Effect Of Ni Additive On Structure And Magnetic Properties Of Co-Zr Alloys

Based on the current research situation of permanent magnetic materials, wedetailedly researched the structural, formation and magnetic properties of thenon-rare-earth containing Co-Zr system alloys in this paper, utilizing melt-spuntechnology and element additive method. The purpose of this paper is to find newpermanent magnetic materials without rare earth.At first, we made dozens ofCo82xNixZr18(where x=0,10,20and30)melt-spun ribbons with the surface speed of30,40and45m/s of the rotating copperwheel. And, heat treatment for the melt-spun ribbons was performed in thetemperature range of500-700℃for2min using rapid thermal processing system.Then to study effects Ni additive makes on Co-Zr alloys’ structure and magneticproperties. At last, we study the effects of different heat treatments and differentannealing speeds forCo72Ni10Zr18melt-spun ribbons.Through the experiments ofCo82xNixZr18melt-spun ribbons with Vs=30m/sand the same heat treatment, we found a new phase bct CoxZr(x≈5) that is quitedifferent from any Co-Zr phase we known. And the CoxZr(x≈5) phase may be thehard magnetic phase. The SEM results show the increase of Ni content can enlarge thegrain size sharply. In the magnetic tests, the coercivity will increase significantly withNi content increasing where0≤x≤10, and peaked at3.0kOe when x=10. However,the coercivity will decrease gradually when10<x≤30.Through the experiments ofCo72Ni10Zr18with the same Vs=30m/s but differentannealing temperature, we found that Ni additive can’t change the major phase andplay an important role in stabilizing the CoxZr phase against thermal decomposition.Through the the experiments ofCo72Ni10Zr18with the same heat treatment butdifferent annealing speed, we found that coercivity will increase as Vs increasing.Besides, the coercivity increases slightly when annealing temperature is relative low (500-600℃) and decreases significantly with temperature increasing.Through this paper, we found a new phase bct CoxZr(x≈5), which is possiblethe hard magnetic phase of theCo82xNixZr18(where x=0,10,20and30) melt-spunribbons. Proper Ni additive proper annealing and proper heat treatment can allimprove the magnetic properties of the Co-Zr alloys. TheCo72Ni10Zr18melt-spunribbons with Vs=45m/s and annealed for2minutes at600℃has the biggestcoercivity4.2kOe.