Effects Of Minor Reactive Elements Addition On The Oxide Particles In Oxide Dispersion Strengthened(ODS) Alloy

Minor reactive element alloying is a very effective way to improve the performance of oxide dispersion strengthened(ODS)alloy.The development of high performance ODS alloy depends on the effects of minor reactive elements addition on the microstructure of ODS alloys.When used in extremely severe serving conditions,such as aircraft engine turbine blade and nuclear fuel cladding tube,the phase,spatial and size distributions and shape of the oxide particles in ODS alloys,especially interface structure information concerning the coherency of the particles and their crystallographic orientation correlations with the matrix,are crucial to the performance of ODS alloys.In the present study,three different styles of ODS alloys,ODS-1,Zr-added ATF-used ODS steel and ATF-used ODS steel without Zr,MS-4 and MS-5,were studied.Combining the usage of two advanced characterization techniques,diffraction contrast techniques and HRTEM,the knowledge of the effects of zirconium,titanium,aluminum and hafnium addition on the phase,dispersion morphologies and metal/oxide interface structure(coherency and orientation relationships between the oxides and the matrix)of nanoparticles are systematically investigated.The following conclusions can be drawn:?For ODS-1 and Zr-added ATF-used ODS steel,the mean size and number density are considerably smaller and much higher,respectively,relative to SOC-9 and ATF-used ODS steel without Zr.?The addition of Zr intensively suppresses the formation of Y-Al-O oxide particle,the ?-phase Y4Zr3O12 particles are formed instead,the orientation relationships between Y4Zr3O12 oxides and the bcc steel matrix are:(?)Y4Zr3O12?(002)M,(?)Y4Zr3O12?(?)M.The addition of Ti promotes the formation of Y2TiO5 and YTiO3 oxide particles.The orientation relationships between Y2TiO5 oxides and the bcc steel matrix are:(200)Y2TiO5?(002)M?(001)Y2TiO5?(?)M.The orientation relationships between YTiO3 oxides and the bcc steel matrix are:(?)YTiO3?(002)M?(?)YTiO3?(?)M.The addition of Al promotes the formation of YAlO3 oxide particles.The orientation relationships between YAlO3 oxides and the bcc steel matrix are:(?)YAlO3?(?)M.In the view of the orientation relationship,the proportion of coherent oxides is increased after the addition of Zr and Ti.?The mean size of oxide particles in MS-4 and MS-5 is 55.6 nm and 47.5 nm,respectively.YAlO3(YAH,yttrium aluminum hexagonal)and Y3Al5O12(YAG,yttrium aluminum garnet)oxides are detected by HRTEM in MS-5 alloy.And most of the oxide particles are YAH phase.?The addition of Hf can not only change the phase of oxide particles and then enhance the thermal stability of the oxide particles,but also can significantly improve the dispersion morphologies of oxide particles.