Effect of Additional Elements (M) on the Thermal Stability of Supercooled Liquid in Fe_(72-x)Al_5Ga_2P_(11)C_6B_4M_x Glassy Alloys

摘要

The dissolution of 2 at percent Nb, 5 percent Mo, 4 percent Cr or 6 percent Co for the Fe_(72-x)Al_5Ga_2P_(11)C_6B_4M_x glassy alloys was found to be effective for the extension of the supercooled liquid region defined by the difference in the glass transition temperature (T_g) and crystallization temperature (T_x), #DELTA#T_x(=T_x- T_g). The #DELTA#T_x value is 60K for the Fe-Al-Ga-P-C-B alloy and in-creases to 66 K for M=2 percent Nb, 62 K for 4 percent Mo, 61 K for 4 percent Cr or 6 percent Co. The increase in #DELTA#T_x is due to the increase in T_x exceeding the degree in the increase in T_g. The crystallization of the glassy alloys with #DELTA#T_x above 60 K takes place through a single stage of amorphous (Am) ->#alpha#-Fe + Fe_3P + Fe_3C + Fe3B and no appreciable change in the crystallized structure with M elements is seen. On the other hand, the addition of 2 percent Cu or 2 percent Ni causes the disappearance of the glass transition phenomenon before crystallization, accompanying the change in the crystallization process to the two stages of Am->Am'+#alpha#-Fe->#alpha#-Fe+Fe_3P+Fe_3C+Fe_3B. It is therefore concluded that the appearance of the wide super-cooled liquid region is due to the retardation of crystallization resulting from the redistribution of the constituent elements on a long range scale which is required for the simultaneous precipitation of the four crystalline phases. The effectiveness of additional Nb, Mo or Cr element is presumably because the redistribution of the constituent elements leading to the crystallization becomes difficult.