TY - JOUR

T1 - The Constitutive Creep Equation for a Eutectic Sn-Ag Alloy Using the Modified Theta-Projection Concept

AU - Kariya, Yoshiharu

AU - Otsuka, Masahisa

AU - Plumbridge, William J.

PY - 2003/12

Y1 - 2003/12

N2 - Creep data for a eutectic tin-silver alloy at temperatures between 298 K and 398 K have been analyzed using the modified theta-projection concept, instead of the steady-state creep constitutive equation in the following formula: εcr = A (1 - exp(-αt)} + B (exp(αt) - 1}, where A, B, and a are constants to be experimentally determined. The equation describes well the creep curves of the eutectic tin-silver alloy up to the tertiary stage. All constants exhibited power law relationships with the applied stress. The rate constant, α, has a high stress exponent, which is attributed to dispersion strengthening. The rate constant a and the strain factor B only showed temperature dependence, while the strain factor A was independent of temperature. The activation energy for α was 65 kJ/mol at high stresses and 90 kJ/mol at low stresses. The energies suggest that the dislocation pipe diffusion and the lattice diffusion are predominant at high stresses and low stresses, respectively.

AB - Creep data for a eutectic tin-silver alloy at temperatures between 298 K and 398 K have been analyzed using the modified theta-projection concept, instead of the steady-state creep constitutive equation in the following formula: εcr = A (1 - exp(-αt)} + B (exp(αt) - 1}, where A, B, and a are constants to be experimentally determined. The equation describes well the creep curves of the eutectic tin-silver alloy up to the tertiary stage. All constants exhibited power law relationships with the applied stress. The rate constant, α, has a high stress exponent, which is attributed to dispersion strengthening. The rate constant a and the strain factor B only showed temperature dependence, while the strain factor A was independent of temperature. The activation energy for α was 65 kJ/mol at high stresses and 90 kJ/mol at low stresses. The energies suggest that the dislocation pipe diffusion and the lattice diffusion are predominant at high stresses and low stresses, respectively.

KW - Constitutive equation

KW - Creep

KW - Lead-free solder

KW - Nonsteady state

KW - Sn-3.5Ag

KW - θ projection

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U2 - 10.1007/s11664-003-0107-1

DO - 10.1007/s11664-003-0107-1

M3 - Article

AN - SCOPUS:0942288661

VL - 32

SP - 1398

EP - 1402

JO - Journal of Electronic Materials

JF - Journal of Electronic Materials

SN - 0361-5235

IS - 12

ER -