10 Important differences between Cold working and Hot working

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Following are the 10 important differences between cold working and hot working Working of metal and alloy below their recrystallization temperature is known as cold working , and working of metal and alloy above their recrystallization temperature is known as hot working . During cold working strain hardening occurs and due to this tensile strength, hardness increases while the impact strength and ductility decreases, whereas, due to hot working strain hardening is removed by recrystallization. Microstructure of cold worked component shows distorted grains, whereas, microstructure of hot worked components shows equiaxed and usually refined grains. Due to cold working defect density increases i.e. vacancies, dislocations, etc. increases and hence the density of material slightly decreases, whereas, due to hot working there is almost no change in defect density of material. Cold working cannot be done indefinitely without cracking of material due to strain hardening, whereas, ho
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Austenitic Microstructure

Austenitic Stainless Steel:(Interface analysis)




Types of boundaries seen:-

  1. Grain boundary.
  2. Twin boundary.


1.Grain boundary:- The simplest type of boundary that is seen in every microstructure is grain boundary. These are high angle grain boundaries between two grains.

2.Twin boundaries:- There are two types of twin boundaries in the above microstructure
  1. Coherent twin boundaries.
  2. Incoherent twin boundaries.

  1. Coherent twin boundaries are lighter in color than both the grain boundary and the incoherent twin boundary. The lighter color is due to the low energy of these boundaries. The reason for low energy is the parallel orientation of both the twin boundary and the twinning plane. This parallel orientation helps the atoms on the boundary plane to fit properly in both the grains and there is no misfit.
  2. Incoherent twin boundaries are darker in color than the coherent twin boundaries and less dark than the grain boundaries. The reason for their dark color is their high energy. The reason for higher energy is basically the orientation of the boundary plane w.r.t the twinning plane. The orientation is not parallel but they are inclined at some angle to each other. As we know that the orientation angle is directly proportional to interfacial free energy, the increase in the angle increases the interfacial free energy, and this is the reason for higher energy.

Energy Comparison of different boundaries in this microstructure:

Grain boundary energy > Incoherent twin boundary energy > Coherent twin boundary







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