Influência do percentual de zircônio nas propriedades térmicas, mecânicas e corrosivas de ligas Ti50Ni50-xZrx com memória de forma.

Abstract

The objective of this work was to study a series of five Ti50Ni50-x Zrx alloy compositions (x = 0, 2, 5, 10 and 15% at.) And to evaluate the interference of nickel substitution by zirconium and the influence of zirconium percentage on thermal, mechanical and corrosive properties. The alloys were produced using the Plasma Skull Push-Pull (PSPP) casting process and studied by various techniques and tests to verify the thermal, mechanical and corrosive characteristics. The alloys were successfully obtained by the PSPP process. It was found that from 15% of zirconium the alloy showed high brittleness due to partial solubility of nickel zirconium percentage. In general we can state that the addition and increase of zirconium percentage favored the formation of secondary phases that directly affected the transformation temperatures, microhardness and corrosion resistance. The transformation from phase B2 to phase B19 'occurs in a single step and temperatures Mi and Ai increase from 2oC to 48oC and from -20oC to 93oC for TiNi50 and TiNi40Zr10 alloys, respectively. The addition of zirconium caused the appearance of second phase particles in the matrix grain boundaries of the alloys with 5.10 and 15% zirconium and these phases have higher microhardness than the matrix phase. The corrosion resistance increased from η20.23KΩ to 1007.30KΩ and the microhardness of the 346HV matrix phase to 805HV for TiNi50 and TiNi40Zr10 alloys respectively.