Preparation And Welding Behaviour Of Oxide Dispersion Strengthened Alloys

Metals and alloys are closely related to modern civilization and social development and act as one of the most important necessities in industrial production and daily life.In order to improve the overall performance of materials,special methods need to be taken.Dispersion strengthening is an effective way to enhance materials by directly adding or in-situ forming hard second-phase particles in the matrix.These particles possess good thermal and chemical stability and effectively hinder the movement of dislocations and grain boundaries,which results in improved mechanical properties both at room temperature and high temperature.This paper foucus on the the changes of nano-sized oxide particles(NPs)on manufraction and welding process.The effects of NPs on microstructure evolution and contributions to mechanical properties are systematically analyzed.In this paper,NPs are successfully introduced into ternary FeCoNi concentrated solid solution alloys(CSAs)by mechanical alloying.These NPs are uniformly distributed in the matrix and materials have shown better mechanical properties than some of the oxide dispersion strengthened(ODS)steels.Meanwhile,ODS 1050 and 2024 aluminum alloys are joined by friction stir welding(FSW)and the welding efficiency is 98%and 85%,respectively.This work is of great importance for the production of large-scale structural ingots and enlarge the application field of ODS aluminum alloys.Research based on FeCoNi CSAs during different stages are carried out and nano-sized Y2Ti2O7 with diameter around 34 nm are uniformlt distributed in the matrix.Submicron grains and the NPs lead to high compressive yield strengths both at room temperature and 700?.Different types of the NPs are introduced into FeCoNi CSAs and it is found that the texture component changes during the hot rolling process,while this evolution is partially suppressed by the Y2O3 particles in FeCoNi-1.5Y2O3(FCNY)CSAs,and further inhibited by finer and higher-volume-fraction Y2Ti2O7 particles in FeCoNi-1.2Ti-1.5Y2O3(FCNTY)CSAs.Monoclinic Y2O3 and pyrochlore Y2Ti2O7 particles are both show a semicoherent relationship with the matrix.Monoclinic Y2O3 particles are transformed from precipitated cubic Y2O3 particles.Higher annealing temperature and shorter annealing time could effectively reduce the size of the NPs.The enhanced strength in FCNY and FCNTY CSAs originates from the refined grains and high-density NPs.Cold rolling ODS 1050 aluminum alloys are successfully joined with the FSW method.?-Al2O3 particles are observed in the base metal(BM)and stir zone(SZ).Al2O3 particles are in near sphere shape and the number densities in BM and SZ are 6.25×1019/m3 and 7.49×1019/m3,respectively.Small angle neutron scattering results indicate diameter of Al2O3 particles in BM is around 69.3 nm.Particles in SZ are reduced slightly and volume fraction is 2.66%.For commercial 1050 and ODS 1050 aluminum alloys,continuous dynamic recrystallization(CDRX)phenomenon is observed in SZ.While discontinuous dynamic recrystallization phenomenon occurs in thermo-mechanically affected zone(TMAZ)due to the existence of nano-sized Al2O3 particles in ODS 1050 alloys.CDRX is the dominant mechanism in SZ in ODS 2024 aluminum alloys.Textures in SZ and TMAZ are similar to those in HAZ,which reveals that microstructures are stable because of the NPs and second phase particles.?-Al2O3 are observed in BM and SZ in ODS 1050 aluminum alloys.Second-phase particles are S(Al2CuMg)phase and ?(CuAl2)phase in BM in commercial 2024 aluminum alloys.S phase and ? phase dissolve into the matrix during welding process and reprecipitate after welding.Complex metallic oxide particles(COMs)Ali.756Mn0.182Fe0.062(O(SiO4))phase and ? phase are observed in BM in ODS 2024 alloys.The COMs remain stable during welding but solution and reprecipitation of? phase results in new formed S phase in SZ.Strength in the whole joint and in SZ of commercial 1050 and ODS 1050 aluminum alloys is close to those in BM.In ODS 2024 aluminum alloys,joint efficiency is 85%for the whole joint.The above results indicate that FSW is a proper way to achieve well bonding joint of aluminum-based alloys.