SiCp/AZ91D镁基纳米复合材料的室温拉伸行为及塑性变形机理

为得到高强度和高塑性的镁基复合材料,通过高能超声分散法和金属型重力铸造工艺制备了SiC纳米颗粒分散均匀的SiCp/AZ91D镁基纳米复合材料,并进行T4固溶热处理和室温拉伸。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)对试样拉伸后的显微组织和塑性变形机理进行观察与研究。结果表明:T4态SiCp/AZ91D镁基纳米复合材料室温下抗拉强度达到296 MPa,伸长率达到17.3%。经室温拉伸变形后复合材料基体微观组织中出现了大量的孪晶和滑移,孪生和滑移是复合材料塑形变形的主要机制。在室温拉伸过程中,α-Mg基体中SiC纳米颗粒周围形成高应变场,高应变场内形成大量位错和堆垛层错,这些位错和堆垛层错在拉伸应变的作用下演变成大量的滑移带和孪晶,这是SiCp/AZ91D镁基纳米复合材料在室温下具有高塑性的微观塑性变形机理。

Tensile behavior and plastic deformation mechanism of SiC_p/AZ91D magnesium matrix nanocomposites at room temperature

To obtain magnesium matrix composites with high strength and high plasticity, SiC_p/AZ91 D magnesium matrix nanocomposites with uniform dispersion of SiC nanoparticles were prepared by high intensity ultrasonic dispersion method and metal mold gravity casting process, following by T4 solution heat treatment and the tensile test at room temperature. The microstructure and plastic deformation mechanism of the specimen after tensile test were investigated by scanning electron microscope and transmission electron microscope. The results show that the tensile strength and elongation of nanocomposites reach up to 296 MPa and 17.3% at room temperature, respectively. A large number of twins and slip are observed in SiC_p/AZ91 D magnesium matrix nanocomposites with T4 state after tensile deformation at room temperature. It is obvious that twinning and slip are the main mechanisms of plastic deformation in the nanocomposites.High strain zones are formed around SiC nanoparticles in the α-Mg matrix during the tensile process at room temperature, and a lot of dislocations and stacking faults are formed in the high strain zones. These dislocations and stacking faults are evolved into a large number of slip bands and twins under the action of tensile strain, which is the plastic deformation mechanism of SiC_p/AZ91 D magnesium matrix nanocomposites with high plasticity at room temperature.