Question

"It is necessary to select a metal alloy for an application that requires a yield strength of at least 345 MPa (50,000 psi) while maintaining a minimum ductility (%EL) of 20%. If the metal may be cold worked, decide which of the following are candidates: copper, brass, and a 1040 steel."

Answer 1

Answer:

Both Brass and 1040 Steel maintain the required ductility of 20%EL.

Explanation:

Solution:-

- This questions implies the use of empirical results for each metal alloy plotted as function of CW% and Yield Strength.

- So for each metal alloy use the attached figures as reference and determine the amount of CW% required for a metal alloy to maintain a Yield Strength Y = 345 MPa.

- Left Figure (first) at Y = 345 MPa ( y -axis ) and read on (x-axis):

                        1040 Steel --------> 0% CW

                        Brass ---------------> 22% CW

                        Copper ------------> 66% CW

The corresponding ductility (%EL) for cold Worked metal alloys can be determined from the right figure. Using the %CW for each metal alloy determined in first step and right figure to determine the resulting ductility.

- Right Figure (second) at respective %CW (x-axis) read on (y-axis)

                       1040 Steel (0% CW) --------> 25% EL

                        Brass (22% CW) -------------> 21% EL

                        Copper (66% CW) ----------> 4% EL

We see that both 1040 Steel and Brass maintain ductilities greater than 20% EL at their required CW% for Yield Strength = 345 MPa.