金属铌对碳化锆陶瓷物相、组织与力学性能的影响

Effect of Nb on phase,microstructure and mechanical properties of ZrC ceramics

碳化锆(ZrC)具有优异的抗辐照损伤和耐腐蚀等核用性能,是第四代核能系统最有应用前景的候选材料之一,但碳化锆熔点高和固相扩散系数低等本征特性导致其烧结困难、烧结温度高,因而限制其在核能系统中的广泛应用。本文采用金属铌作为添加相,利用其高烧结活性以及可与碳化锆形成固溶体特性,实现碳化锆陶瓷低温烧结致密化。结果表明:当Nb的添加量为20 vol%时,1800℃烧结可获得单相致密的(Zr,Nb)C固溶体陶瓷材料,其抗弯强度和断裂韧性分别为200 MPa和3.74 MPa·m^(1/2);随着Nb添加量的增加,材料中开始残留一定量金属Nb而形成(Zr,Nb)C-Nb复合材料,所残留的金属Nb抑制(Zr,Nb)C颗粒长大,起到了明显的强韧化作用;材料的抗弯强度和断裂韧性均随Nb含量的增加而增大,材料的断裂方式也由穿晶断裂为主向穿晶和沿晶混合断裂形式转化。

Zirconium carbide(ZrC)has excellent nuclear radiation damage resistance and corrosion resistance.It is one of the most promising candidate materials for the fourth generation nuclear power system.However,its intrinsic characteristics of high melting point and low solid diffusion coefficient lead to its difficult sintering densification and high sintering temperature,which limits its wide application in nuclear energy system.In this paper,niobium was used as the additive,and its high sintering activity and solid solution with zirconium carbide were used to realize the low-temperature sintering densification of zirconium carbide ceramics.The results show that the dense single-phase(Zr,Nb)C solid solution ceramics can be obtained by sintering at 1800℃when the amount of Nb is 20 vol%,and the flexural strength and fracture toughness are 200 MPa and 3.74 MPa·m^(1/2),respectively.With the increase of Nb content,a certain amount of metal Nb is remained in the material to form(Zr,Nb)C-Nb composite,the residual metal Nb plays a role in inhibiting the growth of(Zr,Nb)C grain,which plays an obvious role in strengthening and toughening.The flexural strength and fracture toughness of the material increase with the increase of Nb content,and the fracture mode of the material changes from transgranular fracture to transgranular and intergranular mixed fracture.