RAMOS, Alana Pereira.
Résumé:
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.
