Evolution Of Microstructure And Properties Of In-situ TiB₂/Al-Cu-Li Composites Under Different Deformation Conditions

The Al-Li based alloys are becoming the new material with great potential in the aerospace industry,owing to their excellent combination of low density,high elastic modulus and high specific stiffness.In order to further improve the comprehensive performance of the Al-Li based alloys,the microsized or nanosized ceramic reinforcement can be added to form an Al-Li matrix composites,as a result overall performance of the material can be further improved by combining the advantages of the reinforcement,such as the high elastic modulus,high specific strength,good wear resistance and chemical stability,etc..TiB₂/Al–Cu-Li composite was synthesized by an in-situ mixed salt reaction method,and the microstructure evolution during deformation and heat treatment was quantitatively evaluated by using scanning electron microscopy,transmission electron microscopy,electron backscatter diffraction technique and X-ray diffraction.The Al–Cu-Li matrix alloy was also studied as a comparison to reveal the effects of in-situ TiB₂ particles on the microstructure and mechanical properties of the matrix alloy.The results show that the average TiB₂ particle size of in-situ TiB₂/Al-Cu-Li composite is⁷1.99nm and most particles?82.9%?are smaller than 100nm.The co-existence of Cu-rich intermetallic phases and TiB₂ particles aggregates can be observed in as-cast or aged composite.There are strong<111>and<l00>fiber textures in as-extruded matrix alloy and composite,however the volume fraction and intensity of<111>and<l00>fibers of alloy decreased rapidly after solution treatment,which are preety stable for the composite,and huge of<l13>fiber textures has emerged in the alloy.Nanosized particles play an important part in modifying the recrystallization behavior of the composite by increasing both the driving force and the retarding force of the process.It is obvious that the volume fraction of recrystallized microstructures is higher in the composite sample since the PSN has developed along with the TiB₂ clusters.But the particles dispersed inside Al grains inhibited the dynamic recovery of the substructure during the deformation due to the Zener pinning effect on dislocation movement.Meanwhile the particles play as as obstacles for grain boundary movement to inhibite the growth of substructure.??,??,T1,and S are observed in the under-aged composite,but there are only??in the alloy.T1 and S phases in peak-aged composite have not only higher number density but also a smaller size.Moreover the T1 phases of the composite have connected with each other to form a continuous network,affecting strength increment.Compared with peak-aged matrix alloy,the yield strength and ultimate tensile strength of composite have increased by248MPa?65.4%?and 152MPa?30.7%?,respectively.Besides,the specific strength improves 33%.At the same time,FSP was used to further improve the microstructure of in-situ TiB₂/Al-Cu-Li composites.The results show that the microstructure the in nugget zone is preety uniform without the presence of particle clusters and Cu-rich intermetallic phases.The average grain size is²?m,and 81.8%grains are recrystallized.Moreover,there are only feeble recrystallization textures and shear textures,and the overall crystallographic textures are almost random.