The test alloy GH706 (/% : 0.034C

16.l0Cr

41. 13Ni

1.64Ti

2.93Nb

0.39Al) and modified alloy (/% : 0.027C

16.30Cr

1.79Ti

2.05Nb

1.21 Al) are melted by a 200 kg vacuum induction furnace and remelted to 150 kg ESR ingot

then homogenizing-treated at 1 180 ℃T for 16 h and forged to Φ15 mm rod and heat-treated at 980 ℃ for 3 h

cooling with 4 K/min to 820 °C for 2 ~ 10 h

air cooling

and at 720℃ for 16 h

furnace cooling. Results show that increasing Ai content and decreasing Nb content in alloy contribute to precipitates of γ′ phase in alloy; precipitation of η phase at grain boundary can be controlled by adjusting the time of secondary heat treatment led to the excellent strength and plasticity combination of alloy

i.e. as alloy has tensile strength level 1 200 MPa the reduction of area of alloy is near to 30%. As the secondary heat treatment process is at 820 ℃ for 2 h

the tensile strength of modified alloy at 700°C is 908 MPa and the reduction of area is up to 54. 8%.