Stress－rupture Property and Microstructure of Yttria Dispersion Strengthened Alloy MA956

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Stress-rupture Property and Microstructure of YttriaDispersion Strengthened Alloy MA956

The streas-rupture property and corresponding deformed microstructures of an yttria dispersionstrengthened alloy bar MA956 ( Fe-20 % , Cr-4. 5 % , Al-0. 5% , Ti-0. 5% , Y_2O_3(wt% ) ) were investi-gated by using tensile stress-rupture testing, fractography (optical and scanning electron micrscopy(SEM)) , and optical metallography. It has been found that the longitudinal strength is much higher thanthe transverse strength, as a result of fracture occurring along grain boundaries in the latter orientationwhen the load direction is normal to the recrystallization grain growth direction. For the same reason, lon-gitudinally tested samples fractured in a ductile manner while transversely tested ones had brittle fracture.It is also found that pre-anneal decreases the longitudinal strength, since it reduces the grin size and there-fore increace the amount of grain boundarings. In addition, the effect of grain size on crack propagation wasexamined .