100 m Figure 1: 100X Micrograph for Grain Size Calculations Calculate the number of grains per square inch at the magnification level established to obtain the photomicrograph. Modify the calculation to obtain the number of grains per square inch at a 100x magnification factor, using the following equation: n100=nMM/100 where n100 is the number of grains per square inch at a 100x magnification factor, and n is the number of grains per square inch at the magnification factor, M, of the photomicrograph The ASTM grain size number, N. (ASTM Designation: E 112) can be calculated using the following equation: N= In() In(2) +1 Next, draw a series of 5 lines across the sample and note their length. You will need to use a good ruler to determine the real length of the line 1. Use a different orientation for each of 5 lines to assure that you randomize the results. Each line should be approximately 10 cm long. The total line length should be a minimum of 50 cm. Count the number of grain boundary intercepts n and determine the grain size d using the formula below where Mis the magnification: d = 1 M Use the average of your measurements as your grain size for comparison.