= Below is the relationship between grain diameter (d) and duration of grain growth (time t). d dm = K t (Equation 7.9) where n and K are material/process properties and do is the initial grain diameter when t = 0. Consider a material that has an initial grain diameter of 1.7x10-2 mm. After a heat treatment for 250 minutes, the grain diameter increased to 4.5x10-2mm. Compute the time required for a specimen of this same material (i.e. do = 1.7x10-2 mm) to achieve a grain diameter of 8.7*10-2 mm while being heated at the same temperature. Assume the grain diameter exponent (n) has a value of 2.1