Al_2O_3-TiAl基复合材料的力学性能与保温时间的关系

RELATIONSHIP BETWEEN MECHANICAL PROPERTIES AND HOLDING TIME OF Al_2O_3-TiAl BASED COMPOSITE

以压力协助放热弥散法原位合成了Al2O3-TiAl基复合材料.研究了复合材料的相组成,以及室温硬度、室温抗折强度和断裂韧性等与保温时间的变化关系.结果表明:由两种烧成制度制备的产物都是由TiAl、Ti3Al、Al2O3以及NbAl3相组成.Nb2O5的掺杂对生成基体内TiAl及Ti3Al的相对含量有一定的调控作用;保温30 min的复合材料相对密度和硬度明显高于保温60 min的复合材料;保温30 min的复合材料抗折强度高于保温60 min的复合材料,并在Nb2O5掺杂量为10%(质量分数)时达到最大,其值为509.5 MPa,而保温60 min的复合材料在Nb2O5掺杂量为6%时达到最大,其值为395.6 MPa;保温30 min的复合材料断裂韧性低于保温60 min的复合材料,保温60 min的复合材料在Nb2O5掺杂量为6%时达到最大,其值为6.9 MPa.m1/2.

Al2O3/TiAl composites were fabricated by PAXD （pressure-assisted exothermic dispersion） method. The phase compositions, room-temperature hardness, bending strength and fracture toughness of the composites were studied. The results show the ultimate phases of the composites consist of TiAl, Ti3Al, Al2O3 and a small amount of NbAl3 after sintering at different holding time. With Nb2O5 added in, it obviously influences on the ratio of TiAl to Ti3 AI phase. The relative density and hardness of the composites with the holding time of 30 minutes are higher than the composites with the holding time of 60 minutes. The bending strength of the composites with the holding time of 30 minutes is higher than the composites with the holding time of 60 minutes, the former with 10wt% Nb2O5 added in has the bettermost bending strength which is 509.5 MPa; the latter with 6wt% Nb2O5 added in has the bettermost bending strength which is 395.6 MPa. The fracture toughness of the composites with the holding time of 30 minutes are lower than the composites with the holding time of 60 minutes, the latter with 6wt % Nb2O5 added in exhibits the bettermost fracture toughness of 6.9MPa·m^1/2.