TiO2粒径对Al-TiO2-C细化剂组织及细化效果的影响

Effect of TiO2 particle size on microstructure and refining effect of Al-TiO2-C refiner

以Al粉,TiO2粉,C粉为原料,通过放热弥散法制备Al-TiO2-C细化剂,其中TiO2的粒径分别为30,60,90,200 nm。研究TiO2的粒径对细化剂组织的影响以及不同细化剂对工业纯铝的细化效果。利用XRD,SEM,EDS技术表征不同TiO2粒径制备的Al-TiO2-C细化剂相组成和显微组织。结果表明:Al-TiO2-C细化剂主要由Al3Ti,TiC和Al2O3相组成。TiO2粒径的变化会直接影响第二相的数量、分布与形貌,当TiO2粒径为30~90 nm时,Al-TiO2-C细化剂中Al3Ti和TiC数量多但有明显的偏聚现象,分布不均匀,其中Al3Ti相呈长条状。当TiO2粒径为200 nm时,第二相分布均匀但数量较少,其中Al3Ti相呈块状。添加30 nm TiO2制备的Al-TiO2-C细化剂后,α-Al形核温度由659.4℃上升到661.8℃,再辉温度由1.2℃下降到0.3℃,平均晶粒尺寸最小为633μm,细化效果最佳。

The Al-TiO2-C refiners were prepared by the in-situ exothermic dispersion method using Al,TiO2 and C powders.The particle sizes of TiO2 were 30,60,90 nm and 200 nm,respectively.The effects of particle size of TiO2 on the refiner microstructure were studied.The refinement effect on industrial pure aluminum was evaluated.The XRD,SEM and EDS techniques were used to characterize the phase composition and the microstructure of Al-TiO2-C refiners.The results show that the Al-TiO2-C refiners compose of Al3Ti,TiC and Al2O3.The particle size of TiO2 directly affects the amount,distribution and morphology of the second phase.When the particle size of TiO2 is 30-90 nm,the amount of Al3Ti and TiC is large.However,the segregation phenomenon is obviously observed.The distribution of particles is not uniform.The Al3Ti is lath-like.When the particle size of TiO2 is 200 nm,the distribution of second phases is uniform and the amount is small.The Al3Ti is blocky.After adding the Al-TiO2-C refiner prepared by 30 nm TiO2,the nucleation temperature ofα-Al increases from 659.4℃to 661.8℃.Re-heating temperature is dropped from 1.2℃to 0.3℃.The minimum average grain size is 633μm.The refinement effect is the best in this condition.