Study On Microalloying Of Ferritic ODS Alloy Prepared By EBPVD

Fe-based oxide dispersion strengthened alloys (ODS) has excellent hightemperature mechanical properties and good resistance performance to radiationdamage, making it the fourth-generation nuclear fission reactors and future fusionreactors＇ first choice material. Its microstructure characterized the highlydispersed distribution of nano-oxide in Fe-base alloy. In order to obtain thisparticular composition and microstructure, there has been carried out variousmethods of preparation. As a mainstream technology, mechanical alloying (MA)process research has made many breakthroughs, but due to technical unfit for MAto make a nuclear fuel cladding thin-walled tube, we need to explore new materialpreparation methods. In this paper, the author studied one of the basic problemsfor electron beam physical vapor deposition (EBPVD) preparation of Fe-basedODS, the key component of Ti and Y.Studies of MA preparation technology have confirmed: For Y-Ti-Oreinforced Fe-based ODS alloys, Ti and Y can significantly affect the content ofthe oxide phase composition, dispersion and particle size. But because of the largedifferences between EBPVD preparation principle and MA, in particular theformation mechanism of oxide nanoparticles completely different, the author carryout related research try to get accurate understanding of the affect of Ti and Y onthe microstructure of the material, and promote the understanding of mechanismsfor EBPVD nanoscale oxide formation in the process of preparing.Three different materials FeCrTi oxide-free alloy, Ti-free FeCr-ODS alloy,and FeCrTi-ODS alloy were prepared using the EBPVD technique. A hightemperature heating densification heat treatment was carried out, to soleve thestate of loose tissue initial materails. With goniometer type XRD, surface probetype XRD studied the phase composition and the material characteristics of thecrystal orientation; using SEM, TEM and HRTEM and EDS analysis techniquescharacterized of the state and the preparation of three materials microstructurebefore and after heat treatment the morphology, as well as Y-Ti-O size anddispersion strengthening phase distribution. The results showed that: the prepared state microstructure constituted of0.22~4.56um α-FeCr phase matrix; a smallamount of α ’chromium rich phase was discovered; Y-Ti-O oxide phase specificsize about7nm, well dispersed in the matrix intragranular and grain boundaries.The base substrate side submicron grains become equiaxed grains, while thedeposition surface of the base side of the columnar crystal grains showing acolumnar crystal grain boundaries exist side through micro-voids. Heat treatmentcan eliminate the original distribution of through type pores in the columnar grainboundaries.Mechanics studies were carried out on three test materials at roomtemperature,600℃and800℃, the tensile properties of the material was found tocontain Ti has a high elongation at break, and a material containing Y2O3higherhigh-temperature strength. For FeCrTi-ODS,when the studied content range of Tiand Y2O3between0and0.45%, optimum Y/Ti of1to1.5can be expected toobtaine the ideal microstructure and excellent mechanical properties.