The figure below shows the copper-nickel phase diagram as well as three possible

Question

The figure below shows the copper-nickel phase diagram as well as three possible cast structures, which can be formed during solidification of a metal in a cold square mold.

For the Cu-Ni system, state the type and/or composition(s) of metal/alloy which would produce the structure in Figure 3-a.

2. Which one of the three possible structures (3-a, 3-b, and 3-c) might result due to the solidification of an alloy with 15 wt% Cu.

3. Calculate the freezing range for the following alloys: 0 wt% Cu, 20 wt% Cu, and 50 wt% Cu.

4. State the practical method for obtaining the cast structure shown in Fig. 3-c

5. Would you expect the alloy with 20 wt.% Cu to have higher or lower

microporosity than the alloy with 50 wt.% Cu. Explain.

Figure 3a

fig 3a, 3b, 3c

The figure below shows the copper-nickel phase diagram as well as three possible cast structures, which can be formed during solidification of a metal in a cold square mold. For the Cu-Ni system, state the type and/or composition(s) of metal/alloy which would produce the structure in Figure 3-a. 2. Which one of the three possible structures (3-a, 3-b, and 3-c) might result due to the solidification of an alloy with 15 wt% Cu. 3. Calculate the freezing range for the following alloys: 0 wt% Cu, 20 wt% Cu, and 50 wt% Cu. 4. State the practical method for obtaining the cast structure shown in Fig. 3-c 5. Would you expect the alloy with 20 wt.% Cu to have higher or lower microporosity than the alloy with 50 wt.% Cu. Explain. fig 3a, 3b, 3c Figure 3a

Explanation / Answer

1)we can see that there is no segregation and no presence of mushy zone(i.e no L+S) phase,as it woun=ld have resulted in equaxed phases .so ,3A may be 100% cu or 100% NI

2)3b is the answer.

as we cool down from liquid ,the transition will go through (L+S) whrere the grains will grom columnar and then the (L+s)in central region will lead to equaxed grains

3)0 wt% Cu,-1084C

20 wt% Cu,-1120 -1180 C(approx)

and 50 wt% Cu.1250-1310 C(approx)

4)the practical method would be heating the walls so that there is shallow temperature graident.

this would lead to forming of equiaxed grains throughout the structure.also cooling withlow temp will lead to rapid solidification leading to equiaxed grains

5)when cooling a liquid meld ,microporosity develops if two phases have different freezing point.the uneven contraction of the phases will result in microporosity .

so ,no looking at the phase diagram you can see that the 50% alloy has a wider (S+L) zone in which case there are two phases with different contraction rate. so there will be hogher microporosity

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