Changes in lamellar microstructure by parallel twinning during creep in soft PST crystal of TiAl alloy  

作　　者：H.Y.Kim K.Maruyama 

机构地区：[1]DepartmentofMaterialScience,GraduateSchoolofEngineering,TohokuUniversity,02Aobayama,Sendai980－8579,Japan [2]DepartmentofMaterialScience,GraduateSchoolofEngineering,TohokuUniversity,02Aobayama,Sendai980－8

出　　处：《中国有色金属学会会刊：英文版》2002年第4期561-568,共8页Transactions of Nonferrous Metals Society of China

摘　　要：Compression creep tests of a Ti-48%Al (mole fraction) alloy were carried out at 1?150?K with soft-orientated PST crystal. Parallel twinning took place during the creep. Changes in lamellar microstructure caused by the parallel twinning were investigated, and their effects on creep deformation behavior were discussed. The results show that the parallel twinning occurs in an early stage of creep, and makes significant contribution to creep strain in the domains favorably oriented for the twinning. The nucleation of parallel twins finishes at a strain of about 3%. There is a critical resolved shear stress for parallel twinning, and it is about 50?MPa in the Ti 48%Al PST crystals at 1?150?K. The activity of parallel twinning increases with increasing applied stress or in a coarse lamellar material. The addition of parallel twins reduces the average value of lamellar spacing. In general, the refinement of lamellar structure should improve creep resistance. However the strengthening by parallel twinning is not evident in creep of the soft PST crystals because the soft deformation modes are the dominant deformation mode in the crystals.Compression creep tests of a Ti-48 percent Al (mole fraction) alloy werecarried out at 1150 K with soft-orientated PST crystal. Parallel twinning took place during thecreep. Changes in lamellar microstructure caused by the parallel twinning were investigated, andtheir effects on creep deformation behavior were discussed. The results show that the paralleltwinning occurs in an early stage of creep, and makes significant contribution to creep strain inthe domains favorably oriented for the twinning. The nucleation of parallel twins finishes at aStrain of about 3 percent. There is a critical resolved shear stress for parallel twinning, and itis about 50 MPa in the Ti-48 percent Al PST crystals at 1150 K. The activity of parallel twinningincreases with increasing applied stress or in a coarse lamellar material. The addition of paralleltwins reduces the average value of lamellar spacing. In general, the refinement of lamellarstructure should improve creep resistance. However the strengthening by parallel twinning is notevident in creep of the soft PST crystals because the soft deformation modes are the dominantdeformation mode in the crystals.

关 键 词：显微结构 TIAL合金 软PST晶体 蠕变 孪晶 

分 类 号：TG146.2[一般工业技术—材料科学与工程]