反复镦挤制备SiC纳米颗粒增强超细晶镁基纳米复合材料的研究

SiC nanoparticles are added into magnesium melt by high intensity ultrasonic method, the SiC nanoparticle reinforced magnesium matrix nanocomposite billets will be obtained after solidification. And then, SiC nanoparticles reinforced magnesium matrix nanocomposites with homogeneous and ultrafine microstructure will be fabricated by repeated upsetting-extrusion (RUE) severe plastic deformation technology to refine and uniform the microstructure, disperse the SiC nanoparticles. We will investigate the effects of initial microstructure of the billets and RUE processing parameters on the microstructure of nanocomposites and the microstructure homogeneity at different position; the effects of SiC nanoparticles on the plastic deformation, recrystallization, precipitation and texture, and the interface of SiC/Mg; study the temperature field, flow field, stress and strain field, deformation behavior and the movement of SiC nanoparticles. We will reveal the evolution of dislocation movement, slip and twin, subgrain, grain, grain boundary and texture during RUE; and illustrate the ultrafine and homogeneous microstructure formation mechanisms; and evaluate the tensile strength, wearability etc, and establish relationships among composition, billet microstructure, processing parameters, and the microstructure and properties of nanocomposites. The project aims at establishing the processing fundaments of repeated upsetting-extrusion severe plastic deformation for SiC nanoparticle reinforced magnesium matrix nanocomposites with homogeneous and ultrafine microstructure, and will inaugurate new technology routes to develop magnesium matrix nanocomposites with high properties and their relevant fabrication and processing technologies.

通过高能超声技术将SiC纳米颗粒加入镁熔体中，凝固获得SiC纳米颗粒增强的镁基复合材料坯料，采用反复镦挤大塑性变形技术，细化和均匀组织，弥散SiC纳米颗粒分布，制备SiC纳米颗粒均匀分布的超细组织镁基纳米复合材料。研究坯料组织、反复镦挤工艺参数对复合材料组织结构的影响及不同位置的组织均匀性；SiC纳米颗粒对塑性变形、再结晶、析出、织构的影响及SiC/Mg界面结构；反复镦挤坯料的温度场、流场、应力场、应变场、变形行为和SiC纳米颗粒的运动。弄清反复镦挤坯料的位错运动、滑移和孪晶、亚晶、晶界、织构等的演化规律；揭示复合材料超细、均匀组织的形成机制；评价复合材料拉伸、耐磨等性能，建立成分、坯料组织结构、制备工艺与复合材料组织结构、性能之间的关系。奠定反复镦挤大塑性变形制备SiC纳米颗粒增强的均匀、超细组织镁基纳米复合材料技术基础。本研究将为高性能镁基纳米复合材料开发及其制备加工技术开辟新途径。

本项目通过高能超声技术将SiC纳米颗粒（n-SiCp）和碳纳米管（CNTs）两种纳米增强相加入镁熔体中，凝固获得n-SiCp/AZ91和CNTs/AZ91两种纳米增强镁基复合材料，采用大塑性变形技术（反复镦压、往复挤压、循环闭式模锻），细化基体组织，弥散纳米增强相，制备纳米增强相均匀分布的超细晶镁基复合材料。研究大塑性变形工艺参数（加工温度、加工道次）对镁基纳米复合材料组织结构、织构的影响规律；弄清加工坯料在反复镦挤过程中的流场、温度场、应力场和应变场；阐明复合材料在大塑性变形过程中的基体组织的细化机制以及纳米增强相的分散机制；评价大塑性变形制得的纳米增强超细晶镁基复合材料的力学性能、摩擦磨损性能和阻尼性能，构建复合材料性能与微观组织、加工工艺之间的关系。奠定大塑性变形制备纳米增强超细晶镁基复合材料的技术基础。本研究将为高性能镁基纳米复合材料开发及其制备加工技术开辟新途径。