【摘要】 利用金相显微镜、扫描和透射电镜等仪器表征了TiAl合金的片层组织及结构特征,研究了Ti-48Al at%合金片层组织的形成机制和片层组织细化工艺及其机理。结果表明,Ti-48Al合金单级热处理能够得到全片层组织,平均晶粒尺寸约150μm,片层间距约1.30μm。其形成过程是:γ相在α相晶内(0001)面上通过全位错分解成核,通过不全位错滑移、层错区扩展而长大。循环热处理和双温热处理均能将片层晶粒尺寸细化到30μm,片层间距0.90μm,前者的细化机理为相变重结晶细化了α相晶粒,后者细化片层组织的关键在于低温段(α2+γ)两相区热处理形成细小的双态组织。更多还原

【Abstract】 The formation mechanism of lamellar structure of Ti-48Al alloy during heat treatments was studied and the procedure and mechanism of refinement of the lamellar structure were discussed.The lamellar structure and its characteristics of a TiAl alloy were examined by OM,SEM and TEM.The results show that the full lamellar structure in Ti-48Alat% alloy is obtained by a single-stage annealing,and the average size of lamellar colony and between lamellars is about 150μm and 1.3μm,respectively.The γ phase nucleates in(0001) plane of α grains by decomposion of a full dislocation and grows by slip of part dislocations and by extension of fault.The average size of lamellar structure and between lamellars can refined to 30μm and 0.90μm,respectively,through a cyclic heat treatment and a two-step heat treatment.The refinement of microstructure results from the α grains refined by transformation recrystallization in the cyclic treatment and from the fine dual structure formed in the first step of the two-step heat treatment.更多还原