The effect of cooling rate on structure and mechanical properties of Co-Cr-Cu-Fe-Ni-Sn high entropy alloys

The paper examines the structure and mechanical properties of multicomponent high-entropy CoCrCuFeNiSnx alloys in as-cast and splat-quenched states. The compositions of investigated alloys is analyzed by using the criteria for predicting the phase composition of high-entropy alloys available in the literature, based both on calculations of the entropy and enthalpy of mixing and on an estimate of the difference between the atomic radii of the component. The alloy films is fabricated by the known technique of splat-quenching. A cooling rate estimated by a film thickness is ~ 106 K/s. The simultaneous formation of two solid solutions (FCC + ordered BCC) has been established in the alloy structure. An increase in the concentration of Sn favors the formation of the ordered (В2 type) solid solution in the structure of the alloys. High values of the microhardness and dislocation density have been obtained in the splat-quenched samples. It is also shown that an increase in the Sn content positively affects the microhardness.

Short-range structure, the role of bismuth and property-structure correlations in bismuth borate glasses

Bismuth-containing borate glasses, xBi2O3-(1-x)B2O3, were synthesized in the broad composition range 0.20≤x≤0.80 by melting in Pt crucibles and splat-quenching between two metal blocks. Infrared reflectance spectra, measured in the range...

Structure, thermal and electrical properties of Fe-B-Co-Nb-Ni-Si high-entropy metallic glass

New nanostructured Fe25B17.5Co21.35Nb3.65Ni25Si7.5 high-entropy metallic glass is synthesized by dint of splat-quenching technique. The estimated cooling rate is ~106 K/s. The coherently scattering domain size (crystallite size) of films of Fe 25B17.5Co21.35Nb3.65Ni25Si7.5 high-entropy metallic glass estimated by the Sherer formula is ~ 3 nm. The high-entropy metallic glass shows a high temperature of glass transition Tg ~ 800 K and the initial temperature of crystallization Tx ~ 863 K. After annealing to ~ 1010 K (above the crystallization temperature) and subsequent slow cooling, the amorphous films crystallize with the formation of several crystalline phases. The temperature dependencies of electrical resistivity of the Fe25B17.5Co21.35Nb3.65Ni25Si7.5 films indicate the occurrence of phase transformations. The phase transformation temperature (temperature of crystallization) is ~ 869 K. This value agrees well with the value obtained from the differential thermal analysis.

Features of the influence of thermal modes of cooling on processes of nonequilibrium crystallization of materials from the liquid state

The quantitative estimation of maximum level of cooling rates in the process of casting microwires in glass insulation is given. The shown possibility of nonequilibrium formation of microwire substance is due to the influence of an amorphous substrate in the form of glass insulation. The amorphous state in the case of thin microwires with cast iron vein Fe‒20 at.% C confirms the implementation of an increased (compared to splat-quenching) level of nonequilibrium formation of microwires in combination with updated rates of cooling and increased degree of supercooling of liquid microwire vein.

Electron Diffraction of ThMn12/Th2Zn17-Type Structures in the Nd-Fe-Ti System

Nd:11Fe:Ti alloys prepared by arc melting followed by splat quenching and annealing have been investigated by electron microscopy. The as-cast microstructure evidenced an α-Fe(Ti) → NdFe11Ti → Nd2(Fe,Ti)17 solidification sequence compatible with a cascade of peritectic reactions. The Nd2(Fe,Ti)17 phase was not detected in the microstructure of the splat-quenched materials, but after annealing the ternary compound grains consisted of a mixture of ThMn12-type and Th2Zn17-type structures exhibiting a consistent (020)1:12//(003)2:17 and [100]1:12//[110]2:17, orientation relation, with the invariant plane sitting at (022)1:12//(333)2:17. A series of 3D microdiffraction experiments carried out on grains presenting a random distribution of planar defects has been used to map the reciprocal space of the intergrown phases.

Effect of Cooling Rate on the Microstructure of Cu80Cr20 Alloys

The effect of cooling rate on the microstructure of Cu80Cr20 alloys was studied by using vacuum non-consumable arc melting, vacuum induction melting, electromagnetic levitation and splat quenching. The microstructure evolution of the Cr-rich were analyzed by scanning electron microscopy (SEM) and optical microscopy. The results showed that nonuniform Cr-rich dendrite distributes on Cu-rich matrix for arc melted alloys and uniform Cr-rich dendrite distributes on Cu-rich matrix for electromagnetic levitation melted alloys and vacuum induction melted alloys. However, the Cr-rich phase show both dendrites and spheroids for splat quenched alloys. This means liquid phase separation occurred during rapid solidification.

Effect of Minor Si and Ag Additions on Glass-Forming Ability of Ti-Cu-Co-Zr-Sn-Be Bulk Metallic Glass

Effect of Minor Si and Ag additions on glass-forming ability (GFA) of the base Ti44Cu38.9Co4Zr6Sn2Be5.1(at. %) alloy are studied. (Ti44Cu38.9Co4Zr6Sn2Be5.1)100-xRx(R = Si, Ag, x=0, 1, 2, 3 at. %) metallic glasses are formed by splat-quenching and copper mold suction casting. It is found that the minor Si and Ag additions enhance the glass-forming ability of Ti44Cu38.9Co4Zr6Sn2Be5.1greatly. The maximum size of fully amorphous structure is increased from 4 mm for base alloy to be larger than 6 mm for alloys containing 1-2 at. % Si/Ag, while Si/Ag more than 2 at. % additions decrease the GFA.

Microstructure Study of Undercooled Hypereutectic Cu95Cr5 Alloys

Microstructure of Cr-rich phase in undercooled hypereutectic Cu95Cr5 alloys was studied by using arc melting, electromagntic levitation melting and splat quenching. The results showed that the alloys generally have a microstructure consisting of a fine Cr-rich dendrites in a Cu-rich matrix. Even there existed strong electromagnetic stirring during solidification process, the nonhomogeneous Cr-rich dendrites were observed in electromagnetic levitation melted alloys. However, fine homogenous primary Cr-rich particles or equiaxed Cr-rich grains distributed in the Cu-rich matrix in splat quenched alloys.

Microstructure of Cu75Cr25 Alloys under Different Conditions

The microstructure of Cu75Cr25 alloys was investigated by using vacuum non-consumable arc melting, electromagnetic levitation and splat quenching. The microstructure and solidification behavior of the Cr-rich were investigated by scanning electron microscopy (SEM). The results showed that inhomogeneous Cr-rich dendrite distributes on Cu-rich matrix for arc melted alloys. The microstructure consisting of a fine dispersion of Cr-rich dendrite in a Cu-rich matrix for electromagnetic levitated alloys. However, the morphology and size of the Cr-rich phase vary greatly with the cooling rate for splat quenched alloys. The Cr-rich phase show both dendrites and spheroids, this means liquid phase separation occurred during rapid solidification.