Study On The Preparation And Properties Of Porous And Polymer Filled Porous TiNiCu Shape Memory Alloy

In order to develop novel high damping materials to meet the urgent needs of human society for vibration and noise reductions,porous and polymer filled porous TiNiCu shape memory alloys（SMAs）with excellent comprehensive properties were fabricated by powder metallurgy and sol-gel processes.The resultant specimens were characterized and their damping and quasi-static compression properties were tested by the measures of SEM,XRD,DSC,DMA and universal testing machine.The results show that the optimal preparation process of porous TiNiCu SMA is:after ball milling for 10 hours,Ti,Ni,Cu mixed powders are pressed at 350 MPa,and then sintered at 950℃for 2 hours under the protection of high-purity argon.The specimens prepared by this process have high sintering quality and stable three-dimensional network structure.The porous TiNiCu SMA is mainly composed of Ti（Ni,Cu）,Ti₂（Ni,Cu）and Ti（Ni,Cu）₂three different phases,and has excellent reverse and direct martensite transformation（MT）behaviors during heating and cooling processes.In the polymer filled porous TiNiCu SMAs,polyurethane and polystyrene can be completely filled in the pores of the alloys,and the interfaces are well bonded,without obvious cracks and other defects.Carbon nanotubes and graphite fillers can form good interfaces with the polymers.Porous TiNiCu SMA has excellent damping property,and its internal friction（IF）peak appears at around-20℃during heating.This peak has obvious dependence on the porosity,measuring frequency and heating rate of the specimen.After polyurethane and polystyrene are filled,the damping of porous TiNiCu SMA is significantly improved,and the addition of carbon nanotubes and graphite fillers in the polymers can further improve the damping.The high damping capacity of polymer filled porous TiNiCu SMAs originates from the superposition effect of many energy dissipation sources.These energy dissipation sources include:the energy dissipation caused by the intrinsic damping of porous TiNiCu SMA,polymer materials and inorganic fillers,as well as the energy dissipation caused by the interfacial damping inside the specimens.The stress-strain curves of the porous TiNiCu SMAs can be divided into three regions:elastic region,platform region and densification region.The long and flat stress platforms make the alloy have excellent quasi-static compression energy absorption characteristics.The introduction of polymers into the pores and the addition of inorganic fillers in the polymers can significantly improve the compression platform stress and energy absorption capacity of the porous TiNiCu SMAs,which is mainly attributed to the supporting effect of polymers on collapsing pores and the increase of mechanical properties of polymers after adding inorganic fillers.Compared with graphite,carbon nanotubes have better intrinsic properties,and after adding,higher density and better interfaces will formed,so its reinforcing effect is better under the condition of equal addition.