| Due to the low density,high strength and good weldability,7B52 laminated(7A62/7A01/7A52)aluminum alloy can be widely used in tanks,armored vehicles,and air defense fortress.However,with the upgrading of military equipment such as anti-tank weapons and long-range strikes,the improvement of elastic resistance of 7B52 laminated aluminum alloy has become a research hotspot.It focused on improving the strength and toughness of 7B52 laminated aluminum alloy,and a suitable interrupted aging process was explored in this work.The mechanical properties of the alloy were tested using the universal testing machine and the split Hopkinson pressure bar device(SHPB).The microstructures of the alloy were analyzed by OM,SEM and TEM.The results are presented as follows:(1)The effect of T6I6 interrupted aging on microstructure and tensile properties of 7B52 laminated aluminum alloy was investigated.It has been found that during the T6I6 aging treatment,since the ?' has undergone two nucleation,compared to the T6 aging,the ?' formed under the T6I6 interrupted aging is more diffuse and finer.and yield and tensile strength have increased by 23 MPa and 21 MPa in comparison with T6 aging,respectively.Due to high-content of Mg and Zn,the secondary precipitation of ?' occurred in 7A62.This leaded to extra reinforcement,and yield and tensile strength of 7A62 were 155.0 and 120.2MPa higher than those of 7A52.The remarkable difference of tensile strength between 7A62 and 7A01 resulted in weak interface bonding between them.By contrast,the bonding strength of7A52/7A01 was relatively high,significant plastic deformation was observed near interface,and fracture section was irregular after tensile test.The best interrupted-aging process was120 ?/2 h + 65 ?/20 d + 120 ?/18 h.(2)The effect of T6I6 interrupted aging on the impact resistance of 7B52 laminated aluminum alloy was investigated.The result showed that the strain rate of 7B52 laminated aluminum alloy has the same variation tendency with the dynamic yield stress and the energy absorption capacity.The dynamic yield stress and energy absorption capacity of 7B52-T6I6 laminated aluminum alloy are greater than those of 7B52-T6 laminated aluminum alloy,while in the same strain rate.Because the density of ?' in 7B52-T6I6 aluminum alloy is larger than that in 7B52-T6 aluminum alloy,the density of dislocation tangles and the stress required for dislocation tangles collapse are both larger than that in 7B52-T6I6 aluminum alloy.Therefore,the impact resistance of 7B52-T6I6 laminated aluminum alloy is higher than 7B52-T6 laminated aluminum alloy.(3)The nonuiform deformation mechanism of 7B52-T6I6 laminated aluminum alloy after dynamic impact was studied.It has been found that,during the impact deformation process,most of the plastic deformation was concentrated in the 7A52 layer alloy,which ascribed to the huge discrepancy between 7A62 and 7B52 layer alloy.When the strain rate increased,the microstructure of 7A52 layer alloy changes from slight deformation to DSB,and from DSB to TSB,while the microstructure of 7A62 layer alloy changed slightly;At the same time,the dislocation density of the 7A52 layer alloy is always greater than that of the7A62 layer alloy during the impact.And the precipitated phase of 7A52 layer alloy is almost completely integrated into the matrix.It is owing to the 7A52 layer alloy sustain higher strain,which leads to a high dislocation density.With the movement of dislocation,the precipitated phase is continuously cut through,and thus the precipitated phase is integrated into the Al matrix.However,in the 7A62 layer,under the combined action of precipitated phases and dislocations,the resistance to deformation increased.Owing to the difference of resistance to deformation between the 7A52 layer and the 7A62 layer,the nonuniform deformation can be observed inthe 7B52-T6I6 laminated aluminum alloy. |
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