放电等离子烧结Fc-Al混合粉的显微组织演化及烧结动力学

摘要

研究了Fe与Al混合粉在放电等离子烧结(SPS)作用下的反应扩散行为.采用X射线衍射及扫描电镜对显微组织演化进行了分析,并揭示了烧结动力学行为.结果表明在SPS温度773～873 K下,Fe2Al5为反应中间相.尽管电流可以提高材料扩散速度,球磨处理可在粉体中产生大量点阵缺陷及晶粒边界,使反应动力学速度得到提高.球磨后,相变动力学速度从球磨前的4.56×10-3提高到0.207.而且,本研究揭示了焦耳热产生行为.作为电流通道,阻抗是重要的焦耳热源.SPS过程中粉末颗粒、模具、冲头、石墨纸之间界面阻抗是焦耳热产生的重要来源.%The reaction diffusion between Fe and Al during spark plasma sintering (SPS) was studied.Microstructural evolution was investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) and the sintering kinetics was disclosed.The main interphase of the SPS sample was Fe2Al5 at 773-873 K.Ball-milling enabled a large number of lattice defects and grain boundaries thus the reaction kinetics was accelerated,although the direct current can also promote those defects.After milling,the phase transformation kinetics was improved from 0.207 before mill to 4.56×10-3.Besides,this work provided more details for the generation of Joule heating.The resistance offered to the electric path was considered to be the source of Joule heating,and particularly the resistance offered by the different contact interfaces of die,punch,graphite foil and the sample played a leading role for the generation of Joule heating during spark plasma sintering.