Does grain refinement increase hardness?

The hardness and microstructure of the grain refinement of a copper alloy which has undergone ECAP process was investigated and the results showed that the grains became gradually more refined and the hardness increased as they underwent further processing.

How does grain refinement increase strength?

Decreasing grain size decreases the amount of possible pile up at the boundary, increasing the amount of applied stress necessary to move a dislocation across a grain boundary. The higher the applied stress needed to move the dislocation, the higher the yield strength.

What does grain refinement do?

Grain refinement, which is obtained by changing the size of grain structure by different techniques, is a preferred method to improve simultaneously the strength and plasticity of metallic materials. Therefore, grain refining of aluminum is regarded as a key technique in aluminum processing industry.

Why are grain refiners added to steel?

Generally, fine-grained microstructure leads to improved formability and to higher strength and toughness of steels. Hence, grain refinement has been regarded as an effective approach to improve the quality of steel products.

Does grain boundaries contribute to the strain hardening in metals and alloys explain?

Answer. Grain boundaries block the continued movement of dislocations in the metal during straining. As more dislocations become blocked, the metal becomes more difficult to deform; in effect it becomes stronger.

What promotes grain refinement?

When progressive grain initiation is dominant, grain refinement is promoted by increasing cooling rate, solute concentration and number density of nucleant particles, but is almost independent of the potency of nucleant particles.

Why does grain refinement increase ductility?

The greater the number of grain boundaries, the greater the tonnage is required to bend the metal. This happens because the energy required to produce movement at the boundaries is stronger than the grain itself. At the same time, a grain boundary that is finer is known to raise ductility.

How does grain size affect steel strength?

Smaller grains have greater ratios of surface area to volume, which means a greater ratio of grain boundary to dislocations. The more grain boundaries that exist, the higher the strength becomes.

How does grain size affect the properties of a metal?

Grain size has a measurable effect on most mechanical properties. Also, fine-grain steels have greater fatigue resistance, and a fine grain size promotes a somewhat greater toughness and shock resistance. Steels made fine grained by addition of aluminum have machinability inferior to those made without aluminum.

Does grain structure affect hardness?

3, the hardness decreases monotonically with increasing indentation depth for a grain size of 80 μm which is considered a large grain. However, for smaller grain sizes, hardness increases with increasing indentation depth at a specific range.

What is the grain refinement process in heat treated steel?

They used a low temperature rolling process to refine the grain size prior to the final hardening treatment: The grain refinement process meant that with sufficiently low hardening temperature they could achieve a very fine grain size in the final heat treated steel.

What is the best method of grain refinement?

Grain refinement can be achieved through the use of chemical grain refiners or other techniques such as the so-called cooling slope, spray forming, etc., all of which create a large number of nuclei that limit dendritic growth and promote the formation of the desired globular microstructure.

What is the best method of strengthening steel without compromising toughness?

Grain refinement is the most effective method among various strengthening mechanisms to enhance strength without compromising toughness of steel [31,32].

Does the hardness of carbon steel change with increasing grain size?

With the medium carbon steel they used the same hardening temperature with increasing time at temperature so that the grain size grew but the carbon content and final hardness saw little change. They saw a similar increase in ductility with finer grain size and also found that with fine grain size the plate martensite was no longer observed.