Why Do Metallurgical Processes Aim for Equilibrium?

[laura001]

hey,

i'm doing a course on materials science as part of an aerospace engineering degree. I'm just trying to gain a full understanding of some of the fundamental concepts involved. Would i be right in saying that, all processes that occur in metallurgy on an atomic scale (like recrystalisation, recovery, grain growth) are all driven by the systems tendency to move towards equilibrium (i.e the minimum free energy)?

If that's correct, why does a system have this tendency to move towards equilibrium? What exactly is the driving force behind this, i guess it's a thermodynamic driving force, but does that mean that these processes actually 'feed' off of heat somehow? What is the source of that heat?

To take dislocation formation as an example of how the energy in a system increases, i understand that if you take a cyrstallite and bend it by some external force, then the energy assosciated with that elastic deformation can be stored by inserting a dislocation, i.e a defect. So as dislocations form, the free energy of a system increases... eventually the same process leads to grain boundaries to form.

But, then there's a reverse process, right? Say you've just plastically deformed a piece of metal, so it now has a high dislocation density... the system will then have an elevated internal energy right? So my limited understanding of what happens then is that processes begin which try to reduce this elevated internal energy i guess? Like recovery, recrystalisation and grain growth. In other words, the system tries to move towards equilibrium (minimum free energy).

Is that basic framework of understanding right or can you add any detalis that will help me understand this stuff? thanks.

 

[PerennialII]

Hi Laura,

I'd interpret the "abundance" of replies [ ] in such a manner that you're on the right track. Thermodynamical principles work on one way or the another to phenomena encountered in materials science & condensed matter problems, no matter at what level you're investigating your problem - and what are the variables under which your system is working in a particular case (always energy involved in one way or another - doesn't have to be heat like you ponder in your post). And the principles are the typical tools of investigating and understanding pretty much everything that goes on "down there" from typical phenomena of physical metallurgy to plasticity and beyond (and different 'phenomena' occur under a different set of "rules" (better understood thinking about the 'driving force' towards a 'change', towards an equilibrium), like your example of plasticity via dislocations, which again under conditions 'enabling' for example recrystallization can lead to such).

 

[ravenprp]

Hi there,

You are correct in saying that all processes in metallurgy on an atomic scale are driven by the system's tendency to move towards equilibrium. This is due to the fact that nature always seeks the most stable state, which is achieved when the system has the lowest possible energy. Therefore, any changes that occur in the system, such as the formation of dislocations or grain boundaries, are driven by this tendency towards equilibrium.

This driving force is indeed thermodynamic in nature. Thermodynamics is the study of energy and its transformations, and it is the underlying principle that governs all physical processes. In the case of materials science, the driving force towards equilibrium is the minimization of free energy. Free energy is a measure of the energy available to do work, and in order to achieve the lowest possible energy state, the system will undergo various processes to reduce its free energy.

In terms of the source of heat, it is important to understand that all materials have an inherent amount of energy, known as thermal energy, which is a result of the movement of atoms and molecules within the material. This thermal energy is what drives the processes towards equilibrium, as it provides the necessary energy for these processes to occur.

You are also correct in your understanding of dislocation formation and its role in increasing the energy of a system. When a material is plastically deformed, it creates a high dislocation density, which increases the internal energy of the system. In order to reduce this energy and move towards equilibrium, the system will undergo processes such as recovery, recrystallization, and grain growth.

Overall, your understanding of these concepts is correct. It is important to remember that materials science is a complex and interdisciplinary field, so there may be additional details and factors at play in each specific situation. However, the basic framework of understanding that you have outlined is a good starting point. I would recommend further research and studying to deepen your understanding of these concepts. Best of luck with your course!