Alloying and magnetic disordering effects on phase stability of Co_(2)YGa(Y=Cr,V,and Ni)alloys:A first-principles study  

作　　者：Chun-Mei Li Shun-Jie Yang Jin-Ping Zhou 李春梅;杨顺杰;周金萍(College of Physics Science and Technology,Shenyang Normal University,Shenyang 110034,China)

机构地区：[1]College of Physics Science and Technology,Shenyang Normal University,Shenyang 110034,China

出　　处：《Chinese Physics B》2022年第5期513-526,共14页中国物理B（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.12174269,11674233and 51301176);the China Postdoctoral Science Foundation(Grant Nos.2013M530133 and 2014T70264);the Natural Science Foundation of Liaoning Province,China(Grant Nos.2019-MS-287 and L201602672)。

摘　　要：The alloying and magnetic disordering effects on site occupation,elastic property,and phase stability of Co_(2)Y Ga(Y=Cr,V,and Ni)shape memory alloys are systematically investigated using the first-principles exact muffin-tin orbitals method.It is shown that with the increasing magnetic disordering degree y,their tetragonal shear elastic constant C′(i.e.,(C_(11)-C_(12))/2)of the L2_(1) phase decreases whereas the elastic anisotropy A increases,and upon tetragonal distortions the cubic phase gets more and more unstable.Co_(2)Cr Ga and Co_(2)VGa alloys with y≥0.2 thus can show the martensitic transformation(MT)from L2_(1)to D0_(22)as well as Co_(2)Ni Ga.In off-stoichiometric alloys,the site preference is controlled by both the alloying and magnetic effects.At the ferromagnetism state,the excessive Ga atoms always tend to take the Y sublattices,whereas the excessive Co atom favor the Y sites when Y=Cr,and the excessive Y atoms prefer the Co sites when Y=Ni.The Ga-deficient Y=V alloys can also occur the MT at the ferromagnetism state by means of Co or V doping,and the MT temperature TMshould increase with their addition.In the corresponding ferromagnetism Y=Cr alloys,nevertheless,with Co or Cr substituting for Ga,the reentrant MT(RMT)from D0_(22)to L2_(1)is promoted and then TMfor the RMT should decrease.The alloying effect on the MT of these alloys is finally well explained by means of the Jahn-Teller effect at the paramagnetic state.At the ferromagnetism state,it may originate from the competition between the austenite and martensite about their strength of the covalent banding between Co and Ga as well as Y and Ga.

关 键 词：FIRST-PRINCIPLES martensitic transformation elastic modulus magnetic ordering shape memory alloys 

分 类 号：TG139.6[一般工业技术—材料科学与工程]