scholarly journals Assessment of the Compositional Influences on the Toughness of TiCr2-Base Laves Phase Alloys

1996 ◽  
Vol 460 ◽  
Author(s):  
Katherine C. Chen ◽  
Samuel M. Allen ◽  
James D. Livingston
Keyword(s):  
Crystal Structure ◽  
Single Phase ◽  
Laves Phase ◽  
Second Phase ◽  
Vickers Indentation ◽  
Toughening Mechanisms ◽  
Two Phase ◽  
Laves Phases ◽  
Effective Factors ◽  
Alloying Effects

ABSTRACTSystematic studies of alloys based on TiCr2 have been performed in order to improve the toughness of Laves phase intermetallics. The extent to which alloy compositions and annealing treatments influence the toughness was quantified by Vickers indentation. The single-phase Laves behavior was first established by studying stoichiometric and nonstoichiometric TiCr2. Next, alloying effects were investigated with ternary Laves phases based on TiCr2. Different microstructures of two-phase alloys consisting of (Ti,Cr)-bcc+TiCr2 were also examined. Various toughening theories based on vacancies, site-substitutions, crystal structure (C14, C36, or C15) stabilization, and the presence of a second phase were evaluated. The most effective factors improving the toughness of TiCr2 were determined, and toughening mechanisms are suggested.

scholarly journals Effect of Nd, Pr substitutional atoms on the magnetic and magnetostrictive properties in (Tb-Dy)(Fe-Co)2 Laves phases

2021 ◽  
Vol 2103 (1) ◽  
pp. 012196
Author(s):  
G A Politova ◽  
M A Ganin ◽  
A B Mikhailova ◽  
D A Morozov ◽  
K E Pankov ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Magnetic Properties ◽  
Laves Phase ◽  
Type Structure ◽  
Partial Substitution ◽  
Laves Phases ◽  
Temperature Range ◽  
Homogenizing Annealing ◽  
Arc Melting ◽  
Magnetostrictive Materials

Abstract Polycrystalline TbxDy1-xR0.1Fe2-zCoz (R = Nd, Pr, x = 0.2, 0.3; z = 0, 1.3) cubic Laves phase alloys with MgCu2-type structure were prepared by arc melting followed by homogenizing annealing. The crystal structure, magnetic properties, and magnetostriction have been investigated. Compounds with high values of magnetostrictive susceptibility were found in the temperature range 150-300 K. Compounds with partial substitution of cobalt for iron demonstrate a change in the sign of anisotropic magnetostriction. This work continues the search for magnetostrictive materials with inexpensive neodymium and praseodymium.

Composition-induced microstructures in rhombohedral carbonates

1987 ◽  
Vol 51 (359) ◽  
pp. 71-86 ◽  
Author(s):  
D. J. Barber ◽  
M. Riaz Khan
Keyword(s):  
Electron Diffraction ◽  
Crystallographic Orientation ◽  
Solid Solubility ◽  
Single Phase ◽  
Crystal Defects ◽  
Second Phase ◽  
Two Phase ◽  
Diffraction Contrast ◽  
Second Phases ◽  
Metallic Impurities

AbstractRecent TEM observations of two-phase microstructures and associated crystal defects in selected, rare dolomites have been extended to calcite-structured (R3̄c) carbonates and to other natural and synthetic carbonates that crystallize with the dolomite (R3̄) structure. The samples included siderites (FeCO3), smithsonites (ZnCO3), ankerites (Ca[Mg,Fe](CO3)2), and kutnahorites (Ca[Mn,Fe](CO3)2).TEM methods show that the forms of second phases which result from the presence of common, divalent, metallic impurities are morphologically similar in R3̄c and R3̄ carbonates and occur more widely than hitherto realized. The most common form consists of thin ribbons of second phase which are coherent with and have the same crystallographic orientation as the host carbonate. Another form of microstructure, manifest as modulations in diffraction contrast, appears to be associated with incipient breakdown of single-phase carbonate. The results of extensive TEM/EDS microanalyses show that in siderite and ankerite the formation of ribbons is promoted by Ca impurity or Ca excess (with respect to R3̄c stoichiometry). In smithsonite, Cu and Ca impurities can play similar roles in relation to modulated microstructures. In kutnahorites, the perfection of grains and the absence of second-phase effects is strongly dependent on the ratio of Fe to Mn but is also affected by Ca in excess of the stoichiometric requirement. Electron diffraction results from several of the minerals show c-type spots, which can be interpreted as indicating ordering within basal layers of cations.The results show that, by correlating analytical TEM data with the study of second phases and incipient two-phase microstructures, it should be possible to determine the limits of solid solubility in carbonate systems.

