Breakpoint (materials science)
In materials science and metallurgy, a stop point refers to a point in the time-temperature diagram at which the temperature of a material remains constant for some time and does not change.
In a system in which heat is constantly supplied or removed from a homogeneous substance , the temperature of the substance rises or falls steadily. However, the temperature form at change in substance different phases or changes the physical state is for this the corresponding specific heat of phase transformation required or given. This causes the constant temperature change to be interrupted for some time - the temperature curve flattens out for some time. This temperature is called the breakpoint and marks the corresponding transformation.
The breakpoints are designated with the letter A (from the French arrêter = to stop). Since the breakpoints show a hysteresis during heating and cooling , they are marked with indices c (for chauffage = heating) - A c and r (for refroidissement = cooling) - A r . A numerical index is also given for important conversions, for example A c1 , A r3 .
See also: iron-carbon diagram
Individual evidence
- ↑ Wolfgang Bechmann, Joachim Schmidt: Introduction to Physical Chemistry For Minor Subjects , 4th Edition, Vieweg + Teubner, GWV Fachverlage GmbH, Wiesbaden 2010, p. 71.
- ↑ Materials technology. mikescafe.de, accessed on February 21, 2016 .