The deformed microstructures of a TiNi shape memory alloy were investigated in present study to clarify the deformation mechanism.It is found that the stress-strain curve was divided into three stages based on the def...The deformed microstructures of a TiNi shape memory alloy were investigated in present study to clarify the deformation mechanism.It is found that the stress-strain curve was divided into three stages based on the deformation modes.The cause of martensitic stabilization effect was also interpreted by paying special attention to the deformed microstructures.Transmission electron microscopic examination revealed that at the early stage of deformation martensitic reorientation and compound twinning relieved some of the elastic strain energy stored in martensite,and this contributes to the martensitic stabilization effect.However,when deformation strain became larger,the density of dislocations increased correspondingly.Antiphase boundaries were also found.The degree of ordering was therefore decreased due to dislocations and antiphase boundaries.So disordering was another cause of martensitic stabilization effect.In the middle stage of deformation martensitic stabilization was attributed to the two reasons above.展开更多
Martensitic stabilization caused by deformation in a TiNi shape memory alloy was studied.Special attention was paid to the deformed microstructures to identify the cause of martensitic stabilization.Martensitic stabil...Martensitic stabilization caused by deformation in a TiNi shape memory alloy was studied.Special attention was paid to the deformed microstructures to identify the cause of martensitic stabilization.Martensitic stabilization was demonstrated by differential scanning calorimetry for the tensioned TiNi shape memory alloy.Transmission electron microscopy revealed that antiphase boundaries were formed because of the fourfold dissociation of [110]B19＇ super lattice dislocations and were preserved after reverse transformation due to the lattice correspondence.Martensitic stabilization was attributed to dislocations induced by deformation,which reduced the ordering degree of the microstructure,spoiled the reverse path from martensite to parent phase compared with thermoelastic transformation,and imposed resistance on phase transformation through the stress field.展开更多
文摘The deformed microstructures of a TiNi shape memory alloy were investigated in present study to clarify the deformation mechanism.It is found that the stress-strain curve was divided into three stages based on the deformation modes.The cause of martensitic stabilization effect was also interpreted by paying special attention to the deformed microstructures.Transmission electron microscopic examination revealed that at the early stage of deformation martensitic reorientation and compound twinning relieved some of the elastic strain energy stored in martensite,and this contributes to the martensitic stabilization effect.However,when deformation strain became larger,the density of dislocations increased correspondingly.Antiphase boundaries were also found.The degree of ordering was therefore decreased due to dislocations and antiphase boundaries.So disordering was another cause of martensitic stabilization effect.In the middle stage of deformation martensitic stabilization was attributed to the two reasons above.
文摘Martensitic stabilization caused by deformation in a TiNi shape memory alloy was studied.Special attention was paid to the deformed microstructures to identify the cause of martensitic stabilization.Martensitic stabilization was demonstrated by differential scanning calorimetry for the tensioned TiNi shape memory alloy.Transmission electron microscopy revealed that antiphase boundaries were formed because of the fourfold dissociation of [110]B19＇ super lattice dislocations and were preserved after reverse transformation due to the lattice correspondence.Martensitic stabilization was attributed to dislocations induced by deformation,which reduced the ordering degree of the microstructure,spoiled the reverse path from martensite to parent phase compared with thermoelastic transformation,and imposed resistance on phase transformation through the stress field.
