Hypothetical Alloying Problem

[cruz_johann]

A and B are completely soluble in the liquid state but completely insoluble in the solid state. Will A, alloyed with a small amount of B, have a higher melting point than pure A? Explain.

 

[Astronuc]

A and B are completely soluble in the liquid state but completely insoluble in the solid state. Will A, alloyed with a small amount of B, have a higher melting point than pure A? Explain.

What would happen to the alloy constituents (elements) upon cooling? Note - the problem states "small amount of B" in A.

 

[cruz_johann]

Its a homework question given to us. No more data is provided...

 

[cruz_johann]

Is there such thing as maximum melting eutectic? Why is the melting point of the eutectic point always minimum? Is that because its not thermodynamically feasible?

 

[DeeNos]

Yes, A alloyed with a small amount of B will have a higher melting point than pure A. This is because when A and B are completely soluble in the liquid state, they form a homogeneous mixture with no distinct boundaries between the two components. However, when they are completely insoluble in the solid state, they will form separate phases with distinct boundaries.

When A and B are alloyed together, the B atoms will be dispersed throughout the A lattice in the liquid state. As the alloy cools and solidifies, the B atoms will not be able to fit into the A lattice and will form separate regions, creating a more complex crystal structure. This increased complexity requires more energy to break apart the bonds and melt the alloy, resulting in a higher melting point compared to pure A.

Additionally, the presence of B atoms in the A lattice can also disrupt the regular arrangement of A atoms, making it more difficult for them to slide past each other and causing an increase in the strength of the bonds. This also contributes to a higher melting point for the alloy compared to pure A.

In summary, the alloying of A and B leads to a more complex crystal structure and an increase in bond strength, both of which contribute to a higher melting point for the alloy compared to pure A.