复相Al_3Ti基金属间化合物亚稳转变及重有序化

METASTABLE TRANSFORMATION AND REORDERING OF MULT-PHASE Al_3Ti-BASED INTERMETALLICS

本文研究了Al67Mn8Ti24Nb1复相金属间化合物在高能球磨过程中的亚稳态转变及亚稳粉末在加热时重有序化．由L12结构的基体和由DO22型Al3（Ti，Nb）第二相组成的Al67MN8Ti24Nb1复相合金在球磨过程中，L12相有序度下降、DO22相溶入，经15h后合金呈化学无序的fcc过饱和固溶体，继续球磨则逐步转变成非晶态，其亚稳转变过程中的结构演变顺序为：Ll2十DO22→Ll2（弱有序）→无序fcc→fcc＋非晶→非晶．利用100／200和110／220二对衍射峰计算有序应，虽然变化趋势相同，但两者下降速率不同，按110／220这一对衍射峰计算的有序度下降更快，表明合金在球磨过程中会造成结构上的异向性；非晶态合金加热时发生重有序化，其结构转变序列为：非晶态→无序fcc→弱有序Ll2并开始析出DO22相→完全有序Ll2并充分析出第二相．

The disordering of multi-phase A167Mn8Ti24Nbl alloy during high-energy ball millingprocess and the heat induced reordering of the metastable powder were studied. During high-energy ballmilling process the degree of order of the L12 structure matrix decreases to zero after 15h balling milling.The DO22 phase dissolved into the mains, forming a disordered super-saturated fee solid solution. Furtherhillling leds to the amorphous transition. So the sequence of structural evolution during ball milling is:Liz+DO22 →Ll2 (weak ordering)→ disordered fee → fee + amorphous→ amorphous. The degree of orderwas determined using the 100/200 and 110/220 diffraction peaks. It is noted that the degree of orderdetermined by 110/220 decreased more rapidly, which implies that the deformation occurred during milling,which results in some structural anisotropy. The heat induced reordering of the amorphous alloy has alsobeen studied and the following structural transformation sequences were found: amorphous→disorderfee→weakly ordered L12 with DO22 phase precipition→ordered Ll2 and completely precipitated DO22second phase.