Microstructures and Wear Resistance of Al1.5CrFeNiTi0.5 and Al1.5CrFeNiTi0.5W0.5 High Entropy Alloy Coatings Manufactured by Laser Cladding

2019 ◽  
Vol 956 ◽  
pp. 154-159 ◽  
Author(s):  
Hui Liang ◽  
Bing Yang Gao ◽  
Ya Ning Li ◽  
Qiu Xin Nie ◽  
Zhi Qiang Cao
Keyword(s):  
Wear Resistance ◽  
Laser Cladding ◽  
Dendritic Structure ◽  
Laves Phase ◽  
High Entropy Alloy ◽  
Second Phase ◽  
Laves Phases ◽  
High Entropy ◽  
Two Phases ◽  
Bcc Phase

For the purpose of expanding the application scope of HEA coating manufactured on the surface modification of materials, in this work, the Al1.5CrFeNiTi0.5 and Al1.5CrFeNiTi0.5W0.5 HEA coatings were successfully manufactured using laser cladding method on SUS304. The microstructures and wear resistance of coatings are researched systematically. It is found that the W0 and W0.5 HEA coatings all exhibit the dendritic structure, which are constituted by BCC phases and Laves phases. With W element addition, the phase structures of W0.5 coating remain unchanged. W is dissolved in both two phases, but the solid solubility in Laves phase is higher compared to that in BCC phase. W0.5 coating with the highest microhardness of 848.34 HV, and the W0 coating with the microhardness of 811.45 HV, both of whose microhardness are four times more than that of SUS304 substrate. Among all samples, the W0.5 coating shows the optimal wear performance because of its larger content of hard second phase ( Laves phase).

Orientation Relationships in the System Nb-NbCr2

1997 ◽  
Vol 3 (S2) ◽  
pp. 707-708
Author(s):  
P. G. Kotula ◽  
K. C. Chen ◽  
D. J. Thoma ◽  
F. Chu ◽  
T. E. Mitchell
Keyword(s):  
Microstructural Characterization ◽  
Laves Phase ◽  
Orientation Relationships ◽  
Ion Milling ◽  
Two Phase ◽  
Laves Phases ◽  
Arc Melting ◽  
Transmission Electron ◽  
Structural Applications ◽  
Two Phases

Laves-phase intermetallics are of potential use as high-temperature structural materials. NbCr2-based C15-structured alloys are of particular interest for such applications. by themselves, Laves phases generally have poor ductility and fracture toughness at low temperatures. Two phase alloys (i.e., Laves phase and the ductile bcc phase) are considered more promising for structural applications. The orientation relationships between the two phases can contribute to the mechanical behavior of the material. In this study, observations of two different orientation relationships in a Nb-NbCr2 eutectic are discussed and compared with previous studies of the NbCr2 system, as well as the TiCr2 system.A Nb-NbCr2 eutectic alloy was prepared by arc-melting high-purity alloys followed by annealing at 1400°C for 100 h and then cooling at l°C/min. The complete details of the materials preparation have been given elsewhere. Specimens were prepared for observation in the transmission electron microscope (TEM) by cutting 3 mm discs with a coring saw, followed by dimpling and ion milling. Microstructural characterization was performed with a Philips CM30 TEM operating at 300 kV.

Investigation of a New Type of Al3Ti-Based Ll2 Alloy With Second Phase Precipitation

1994 ◽  
Vol 364 ◽  
Author(s):  
Gengxiang Hu ◽  
Jian Sun ◽  
Xiaojun Weng ◽  
Tong Li ◽  
Shipu Chen
Keyword(s):  
Single Phase ◽  
Solution Treatment ◽  
Second Phase ◽  
Quaternary Alloys ◽  
Two Phase ◽  
Ti Alloys ◽  
Second Phase Particles ◽  
New Type ◽  
Temperature Aging ◽  
Nb Additions

