Study Of Preparation And Spinodal Decomposition Of(Ti,Zr)C Solid Solution

Ti（C,N）-base cermets have attracted more and more attentions from researchers due to low density,high hardness and high temperature oxidation resistance.However,the poor toughness of Ti（C,N）-base cermets has seriously affected the application of Ti（C,N）-base cermets.Consequently,the study on toughening of Ti（C,N）-base cermets is of great importance.This paper reviews the development history,research status and future development direction of Ti（C,N）-base cermets,and introduces the toughening methods of Ti（C,N）-base cermets in details.The phase diagram simulation finds that when Zr is added as an element,Ti C and Zr C can form an infinite solid solution at high temperatures,and（Ti,Zr）C solid solution may undergo spinodal decomposition by aging at lower temperatures,toughening treatment of cermets by introducing spinodal decomposition in（Ti,Zr）C solid solution was chosen as the target in this work.The main work and innovation points of this work are as follows:（1）Firstly,the solid solution powder of（Ti,Zr）C was prepared.Through experiments,the advantages and disadvantages of three kinds of mixing methods,namely,physical dry grinding,high-energy ball grinding and chemical post-synthesis ball grinding,were compared,and the most suitable wet grinding process for the raw powder mixing of（Ti,Zr）C was determined.（2）Three kinds of（Ti,Zr）C solid solutions with different proportions of Ti and Zr were prepared,and the spinodal decomposition of（Ti,Zr）C solid solutions was theoretically analyzed through the first-principles method,and the optimal solution temperature of(Ti_0.8,Zr_0.2)C solid solutions was determined to be 2100℃,and 2150℃and2200℃for(Ti_0.5,Zr_0.5)C and(Ti_0.2,Zr_0.8)C solid solutions,respectively.According to the first-principles calculations,the driving forces of the spinodal decomposition of(Ti_0.2,Zr_0.8)C and(Ti_0.8,Zr_0.2)C are greater than that of(Ti_0.5,Zr_0.5)C.（3）Taking(Ti_0.5,Zr_0.5)C solid solution as the research object,the spinodal decomposition temperature is 1250℃,where the spinodal decomposition only takes place at local regions with tiny stripes.With the increase of aging temperature,the spinodal decomposition is strengthened with the decomposition regions and the width of stripes enlarged.When keeping increasing the aging temperature,the stripes gradually enlarge and even form doughs.（4）Five kinds of（W,Ti,Zr）C solid solutions with different WC mass fractions were prepared.The aging treatment of five（W,Ti,Zr）C solid solutions was carried out,and the rule of spinodal decomposition was summarized.The higher W content is the more difficult the spinodal decomposition is,and the decomposition is not complete.The average phase produced is from the coefficient difference decreases gradually,and the phase cannot be observed by SEM backscattering when the WC mass percentage reaches 60%.（5）Theoretical analysis of(Ti_0.5,Zr_0.5)C solid solution and（W,Ti,Zr）C solid solution was conducted through phase field simulations,and the data obtained by simulation were found to be consistent with the experimental results.The rule of spinodal decomposition is explained in theory.This paper summarizes the conclusions and significance of the study,and predicts the future research directions and difficulties of（Ti,Zr）C solid solution spinodal decomposition.