Significant two-way shape memory effect(TWSME)was achieved in single crystals of single-phase multielement Ni42-x Cu8 Cox Mn37 Ga13(8≤x≤12)alloys by performing thermomechanical training.However,anomalous dependence ...Significant two-way shape memory effect(TWSME)was achieved in single crystals of single-phase multielement Ni42-x Cu8 Cox Mn37 Ga13(8≤x≤12)alloys by performing thermomechanical training.However,anomalous dependence of the martensitic transformation temperature span on Co content was observed.Before training,quite a narrow temperature span of the martensitic transformation,nearly independent of the Co content,was observed in all single crystals.After training the temperature span was still narrow for 8≤x≤10.9 but was obviously expanded for 10.9<x≤12.High-resolution transmission electron microscopy revealed that at the atomic scale,there exists incommensurate modulated structure in the single phase single crystals,as evidenced by nonperiodic satellite spots in the selected area electronic diffraction patterns.Moreover,the modulated wave vector of the satellite spots was increased by higher Co contents.Combining first principal calculations it was considered that the incommensurate modulated structure originates from the formation of Co-Co pairs.After training arrays of ordered dislocations with the same Burgers vector were introduced for 8≤x≤10.9 but the network of dislocations was formed for 10.9<x≤12.Based on analysis of transmission electron microscopy,geometric phase,thermodynamics,and Landau theory,it was considered that the austenite/martensite phase interface was pinned by the network of dislocations,expanding the temperature span of the martensitic transformation.This work supplies new insights for understanding the microstructure and martensitic transformation of Ni-Mn-Ga-based alloys.展开更多
The LaFe11.9–x Cox Si1.1 B0.25 with x=0.9 and x=0.82 compounds were synthesized from commercial purity raw materials.The magnetic property of LaFe11.9–x Cox Si1.1 B0.25 and Gd particles were tested on the reciprocat...The LaFe11.9–x Cox Si1.1 B0.25 with x=0.9 and x=0.82 compounds were synthesized from commercial purity raw materials.The magnetic property of LaFe11.9–x Cox Si1.1 B0.25 and Gd particles were tested on the reciprocating refrigerator at the same condition in order to compare the cooling capacity of the two materials.The results showed that the cooling velocity of Gd was obviously higher than that of LaFe11.9–x Cox Si1.1 B0.25.The maximum temperature span was 12.7 oC for LaFe11.0 Co0.9 Si1.1 B0.25,14.9 oC for Gd metal whose mass is the same as that of LaFe11.0 Co0.9 Si1.1 B0.25,8.1 oC for Gd metal whose volume is the same as that of LaFe11.0 Co0.9 Si1.1 B0.25.Series connection of LaFe11.0 Co0.9 Si1.1 B0.25 and LaFe11.08 Co0.82 Si1.1 B0.25 had the maximum cooling temperature span of 15.3 oC.展开更多
基金support from the National Key Research and Development Program of China(Grant No.2021YFB3501402)the National Natural Science Foundation of China(Grant Nos.52250313 and 52121001)Yang Liu and Chen Si acknowledge financial support from the National Natural Science Foundation of China(Grant No.12274013).
文摘Significant two-way shape memory effect(TWSME)was achieved in single crystals of single-phase multielement Ni42-x Cu8 Cox Mn37 Ga13(8≤x≤12)alloys by performing thermomechanical training.However,anomalous dependence of the martensitic transformation temperature span on Co content was observed.Before training,quite a narrow temperature span of the martensitic transformation,nearly independent of the Co content,was observed in all single crystals.After training the temperature span was still narrow for 8≤x≤10.9 but was obviously expanded for 10.9<x≤12.High-resolution transmission electron microscopy revealed that at the atomic scale,there exists incommensurate modulated structure in the single phase single crystals,as evidenced by nonperiodic satellite spots in the selected area electronic diffraction patterns.Moreover,the modulated wave vector of the satellite spots was increased by higher Co contents.Combining first principal calculations it was considered that the incommensurate modulated structure originates from the formation of Co-Co pairs.After training arrays of ordered dislocations with the same Burgers vector were introduced for 8≤x≤10.9 but the network of dislocations was formed for 10.9<x≤12.Based on analysis of transmission electron microscopy,geometric phase,thermodynamics,and Landau theory,it was considered that the austenite/martensite phase interface was pinned by the network of dislocations,expanding the temperature span of the martensitic transformation.This work supplies new insights for understanding the microstructure and martensitic transformation of Ni-Mn-Ga-based alloys.
基金supported by National High Technology Research and Development Program of China(2011AA03A404)International Cooperation Program(2011DFA53230)+1 种基金National Natural Science Foundation of China(51261001)Science Foundation of Inner Mongolia(2011MS0801)
文摘The LaFe11.9–x Cox Si1.1 B0.25 with x=0.9 and x=0.82 compounds were synthesized from commercial purity raw materials.The magnetic property of LaFe11.9–x Cox Si1.1 B0.25 and Gd particles were tested on the reciprocating refrigerator at the same condition in order to compare the cooling capacity of the two materials.The results showed that the cooling velocity of Gd was obviously higher than that of LaFe11.9–x Cox Si1.1 B0.25.The maximum temperature span was 12.7 oC for LaFe11.0 Co0.9 Si1.1 B0.25,14.9 oC for Gd metal whose mass is the same as that of LaFe11.0 Co0.9 Si1.1 B0.25,8.1 oC for Gd metal whose volume is the same as that of LaFe11.0 Co0.9 Si1.1 B0.25.Series connection of LaFe11.0 Co0.9 Si1.1 B0.25 and LaFe11.08 Co0.82 Si1.1 B0.25 had the maximum cooling temperature span of 15.3 oC.