AbstractSince the L12 structured Al3Ti alloy exists only in a narrow compositional range, further alloying of the single phase Ll2 alloy to improve its property seems hardly successful. Developing two-phase or multiphase Al3Ti alloys may be an effective approach for strengthening and toughening. In this article, a new type of Al3Ti-based alloy which has a Ll2 matrix with precipitates of a second phase is reported. The quaternary alloys based on Al67Mn8Ti25, and modified with Nb additions, consist of an Ll2 matrix and DO22 second phase particles in the annealed state, but the second phase can be dissolved by solution treatment and precipitated during high temperature aging. Remarkable strenghtening and promising compressive ductility were exhibited by the experimental alloy. The influence of composition on the microstructure and properties of the alloys are reported also.

scholarly journals The Interface Microstructures and Mechanical Properties of Laser Additive Repaired Inconel 625 Alloy

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4416
Author(s):  
Yiyun Wei ◽  
Guomin Le ◽  
Qingdong Xu ◽  
Lei Yang ◽  
Ruiwen Li ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Tensile Properties ◽  
Dendritic Structure ◽  
Laves Phase ◽  
Inconel 625 ◽  
Second Phase ◽  
Equiaxed Crystal ◽  
Columnar Crystal ◽  
Inconel 625 Alloy ◽  
Deposition Thickness

The microstructure and micro-mechanics around the repaired interface, and the tensile properties of laser additive repaired (LARed) Inconel 625 alloy were investigated. The results showed that the microstructure around the repaired interface was divided into three zones: the substrate zone (SZ), the heat-affected zone (HAZ), and the repaired zone (RZ). The microstructure of the SZ had a typical equiaxed crystal structure, displaying simultaneously precipitated block-shaped MC-type carbides (NbC, TiC), with bimodal sizes of approximately 10 μm and 0.5 μm and an irregularly shaped flocculent Laves phase. Recrystallization occurred in the HAZ, and led to significant grain growth; a portion of the second phase dissolved in the original grain boundaries. In the RZ, there was a columnar crystal structure, and the size increased with increasing deposition thickness. Moreover, the microstructure between the layer interface and layer interior was quite different, presenting an overlapping transition zone (OTZ), in which the dendritic structure coarsened and more Laves phase were precipitated, compared to in the layer interior. The hardness and tensile properties of the LARed samples were equivalent to those of the wrought substrate, which indicates that laser additive repairing (LAR) is a reliable repair solution for damaged and mis-machined components comprising Inconel 625 alloy.

scholarly journals Laves Phase Formation in High Entropy Alloys

2021 ◽  
Author(s):  
Roman Ryltsev ◽  
Svetlana Estemirova ◽  
Evgenii Sterkhov ◽  
Lubov Cherepanova ◽  
Denis Yagodin ◽  
...  
Keyword(s):  
Phase Formation ◽  
Single Phase ◽  
Laves Phase ◽  
Structural Defects ◽  
Clear Understanding ◽  
High Entropy Alloys ◽  
Laves Phases ◽  
Important Conclusion ◽  
High Entropy ◽  
Chemical Complexity

One of the intriguing recent results in the field of high-entropy alloys is the discovery of single-phase equiatomic multi-component Laves intermetallics. However, there is no clear understanding that a combination of chemical elements will form such high-entropy compounds. Here we contribute to understanding this issue by modifying the composition of duodenary TiZrHfNbVCrMoMnFeCoNiAl (12x) alloy in which we recently reported the fabrication of hexagonal C14 Laves phase. We consider three alloys based on 12x: 7x=12x-VCrMoMnFe, 12x+Sc, 12x+Be and observe that all of them crystalize with the formation of C14 Laves phase as a dominant structure. We report that 12x+Be alloy reveals single-phase C14 structure with very high concentration of structural defects and ultra-fine dendritic microstructure with almost homogenous distribution of the constituted elements over the alloy matrix. The 7x and 12x+Sc alloys contain C14 as a main phase and unknown impurity phases. To characterize the materials, we examine their heat capacity, electrical conductivity and magnetic properties. The measurements reveal that the Laves phases are Curie-Weiss paramagnets, which demonstrate metallic conduction; 7x and 12x alloys also reveal a pronounced Kondo-like anomaly. Analysis of experimental data as well as ab initio calculations suggests that chemical complexity and compositional disorder cause strong s-d band scattering and thus the rather high density of d-states in the conduction band. Analysis of the results suggests that the mechanism of Laves phase formation in multicomponent multi-principal element metallic alloys is may be the same as in polydisperse hardspheres mixtures. Another important conclusion is that the configurational entropy is a negligible factor in the stabilization of multi-element Laves phases.

