   # Engineering Materials Week 6

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Engineering Materials Week 6
9.7 Given here are the solidus and liquidus temperatures for the copper-gold system. Construct the phase diagram for this system and label each region.

9.22 For 5.7 kg of a magnesium-lead alloy of composition 50 wt% Pb-50 wt% Mg, is it possible, at equilibrium, to have α and Mg₂Pb phases with respective masses of 5.13 and 0.57 kg? If so, what will be the approximate temperature of the alloy? If such an alloy is not possible, then explain why.
It is not possible.

From the figure the maximum concentration of Pb in the α + Mg₂Pb phase filed is about 42 wt% Pb.

9.39 The room temperature tensile strengths of pure copper and pure silver are 209 MPa and 125 MPa.
a). Make a schematic graph of the room temperature tensile strength versus composition for all compositions between pure cooper and pure silver.
b). On the same graph schematically plot tensile strength versus composition at 600C.

c). Explain the shapes of these two curves, as well as any differences between them.
Silver is insoluble in cooper due to there being no α-phase region and vice versa for the β-phase region. Therefore only the α and β phase will exist at room temperature for all compositions. The tensile strengths of each of these phases are determined by:

In which TS and V denote the tensile strength and volume fraction and the subscripts denote the phases. At 600C the curve will be shifted to lower tensile strengths since tensile strength diminishes with increasing temperature.
9.41 What is the principal difference between congruent and incongruent phase transformations?
The principal difference between congruent and incongruent phase transformations is that for congruent, no compositional changes occur with any of the phases that are involved in the transformation. For incongruent there will be compositional alterations of the phases.
9.65 A steel alloy contains 95.7 wt% Fe, 4.0 wt% W and 0.3 wt% C.
a). What is the eutectoid temperature of this alloy? 900C
b). What

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