【摘要】 针对Ti₄₅Zr₃₈Ni₁₇与Ti₄₀Zr₄₀Ni₂₀准晶合金用X射线衍射仪、透射电子显微镜与金相等手段研究了不同含量的Pd替代对其结构的影响.在吸铸态下,前一个合金形成了二十面体准晶相（IQC）与少量配位数为8的bccβ-（Ti,Zr）相,用2%Pd（原子分数,下同）对合金的Ti或Zr组元替代,抑制了β-（Ti,Zr）相析出并促使配位数为14的MgZn₂结构的简单六方C14 Laves相生成.而后一个合金中IQC相则与少量简单六方α-（Ti,Zr）共存,在2%Pd替代后α-（Ti,Zr）消失,生成了单一的IQC相,但当Pd替代量增加到6.7%或13.3%时,配位数为12的IQC相急剧减少而C14相大量析出,并在Ti₄₀Zr_26.7Ni₂₀Pd_13.3合金中生成了单一C14相.结果表明,添加中等尺寸的Pd原子有利于提高Ti-Zr-Ni合金的原子密堆性,使合金趋于生成高配位数的Laves相,这种相的Fermi面与Brillouin区的相互作用不显著,偏离了电子相的稳定机制.更多还原

【Abstract】 Quasicrystals are a kind of special crystals,combining aperiodicity with long-range translational order and displaying a strong potential of applications.However,the forming law of quasicrystals,especially icosahedral,which have drawn a lot of attention since the discovery of the first quasicrystal,are not clearly known.A general knowledge,derived from the past work,is that the quasicrystal belongs to Hume-Rothery phase with special electron concentration per atom（e/a）,and furthermore needs meeting the topological packing of atoms.Based on this,certain criteria named by e/a constant line,e/a-variant line and cluster line,et al.,have been used to design novel quasicrystals, especially in ternary alloy systems.But,as indicated in the previous work,these rules would not work very well in pseudo-ternary or quaternary systems built on Ti-Zr-Ni quasicrystals with the addition of Co or Cu.In order to further specify the quasicrystal formation in multi-component systems, in the present study an investigation was conducted in an alloy system,based on Ti₄₅Zr₃₈Ni₁₇ and Ti₄₀Zr₄₀Ni₂₀ alloys with the addtion of Pd,because Pd is the neighbourship of Ni in the element table like Co and Cu and has the atom size and e/a between Ti（or Zr） and Ni.Using XRD,TEM and OM,it is found that in the suction cast alloys,the icosahedral quasicrystal（IQC） phase is formed in the coexistence of a little bccβ-（Ti,Zr） in Ti₄₅Zr₃₈Ni₁₇ alloy and of a bit hexagonalα-（Ti,Zr） in Ti₄₀Zr₄₀Ni₂₀ alloy.And after 2%Pd（atomic fraction） substitution for Ti and Zr,a MgZn₂-type Laves C14 phase with coordination number of 14 is precipitated along with the disappearance ofβ-（Ti,Zr） with coordination number of 8 in the former alloy,while only a complete IQC phase with coordination number of 12 is yielded in the latter alloy.However,as the subtitution is increased up to 6.7%or 13.3% in Ti₄₀Zr₄₀Ni₂₀ alloy,the formation of IQC is prevented and the C14 phase occurs instead till a single C14 phase forms in Ti₄₀Zr_26.7Ni₂₀Pd_13.3 alloy.The results show that the Pd addition in Ti-Zr-Ni alloys would promote closer atom packing,being beneficial to the formation of Laves phase because of the weak interaction between Fermi surface and Brillouin zone in Hume-Rothery phase like IQC.更多还原