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Strain Rate Effects in Titanium, Tantalum and Iron Titanium Keyur Karandikar, Marc A. Meyers, Mechanical and Aerospace Engineering Department, UC San Diego, USA. Felipe Perissé D. Lopes, Sergio N.Monteiro, Mechanical and Materials Section, IME, Rio de Janeiro, Brazil. • Commercially pure Titanium (CP Ti) grade 4. • CP Ti is better than Ti-6Al-4V for implants. • Nano Ti, mechanical strength was improved by ECAP-Conform. • Anomalous effect under mechanical tests . • Graph of Yield stress versus strain rate in compression test. • Dislocations motions in different strain rates. Method Acknowledgements: • Pure Ti nano and conventional grain size compared with Ti alloy. ECAP-Conform Purpose : To find the ratio of Activation Energy over temperature (EK /kT) and study the effects of Strain rate and temperature in α-Iron and Tantalum monocrystal. The activation energy can be thought as the energy required dislocation to overcome the barrier at a given thermal conditions. The A.E ratio model developed here and its different significances are based on dislocation mobility law which is thought to affect brittle to ductile transition condition in BCC metals. To study strain rate effects in Titanium, was investigate with more details the Dynamic Strain Aging (DSA), this is a effect of the interaction between intertitials elements (C,N,H and O) and dislocations. Swegle-Grady Eqn m P a B D v kT E A v K D exp 7 10 )) / ( 40 52 . 0 ( P a A 4 Shock P a 1 2 2 1 Shock P m P S B A v exp 1 Prefactor B & Exponent M depend on Temperature kT E k m o o D exp m(t), (t) & (t) are Third order polynomials dependent on Temperature o o Results: Tantalum α- Iron • Uniform Activation energy ratio ~ 25 during the DBT condition • BDTT shift under effect of ̇ in Iron but not in Tantalum • A.E ratio ~ rate of intensity of fracture • Predict Sharp/Gradual Brittle to Ductile transition in BCC metals • DSA happens at RT for different Ti, with more or less magnifications. Conclusions o o Tantalum α- Iron λ Nano λ CG CG Nano v 1 v 2 Orowan Equation γ = ρbλ ; ρ Nano >>ρ CG , at constant γ γ = ρbv ; . v for DSA = v dsa γ = v dsa λb γ Nano = γ CG ρ CG γ Nano = ρ Nano γ CG λ Nano b λ CG b • Confirming what is happening . . . . .

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Strain Rate Effects in Titanium, Tantalum and Iron

Titanium

Keyur Karandikar, Marc A. Meyers, Mechanical and Aerospace Engineering Department, UC San Diego, USA.

Felipe Perissé D. Lopes, Sergio N.Monteiro, Mechanical and Materials Section, IME, Rio de Janeiro, Brazil.

• Commercially pure Titanium (CP Ti) grade 4.

• CP Ti is better than Ti-6Al-4V for implants.

• Nano Ti, mechanical strength was improved by ECAP-Conform.

• Anomalous effect under mechanical tests .

• Graph of Yield stress versus strain rate in compression test.

• Dislocations motions in different strain rates.

Method

Acknowledgements:

• Pure Ti nano and conventional grain size compared with Ti alloy.

ECAP-Conform

Purpose: To find the ratio of Activation Energy over temperature (EK /kT) and study the effects of Strain rate and temperature in α-Iron and Tantalum monocrystal. The activation energy can be thought as the energy required dislocation to overcome the barrier at a given thermal conditions. The A.E ratio model developed here and its different significances are based on dislocation mobility law which is thought to affect brittle to ductile transition condition in BCC metals. To study strain rate effects in Titanium, was investigate with more details the Dynamic Strain Aging (DSA), this is a effect of the interaction between intertitials elements (C,N,H and O) and dislocations.

Swegle-Grady Eqn m

EAv

D exp

710))/(4052.0( PaA

ShockPa

21ShockP

S BAv

exp1

Prefactor B & Exponent M depend on Temperature

oD exp

m(t), (t) & (t) are Third order polynomials dependent on Temperature o o

Results: Tantalum α- Iron