Al含量对Nb-Ti-C合金组织的影响

利用真空非自耗电弧炉制备了不同Al含量的Nb-21Ti-4C(βNb-Ti)合金,研究了Al元素含量变化对Nb-21Ti-4C合金组织和晶格常数的影响。研究表明:铸态条件下合金由枝晶生长的Nb基固溶体(Nbss),碳化物((Nb,Ti)C),Nb3Al和枝晶间Nbss/MC共晶组织构成;Al元素部分固溶进入Nbss和MC中,随着Al含量增加,以Nb3Al相生长在Nbss内部。Al元素含量增加,使得Nbss枝晶先变大后变小。1100℃,24h热处理后,Nbss内部析出针状或片状碳化物和Nb3Al,导致Nbss晶格常数增大;枝晶间碳化物内部Nbss进一步长大,Nb原子的析出和Al元素固溶含量变化导致碳化物晶格常数改变。

Effects of Al Contents on Microstructure of Nb-Ti-C Alloys

Nb-21Ti-4C (βNb-Ti) alloys with different Al contents were fabricated by a vacuum non-consumable arc-melting method.The effects of Al content on the microstructure and lattice parameters of the alloys were studied.The results indicate that the as-cast alloys contain dendritic-growth niobium solid solution Nbss,carbide (Nb,Ti)C,Nb3Al and interdendritic eutectic of Nbss/MC.The nucleation and growth of Nb3Al are in dendritic Nbss,and other Al elements dissolve into Nbss and MC.The Nbss dendritic size increases first and then decreases with Al content increasing.After heat treatment at 1100 oC for 24 h,Nbss of interdendritic eutectic grows further as a discontinuous precipitation process,and needle-like or plate-like MC and Nb3Al precipitate from Nbss,resulting in lattice parameters becoming larger;the lattice parameters of MC changes with Al content change and Nb precipitation.