Date of Award


Embargo Period


Degree Type


Degree Name

Doctor of Philosophy (PhD)




Measurements were made of the magnetostriction of Fe-Si alloys varying in composition of 2.5 to 8 percent silicon by weight. Calculations were made to show how the magnetostriction constants can be obtained accurately from the measurements. The "form effect" of the specimens was calculated and subtracted from the measured values. For each of the alloys only two constants were found necessary to describe the strain. For annealed material the constant h1 (in Becker's notation ) was found to be zero at about 6 wt. percent silicon and h2 to be zero at about 5 wt. percent. Measurements on quenched crystals show that at about 9 or 10 atomic percent silicon a difference in the constant h1 from that for the annealed crystals begins to appear. Presumably the order-disorder transformation begins at about this percentage. In part II a survey is made of previous magnetostriction theories. The only one susceptible to calculation is the magnetic dipole theory. For silicon-iron this theory leads to values which are too small, but not always negligible. In the absence of exact knowledge as to the principal cause of magnetostriction a semi-empirical theory is proposed.