热压温度和时间对Fe3Al/Al2O3纳米复相陶瓷结构和性能的影响

EFFECTS OF HOT PRESSING TEMPERATURE AND TIME ON THE MICROSTRUCTURE AND PROPERTIES OF Fe_3Al/Al_2O_3 NANO-COMPOSITE CERAMICS

以自制的纳米晶Fe3Al(有序DO3结构)为增强相,纳米粉Al2O3为基体相,采用热压烧结制备了Fe3Al/Al2O3纳米复相陶瓷,研究了热压温度和时间对复相陶瓷显微结构和力学性能的影响。结果表明:复相陶瓷的相组成为Fe3Al和Al2O3。热压温度为1400℃时,部分晶粒尺寸从0.5μm增大到1μm,板片状Al2O3晶粒消失;热压时间为60min时,晶粒尺寸趋于一致,为1μm左右,呈现出较致密的准球形堆积状态。随着热压温度的升高或热压时间的延长,复相陶瓷的相对密度、Vickers硬度和断裂韧性均有不同程度的提高,最大值分别为93.31%,975MPa和8.30MPa·m1/2。对显微硬度压痕裂纹进行扫描电镜观察和分析表明:材料断裂韧性的提高,是通过对裂纹的偏转和吸收、超细晶韧化和Fe3Al的补强和增韧等方式进行的。

Fe3Al/Al2O3 nano-composite ceramics were prepared by hot-pressing sintering using nano-powder Al2O3 as matrix material and self-made nano-crystal Fe3Al （ordered structure of DO3） as strengthening phase. The effects of the hot pressing temperature and holding time on the microstructure and mechanical properties of composite ceramics were investigated. The results show that the phase compositions of the ceramics consist of Fe3Al and Al2O3. The partial grains increase from 0.5 to 1 μm, and flaky grains of Al2O3 vanish when the ceramics are sintered at 1 400 ℃. The average size of the ceramic grains is uniformly around 1μm when hot-pressed at 1 400 ℃ for 60 min, and dense with torispherical accumulation. With the increase of hot-pressing temperature and the elongation of holding time, the composite ceramics with higher relative density, Vickers-hardness and fracture toughness were obtained, and their maximum values were 93.31%, 975 MPa and 8.30 MPa·m1/2, respectively. Microhardness indentation crack was observed and analyzed by scanning electron microscopy. The results show that fracture toughness is enhanced by means of deflecting and absorbing the cracks, ultra-fine grain toughen and reinforcement of Fe3Al.