Effects Of Gas/Liquid/Solid Processing On The Ordered Phase Formation And Properties In High-Entropy Alloys

The preparation process has a direct correlation with the microstructure of materials,and process control is an important way to realize the diversification of properties.Since the conception of high-entropy alloys is proposed,it has been found that they have many excellent properties.For high entropy alloys,the concept is based on"high entropy promotes the formation of solid solution structures in alloys".There are still many problems in how to optimize the microstructure and properties of high-entropy alloys,and how to establish the relationship among process parameters,phase structures,and properties.However,due to the diversity of its composition combinations,the current study found that the generation of ordered phases in high-entropy alloys has important research value for the diversification of their microstructures and properties.In this paper,from the technological point of view,three processing methods,including magnetron sputtering,casting,and plastic deformation,are used to study the effect of "gas-solid forming","liquid-solid forming",and "solid-solid forming"on the microstructures and properties.The main work is as follows.From the perspective of gas-solid forming,the rapid preparation,composition screening,microstructures,and property characterization of W-Ta-(Cr,Fe,Ni)highentropy alloy thin films were realized by magnetron sputtering high-throughput technology.The hardness reaches-20.6 GPa in the film.The formation law of theΩ～δ was studied,and the Ω～δ rules of the bulk alloy was corrected,thereby realizing the prediction of the phase structure of the alloy film.By studying the relationship between the hardness and composition,it is found that there is a nonlinear relationship between the performance and the mixing entropy(ΔSmix).In addition,it is found that the composite strengthening of amorphous+nanocrystalline+strong solid solution strengthening leads to the ultra-high hardness of the alloy film.From the perspective of liquid-solid forming,the microstructure and properties of low-density high-entropy alloys are studied and developed.The microstructure evolution,properties and.serration behaviors of AlMgZnCu alloy with Si,Li and other additive elements are studied by induction melting.A high-strength A180Mg10Zn2Cu2Si5Li1 alloy with eutectic structure is developed,and the compressive strength reaches～850 MPa.The effect of Si element on the microstructure evolution of the Al86-xMg10Zn2Cu2Six alloy and the serration behavior during compression are studied.The microstructure and properties of a low-density AlTiCoNiX(Si,V,Y)highentropy alloys are studied.We develop a dual-phase AlTiCoNiV high-entropy alloy with a high-entropy intermetallics and a semi-coherent body-centered cubic structure.The alloy exhibits excellent room temperature specific yield strength and high temperature(600 ℃)specific strength,reaching～261 and～210 MPa·g-1·cm3,respectively.The high temperature inflection point(TBreak)of the alloy is predicted to be 700℃ by that of the high temperature resistant superalloy.The high temperature softening mechanism of the alloy is studied,and it is found that the alloy undergoes dynamic recrystallization and softening at high temperature,resulting in a decrease in the strength and an increase in the plasticity.The effects of Si,Cr,and Mo elements on the low-density Al-Ti-Zr-Nb lowdensity high-entropy alloys are studied.It is found that the addition of Si,Cr,and Mo elements can improve the strength,but the addition of Si and Cr decrease the plasticity sharply.Furthermore,it is found that the negative effect of δ on the plasticity of the alloy is greater than that of Ω.From the perspective of solid-solid forming,the effects of rolling and heat treatment on the microstructure and properties of large-size face-centered cubic Al0.3CoCrFeNi high-entropy alloys are studied.A large-sized alloy of 3500 mm ×150 mm × 0.5 mm is prepared,and the preparation of ultra-fine-grained alloy is realized.The yield strength of the alloy exceeds 1.2 GPa,which is more than 5 times higher than that of the as-cast alloy,and the elongation at break reaches-20%.This realizes the strength and toughness matching of the alloy,and has good engineering application prospects.In addition,a deformable Al5Ti30Zr43Nb12 bodycentered cubic high-entropy alloy is developed.After rolling,the tensile strength of the alloy reaches～1450 MPa,and the elongation at break reaches～8%.By studying the heat treatment of the alloy enhance the precipitate of the ordered phase.After the alloy is treated at 850℃～900 ℃,the hardness of the Al15Ti30Zr43Nb12 alloy is reduced due to the orderly reflection and re-crystallization.