How the ductility of metal change when grains is decreased ?

In summary, when the grain size of a metal is decreased through heat treatment, the ductility of the metal decreases due to the increased resistance for the motion of dislocations caused by the increased grain boundary area and frequent change in orientation of slip planes. This also implies that the strength of the material increases and can be calculated using the Hall-Petch equation. A comprehensive reference for this topic can be found in the book "Material science basics" by Callister, specifically in the section on dislocations. Additionally, when Mg is doped in AlSb at a rate of 25%, it can cause the formation of rods instead of grain size, which can be observed through a scanning electron microscope. The reason for this is still unknown and further research
  • #1
QuyetThangTr
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How the ductility of metal change when grains is decreased ?

Hello every body, I'm from Vietnam. I have a question that : if we decrease the size of the grain of metal by heat treatment, what happen to the ductility of that metal, increase or decrease, and why ? for example, the metal of plain steel.
P/S: It's the first time I post my question, if I make any mistake, please forgive to me, hi
 
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If the grain size is larger the material is less brittle so the ductility is higher
 
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If the grain size decreases, there is greater resistance for the motion of dislocations due to increased grain boundary area and frequent change in orientation of slip planes due to misorientation of grains.Hence a larger stress would be required to move dislocations. This would imply that the strength of material has increased.
It is calculated using hall petch equation.
 
  • #4
Dear Sir, Kindly send me the proper referance of the following statement)
If the grain size decreases, there is greater resistance for the motion of dislocations due to increased grain boundary area and frequent change in orientation of slip planes due to misorientation of grains.Hence a larger stress would be required to move dislocations. This would imply that the strength of material has increased.
It is calculated using hall petch equation.
 
  • #5
You can go through the book on Material science basics by Callister.
Read dislocations section.
I am sorry, i do not remember full name of the book
 
  • #6
hi i am from pakistan. i want to make thin film of Mg doped AlSb. when 25% magnasium (Mg) is doped in AlSb I saw rods instead of grain size from SEM (Scanning Electron microscope) graph. can anybody tell me this reason with referance.
thanks
 
  • #7
hi i am from pakistan. i want to make thin film of Mg doped AlSb. when 25% magnasium (Mg) is doped in AlSb I saw rods instead of grain size from SEM (Scanning Electron microscope) graph. can anybody tell me this reason with referance.
thanks
 

FAQ: How the ductility of metal change when grains is decreased ?

How does decreasing grain size affect the ductility of metal?

Decreasing grain size can increase the ductility of metal. This is because smaller grains have a higher number of grain boundaries, which act as obstacles to dislocation motion. This impedes the movement of dislocations and promotes plastic deformation, resulting in increased ductility.

Is there a limit to how much the ductility of metal can increase with decreasing grain size?

Yes, there is a limit to how much the ductility of metal can increase with decreasing grain size. This is because as the grain size decreases, the number of grain boundaries increases, leading to a decrease in the overall strength of the material. This can result in a decrease in the load-bearing capacity and ultimately limit the increase in ductility.

How does the type of metal affect the change in ductility with decreasing grain size?

The type of metal can significantly affect the change in ductility with decreasing grain size. Some metals, such as copper and aluminum, have a higher tendency to exhibit increased ductility with decreasing grain size, while others, like steel, may not show a significant change in ductility. This is due to variations in the crystal structure and the presence of different types of grain boundaries in different metals.

Can the ductility of metal decrease with decreasing grain size?

Yes, the ductility of metal can decrease with decreasing grain size in some cases. This is often observed in metals with a high proportion of brittle intermetallic compounds, which can form at grain boundaries and reduce the ductility of the material. Additionally, if the decrease in grain size is not uniform throughout the material, it can lead to the formation of cracks and decrease the overall ductility.

What are some methods for controlling the grain size of metals to achieve desired ductility?

There are several methods for controlling the grain size of metals to achieve desired ductility. These include processes such as grain refinement through severe plastic deformation, controlled annealing, and adding alloying elements. It is essential to carefully select the appropriate method for a specific metal to achieve the desired balance between strength and ductility.

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