The formation mechanism of novel Fe-P-B metallic glasses : A perspective from nearly free electron model

By a systematic investigation on the accumulating experimental data of various Fe-based metallic glasses (MGs), we have found a negative relationship between the electron concentration, e/a, and the composition of Fe. The thermodynamic basis for the relationship can be interpreted from the modified nearly-free-electron model using idealized atomic packing theory. The results indicate that the e/a dependence of glass forming ability in Fe-based MGs with admixture of metalloid elements results from the change of coordination number in corresponding atomic configuration around the metalloid elements, which can be predicted from their different atomic size ratios by the quasi-equivalent cluster model. And a novel Fe-B-P metallic glass system is discovered based on this relationship. The range of e/a together with mismatch entropy will provide new guideline on the accurate control of the metalloid concentration for developing Fe-based MGs with good soft magnetic properties and high glass forming ability.