solid solution

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types of solid solution and Hume Rothery’s Rules

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Solid Solution Dipen M. Vekariya Mechanical:-D3(3 rd sem.) Roll no:-11me040 En:-110040119040 Email:- Vekariyadipen17@yahoo.com

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Content:- Defination of solvent ,solute and solid solution. Types of solid solution 1.Substitution solid solution -Disordered (b) -Ordered (c) 2.Interstitutional solid solution Hume Rothery’s Rules Crystal Structure Factor 2. Relative Size Factor 3. Chemical-affinity Factor 4.Relative Valence Factor

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What is solvent and solute???????? Solvent definition :-the component of a solution that is present in the greatest amount .it is the substance in which the solute is dissolved. Ex:- the solvent for seawater is water. the solvent for air is nitrogen. Solute definition :-the substance that is dissolved in a solution .for solution of fluid the solvent is present I greater then solute. Example:-salt in water

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What is solid solution????? Any homogenous crystalline solid, consisting of more than one type of molecule or atom randomly dispersed, in which the structure is independent of its composition Ex.:- brass is a solid solution ( copper 64% & zinc 36% )

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Types of solid solution Substitution solid solution ( brass ) Disordered ( b ) Ordered ( c ) 2.Interstitutional solid solution

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Substitutional solid solution One type of atom for another so that solute(cu) enter the crystal to take positions normally occupied by solvent atoms (nickel) The great majority of the solid solution are substitutional type Example:-Cu- Ni,Cd -mg.

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Disordered substitutional solid solution Soluant atom do not occupy any specific position Random in the lattice structure of the solvent. example :- alloy

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Ordered substitutional solid solution The alloy in the disordered condition, If in I cooled slowly, under-goes a re-arrange mentof the atoms because of the diffusion that takes place during cooling.

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INTERSTITIAL SOLID SOLUTION Small solute vs. large solvent More common for C, N, O, and H as solutes More easily dissolved in transition metal solvent Solubility is limited Solute diffuses easily via interstitial diffusion route.

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The C is still too large for the interstitial sites so the Fe lattice is badly strained.

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Hume Rothery’s Rules Types of Hume Rothery’s Rules : Crystal Structure Factor 2. Relative Size Factor 3. Chemical-affinity Factor 4. Relative Valence Factor William Hume- Rothery (1899-1968)

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Crystal Structure Factor:- The Crystal lattice structure of the two elements should be same for complete solubility, otherwise the two solution would not merge into each other. Also, for complete solid solubility the size factor must usually be less than 8%

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Example:-Al and Si Al and Si is partially soluble . (phase diagram ) Si => diamond cube Structure Al => F.C.C. Structure

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2. Relative Size Factor(the 15%):- If two metals are to exhibit extensive solid solubility in each other it is essential that their atomic diameter shall be fairly similar, since atoms differing greatly in size cannot be accommodated readily in the same structure. If the relative size factor is between 8% and 15%, the alloy system usually shows a minimum and if this factor is greater than 15%, substitutional solid solution formation is very limited Mismatch= r(solute)-r( solvant ) *100<=15% r( solvant )

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EXAMPLE:- Al and Si Radius of Aluminum is 0.0143 nm Radius of silicon is 0.117 nm %different = r Al - r si *100 r Al = 0.0143-0.117 *100 0.0143 = 18.2% >15%

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3. Chemical-affinity Factor The greater the chemical affinity of two metals, the more restricted is their solid solubility. When their chemical affinity is great, two metals tend to form an intermediate phase rather than a solid solution. Generally, the farther apart the elements are in the periodic table, the greater is their chemical affinity. EXAMPLE:- Al and Si Al electro negativity is 1.6 , Si electro negativity is 1.9

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4. Relative Valence Factor Consider two atom ,one with large valence electron and the other with small number of valence electrons EXAMPLE:- Al and Si Al has a +3 charge Si has a +4 charge

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Another Example is :- in the Al-Ni alloy system, both metals have f.c.c . structure. The relative size factor is approximately 14 % . However, Ni is lower in valance than Al and thus solid nickel dissolves 5% aluminums, but the higher valance Al dissolves only 0.04% Ni.

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A ny Question????

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GUIDENER:-N.S.DOSHI

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