Jeevan Jaidi
Research Scholar,
Mechanical Engineering Department,
Indian Institute of Science,
Bangalore-560012,
INDIA.
E-mail: jaidi@mecheng.iisc.ernet.in
Added to MAP: December 2002.
This code calculates the grain size (diameter) variation at a given position within the heat-affected zone (HAZ) in the presence dissolving precipitates (carbides/nitrides) during a weld cycle.
Language: | FORTRAN-90 |
Product form: | Source code |
Complete program.
In general, depending up on the the peak temperature and heating/cooling rates the precipitates will either coarsen or dissolve or coarsen and dissolve. In continous welds, the heating period is less significant as compared to the cooling period. This is due to short heating period (2 - 3 seconds). Thus, at a given position within the HAZ whether the precipitates coarsen or dissolve depend primarily on the peak temperature of the thermal cycle.
If the peak temperature of the thermal cycle is higher than the equilibrium solvus of the precipitates then the precipitiates will dissolve during the cooling period. During the process of precipitate dissolution, the grain boundary pinning force will retard. As a result, the grain growth rate will become faster.
The rate of change of average grain size in the presence of precipitating elements or impurities is expressed by the following semi-empirical equation:
The time exponent, n, is a strong function of temperature. For most metals and alloys, n varies typically in the range of (0.1 - 0.4). According to Akselsen et al., if the time constant (time to cool from 800oC - 500oC) is less than 15 seconds, the time exponent would be expected to be high and close to the upper theoretical limit (n = 0.5) at all the temperatures.
In the presence of dissolving precipitates, the limiting grain size is given by the following expression:
where I3 is the kinetic strength of the thermal cycle w.r.t dissolving precipitates and is given by the following expression:
and
The ISTART and IEND for heating/cooling periods must be given correctly, else result in incorrect temperature during interpolation.
No information supplied.
None.
Complete program.
See file ags4.in
See file ags4out.m
None
Average grain size, peak temperature, thermal cycle, precipitate dissolution.
MAP originated from a joint project of the National Physical Laboratory and the University of Cambridge.