DEPARTMENT OF MECHANICS AND MATHEMATICAL SIMULATION Tensile testing

DEPARTMENT OF MECHANICS AND MATHEMATICAL SIMULATION Tensile testing of Ti-6 Al-4 V alloy superplasticity Sergey Aksenov, Ph. D. Tarusa July 09 -11, 2013

Introduction As a titanium alloys have remarkable properties in terms of mechanical characteristics, low density and elevated corrosion resistance, it is widely used in many fields including aerospace, automotive, electronics and even bio-medical industry. At the same time the semi-finished parts of titanium alloys are rather expensive in particular because of the number and complexity of technological operations. The superplastic forming (SPF) is an effective way to manufacture very complex thin-shape components, which allows at the same time to decrease its cost. The major advantages of SPF: • The possibility of form a large and complex workpieces in one operation • Excellent precision of a finished products • Fine surface finish of a products Tarusa July 09 -11, 2013 2

Typical titanium alloys SPF applications Tarusa July 09 -11, 2013 3

Material Ti-6 Al-4 V is the most popular titanium alloy which covered more than 50% of titanium alloy production Physical properties: Chemical composition Density Melting Range Specific Heat C Fe N 2 O 2 Al V H 2 Ti 4. 42 g/cm 3 1649± 15°C 560 J/(kg °C) Mechanical properties: Tensile Strength 1000 Elastic Modulus 114 Mpa Gpa Tarusa < 0. 08% < 0. 25% < 0. 05% < 0. 2% 5. 5 -6. 76% 3. 5 -4. 5% < 0. 015% Balance July 09 -11, 2013 4

Constitutive model • Tarusa July 09 -11, 2013 5

Constitutive model • Tarusa July 09 -11, 2013 6

Constitutive model • Tarusa July 09 -11, 2013 7

Dynamic materials model Y. V. R. K. Prasad et al. suggested the dynamic materials modeling (DMM) approach for describing the material behavior under processing conditions by means of processing maps. Tarusa July 09 -11, 2013 8

Dynamic materials model • Efficiency of power dissipation Instability criterion Tarusa July 09 -11, 2013 9

Experiment As received Ti-6 Al-4 V alloy was used in the investigation. Each specimen was set in clamps of the test machine, placed in the furnace and heated up to the preset temperature. Then isothermal tensile-tests were carried out in the temperature range of 700 – 925 °С. Tarusa July 09 -11, 2013 10

Stress-strain rate curves The experimental (markers) and predicted (solid lines) stress-strain curves obtained by stepped tensile-tests Tarusa July 09 -11, 2013 11

Stress-strain rate curves 180. 00 160. 00 S 0 Expon. (S 0) s 0 | ss , MPa R 2 = 0. 7359 Expon. (Ss) 120. 00 80. 00 Ss S 0 140. 00 1000. 00 Ss R 2 = 0. 7359 60. 00 10. 00 40. 00 R 2 = 0. 5597 20. 00 1. 00 725 750 775 800 825 850 875 900 925 950 T, 0 C Tarusa 700 725 750 775 800 825 850 875 900 925 950 T, 0 C July 09 -11, 2013 12

Stress-strain rate curves 3. 50 E+05 1. 00 E+06 3. 00 E+05 1. 00 E+05 2. 00 E+05 K, - 2. 50 E+05 1. 00 E+04 1. 00 E+05 R 2 = 0. 9465 5. 00 E+04 0. 00 E+00 1. 00 E+03 700 725 750 775 800 825 850 875 900 925 950 T, 0 C Tarusa 700 725 750 775 800 825 850 875 900 925 950 T, 0 C July 09 -11, 2013 13

Stress-strain rate curves 2. 500 2. 000 mv, - 1. 500 1. 000 0. 500 0. 000 725 750 775 Tarusa 800 825 T, 0 C 850 875 July 09 -11, 2013 900 925 950 14

Strain rate sensitivity exponent Tarusa July 09 -11, 2013 15

Optimum strain rate Tarusa July 09 -11, 2013 16

Efficiency of power dissipation Tarusa July 09 -11, 2013 17

Processing maps Narayana Murty Prasad Tarusa July 09 -11, 2013 18

Tarusa July 09 -11, 2013 19

Tension at 825 °C 50 Stress, MPa 40 30 rate 7. 57 e-4 rate 5. 7 e-4 rate 3. 8 e-4 rate 2 e-4 rate 1 e-4 20 10 0 0 0. 2 0. 4 0. 6 0. 8 Strain 1 1. 2 1. 4 Optimum = 3. 8 e-4 Tarusa July 09 -11, 2013 20

Tension at 875 °C 55 50 45 40 Stress, MPa 35 30 25 rate 2. 88 e-3 rate 1. 9 e-3 rate 8. 54 e-4 rate 5 e-4 rate 3 e-4 20 15 10 5 0 0 0. 2 0. 4 0. 6 0. 8 1 1. 2 1. 6 Optimum = 8. 54 e-4 Strain Tarusa 1. 4 July 09 -11, 2013 21

Tension at 925 °C 45 40 Stress, MPa 35 30 25 rate 4. 4 e-3 20 rate 2. 9 e-3 15 rate 1. 4 e-3 10 rate 1 e-3 rate 3 e-4 5 0 0. 2 0. 4 0. 6 0. 8 1 1. 2 1. 6 Optimum = 1. 4 e-3 Strain Tarusa 1. 4 July 09 -11, 2013 22

Stress-strain curves 70 Stress [MPa] 60 50 40 30 Temperature [°C] 750 775 800 825 850 875 900 925 950 20 10 0 0 0. 5 1 Effective strain [-] Tarusa July 09 -11, 2013 1. 5 23

Stress-strain rate curves 70 0. 2 0. 6 1 stepped Stress [MPa] 60 50 40 30 20 10 0 650 750 850 Temperature [°C] Tarusa July 09 -11, 2013 950 24

Summary • Tarusa July 09 -11, 2013 25

DEPARTMENT OF MECHANICS AND MATHEMATICAL SIMULATION Thank you for your attention! Tarusa July 09 -11, 2013