Dual phase magnetic material component and method of forming
A magnetic component having intermixed first and second regions, and a method of preparing that magnetic component are disclosed. The first region includes a magnetic phase and the second region includes a non-magnetic phase. The method includes mechanically masking pre-selected sections of a surface portion of the component by using a nitrogen stop-off material and heat-treating the component in a nitrogen-rich atmosphere at a temperature greater than about 900° C. Both the first and second regions are substantially free of carbon, or contain only limited amounts of carbon; and the second region includes greater than about 0.1 weight % of nitrogen.
1. A method of preparing a magnetic component, comprising:
mechanically masking pre-selected sections of a surface portion of the component, using a nitrogen stop-off material to form a masked region in the component; and
heat-treating the component in a nitrogen-rich atmosphere at a temperature greater than about 900° C. to form intermixed first and second regions in the magnetic alloy, wherein
(a) the first region comprises a magnetic phase;
(b) the second region comprises a non-magnetic phase;
(c) a concentration of carbon in both the first and second regions is zero or less than about 0.05 weight %; and
(d) the second region comprises greater than about 0.1% of nitrogen.
2. The method of claim 1 , wherein the masked region in the surface portion of the component corresponds to the first region, and a region that is not masked by the nitrogen stop-off material corresponds to the second region.
3. The method of claim 1 , wherein a thickness of the component is in a range from about 0.1 mm to about 5 mm.
4. The method of claim 3 , wherein a width of the second region in a plane perpendicular to the thickness is greater than about 0.5 mm.
5. The method of claim 1 , wherein the nitrogen-rich atmosphere comprises more than about 90% of nitrogen.
6. The method of claim 1 , wherein the nitrogen-rich atmosphere is maintained at a pressure greater than about 0.5 atmosphere.
7. The method of claim 6 , wherein the pressure of the nitrogen-rich atmosphere is greater than 1 atm.
8. The method of claim 1 , wherein the temperature of heat-treatment is greater than about 1000° C.
9. The method of claim 1 , wherein the second region comprises greater than about 0.4 weight % of nitrogen.
10. The method of claim 1 , wherein the magnetic component is a portion of a synchronous reluctance machine.