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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

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Austenitic Stainless Steel :(Interface analysis) Types of boundaries seen:- Grain boundary. 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 Coherent twin boundaries. Incoherent twin boundaries. 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. Incoherent twin boundaries are darker in color than the coherent twin boundaries and less dark than the grain boundaries. The reason for their da
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DIFFUSION TYPES

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TYPES OF DIFFUSION : Hello Everyone! In this blog, we are going to discuss different types of diffusion, instead, we can also call it different types of mechanism by which diffusion occurs. Basis of classification : Diffusion is classified based on the type of site occupied by the atoms. Substitutional diffusion occupies vacant sites. Interstitial diffusion occupies the interstitial space between the atoms. Types of mechanisms of diffusion: There are two mechanisms by which diffusion takes place: Substitutional diffusion. Interstitial diffusion. Explanation : Substitutional diffusion: Substitutional diffusion mainly occurs due to the migration of atoms to the neighboring vacancy site i.e. by vacancy migration mechanism. Interstitial diffusion: Interstitial diffusion occurs due to jumping of atoms to the neighboring interstitial site. The mechanism basically comprises an atom pushing or forcing through larger atoms making its way to the interstitial site.
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DIFFUSION DEFINITION

Metallurgical definition of diffusion : THEORY : Diffusion is basically the movement of atoms due to the presence of concentration gradient i.e. movement of atoms from a region of higher concentration to a region of lower concentration. We can also define diffusion in terms of the difference in chemical potentials i.e diffusion is basically the movement of atoms from the region of higher chemical potential to a region of lower chemical potential. Thus we can say that diffusion is possible both due to the chemical potential gradient as well as due to the concentration gradient. CONCLUSION : Final Definition for DIFFUSION in metallurgy terms: Diffusion is defined as the movement of atoms in the lattice either interstitially or substitutionally because of the presence of concentration gradient or chemical potential gradient. Please feel free to ask questions in comments!!!
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DIFFUSION DRIVING FORCE

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a),b),c),d) Shows diffusion due to concentration gradient both downhill and uphill respectively e),f) Shows images of diffusion due to difference in chemical potentials  Driving force for diffusion : Theory: There can be a little bit of confusion in your mind related to the driving force of diffusion, believe me, most of the students think that the driving force for diffusion is the concentration gradient. But unfortunately, you will be surprised to know that those who think that the driving force for diffusion is the concentration gradient are wrong. The driving force for diffusion is the difference in chemical potentials . Explanation: Diffusion basically occurs to reduce the Gibbs free energy of the system. If you observe the diagrams a) and b) carefully you will note that the diffusion of A atoms is taking place from the region of higher concentration to the region of lower concentration and the b) graph also shows the reduction of Gibbs free energy. Si
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