水冷铜模铸造Fe_3Al金属间化合物的组织和力学性能

Microstructure and mechanical properties of intermetalics Fe_3Al cast with copper water-cooled mould

采用中频感应炉熔炼、水冷铜模冷却的方法制备Fe3A1合金.利用X射线衍射、金相显微镜、扫描电镜及力学性能测试对铸态及热处理后合金的组织、力学性能和冲击断裂行为进行研究.结果表明:合金的铸态组织为等轴晶,晶粒尺寸大小不均;合金经1 000℃、15 h均匀化退火+炉冷+600℃、1 h中温回火+油淬热处理后,晶界得到细化,晶内和晶界上析出弥散分布的第二相,晶粒尺寸明显长大;热处理后合金的σb提高73 MPa,硬度由铸态时的22.3 HRC提高到了26.2 HRC,但合金的冲击韧性有所下降;铸态时合金的断裂方式主要以沿晶断裂为主,热处理后合金断口呈沿晶+穿晶的混合型断裂特征.

Intermetalics Fe3Al was melted in intermediate-frequency induction furnace and cooled in a water-cooled copper mould.Its microstructure,mechanical properties and impact fracture were studied by means of X-ray diffraction（XRD）,optical and scanning electron microscopy（SEM） and mechanical property tests in its as-cast condition and after its heat-treatment.The results showed that its as-cast microstructure was of characterized by equiaxial grains and the grain size was non-uniform.After heat-treatment,including 1 000 ℃/15 h homogenizing annealing,furnace-cooling,600 ℃/1 h tempering,and oil quenching,the grain boundary was refined and the grain size increased.The dispersive secondary phase was precipitated within the grains and on the grain boundary.Due to the heat-treatment,the tensile strength of the alloy increases by 73 MPa and the hardness increases slightly,but the impact toughness decreased.The impact fracture transformed from intercrystalline fracture to intercrystalline plus transcrystalline mixed fracture after heat-treatment.