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Evirgen 1 , I. Karaman 1 , R. Santamarta 2 , J. Pons 2

TAMU-UIB collaboration: characterization of Ni-Ti-Zr and Ni-Ti-Hf high temperature shape memory alloys. Evirgen 1 , I. Karaman 1 , R. Santamarta 2 , J. Pons 2 1. Dept. of Mechanical Eng., Texas A&M University, TX, USA 2. Dept. of Physics, Univ. Balearic Islands, Palma de Mallorca, Spain.

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Evirgen 1 , I. Karaman 1 , R. Santamarta 2 , J. Pons 2

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  1. TAMU-UIB collaboration: characterization of Ni-Ti-Zr and Ni-Ti-Hf high temperature shape memory alloys • Evirgen1, I. Karaman1, R. Santamarta2, J. Pons2 • 1. Dept. of Mechanical Eng., Texas A&M University, TX, USA • 2. Dept. of Physics, Univ. Balearic Islands, Palma de Mallorca, Spain

  2. Activity in the framework of IIMEC in 2011 PhD Student Exchange Activity: TAMU – UIB Summer research stay of ALPER EVIRGEN (I. Karaman’s PhD student) in UIB. July 2011 Financed by IIMEC Research topic: Study of (Ni-rich) Ni-Ti-Zr and Ni-Ti-Hf HTSMAs

  3. Activity in the framework of IIMEC in 2011 PhD Student Exchange Activity: TAMU – UIB Summer research stay of ALPER EVIRGEN (I. Karaman’s PhD student) in UIB. July 2011 Financed by IIMEC Research topic: Study of (Ni-rich) Ni-Ti-Zr and Ni-Ti-Hf HTSMAs High industrial interest (automotive, aerospace, …) NiTi: TM ~ 80ºC Increase of Ni content → TM drops Substitution of Ti by Hf or Zr raises TM  (Ti+Hf/Zr)-rich ternary alloys Recently, study of Ni-rich ternary alloys

  4. Activity in the framework of IIMEC in 2011

  5. Materials Materials: Selected in TAMU Ni50.3Ti34.7Zr15 15Zr (at%) Ni50.3Ti29.7Zr20 20Zr Ni50.3Ti34.7Hf1515Hf Hot extruded (900ºC) Solution Heat Treatment:900oC, 1h + WQ (SHT)

  6. Collaboration plan “Macroscopic” characterization of functional properties DSC Thermal cycling under stress Thermal treatments to improve functional properties Alper’s PhD Microstructural characterization TEM, HRTEM EDX Most of observations performed during Alper’s stay Afterwards: Analysis of results

  7. General Results VERY FRUITFUL ACTIVITY:  Education: Intense immersion in practical TEM/HRTEM work (preparation of samples and observations)  Personal life: Stay in a country with different culture  Collaboration: Strong impulse to TAMU-UIB collaboration  Scientific: Good results suitable for several publications

  8. Scientific Results As extruded and Solution Heat Treated state 20Zr 15Hf Low TM temperatures and poor reproducibility Thermal treatments to improve the alloy performance

  9. Scientific Results 20Zr DSC results

  10. Scientific Results 15Hf DSC results

  11. Scientific Results 20Zr Furnace cooling from 700ºC to 100ºC in 48h

  12. Scientific Results 15Hf SHAPE MEMORY EFFECT 10h at 550ºC ~ 2.5%

  13. Scientific Results Microstructural observations in aged samples Precipitation of a new phase Ni-rich NiTi  Ni4Ti3 or Ni3Ti Not in ternary alloys

  14. Scientific Results 15Zr 200h at 500ºC Austenite at RT TEM HRTEM Lenticular precipitates in austenitic matrix. ~ 20 nm

  15. Scientific Results 15Zr 200h at 500ºC Austenite at RT The precipitates show an enhanced contrast every three 011 planes and extra spots in the diffraction patterns. They are fully coherent with austenitic matrix.

  16. Scientific Results 15Hf 10h at 450ºC Austenite at RT Nanometric precipitates (~5 nm)

  17. Scientific Results Precipitates in martensite 20Zr 48h at 500ºC 15Hf 3h at 500ºC

  18. Scientific Results 20Zr 700ºC-100ºC FC Long precipitates O(100 nm)

  19. Scientific Results EDX Microanalysis 15Hf 10h at 600ºC 20Zr 700ºC-100ºC FC Precipitates are richer in Hf/Zr and poorer in Ti, and a bit richer in Ni.

  20. Scientific Results Twinning modes of B19’ martensite in samples with precipitates

  21. Scientific Results Twinning modes of B19’ martensite in samples with precipitates (001)B19’ compound twinning(internal twins - LIS) (011)B19’ Type I twinning Twin plane || intervariant boundary {111} and {113}-typeintervariant boundaries Same twinning modes and boundaries as reported in literature for Ni-Ti-Hf alloys

  22. Scientific Results Intervariant boundaries (011) Perfect (011) boundaries || twin plane {111} or {113}-type boundaries quite irregular

  23. Scientific Results Intervariant boundaries (011) Perfect (011) boundaries || twin plane {111} or {113}-type boundaries quite irregular

  24. Scientific Results Structural model of the precipitate new phase

  25. Benefits received from IIMEC Benefits in Alper’s education and personal life The summer stay provided a strong impulse to TAMU-UIB collaboration Several good publications envisaged Creation of a good scientific common background for possible future applications of research projects in International Programs (NSF, EU, …)

  26. Thanks for your attention!!!

  27. Scientific Results 15Hf SHAPE MEMORY EFFECT SHT ~ 3.5%

  28. Scientific Results 20Zr Af temperature vs ageing time

  29. Scientific Results 15Hf Af temperature vs ageing time

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