【摘要】 以硼热/碳热还原合成高熵二硼化物粉体为原料,在2000℃/单轴加压50 MPa条件下,经10分钟放电等离子烧结,成功制备了含有～2 vol%的氧化物和～1 vol%气孔的高熵(Ti_0.2Zr_0.2Nb_0.2Hf_0.2Ta_0.2)B₂陶瓷（HEBs）.经研究确认,其中残留氧化物是固溶少量硼和碳的m-（Hf,Zr）O₂.室温下HEBs的弹性模量、维氏硬度和断裂韧性分别为508.5 GPa、17.7±0.4 GPa和4.2±0.2 MPa m^1/2.烧结得到的HEBs具有优良的抗弯强度,特别是其高温强度.HEBs在室温、1600和1800℃下的四点抗折强度分别为400.4±47.0 MPa、695.9±55.9 MPa和751.6±23.2 MPa.对1800℃下断裂的HEBs样品进行了失效分析,在其拉伸和断裂面附近区域,仅在裂纹尖端和孔隙边缘发现了数量有限的位错线的存在,没有观察到位错运动的痕迹.本研究首次报道了高熵二硼化物陶瓷的高温强度,发现其强度直至1800℃并无衰减,并对其高温下的强韧化机制进行了有益的探讨.更多还原

【Abstract】 In this study,a type of high-entropy boride（HEB）ceramics((Ti_0.2Zr_0.2Nb_0.2Hf_0.2Ta_0.2)B₂)with ～2 vol%oxides and ～1 vol% porosity was successfully consolidated by spark plasma sintering at 2000℃ under a uniaxial load of50 MPa for 10 min,using self-synthesized high entropy diboride powders from a boro/carbothermal reduction approach.The residual oxides were determined to be m-（Hf,Zr）O₂,which were incorporated with minor amounts of boron and carbon.Elastic modulus,Vickers hardness and fracture toughness of HEBs at room temperature were508.5 GPa,17.7±0.4 GPa and 4.2±0.2 MPa m^1/2,respectively.The as-obtained ceramics possessed excellent flexural strength,particularly at high temperatures.The four-point flexural strengths of HEBs at room temperature,1600,and1800℃ are 400.4±47.0,695.9±55.9,and 751.6±23.2 MPa,respectively.Postmortem analysis was conducted on HEB fractured at 1800℃,in the region near their tensile and fracture surfaces,and microstructure observations show that limited dislocation lines were present adjacent to the crack front and edge of the pore,without noticing any trace for dislocation motions.It is the first report on the high-temperature strength of high-entropy diboride ceramics and the strengthening mechanism at high temperatures was also discussed.更多还原