Francisco M. Braz Fernandes

Heat Treating of NiTi Shape Memory Alloys

Ni-Ti System

Ligasricas em Ti

Ligasricas em Ni

W. Tang, B. Sundman, R. Sandström, C. Qiu. Acta materialia 47 (1999) 3457-3468

Austenite(B2)

Cubic

Martensite(B19’)

Monoclinic

R-phase(R)

Rhombohedral

-20 0 20 40 60 80 100 120 140-500-400-300-200-100

0100200300400500600700

Hea

t Flo

w (W

/g) x

10-3

Temperature (ºC)-60 -40 -20 0 20 40 60 80

-300-250-200-150-100-50

050

100150200250300

Hea

t Flo

w (W

/g) x

10-3

Temperature (ºC)-60 -40 -20 0 20 40 60

-300-250-200-150-100-50

050

100150200250300

Hea

t Flo

w (W

/g) x

10-3

Temperature (ºC)-80 -60 -40 -20 0 20 40 60

-300-250-200-150-100-50

050

100150200250300

Hea

t Flo

w (W

/g) x

10-3

Temperature (ºC)

AR 400C 450C 500C 550C 600C-30-15

0153045607590

105120135150

Tran

sfor

mat

ion

Tem

pera

ture

(ºC

)

Sample ConditionAR 400C 450C 500C 550C 600C

-60-45-30-15

0153045607590

Tran

sfor

mat

ion

Tem

pera

ture

(ºC

)

Sample ConditionAR 400C 450C 500C 550C 600C

-75-60-45-30-15

015304560

Tran

sfor

mat

ion

Tem

pera

ture

(ºC

)

Sample ConditionAR 400C 450C 500C 550C 600C

-90-75-60-45-30-15

015304560

Tran

sfor

mat

ion

Tem

pera

ture

(ºC

)Sample Condition

IncreasingIncreasing NiNi contentcontent

Heat treatments / chemical composition

[347] FanG, ChenW, Yang S, Zhu J, RenX, Otsuka K. Acta Mater 2004;52:4351.

Precipitation

HeatHeat TreatmentTreatmentTemperatureTemperature: : 350350ººC C 450450ººCC 550550ººCC

Functionally Graded Materials

Thermomechanical treatments

× / +× / +⊗ / ⊕⊗ / ⊕⊗ / ⊕600ºC

×× / +×× / +× / +× / ⊕⊗ / ⊕550ºC

×× / +×× / +× / +× / ⊕⊗ / ⊕500ºC

×× / +×× / +×× / +×× / +× / ⊕450ºC×× / +×× / +×× / +×× / +×× / ⊕400ºC×× / +×× / +×× / +×× / +×× / ⊕AR

Alloy “N”(51.0 at% Ni)

Alloy “S”(50.8 at% Ni)

Alloy “B”(50.2 – 50.4 at% Ni)

Alloy “M”(49.8 – 50.0 at% Ni)

Alloy “H”(49.4 – 49.6 at% Ni)

Phase Transformation on Cooling / on HeatingSample

Condition

× / +× / +⊗ / ⊕⊗ / ⊕⊗ / ⊕600ºC

×× / +×× / +× / +× / ⊕⊗ / ⊕550ºC

×× / +×× / +× / +× / ⊕⊗ / ⊕500ºC

×× / +×× / +×× / +×× / +× / ⊕450ºC×× / +×× / +×× / +×× / +×× / ⊕400ºC×× / +×× / +×× / +×× / +×× / ⊕AR

Alloy “N”(51.0 at% Ni)

Alloy “S”(50.8 at% Ni)

Alloy “B”(50.2 – 50.4 at% Ni)

Alloy “M”(49.8 – 50.0 at% Ni)

Alloy “H”(49.4 – 49.6 at% Ni)

Phase Transformation on Cooling / on HeatingSample

Condition

-40 -20 0 20 40 60 80 100 120-300-250-200-150-100-50

050

100150200250300

Hea

t Flo

w (W

/g) x

10-3

Temperature (ºC)AR 400C 450C 500C 550C 600C

-30-15

0153045607590

105120

Tran

sfor

mat

ion

Tem

pera

ture

(ºC

)

Sample Condition

εε(N=1) (N=1) = = 0,610,61

Severe Plastic DeformationECAP (Equal Channel Angular Pressing)

HeCeTo

Severe Plastic DeformationECAP (Equal Channel Angular Pressing)

XRD

2- Theta º

Resultados

2- Theta º

Resultados

2- Theta º

Resultados

2- Theta º

PowderMetallurgy

AcknowledgementsA. Pereira (CENIMAT)A.S. Paula (CENIMAT, now with Universidade Federal Fluminense – UFF),C. Baetz (ROBL – ESRF; HZDR),F. Neves (CENIMAT, now with LNEG),K.K. Mahesh (CENIMAT, now with Vivekananda College of Engineering & Technology), M.T. Nogueira (CENIMAT),N. Schell (P07-PETRA, HZG), R.J.C. Silva (CENIMAT),R.M.S. Martins (CENIMAT, ITN),