Microstructure And Performance Of Mn-Ga Magnetic Nano Material Fabricated By Mechanical Alloying

With the development of science and technology,powerful permanent magnet plays an increasingly important role in the progress and innovation of many technologies.Nowadays,sintered NdFeB is widely used in industrial production of permanent magnets with excellent magnetic property,but as a result of the limitation of supply and refining process of environmental impact,and volatile prices of rare earth,the consumer have to find their replacements.This has led to the search for a non-rare earth containing bulk material that will achieve similar magnetic strength and energy product as its rare earth counterpart.Mn-Ga binary alloy with a magnetic anisotropy have been given much attention as a possible alternative to rare earth permanent magnets.Mn-20at%Ga alloy fabricated by mechanical alloying combined with annealing treatment has a large number of nanoparticles,the average grain size of which are between 150 nm to 200 nm.Mn3Ga were mainly existed while other magnetic phases are also generated,such as Mn0.85Ga0.15 and MnGa,the oxidation in the process of the mechanical alloying lead to a small amount of MnO phase.The elements are well distributed through mechanical alloying and no obvious element enrich area exists.With the extension of the ball milling time,the grain size of Mn-20at%Ga alloy decreases gradually after annealingand eventually tends to a fixed value.The proportion of Mn3Ga phase is larger and the grain refinement effect is better when the ball milling is 3.5 h.Ball milling time also have a significant effect on Mn-20at%Ga alloy,Mn-20at%Ga alloy achieve most comprehensive magnetic properties when the ball milling time is 3.5 h,the remanence is obviously higher than other milling time,although the coercivity dropped a little,but the maximum energy product significantly improved.The annealing time and annealing temperature have an important influence on the microstructure and properties of Mn-20at%Ga alloy.With the extension of annealing time and the increase of annealing temperature,the proportion of Mn3Ga phase in the sample increases gradually,but the grain will be gradually coarsened at the same time.In this process,the magnetic properties of coercivity and remanenceare rised with the increase of the proportion of Mn3Ga phase,and then decrease with the coarsening of grain.The magnetic properties reach the best value when the annealing time is 6 h and the annealing temperature is 385?,because of the pinning effect of grain boundaries,all the magnetic phases inside the sample are well coupled at the same time.The addition of FeCrCo alloy powder to Mn-20at%Ga alloy increases the grain size of the alloy,the composition of thenanocomposites are mainly Mn3Ga phase and also contains Mn0.85Ga0.15,MnGa and other magnetic phases,a small amount of MnO are also existed.The FeCrCo additive is granular distributed in the alloy which is easy to appear in the impure area containing W.The FeCrCo/MnGa nanocomposites have better remanence and magnetic properties when the addition of FeCrCo powder is 2.5 mol%and the magnetic phase is better coupled.