铝晶粒细化剂Al-5Ti-1B合金的晶粒细化机理

Grain Refinement Mechanism of Al-5Ti-1B Master Alloy on Aluminum Alloy

分别采用Al-5Ti-1B、Al-10Ti、Al-4B合金和TiB2粉末对纯铝进行细化实验,比较了TiAl3、TiB2和AlB2对纯铝的晶粒细化作用,利用光学显微镜、X射线衍射仪、扫描电镜和透射电子显微镜研究了Al-5Ti-1B合金的晶粒细化机理。结果表明,TiAl3是铝晶粒的有效异质形核相,但Al-5Ti-1B合金中的TiAl3因在铝熔体中会熔化而不是铝晶粒的直接形核相。单独的AlB2和TiB2都不是铝晶粒的有效异质形核相,但TiB2通过表面包覆TiAl3后可成为铝晶粒的有效异质形核相。Al-5Ti-1B合金的晶粒细化机理为TiAl3熔解于铝熔体中释放Ti原子,部分Ti原子通过浓度起伏形成TiAl3,TiAl3再与铝熔体发生包晶转变形成α-Al晶粒直接起到晶粒细化作用;部分Ti原子在TiB2表面偏聚形成TiAl3,TiAl3再与铝熔体发生包晶转变形成α-Al晶粒起到晶粒细化作用。

The pure Al was refined by adding Al-5Ti-1B,Al-10Ti,Al-4B master alloy and TiB2 powder,respectively.The effects of TiAl3,TiB2 and AlB2 phases on grain refinement of pure Al were compared.The grain refinement mechanism of Al-5Ti-1B master alloy was investigated by optical microscope,X-ray diffraction,scanning electron microscope and transmission electron microscope.The results show that the TiAl3 is an effective nucleation phase,but the TiAl3 in Al-5Ti-1B master alloy can not be nucleation phase due to their dissolving in aluminum melt.The AlB2 and TiB2 can not be nucleation phase alone.However,the TiB2 can become an effective nucleation core when the TiB2 is coated with TiAl3.The grain refinement mechanism of Al-5Ti-1B master alloy on pure Al is that some Ti atoms originating from TiAl3 melting react peritecticaly with Al melt to form TiAl3 phase as the nucleation core of grain; remaining Ti atoms segregate on the TiB2 surface to form TiAla phase as the nucleation core of grain.