二氧化钛添加对α-Al_2O_3粉末烧结行为及其机械性能的影响

Effects of TiO_2 addition on sintering behavior and mechanical property of α-Al_2O_3 powders

将二氧化钛添加至约含5%(质量分数)的二氧化锆的三氧化二铝粉末中,探讨二氧化钛添加对其烧结行为、各相间的反应及机械性能的影响。结果显示二氧化钛添加量为4%时可将烧结温度由1 450℃降至1 350℃,同时三氧化二铝晶粒成长也明显加速,这是由于Ti4+取代Al3+产生铝离子空缺并造成原子扩散速率增加的缘故;二氧化钛添加量较多或烧结温度较高时,烧结体中存在钛酸锆(ZrTiO_4)、钛酸铝(Al_2TiO5_)等低弹性常数的物质,导致硬度由19.3 GPa降至17.9 GPa;样品晶粒从0.6μm成长至2.44μm时其韧性可由4.4 MPa·m1/2增至5.2 MPa·m1/2,其原因是二氧化钛添加既引起晶粒的成长又会导致破裂模式转为完全延晶破裂。

TiO2 powders were added into Al2O3 powders with 5%（mass fraction） Zr O2 and the effects of TiO2 addition on sintering behavior,phase reactions,and mechanical properties were also investigated.Results showed that the sintered temperature can decrease from 1 450 ℃ to 1 350 ℃ and the growth of Al2O3 grain was accelerated obviously for TiO2 mass fraction of4%.This was due to Al3＋defects produced by Ti4＋replacing Al3＋led to atom diffusion velocity increasing.The matters of ZrTiO4 and Al2TiO5 with low elastic constant presented in sintered bodies could cause the hardness to decrease from 19.3 GPa to17.9 GPa for the more TiO2 content or higher sintered temperature.The fracture toughness increased from 4.4 MPa·m1/2to5.2 MPa·m1/2when the gain size grew from 0.6 μm to 2.44 μm.The reasons were TiO2 addition may lead to the grain growth and can make fracture mode be fully intergranular crack.