1.Introduction.The Ti6Al4V alloy is extensively utilized across various indus-trial sectors due to its favorable characteristics,such as lightweight design,high strength,and resistance to corrosion[1].In effort s to f...1.Introduction.The Ti6Al4V alloy is extensively utilized across various indus-trial sectors due to its favorable characteristics,such as lightweight design,high strength,and resistance to corrosion[1].In effort s to further reduce weight,functional elements like electric actuators can be substituted with intelligent materials like shape memory alloys(SMAs)[2,3].Among SMAs,NiTi alloy stands out for its sens-ing and actuation capabilities,significantly enhancing the safety and reliability of engineering structures[4,5].Integrating Ti6Al4V and NiTi alloys within a single component holds the potential to provide precise feedback on mechanical,thermal,or environmen-tal conditions[6,7].展开更多
It is well known that coarse-grained super-elastic NiTi shape memory alloys(SMAs)exhibit localized rather than homogeneous martensite transformation(MT),which,however,can be strongly influenced by either internal size...It is well known that coarse-grained super-elastic NiTi shape memory alloys(SMAs)exhibit localized rather than homogeneous martensite transformation(MT),which,however,can be strongly influenced by either internal size(grain size,GS)or the external size(geometric size).The coupled effect of GS and geometric size on the functional properties has not been clearly understood yet.In this work,the super-elasticity,one-way,and stress-assisted two-way shape memory effects of the polycrystalline NiTi SMAs with different aspect ratios(length/width for the gauge section)and different GSs are investigated based on the phase field method.The coupled effect of the aspect ratio and GS on the functional properties is adequately revealed.The simulated results indicate that when the aspect ratio is lower than about 4:1,the stress biaxiality and stress heterogeneity in the gauge section of the sample become more and more obvious with decreasing the aspect ratio,which can significantly influence the microstructure evolution in the process involving external stress.Therefore,the corresponding functional property is strongly dependent on the aspect ratio.With decreasing the GS and the aspect ratio(to be lower than 4:1),both the aspect ratio and GS can affect the MT or martensite reorientation in each grain and the interaction among grains.Thus,due to the strong internal constraint(i.e.,the constraint of grain boundary)and the external constraint(i.e.,the constraint of geometric boundary),the capabilities of the functional properties of NiTi SMAs are gradually weakened and highly dependent on these two factors.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52235006)the National Key Research and Development Program of China(Grant No.2022YFB4600500)+3 种基金the National Natural Science Foundation of China(Grant Nos.52025053 and 52105303)the Natural Science Foundation of Jilin Province(Grant No.20220101209JC)the Postdoctoral Fellow-ship Program of CPSF(Grant GZC20240587 and GZC20230944)the Graduate Innovation Fund of Jilin University(2024CX063).
文摘1.Introduction.The Ti6Al4V alloy is extensively utilized across various indus-trial sectors due to its favorable characteristics,such as lightweight design,high strength,and resistance to corrosion[1].In effort s to further reduce weight,functional elements like electric actuators can be substituted with intelligent materials like shape memory alloys(SMAs)[2,3].Among SMAs,NiTi alloy stands out for its sens-ing and actuation capabilities,significantly enhancing the safety and reliability of engineering structures[4,5].Integrating Ti6Al4V and NiTi alloys within a single component holds the potential to provide precise feedback on mechanical,thermal,or environmen-tal conditions[6,7].
基金supported by the National Natural Science Foundation of China (Grant Nos.12202294 and 12022208)the Project funded by China Postdoctoral Science Foundation (Grant No.2022M712243)the Fundamental Research Funds for the Central Universities (Grant No.2023SCU12098).
文摘It is well known that coarse-grained super-elastic NiTi shape memory alloys(SMAs)exhibit localized rather than homogeneous martensite transformation(MT),which,however,can be strongly influenced by either internal size(grain size,GS)or the external size(geometric size).The coupled effect of GS and geometric size on the functional properties has not been clearly understood yet.In this work,the super-elasticity,one-way,and stress-assisted two-way shape memory effects of the polycrystalline NiTi SMAs with different aspect ratios(length/width for the gauge section)and different GSs are investigated based on the phase field method.The coupled effect of the aspect ratio and GS on the functional properties is adequately revealed.The simulated results indicate that when the aspect ratio is lower than about 4:1,the stress biaxiality and stress heterogeneity in the gauge section of the sample become more and more obvious with decreasing the aspect ratio,which can significantly influence the microstructure evolution in the process involving external stress.Therefore,the corresponding functional property is strongly dependent on the aspect ratio.With decreasing the GS and the aspect ratio(to be lower than 4:1),both the aspect ratio and GS can affect the MT or martensite reorientation in each grain and the interaction among grains.Thus,due to the strong internal constraint(i.e.,the constraint of grain boundary)and the external constraint(i.e.,the constraint of geometric boundary),the capabilities of the functional properties of NiTi SMAs are gradually weakened and highly dependent on these two factors.
