Effect of pre-strain on tensile mechanical properties of 2195 aluminum-lithium alloy
The effects of different stretching pre-strains on the tensile mechanical properties of 2195 aluminum-lithium alloy after aging at 155℃were studied by hardness test,room temperature tensile test,electron backscatter diffraction analysis(EBSD),transmission electron microscopy(TEM)and digital image correlation(DIC).The results show that the ultimate tensile stresses at the stretching pre-strain of 2%,4%,6%and 8%are 560.4 MPa,570.8 MPa,573.6 MPa and 575.9 MPa.With the increase of stretching pre-strain,the strength of the alloy continues to increase,which is because the dislocation is a favorable nucleation point for the strengthened phase T1 phase,and the increase of stretching pre-strain increases the dislocation density and the number density of T1 phase.However,with the increase of stretching pre-strain,the strength increase amplitude of stretching pre-strain on the alloy gradually decreases,which is mainly caused by entanglement and accumulation of dislocation and precipitation of phase nucleation points.As the stretching pre-strain increases from 2%to 8%,the elongation of the alloy decreases from 9.6%to 6.4%.It can be observed that the increase of stretching pre-strain makes the strain concentration phenomenon in the tensile process advance and the necking stability decreases by digital image correlation.This is due to the large stretching pre-strain will cause the strain distribution of the alloy in the stretching pre-strain to be uneven,and broken deformation microstructure grains appear in the alloy.The grain orientation of these deformation microstructure grains are different from other grain around them,which is more conducive to the initiation and propagation of microcracks.Therefore,considering the tensile mechanical properties of 2195 aluminum-lithium alloy under different stretching pre-strain,4%stretching pre-strain can make 2195 aluminum-lithium alloy achieve the best strong plastic matching,with ultimate tensile stress of 570.8 MPa,yield stress of 543.4 MPa and elongation of 8.7%.
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