Mechanism of plasticity enhancement of AZ31B magnesium alloy sheet by accumulative alternating back extrusion

Accumulative alternating back extrusion was a potential fine-grain modification method.In this paper,it was an innovative attempt to develop high-performance magnesium alloy sheet by this process.Under the condition of 350 K,commercial AZ31 magnesium alloy was made into billet by accumulative alternating back extrusion,and then extruded into fine-grain magnesium alloy sheet.Through a systematic study of its microstructure and mechanical properties,the results showed that the initial state had an important influence on the evolution of the structure during extrusion.After accumulative alternating back extrusion to produce the billet,the grain size of the sheet obtained by extrusion was significantly refined,which was related to the accumulation of deformation and grain refinement during the alternating loading process.Grain refinement caused the proportion of dynamic recrystallization inside the sheet with 2 cycles of accumulative alternating back extrusion to drop to 27%.With the increase of extrusion cycles from 2 to 4,the high density of dislocations led to an increase in the proportion of dynamic recrystallization and finer grains.The texture changed from strong basal texture to weak bimodal texture.The results of uniaxial tensile test show that due to grain refinement and texture change,the yield strength was significantly reduced,and the plasticity was significantly improved.It was verified that accumulative alternating back extrusion was meaningful for subsequent processing,and it also provided scientific guidance for the development of fine-grained magnesium alloy sheet.

Low-temperature processing of LiZn-based ferrite ceramics by co-doping of V_(2)O_(5)and Sb_(2)O_(3):Composition,microstructure and magnetic properties

Low-temperature fired ferrites or ceramics are usually processed by using low-melting materials(e.g.,glasses,oxides,and eutectics)as sintering aids to obtain compact and uniform microstructures.Herein,a dual-strategy of co-doping with V_(2)O_(5)and Sb_(2)O_(3)oxides and forming a eutectic liquid phase has been employed to reduce the melting point of LiZn ferrite ceramics in an effective way.The results indicate that miniscule amounts of V_(2)O_(5)and Sb_(2)O_(3)co-doping contribute in producing dense and uniform microstructures with enhanced magnetic performance by low-temperature firing.The phase structural and microstructural evolutions have been studied in detail.Thereafter their correlations with magnetic properties have been revealed.Enhanced magnetic performance(B_(s)=475.4 mT,M_(s)=82.51 emu/g,B_(r)/B_(s)=0.85,H_(c)=2.2 Oe,ΔH=153.8 Oe)of the LiZn-based ferrite ceramics is achieved by optimized composition and microstructure,which shows great potential for microwave applications including phase shifters and radars.More importantly,such a co-doping strategy can be also extended to other material systems,like dielectric ceramics,hexagonal ferrites or piezoelectric ceramics.