1. (i) (2 points) Comparing to micro-structured Cu-Ni alloy, Cu-Ni alloy with nanostructured boundaries has ( ). (A)Large grains (B)Low ductility (C)Low yield strength (D)Low tensile stress (ii) (8 points)

An alloy shows the resistance of lattice to dislocation motion at 70 MPa. The SEM analysis shows the alloy consisting of multiple grains as below. Please use the SEM image shown below (the physical length of the Scale bar is 1.27" in the image) to determine the yield strength of the alloy (assuming the strengthening coefficient 1.7 Mpa/m", physical length of each red line drawn on the image is 2.62").