Materials Science And Engineering Properties
Materials Science And Engineering Properties
1st Edition
ISBN: 9781111988609
Author: Charles Gilmore
Publisher: Cengage Learning
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Chapter 9, Problem 9.4P
To determine

The activation enthalpy between 973 K and 1053 K .

Expert Solution & Answer
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Answer to Problem 9.4P

The activation enthalpy between 973 K and 1053 K for zirconium is 2.953 eV/atom .

Explanation of Solution

Given:

The logarithm of stress is 7.10 .

Concept used:

Write the expression for tensile stage II creep rate.

  dεIIdt=Aσnexp(ΔHpkT) …… (1)

Here, dεIIdt is the tensile stage II creep rate, A is the constant and σ is the stress, ΔHp is the activation enthalpy, k is the Boltzmann constant and T is the temperature.

Calculation:

Refer to Figure 9.5 “The log of the stage II creep strain rate of zirconium as function of the log of stress, at three temperatures” to obtain the value of strain rate corresponding to logarithm of stress as 7.10 at 973 K and 1053 K as 1.0×105 s1 and 1.55×104 s1 respectively.

Substitute 1.0×105 s1 for dεIIdt , 8.62×105 eV/atomK for k and 973 K for T in equation (1).

  1.0×105 s1=A(σ)nexp(ΔHp( 8.62× 10 5  eV/atomK)( 973 K)) …… (2)

Substitute 1.55×104 s1 for dεIIdt , 8.62×105 eV/atomK for k and 1053 K for T in equation (1).

  1.55×104 s1=A(σ)nexp(ΔHp( 8.62× 10 5  eV/atomK)( 1053 K)) …… (3)

Divide equation (2) by equation (3).

  1.0× 10 5  s 11.55× 10 4  s 1=A ( σ )nexp( Δ H p ( 8.62× 10 5  eV/atomK )( 973 K ) )A ( σ )nexp( Δ H p ( 8.62× 10 5  eV/atomK )( 1053 K ) )0.0645=exp( Δ H p ( 8.62× 10 5  eV/atomK )[ 1 973 K 1 1073 K])ΔHp=ln( 0.0645)( 8.62× 10 5  eV/atomK)0.8× 10 4  K 1ΔHp=2.953 eV/atom

Conclusion:

Thus, the activation enthalpy between 973 K and 1053 K for zirconium is 2.953 eV/atom .

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