Research On Irradiation Stability Of Second Phase Particles In PH 13-8 Mo And 14Cr-FeCrAl ODS Alloys

In this thesis,a martensitic alloy PH 13-8 Mo containing intermetallic type second phase particles and a domestically-made advanced 14Cr-FeCrAl ODS alloy containing ceramic type second phase particles were selected.Irradiation experiments were conducted with 400 keV Fe+ beam at room temperature.A study was carried out on the radiation stability of the second phase particles after irradiation.In terms of different aging conditions,PH 13-8 Mo samples containing intermetallic NiAl with average sizes of 2.5 nm,4.9 nm and 8.1 nm were prepared.Transmission electron microscope(TEM)was used to characterize the irradiation performance of NiAl and the irradiation defects.With accumulated irradiation damage up to 8 dpa,NiAl precipitates lost their superlattice structure.Irradiation-induced dissolution and spinodal decomposition occurred on some of the damaged NiAl precipitates.Hypothesis of ballistic mixing and irradiation induced segregation were introduced for further discussion.The smallest irradiation induced interstitial type dislocations was 3.5±0.5 nm,found in the sample with 2.5 nm NiAl precipitates.TEM characterizations were carried out on two types of 14Cr-FeCrAl ODS alloys(with/without Zr addition)to study the irradiation resistance of the nano-scale ceramic type second phase particles.It was found that Zr addition could refine particle size,increase number density,and result in Y2(Ti0.4Zr0.6)2O7 formation.With accumulated irradiation damage up to 25 dpa,average sizes and number densities of second phase particles decreased in both samples.YAlO3 type particles were believed to be amorphized while Y2(Ti0.4Zr0.6)2O7 type particle in the Zr addition sample sustained as before.