Answer the following questions by referring to the Cu-Al phase diagram shown below.
(a) What is the lowest temperature at which a liquid can be found in a system of any composition of Cu-Al?
correct
(b) A common alloy composition used in airplanes is 4 at. % Cu - 96 at. % Al. For this overall system composition, identify what phases are present at 500 degrees C. Select all phases present:
Liquid
Vapor
Al
Cu
CuAl2
CuAl
Cu1.5Al
Cu9Al4
Cu4Al
Cu0.75Al0.25
(c) What phases are present at a 50/50 mixture of Al/Cu at 660 degrees C? Select all phases present:
Liquid
Vapor
Al
Cu
CuAl2
CuAl
Cu1.5Al
Cu9Al4
Cu4Al
Cu0.75Al0.25
You have used 1 of 3 submissions
(d) In the previous question, you should have identified two phases. What is the phase fraction of the first phase you identified?
In the previous question, the two phases identified at a 50/50 mixture of Al/Cu at 660 degrees C are:
1. CuAl2
2. CuAl
The phase fraction of the first phase (CuAl2) is not provided in the given information.
To answer question (a), we need to refer to the Cu-Al phase diagram. The phase diagram shows the relationship between temperature and composition for the Cu-Al system.
To find the lowest temperature at which a liquid can be found in a system of any composition of Cu-Al, we look for the liquidus line on the phase diagram. The liquidus line separates the regions where the alloy is completely liquid from the regions where it is a solid or a mixture of solid phases.
In this case, the liquidus line starts at around 660 degrees Celsius on the left side of the diagram and goes down to around 550 degrees Celsius on the right side. So, the lowest temperature at which a liquid can be found in a system of any composition of Cu-Al is 550 degrees Celsius.
Now let's move on to question (b). The question asks about the phases present at a specific composition (4 at. % Cu - 96 at. % Al) and temperature (500 degrees Celsius). To determine the phases present, we need to find the corresponding point on the phase diagram.
To do this, we locate the composition (4 at. % Cu - 96 at. % Al) on the horizontal axis and find the corresponding temperature (500 degrees Celsius) on the vertical axis. Then, we look for the intersection point on the phase diagram.
At this specific composition and temperature, the phases present are CuAl2 and Al. Therefore, the correct answer is CuAl2 and Al.
Moving on to question (c), it asks about the phases present at a 50/50 mixture of Al/Cu at 660 degrees Celsius. Similarly, we locate the composition (50/50 mixture of Al/Cu) and the temperature (660 degrees Celsius) on the phase diagram.
At this specific composition and temperature, the phases present are CuAl2 and Liquid. Therefore, the correct answer is CuAl2 and Liquid.
Now let's answer question (d). In the previous question, we identified two phases, CuAl2 and Liquid, at a 50/50 mixture of Al/Cu and 660 degrees Celsius. The question asks for the phase fraction of the first phase identified, CuAl2.
To determine the phase fraction, we look at the boundaries of the composition range where CuAl2 phase is present. Based on the phase diagram, the CuAl2 phase exists in a narrow composition range. It's difficult to determine the exact phase fraction without more specific information about the composition within the 50/50 mixture.
Therefore, without additional information, we cannot determine the phase fraction of CuAl2 in the 50/50 mixture.