摘要
Combustion synthesis involving metallothermic reduction of Fe2O3 and TiO2 was conducted in the mode of self-propagating high-temperature synthesis(SHS)to fabricate FeAl-based composites with dual ceramic phases,TiB2/Al2O3 and TiC/Al2O3.The reactant mixture included thermite reagents of 0.6Fe2O3+0.6TiO2+2Al,and elemental Fe,Al,boron,and carbon powders.The formation of xFeAl−0.6TiB2−Al2O3 composites with x=2.0−3.6 and yFeAl−0.6TiC−Al2O3 composites with y=1.8−2.75 was studied.The increase of FeAl causes a decrease in the reaction exothermicity,thus resulting in the existence of flammability limits of x=3.6 and y=2.75 for the SHS reactions.Based on combustion wave kinetics,the activation energies of Ea=97.1 and 101.1 kJ/mol are deduced for the metallothermic SHS reactions.XRD analyses confirm in situ formation of FeAl/TiB2/Al2O3 and FeAl/TiC/Al2O3 composites.SEM micrographs exhibit that FeAl is formed with a dense polycrystalline structure,and the ceramic phases,TiB2,TiC,and Al2O3,are micro-sized discrete particles.The synthesized FeAl−TiB2−Al2O3 and FeAl−TiC−Al2O3 composites exhibit the hardness ranging from 12.8 to 16.6 GPa and fracture toughness from 7.93 to 9.84 MPa·m1/2.
通过Fe2O3和TiO2金属热还原自蔓延高温合成(SHS)制备添加TiB2/Al2O3 and TiC/Al2O3陶瓷相的铁铝基金属(FeAl)复合材料。反应物粉末包括铝热剂0.6Fe2O3+0.6TiO2+2Al以及元素铁、铝、硼与炭黑。复合材料成分为xFeAl−0.6TiB2−Al2O3(x=2.0~3.6)和yFeAl−0.6TiC−Al2O3(y=1.8~2.75)。当复合材料中FeAl含量增加时,燃烧反应的放热量下降,最终两组燃烧反应的可燃极限分别为x=3.6和y=2.75。根据燃烧波的动力学分析,合成两种FeAl复合材料的反应活化能为Ea=97.1 and 101.1 kJ/mol。从产物的XRD分析可确认生成FeAl/TiB2/Al2O3和FeAl/TiC/Al2O3复合材料。SEM显示FeAl为致密多晶结构,而陶瓷成分TiB2、TiC和Al2O3呈微米颗粒状分散于复合材料中。合成的FeAl−TiB2−Al2O3和FeAl−TiC−Al2O3复合材料的硬度为12.8~16.6 GPa,断裂韧性为7.93~9.84 MPa·m1/2。
