Effect Of Second Phase Particles On Flow Stress And Work Hardening Behaviors In Al-Mg Alloy

Al-Mg alloy is used in transport manufacturing and medical equipment due to its excellent properties like high specific strength and good corrosion resistance.However,the low strength of Al-Mg alloy limits its development and industrial applications in the frontier.In academic research,strategies like work hardening and second phase particle strengthening are often used to enhance the strength of Al-Mg alloy.Flow stress and work hardening behaviors are dominated by dislocation behaviors.The flow stress and work hardening behaviors of alloy materials have been studied extensively;however,the studies of alloys or composites reinforced by particles have been rarely reported.The particle-dislocation interactions contain shearing mechanism and bypassing mechanism,which corresponds to the shearing strengthening and Orowan strengthening.Different interactions between particles and dislocations have different effects on flow stress and work hardening behaviors of materials,but the mechanism of such effects is still unclear.Therefore,Al-Mg-Sc-Zr alloys and Ti B₂/Al-Mg composites were selected in this work to study the effect of nano shearable precipitates,nano non-shearable precipitates and non-shearable ceramic particles on flow stress and work hardening behaviors of Al-Mg alloy.In this work,Al-Mg alloy was selected as the basic research alloy.On the one hand,Sc and Zr elements were introduced to obtain Al-Mg-Sc-Zr alloys with different Al₃（Sc,Zr）precipitates by controlling the aging conditions;on the other hand,Ti B₂/Al-Mg composites reinforced by Ti B₂nano-ceramic particles were obtained by in-situ method.Firstly,the morphology and distribution of Al₃（Sc,Zr）precipitates in Al-Mg-Sc-Zr alloys and Ti B₂ nano-ceramic particles in Ti B₂/Al-Mg composites were studied by microstructure characterization.Then,the results of experiments and theoretical model show that the shearable and non-shearable precipitates and the ceramic particles have important effects on the dislocation multiplication,movement,storage and annihilation.Shearable precipitates leads to planar slip of dislocations and deformation band with higher local dislocation density,which brings a large amount of dislocation pile-ups and the increase of dislocation density.Lots of Orowan loops will accumulate around the non-shearable precipitates,and these accumulated Orowan loops could promote dislocation storage and dynamic recovery.Around Ti B₂ particles,a large number of geometric necessary dislocations（GNDs）that could promote back stress strengthening will be induced.In addition,this work also studied the influence of the strain rate on the flow stress and the working hardening behaviors of Al-Mg alloy reinforced by the second phase particles,and revealed the influence of the second phase particles on the dynamic recovery rate quantitatively by characterizing the dislocation density during deformation.In this paper,the flow stress and work hardening behaviors of the alloys and composites reinforced by the second phase particles are studied.The interaction between particles and dislocations is explored,which provides new insights for understanding the mechanical behaviors of alloys and composites reinforced by the second phase particles,as well as for designing new alloys and composites.