First-principles Study On The Structure And Mechanical Properties Of Alloyed Mo₂NiB₂

Mo₂NiB₂ based cermets has become a promising alternative to conventional cemented carbide,because of its good of wear resistance,excellent corrosion resistance and high temperature stability.However,Mo₂NiB₂ based cermets have the following problems:At room temperature,its bending strength and hardness is still different from that of WC-Co cemented carbide.As a potential alternative to traditional cemented carbide,it needs the further improvement,that alloying plays an important role in the modification of Mo₂NiB₂ based cermets.But related researches mainly focused on the use of experimental methods for analysis,and cannot flully reveal the intrinsic causes of the influence of alloying elements on the properties of Mo₂NiB₂ based cermets.Therefore,in order to improve the properties of Mo₂NiB₂ based cermets,the influence of alloying elements on the structure and mechanical properties of Mo₂NiB₂ was investigated.The electronic structure of?Mo,X?2?Ni,X?B2?X=Cr,V,Co,Fe,Mn,Ti,Nb,Zr?systems is calculated by first principles.Crystal structure and mechanical properties are systematically studied;the thermodynamic stability of the Mo₂NiB₂ alloying system was determined;the electronic structure properties such as the density of states and the elastic modulus,shear modulus,Young's modulus,Poisson's ratio,hardness and other mechanical properties of the system were calculated;the influence of the Mo₂NiB₂ alloying system was analyzed.The intrinsic causes of mechanical properties provide a scientific basis for composition design and sintering process optimization of Mo₂NiB₂ based cermets.The results calculated in this paper are as follows:?1?The addition of Cr elements in Mo₂NiB₂,the structure changes from rhombic square to square,which can increase its corrosion resistance.The crystal structure of Cr atoms replacing Ni and Mo in the tetragonal Mo₂NiB₂ is more stable,and the crystal structure of the tetragonal Mo₂NiB₂ is more stable and excellent mechanical properties as the increaseing of Cr content.According to the calculation of the formation of crucible,the mechanical properties and the electronic structure,the alloy compound obtained when the Cr content is 10 at.%to 15 at.%is more stable than the crystal structure of the orthogonal Mo₂NiB₂ with more excellent mechanical properties.?2?After the structure of V doped in Mo₂NiB₂ is changed,the crystal structure of V atoms replacing Ni and Mo in the tetragonal M22NiB2 is more stable,and the crystal structure of tetragonal Mo₂NiB₂ is more stable and excellent mechanical properties as the V content increases.According to the calculation of the formation of the crucible,the mechanical properties and the electronic structure,the alloy compound obtained when the V content is 15 at.%is more stable than the crystal structure of orthogonal Mo₂NiB₂ with more excellent mechanical properties.?3?Without transforming the structure of Mo₂NiB₂,10 at.%of X?X = Co,Fe,Mn,Ti,Nb,Zr?atoms were added replace the central atom Ni,and their formation enthalpies,mechanical properties,and electronic structures were calculated,respectively.After the comparison,the physical properties of purely orthogonal Mo₂NiB₂ are not good.