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The table shows the solidification temperatures for various alloys of Cadmium and Bismuth - Leaving Cert Engineering - Question b - 2021
Question b
The table shows the solidification temperatures for various alloys of Cadmium and Bismuth. The melting temperature of Bismuth is 268°C and the melting temperature of... show full transcript
Worked Solution & Example Answer:The table shows the solidification temperatures for various alloys of Cadmium and Bismuth - Leaving Cert Engineering - Question b - 2021
Step 1
Draw the equilibrium diagram
Answer
To draw the equilibrium diagram:
- Plot the % of Cadmium in the alloy on the x-axis ranging from 0 to 100%.
- Plot the corresponding start and end solidification temperatures on the y-axis, which range from 140°C to 321°C.
- Connect the data points for the start of solidification using a curve to represent the liquidus line.
- Connect the data points for the end of solidification to create the solidus line.
- Identify the eutectic point, which occurs at around 64% Cadmium, at a temperature of approximately 143.5°C, and mark it on the diagram.
Step 2
For the alloy containing 75% Cadmium, determine from the diagram the ratio of the phases at 200°C.
Answer
From the diagram, at 75% Cadmium and 200°C:
- Locate the point on the liquidus and solidus lines at 75% Cadmium. The temperature intersects the liquidus line at 200°C and the solidus line above this temperature.
- The lengths of the segments between these points give the ratio of liquid to solid.
- Let |AB| be the distance of liquid and |BC| be the distance of solid. The ratio of liquid to solid is calculated as follows:
Step 3
For the alloy containing 20% Cadmium, describe, with the aid of a diagram, the cooling curve.
Answer
For the 20% Cadmium alloy:
- As the alloy cools from 205°C, it begins to solidify when it reaches the start of solidification at that temperature.
- As cooling continues, the temperature remains constant at 205°C until solidification begins.
- Once solidification starts, the temperature drops to the end of solidification at 140°C, indicating that the alloy will complete its phase transition to solid at this temperature. The cooling curve should be represented as a horizontal line at 205°C and then decrease to 140°C where the solidification ends.