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# Hollomon-Jaffe parameter

The Hollomon-Jaffe parameter, or HP, describes the effect of a heat treatment at a temperature for a certain time.

## Effect

The effect of the heat treatment depends on its temperature and its time. The same effect can be achieved with a low temperature and a long holding time, or with a higher temperature and a short holding time.

## Formula

In the Holloman-Jaffe parameter, This exchangability of time and temperature can be described by the following formula:

$H_p = \frac {(273.15 + T)}{1000} \cdot (C + log(t))$

This formula is not consistent concerning the units; the parameters must be entered in a certain manner. The argument of the logarithmic function has the unit minutes. The Hollomon parameter itself is unitless and realistic numeric values vary between 15 and 21.