Creep Behaviour Of Lamellar TiAl Alloy With Different W Contents

The creep property of three fully-lamellar castγ-TiAl based alloys (contains 0W,1.0W and 1.4W(tungsten,at.%),respectively) has been studied in this thesis.The three alloys were crept on 700℃air continue 1000 hours on several stress.The microstructure changes pre- and post creep in microstructure have been investigated in detail.The result showed that 1%W element content alloy has the best creep property,1.4%W element contained alloy has the worst.The grain size has a decisive effect on the creep resistance of fully-lamellar TiAl alloy.Grain refinement is bad for alloy's creep property.W can stable the a₂ lamellae andγlamellae.After 1000 hours creep,the a₂ lamellae andγlamellae of two alloy which content W element kept stable,but the a₂ lamellae of alloy which content no W began to parallel decompose and the a₂ lamellae content decreased.It's also found that a certain amount B2+ωphase is good for creep property.All the intragranular-creep mechanismths of three alloy are dislocation gliding and dislocation climbing.After creep,large quantity dislocations appear inγlamellae and move to the center ofγlamellae.There dislocations pile up,but them can't pass over a₂ lamellae.