摘要
用扫描电镜 ( SEM)和透射电镜 ( TEM)并应用搅熔铸造工艺研究了预处理过的 Si C颗粒在加镁 ZA-2 7合金中的卷入、分散和润湿过程。在低温搅拌 ( 4 70℃ )时 ,预处理过的 Si C颗粒首先呈较大尺寸团聚体被卷入 ZA-2 7合金半固态浆料中 ,随后在搅拌剪切力的作用下 Si C团聚体逐渐变小 ,且由于发生了存在于 Si C表面的 Si O2与由于加 Mg而降低表面能的合金液间的润湿 ,并在旋涡能的促进下 ,Si C能呈单粒状分散在熔体中 ;在高温( 5 5 0℃ )搅拌时 ,由于 Si O2 与合金液中的活性原子 Mg和 Al等发生界面反应 ,促进了 Si O2 与合金液间的进一步润湿 ,随后 Si C能与合金液发生非反应润湿的主要原因是界面反应提供了无气洁净的 Si C表面。结合电镜观察和热力学计算及动力学分析 ,确认界面反应产物是尖晶石。探讨了搅拌时界面反应的过程并建立了反应润湿的模型 ,得出 Si C表面的残余 Si O2 厚度 X与反应时间 t成线性关系 ,即
The incorporation and dispersion as well as wettability processes of pretreated SiC particles in a commercial ZA-27 alloy modified by 1% Mg are studied by means of SEM, TEM and application of stirring melt alloy process. At lower stirring temperature (470℃),the pretreated SiC particles are incorporated into the semi-solid alloy in an agglomerated style, and then the volume of the agglomerated SiC particles is gradually reduced by continuous stirring. Finally, a single SiC particle exits in the semi-solid alloy because of the wettability of SiO 2 at the SiC surface and lower surface energy melt induced by addition of a little Mg and by the promotion of stirring vortex energy. At higher temperature (550℃), an interface reaction among SiO 2 and active Mg and Al in the melt is taken place. The further reaction promotes the wettability between SiO 2 and the melt. The main cause that SiC can be wetted by the melt is that the reaction provides a non-gas and cleaned SiC surface. One of interface reaction products, spinel, is confirmed by TEM observation and thermodynamic calculation as well as dynamic analysis. The process of the interface reaction is studied and a reaction model is suggested. A linear relationship between thickness of residual SiO 2 X and reaction time t is obtained, namely X=L-DKV mt.
出处
《南京航空航天大学学报》
EI
CAS
CSCD
北大核心
2002年第3期240-244,共5页
Journal of Nanjing University of Aeronautics & Astronautics
