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The table shows the temperatures at which solidification starts and ends as the alloys of cadmium and zinc are cooled from liquid to solid - Leaving Cert Engineering - Question b - 2008
Question b
The table shows the temperatures at which solidification starts and ends as the alloys of cadmium and zinc are cooled from liquid to solid. Amount of zinc % | 0 | 1... show full transcript
Worked Solution & Example Answer:The table shows the temperatures at which solidification starts and ends as the alloys of cadmium and zinc are cooled from liquid to solid - Leaving Cert Engineering - Question b - 2008
Step 1
Using the graph paper supplied, draw the thermal equilibrium diagram.
Answer
To draw the thermal equilibrium diagram, follow these steps:
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Set up the axes: The horizontal axis should represent the percentage of zinc (from 0% to 100%), while the vertical axis represents the temperature (in °C).
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Plot the points: Using the data from the table, plot the solidification start and end temperatures for each percentage of zinc. For example:
- At 0% zinc, the solidification start is 321°C, and the end is 266°C.
- At 100% zinc, the solidification start is 410°C, and the end is 266°C.
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Connect the points: Draw smooth lines connecting the solidification start temperatures, forming a curve that decreases as zinc content increases. Then, draw a horizontal line at 266°C from 0% to 100% for the solidification end.
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Identify key areas: Highlight the areas that represent the liquid phase, liquid/solid phase, and solid phase on the diagram.
Step 2
Label the diagram and describe the main features.
Answer
Once the diagram is drawn, label the key features:
- Liquid region: Above the liquidus line where the alloy is entirely liquid.
- Liquidus line: The line separating the liquid region from the liquid/solid region, marking the beginning of solidification.
- Liquid + solid phase: The region below the liquidus line but above the solidus line where the alloy is in a pasty state.
- Solidus line: The line indicating the completion of solidification; below this line, the alloy is entirely solid.
- Solid region: Below the solidus line, where the alloy has completely solidified.
- Eutectic point: The composition and temperature where the alloy transitions without passing through a pasty phase, typically located around 20% zinc and corresponding eutectic temperature on the graph.