稀土铝钛硼中间合金的细化能力与长效性

Refining performance and long time efficiency of Al-Ti-B-RE master alloy

采用铝热反应法制备Al5Ti1B和Al5Ti4RE1B中间合金,并对其进行物相、微观组织和细化效果分析;对比中间合金中第二相的晶体结构以及形核能力,并从第二相分解和沉淀的角度分析Al5Ti1B1RE的细化长效性。结果表明:Al5Ti4RE1B比Al5Ti1B具有更强的细化能力和细化长效性;XRD和EDS分析显示,RE和TiAl3结合生成Ti2Al20RE相,该相为面心立方结构,晶格常数为1.469 nm;相比TiAl3而言,Ti2Al20RE具有更多的晶面和Al晶体匹配,使得Al5Ti4RE1B比Al5Ti1B具有更强的细化能力;Ti2Al20RE比TiAl3的溶解温度高,溶解过程中稀土对铝液粘度的影响是造成Al5Ti4RE1B细化长效性好的主要原因。

Al5Ti1B and Al5Ti4RE1B master alloys were prepared by the reaction of complex halide salts with molten aluminum and rare earth at high temperature, XRD measurement, microstructure analysis and refining experiments were conducted. The crystal structure and nucleating potential of second phase were investigated and the long time refining efficiency was studied by comparing the decomposition/dissolution and precipitation rate of different phases. The results show that Al5Ti4RE1B has stronger refining performance and long time efficiency than Al5Ti1B. TiAl3 reacts with RE to form face-centered cubic Ti2Al20RE, with lattice parameter of 1.469 nm. Ti2Al20RE has more lattice planes matching with aluminum than TiAl3, which provides Al5Ti4RE1B with strong ability of resisting the decline of refinement. Besides Ti2Al20RE decomposes and dissolves at a higher temperature and a lower speed than TiAl3, the viscosity increase of aluminum melt resulting from the release of rare earth from Ti2Al20RE is also responsible for the long time efficiency of Al5Ti4RE1B.