Random textures are shown for the SLM Inconel 718 samples. Nanoindentation tests identify the Young’s modulus and hardness of about 200 GPa and 7 GPa, respectivley.Copyright © 2015 by ASME