The Preparation Of Composite Material And Magnetostructural Transition Control Based On MM'X Alloy

Magnetostructural coupling in MM'X(M=Mn,Co or Ni,X=Si or Ge)system attracts considerable attention for the accompanied multi-magnetoresponsive effects.However,due to the large stress generated from the structural transformation,the alloys become shattered or powder-like,hindering the further investigation and their applications.The possible solution is embedding the MM'X powders into some metal matrix by hot pressing to improve its mechanical property.In this paper,we choose(MnNiSi)0.66(Fe2Ge)0.34 as a representative of MM'X alloy and produce(MnNiSi)0.66(Fe2Ge)0.34/Sn composite bulk by hot pressing.The composites exhibit stable magnetostructural transformation,large negative thermal expansion,improved magnetic-field driving capacity and broadened operating temperature range.Additionally,we also propose a simple formula based on the entropy-temperature diagram to calculate the isothermal entropy change,which is consistent with the results obtained by the Maxwell relation.Meanwhile,we selected MnCoGe alloy as the research object,using Sb elements to replace Ge elements to increase the distance between Mn elements and adjust the structural phase transition temperature to the Curie temperature window.Our study found that the structural phase transition temperature of MnCoGe1-xSbx alloy decreased with increasing Sb doping and the transition temperature was around room temperature in x = 0.05.The values of magnetic entropy change in MnCoGe0.95Sb0.05 alloy were 4.35 and 10.5 J·-kg-1·K-1 with ?B = 2 T and 5 T,respectively.The range of transformation temperature was more than 40 K.The values of refrigerate capability reached 53.78 and 131.35 J/kg with ?B = 2 T and 5 T,respectively.