Effects of Isothermal Aging at 850℃on Microstructure and Mechanical Properties of High Nb-TiAl Alloy
The microstructure and mechanical properties of high Nb-TiAl alloy exposed to isothermal aging at 850℃processing were investigated using optical microscope(OM),scanning electron microscope(SEM),X-ray diffractometer(XRD)and microhardness and other testing methods.The results indicate that the microstructure of the as-forged high Nb-TiAl alloy is a near-laminated structure with jagged grain boundary,the sheet mass size is about 112 μm,and the interlamellar spacing is about 1.6 μm.The microstructure of the alloy is mainly composed of γ phase and α2 phase.During an 850℃isothermal period of 5 min,5 h,10 h,20 h,respectively,the microstructure mainly consists of lamellar structures formed by γ phase,α2 phase and a small amount of β phase during the high-temperature aging.With the extended isothermal time,both the alloy sheet layer group and the sheet layer spacing have obvious coarsening phenomenon.In different isothermal time time,the surface of the alloy shows a relatively high hardness value(420-460 HV),and its microhardness decreases with the extension of the insulation time.
high Nb-TiAl alloyheat treatmentmicrostructuremicrohardness
NETL
NSTL
万方数据
