Equations · equation
Zener–Hollomon Parameter
Materials Science · 1944
- Equation
- Z = ε̇·exp(Q/RT)
- Field
- Materials Science
- Named After
- Clarence Zener and John Hollomon
- Year
- 1944
Symbols
Z the temperature-compensated strain rate · ε̇ the strain rate · Q the activation energy for hot deformation, about 300 kJ/mol in austenite · R the gas constant · T absolute temperature
Significance
Hot metal does not respond to temperature and speed separately, only to this combination of them: deforming ten times faster is worth about 130 °C of cooling. It sets the flow stress in every forging, rolling mill and extrusion press, decides whether the grains recrystallise while they are being deformed or only afterwards, and is why a slow press reaches the centre of a billet where a fast hammer moves only its skin.
Referenced by
equation
skill
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