Abstract
Grain refinement of Ni-Cr alloys containing zirconium was investigated.Nineteen ingots of alloys(ten Ni-Cr-Zr alloys, five Ni-Cr-Ti-Zr alloys, two commercial dental casting Ni-Cr alloys and two above alloys addedzirconium)were produced by melting pure nickel, chromium, titanium and zirconium, in a high-frequency induction furnace in a vacuum.Test specimens were prepared by using a standard mold preparation of phosphate-bonded investment, and using a high-frequency induction furnace with an insert atmosphere of argon.The etched surface of these specimens were photographed through the metallurgical microscope and the grain size were determined by these photomicrographs.As a result, a grain of Ni-Cr alloys containing minor zirconium was refined and the grain size was almost unchanged even by varying the amount of zirconium.0.03wt% addition of zirconium was efficient in grain refinement of Ni-Cr-Ti alloys.Relatively coarse grains of commercial dental casting Ni-Cr alloys have disappeared, depending on 0.03wt% addition of zirconium.
