Effects Of Elemens Addition And Parent Phase Aging On The Damping And Mechanical Properties Of A Cu-Al-Mn Shape Memory Alloy

As a kind of very important high damping material,Cu-based shape memory alloys(SMAs)have a very broad application prospect.However,at present,the mechanical properties of these alloys are still low,and the damping ability still needs to be further improved.Therefore,in this paper,the effects of Nb and Ag additions and parent phase aging on the damping and mechanical properties of the Cu-11.9Al-2.5Mn(wt.%)SMA were systemically studied with the aim of providing ideas and theoretical basis for the improvement of comprehensive properties of Cu-based SMAs.The results show that parent phase aging has important effects on both martensitic transformation(MT)and damping properties of the Cu-Al-Mn SMA:with the increase of aging temperature,the characteristic temperatures(CTs)of the direct MT increase first and then decrease,while that of the reverse MT decrease monotonously;the damping at low temperatures and the internal friction(IF)peak arising from the reverse MT increase first and then decrease.When the aging temperature is 600?,they all reach the highest level.It is believed that the change of CTs of the MT is related to the precipitation of non-martensitic phases,the change of Al content and the annihilation of quenched-in vacancies,while the change of damping can be ascribed to the changes of interfacial mobility and the content of martensite.Nb element forms AlNb₃ phase in the Cu-Al-Mn SMAs,and due to its pinning effect on grain boundaries,the grains of the Cu-Al-Mn SMAs can be remarkably refined.When the content of Nb is 0.9 wt%,the average grain size can be reduced to about 30?m from the original 120?m.However,the Ag₃Al phase formed after adding Ag element has no obvious refining effect on grains.With the increase of Nb content,the CTs of MT decrease,and that of reverse MT increase.With the increase of Ag content,the CTs of MT decrease first and then increase,while the CTs of reverse MT increase monotonously.It is believed that the changes of MT CTs are related to the changes of grain boundary density,Al content and the formation of Nb-rich or Ag-rich phases.Proper additions of Nb and Ag elements can significantly improve the damping ability and mechanical properties of the Cu-Al-Mn SMA.In addition,compared with Nb element,the addition of Ag element has a higher damping enhancement ability for the Cu-Al-Mn shape memory alloy.The increase of damping capacity caused by Nb element can be attributed to the formation of Al Nb₃phase and the increase of various interface densities.The increase of damping capacity caused by Ag element can be attributed to the formation of Ag₃Al phase and the formation of Ag₃Al/Cu-Al-Mn interface.The increase of mechanical properties caused by Nb element can be attributed to the fine grain strengthening mechanism and Orowan strengthening mechanism.The increase of mechanical properties caused by Ag element can be attributed to the Orowan strengthening mechanism.