摘要
采用机械合金化(MA)和放电等离子烧结(SPS)工艺制备致密的块体Al-Fe合金.微观结构分析表明,MA 0和10 h的粉末经过SPS后,在Al基体上分布着Al/Al_(13)Fe_4/Al_5Fe_2/Fe层状结构的大颗粒铝铁金属间化合物相和细小的条状或点状的Al_(13)Fe_4金属间化合物相;MA 20 h的粉末经过SPS后只有单一的Al_(13)Fe_4相均匀弥散分布于Al基体上.对Al-Fe二元体系进行热力学和动力学分析,在SPS过程中Al/Fe界面上的初生形核相为Al_(13)Fe_4,但由于Al_5Fe_2的Gibbs自由能比Al_(13)Fe_4低,大颗粒中心部分的Fe与接触的Al_(13)Fe_4能进一步发生反应,生成Al_5Fe_2的同时Fe颗粒自身尺寸相应减小,这是大颗粒铝铁金属间化合物中Al/Al_(13)Fe_4/Al_5Fe_2/Fe层状结构形成的原因.
A1-Fe alloys have wide potential applications in automobile and aerospace indus- tries due to their high specific strength, high specific stiffness, good stability of microstructure and excellent high temperature strength. However, a wide variety of metastable phases can be formed in A1-Fe binary system, such as Al（Fe） supersaturated solid solution, amorphous and intermetallic phase. In order to better understand the phase formation in A1-Fe alloys, a systematic investiga- tion of microstructure evolution is necessary. In this work, bulk dense A1-5Fe alloys were fabri- cated by mechanical alloying （MA） and spark plasma sintering （SPS）. The phases, microstructures and morphologies of MA powders and the corresponding sintered samples were characterized by XRD, SEM and EDS. Special attention was paid to the effects of different milling times on struc- tural change of phases during MA SPS process. The results showed that during the MA, the size of alloy powders increased with increasing milling time （0--10 h）, and then decreased with further milling time （10--20 h）. The （lll）A1 peaks in XRD spectra of MA powders shifted to higher angles with the increase of milling time, indicating the dissolution of Fe atoms into the A1 crystal lattice.Homogeneous AI（Fc） solid solutions were obtained after MA for 20 h. Bulk samt^les sintered fl＇om MA powders of 0 and 10 h contained A1/AllaFe4/A15Fe2/Fe layer structure internmtallic phase and tiny AllaFe.~ phase in the A1 nmtrix. However, bulk sample sintered from MA powders of 20 h contained only relatively snmll AllaFe4 phase ill the A1 matrix. Based on thermodynmnic analysis （effective heat of fornmtion theory） and kinetic analysis （spherical shell model）, the primary phase that formed on the interfacial layer of A1/Fe was AllaFe4, and then A15Fe2 can be formed by the reaction of residual Fe and AllaFe4 tor the lower Gibbs free energy of A15Fe2 compared to that of All：~Fe.~, leading to the formation of A1/Al13Fe4/A15Fe2/Fe layer structure intermetallic phase. The absence of Al and F phases in sample sintered from MA powders of 20 h were attributed to the complete reaction between relatively small Fe particles and A1 melt during SPS process.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2013年第4期435-442,共8页
Acta Metallurgica Sinica
基金
国家重点基础研究发展计划项目2012CB619600
国家自然科学基金项目51002054
中央高校基本科研业务费项目2011TS014资助~~
