The bainite structure in a Cu-Zn-A1 alloy related to the reverse shape memory effect has been observed by means of TEM.The reverse memory effect may be improved by up to one order of magnitude under applied constraint...The bainite structure in a Cu-Zn-A1 alloy related to the reverse shape memory effect has been observed by means of TEM.The reverse memory effect may be improved by up to one order of magnitude under applied constraint stress.The widespread propagation of bainite was confirmed to be the diffusion controlled shear process by the parabolic configuration of side interface of bainite plate and the twisting of intersected bainite plates.展开更多
The interior structural evolution accompanying reverse shape memory effect (RSMEin a Cu-Zn-Al alloy was studied by means of transmission electron microscopy. It was found that RSME is closely related to bainitic trans...The interior structural evolution accompanying reverse shape memory effect (RSMEin a Cu-Zn-Al alloy was studied by means of transmission electron microscopy. It was found that RSME is closely related to bainitic transformation in this alloy during the isothermal reaction at moderate temperatures. At a given temperature and a certain external constraint stress, the shape memory effect depends mainly on the aging time.During the early stage, the shape memory effect enhances with the increase of reactiotn time. Then it will decrease gradually apon further aging. If the alloy is overaged, the stacking faults of bainite will disappear gradually by the motion of partial dislocations through which long range diffusion of solute atoms takes place, giving rise to the deterioration of RSME. When all the bainite transforms to α phase, RSME will lose completely.展开更多
Polymers with reversible plasticity shape memory effect(RPSME)have attracted considerable attention due to their simple programming and large deformation.However,the exact mechanisms of RPSME are still not thoroughly ...Polymers with reversible plasticity shape memory effect(RPSME)have attracted considerable attention due to their simple programming and large deformation.However,the exact mechanisms of RPSME are still not thoroughly understood.In this work,the RPSME of SEBS/crystallizable paraffin was investigated by comparatively analyzing the performances and microstructures of samples with different paraffin content.It was found the shape fixing ratios(Rfs)of samples increased with the paraffin content,and interestingly,a significant improvement in Rf was observed when the paraffin content exceeded 60 wt%.Tensile test results showed that the deformation characteristics of samples changed from elastic to plastic as the paraffin content increased above 60 wt%.By exploring the crystallization behaviors of paraffin in various SEBS/paraffin samples,it was revealed that the microstructures of SEBS/paraffin were different when the paraffin content was below 50 wt%and above 60 wt%.In samples with low paraffin content(below 50 wt%),nearly all paraffin was co-crystallized with ethylene-co-butylene(EB)chains and its crystallization was severely restricted;while in samples with high paraffin content(above 60 wt%),“excess”paraffin appeared and this part of paraffin crystallized on the template of the EB/paraffin co-crystals,which might be responsible for the elastic-to-plastic transition and the sharp increase in Rf.Based on the above results,a possible structural model was proposed to explain the exact mechanism of RPSME in SEBS/paraffin.展开更多
文摘The bainite structure in a Cu-Zn-A1 alloy related to the reverse shape memory effect has been observed by means of TEM.The reverse memory effect may be improved by up to one order of magnitude under applied constraint stress.The widespread propagation of bainite was confirmed to be the diffusion controlled shear process by the parabolic configuration of side interface of bainite plate and the twisting of intersected bainite plates.
文摘The interior structural evolution accompanying reverse shape memory effect (RSMEin a Cu-Zn-Al alloy was studied by means of transmission electron microscopy. It was found that RSME is closely related to bainitic transformation in this alloy during the isothermal reaction at moderate temperatures. At a given temperature and a certain external constraint stress, the shape memory effect depends mainly on the aging time.During the early stage, the shape memory effect enhances with the increase of reactiotn time. Then it will decrease gradually apon further aging. If the alloy is overaged, the stacking faults of bainite will disappear gradually by the motion of partial dislocations through which long range diffusion of solute atoms takes place, giving rise to the deterioration of RSME. When all the bainite transforms to α phase, RSME will lose completely.
基金financially supported by the National Natural Science Foundation of China (Nos.51773040 and 52173056)。
文摘Polymers with reversible plasticity shape memory effect(RPSME)have attracted considerable attention due to their simple programming and large deformation.However,the exact mechanisms of RPSME are still not thoroughly understood.In this work,the RPSME of SEBS/crystallizable paraffin was investigated by comparatively analyzing the performances and microstructures of samples with different paraffin content.It was found the shape fixing ratios(Rfs)of samples increased with the paraffin content,and interestingly,a significant improvement in Rf was observed when the paraffin content exceeded 60 wt%.Tensile test results showed that the deformation characteristics of samples changed from elastic to plastic as the paraffin content increased above 60 wt%.By exploring the crystallization behaviors of paraffin in various SEBS/paraffin samples,it was revealed that the microstructures of SEBS/paraffin were different when the paraffin content was below 50 wt%and above 60 wt%.In samples with low paraffin content(below 50 wt%),nearly all paraffin was co-crystallized with ethylene-co-butylene(EB)chains and its crystallization was severely restricted;while in samples with high paraffin content(above 60 wt%),“excess”paraffin appeared and this part of paraffin crystallized on the template of the EB/paraffin co-crystals,which might be responsible for the elastic-to-plastic transition and the sharp increase in Rf.Based on the above results,a possible structural model was proposed to explain the exact mechanism of RPSME in SEBS/paraffin.
