| In this paper,Cu-Al-Mn-La shape memory alloy is considered as an object of study.The use of OM,SEM,TEM,XRD,DSC,tensile test,bending test and memory performance test,multi-functional internal instrument and other means to study four different groups of Al and Mn contents were 1#:Cu-7.7Al-8.7Mn-0.3La,2#:Cu-8.1Al-7.2Mn-0.3La,3#:Cu-8.8Al-5.9Mn-0.3La and 4#:Cu-10.3Al-4.4Mn-0.3La alloy;and after 1.7%,3.5%,5%,7.9%,9.8% pre-stretching deformation of 3#:Cu-8.8Al-5.9Mn-0.3La microstructure,the shape recovery rate,mechanical properties,phase change properties,damping property changes.The results of the study show that:Prepare four groups of aluminum alloy,low content of 1# alloy under high temperature,the component falls in the ?+? phase region,resulting in the alloy solution and aging heat treatment after the order degree is too low and contains a large number of ?' martensite,memory performance is only 15.2%,no phase damping peak;while the 2# alloy based on 1# the content of aluminum alloy to 8.1%,although the disordered ?' martensite decreased,alloy overall order has increased,but the memory performance is only 43%,the damping peak is only 0.0481.Therefore,although the 1# and 2# alloy with low aluminum content has excellent mechanical properties(1# alloy strength is as high as 904.2MPa,the elongation rate is 11.33%),but because of the low order degree,the memory and damping properties are too poor,so that the two alloys have no practical value.Compared with 2# alloy,3# alloy increased the aluminum content to 8.8%,the order degree of the alloy also increased,the shape recovery rate of bending deformation was 95.4%,the damping peak value of phase transformation was 0.0996,the tensile strength was 674.6MPa,the elongation rate was 8.6%,and the comprehensive properties were excellent.Continue to increase the content of aluminum to 10.3% while the order of the phase transition continues to rise,the damping peak is greatly improved,the memory performance of up to 100%,but because of the brittle phase,the serious deterioration of the mechanical properties of the alloy,the tensile strength decreases to 450 MPa,the elongation rate is only 2.9%,which belongs to brittle fracture.According to the preparation of four different components of the memory alloy,the 3#Cu8.8Al5.9Mn0.3La alloy has good comprehensive properties and has the potential of practical use.Different degrees of tensile deformation were made on the basis of the aged 3# alloy.It is found that martensite reorientation has been started at 1.7% deformation,and reorientation is complete when the deformation amount is 5%.A large number of deformation twins and martensite rotations crushing are produced when the pre-deformation continues to increase,which has a negative effect on the continuity of the original martensite interface.The pre-deformation will increase the temperature of the martensitic positive inversion in varying degrees,and the higher the pre-deformation amount,the greater the temperature rise.The strain energy provided by the pre-deformation is stored in the reorientation martensite,which increase the starting temperature of the martensitic positive phase transition.The large number of dislocation produced by the deformation increases the friction resistance of the positive and inverse phase transition,thus improving the thermal hysteresis of the phase transition.The change of the internal friction of the alloy before and after the pre-deformation is better in accordance with the G-L dislocation model.The deformation is less than 5% with the increase of pre-deformation alloy,movable dislocation density increasing,the damping performance is improved;but the deformation is too large due to a large number of dislocation tangles and martensite deformation caused by rotation of breakage and deformation twinning as strong pinning dislocation,the dislocation mobility decreased,which reduce the damping properties. |
PDF Full Text Request