(北京航空航天大學 材料科學與工程系，北京 100083)
摘 要: 探討了雙態(tài)組織TiAl基合金中晶粒尺度對合金常溫拉伸塑性的影響。對等溫鍛造后的γ TiAl基合金進行了熱處理，獲得了含有不同等軸γ晶粒及片層晶粒體積比的雙態(tài)組織。采用單軸拉伸實驗，對斷口進行分析發(fā)現(xiàn)：雙態(tài)組織的斷裂方式是脆性斷裂，在片層區(qū)域以穿晶解理斷裂為主，而在以等軸γ區(qū)域為主的細晶區(qū)以沿晶斷裂為主。通過統(tǒng)計斷裂力學分析，建立了雙態(tài)組織TiAl基合金拉伸塑性模型，并得出結論： 只有在晶粒半徑細化到50μm以下，才會對拉伸塑性產生較大的影響。
關鍵字: TiAl基合金； 雙態(tài)組織； 拉伸塑性； 晶粒尺度； 微裂紋
TiAl alloy with duplex structure
（Department of Materials Science and Engineering，
Beijing University Aeronautics & Astronautics， Beijing 100083，P.R.China）
Abstract:The effects of grain size on the tensile ductility in a TiAl alloy with duplex structure have been studied. Isothermally forged γ-TiAl alloy was heat treated， and a series of fine duplex microstructures with different volume fraction of equiaxed γ grains and lamellar colonies (α2+γ) were achieved. Uniaxial tension experiment was carried out at room temperature. Fracture surfaces analysis shows that the fracture mode of duplex structure is brittle fracture. In lamellar area， the fracture is dominated by transgranular cleavage， while in equiaxed γ grain area， intergranular decohesion is the main mode of failure. On the basis of an analysis of statistical fracture mechanics， a tensile ductility model of the TiAl alloy with duplex structure was established. And a conclusion is obtained that grain size has prominent effect on tensile ductility of this material only when the grain radius is refined to below 50μm.
Key words: TiAl alloys； duplex structure； tensile ductility； grain size； microcrack
