(Ti0.25Zr0.25Nb0.25Ta0.25)C高熵陶瓷的制备、力学性能及氧化行为研究

本文通过对碳化物粉末进行放电等离子烧结(SPS),成功制备了(Ti_0.25Zr_0.25Nb_0.25Ta_0.25)C高熵陶瓷(HECs),系统研究了HECs的微观结构演变、力学性能和氧化行为。结果表明,单相HECs的形成温度为1 800 ℃,低于已报道的HECs烧结温度。1 900 ℃烧结的陶瓷晶粒细小,平均晶粒尺寸约7.5 μm,元素分布均匀,相对密度高达99.2%。1 800 ℃和1 900 ℃烧结的HECs的室温显微硬度值分别为30.9 GPa和33.2 GPa,断裂韧性值分别为(4.6±0.24) MPa·m^1/2和(4.5±0.31) MPa·m^1/2,高于大多数已报道的HECs。原位高温纳米压痕试验结果表明,HECs的硬度随温度的升高而降低,当温度达到500 ℃时,1 800 ℃和1 900 ℃烧结的陶瓷硬度分别下降到21.9 GPa和22.2 GPa,具有突出的高温稳定性。此外,HECs在温度低于500 ℃时无明显氧化,当温度超过650 ℃时会发生明显氧化,氧化速率随温度升高而增加。

Preparation,Mechanical Properties and Oxidation Behavior of (Ti0.25Zr0.25Nb0.25Ta0.25)C High-Entropy Ceramics

In this work, (Ti_0.25Zr_0.25Nb_0.25Ta_0.25)C high entropy ceramics (HECs) was successfully prepared by spark plasma sintering (SPS) of carbide powder. The microstructure evolution, mechanical properties and oxidation behavior of HECs were systematically studied. The results show that the formation temperature of single-phase HECs is 1 800 ℃, which is below the reported HECs sintering temperature. The ceramic grains sintered at 1 900 ℃ are fine, average grain size is about 7.5 μm, and the element distribution is uniform, with a relative density of 99.2%. The room temperature microhardness of HECs sintered at 1 800 ℃ and 1 900 ℃ is 30.9 GPa and 33.2 GPa, respectively, and the fracture toughness is (4.6±0.24) MPa·m^1/2 and (4.5±0.31) MPa·m^1/2, respectively, higher than most reported HECs. The results of high-temperature nanoindentation test show that the hardness of HECs decreases with the increase of temperature. When the temperature reaches 500 ℃, the hardness of the ceramics sintered at 1 800 ℃ and 1 900 ℃ decreases to 21.9 GPa and 22.2 GPa, respectively, with outstanding high temperature stability. When the temperature is lower than 500 ℃, there is no obvious oxidation of HECs. When the temperature is higher than 650 ℃, there is obvious oxidation and the oxidation rate increases with the increase of temperature.