| In recent years,high-entropy alloys(HEAs),as a new alloy design concept,has become a research hotspot in the field of metal materials due to its adjustable composition,structure and properties,which has a broad application prospect in aerospace,petrochemical,automobile manufacturing,electronics and electrical fields.At present,the preparation processes of high-entropy alloys and high-entropy alloy matrix composites mostly use smelting and powder metallurgy methods.The complexity and high cost of these two preparation technologies limit the practicality application of high-entropy alloys and their composites to a certain extent.Therefore,the development of an efficient,fast,and low-cost alloy preparation method is conducive to promoting the research and development of high-entropy alloys.In this paper,the thermite method was applied to the preparation of high-entropy alloys and high-entropy alloy matrix composites.Firstly,the composition control of multi-principal alloys is studied.Based on the five oxides of Fe3O4,Co2O3,Ni2O3,Mn O2 and Cr O3,26 alloys of the Co-Cr-Fe-Ni-Mn series are formed after thermite reaction.The corresponding relationship between the negative enthalpy of the thermite reaction of a variety of different oxides and the composition of the thermite reduction products was investigated.The general law between the negative enthalpy value of various oxides of thermal reaction and the composition after reaction is extended,and the corresponding functional relations are put forward.Based on this,a CoCrFeNiMnAl high-entropy alloy with approximately equimolar ratio was prepared,so as to realize the control of the composition of multi-principal element high entropy alloy prepared by thermite method.On this basis,the(CoCrFeNiMnAl)100-xWx(x=2.0,2.5,3.0)series high-entropy alloys with nearly equimolar ratio were prepared,and the effect of W content on the phase structure,microstructure and properties of CoCrFeNiMnAl high-entropy alloys was explored.The results show that(CoCrFeNiMnAl)100-xWx(x=2.0,2.5,3.0)high-entropy alloys are composed of FCC+BCC phase structure,and the microstructures are all dendrite and interdendritic structure.With the increase of W content,the Vickers hardness of the alloy increases from 533.2 HV to 604.6 HV,and the wear resistance is also improved accordingly.The friction coefficient and wear rate of the CoCrFeNiMnAl97.0W3.0 alloy are 0.684 and 1.06×10-5 mm3/N·m,respectively,the wear mechanism changes from adhesive wear to a combination of adhesive wear and abrasive wear,and finally to abrasive wear.The corrosion resistance of(CoCrFeNiMnAl)100-xWx(x=2.0,2.5,3.0)high-entropy alloy in 3.5wt%Na Cl solution increases with the increase of W content,and the corrosion current density is from6.08×10-6 A/cm2 Reduce to 1.72×10-6 A/cm2,the corrosion rate gradually decreases.Furthermore,the content of W increased and the composition of high entropy alloy optimized,W/FeNiMnAlW high-entropy alloy matrix composite material was prepared by in-situ.The high-entropy alloy matrix was composed of FCC phase,B2 phase and W2C phase.The reinforcing phase W particles are uniformly distributed in the matrix structure,and their volume fraction and average grain size are 30.9%and 13.57?m,respectively,and the tungsten particles form a good metallurgical bond with the matrix.The hardness of W phase,B2 phase and FCC phase are 681.48 HV,533.82 HV and286.70 HV,respectively.The yield strength of W/FeNiMnAlW composite is 1241 MPa,and the maximum compressive strength and the maximum plastic strain are more than2530 MPa and 15%,respectively,showing good mechanical properties.The volumetric wear and wear rate of W/FeNiMnAlW composites are 0.42 mm3 and 4.95×10-3mm3/N·m,respectively.The wear mechanisms are mainly adhesive wear and abrasive wear.The corrosion potential and corrosion current density of the composite in 3.5wt%Na Cl solution are-0.505 Vsce and 1.002×10-5 A/cm2,respectively.The analysis suggests that the nearly spherical uniform distribution of W particles and the effective combination of FCC phase and B2 phase are the main reasons for the good performance of the composites. |
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