Novel Concept of Austenitic Heat Resistant Steels Strengthened by Intermetallics

2007 ◽  
Vol 539-543 ◽  
pp. 3012-3017 ◽  
Author(s):  
Masao Takeyama
Keyword(s):  
Ternary Systems ◽  
Phase Region ◽  
Homogeneity Region ◽  
Laves Phase ◽  
Model Alloy ◽  
Two Phase ◽  
Laves Phases ◽  
Heat Resistant ◽  
Novel Concept ◽  
Heat Resistant Steels

Alloy design concept for the development of a new class of austenitic heat resistant steels strengthened by Fe2M Laves phases (M: transition metals) has been proposed. The phase diagram studies on Fe-Ni-M ternary systems demonstrate that Fe2Nb with C14 structure is the most promising, because more than 40at% Ni can dissolve into the Fe sublattice sites and large γ+Fe2Nb two-phase region exists along the equi-niobium concentration direction. The control of the c/a ratio of the Laves phase using the composition homogeneity region by alloying makes it possible to disperse the Laves phase finely in the γ matrix. Based on the knowledge, a model alloy Fe-20Cr- 30Ni-2Nb (at%) was proposed and the TTP diagram of the Laves phase was constructed. The Laves phase homogeneously nucleates in the matrix and its fine morphology remains almost unchanged even after long-term aging at 1073K.

Composition Dependence of the Hardness of Laves Phases in the Fe-Nb and Co-Nb Systems

2008 ◽  
Vol 1128 ◽  
Author(s):  
S. Voß ◽  
F. Stein ◽  
M. Palm ◽  
D. Grüner ◽  
G. Kreiner ◽  
...  
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Composition Dependence ◽  
Stoichiometric Composition ◽  
Laves Phase ◽  
Indentation Fracture ◽  
Laves Phases ◽  
Slow Cooling ◽  
Arc Melting ◽  
Indentation Fracture Toughness

AbstractSingle-phase Fe-Nb and Co-Nb Laves phase alloys were produced by arc melting and levitation melting. By casting the levitation melted alloys in a preheated mould and subsequent slow cooling to room temperature, solid rods of 15 mm in diameter and about 100 mm length of the brittle Laves phases were obtained. Within the extended homogeneity ranges of the NbFe2 and NbCo2 Laves phases, the Vickers hardness was measured in dependence on composition. The results show that the hardness has a maximum at the stoichiometric composition in both systems, indicating defect softening. Nanoindentation measurements on a Co-Nb diffusion couple confirm the dependence of the hardness on composition. In addition, these measurements indicate that the crystal structure of the Laves phase polytype – cubic or hexagonal – seems to have no effect on the hardness. Indentation fracture toughness KIC-IF data for the different polytypes of the Laves phases were evaluated from the Palmquist cracks originating from the edges of the Vickers indentations.

Microstructure and Dielectric Properties of (Ba, Ta) Co-Doped Sr2Nb2O7 Ceramics

2015 ◽  
Vol 815 ◽  
pp. 125-128
Author(s):  
Gang Chen ◽  
Chun Wei Gong ◽  
Chun Lin Fu ◽  
Xiao Dong Peng ◽  
Wei Cai ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Dielectric Constant ◽  
Grain Size ◽  
Dielectric Properties ◽  
Solid State ◽  
Surface Morphology ◽  
Single Phase ◽  
Second Phase ◽  
Maximum Value ◽  
Co Doped

(Sr1-xBax) 2(Nb0.9Ta0.1) 2O7 (SBNT) ceramics were prepared by solid state reaction. The crystal structure of SBNT ceramics, surface morphology and dielectric properties were studied using XRD, SEM and LCR instrument analyzer, respectively. The results show that the grain size decreases with increasing Ba concentration, and all samples show single phase, no second phase can been observed. Addition of Ba ion can improve the dielectric properties of SBN ceramics. The dielectric constant increases first, then decreases; the maximum value (εr=97) can be obtained at x=0.1, the dielectric constant changes slightly with increasing wide frequency.

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