The flow stress of a coarse-grained dilute copper alloy increased from 2 to 55 MPa when the dislocation density was increased from a low value of 107cm2 via cold working to a modest value of 1010cm2. Calculate the flow stress for this alloy when heavy cold working introduces a dislocation density of 1012cm2. An equation similar to the Hall-Petch equation has been proposed for dislocations, and is: flow=o+kddisl where flow is the flow stress (i.e., the force per unit area necessary to get plastic deformation), disl is the dislocation density (the dislocation line length per unit volume), and o and kd are constants for a given material. The easiest way to solve this problem is to put values into this equation twice, subtract one expression from the other, and solve for kd. Then enter your value of kd into either original equation to determine o. Keep track of units, and then solve the problem stated above. A low-carbon steel has a yield strength of 622MPa when the average grain diameter is 180m. When the grain diameter is reduced to 22m, the yield strength increases to 663MPa