FORMATION AND PROPERTIES OF MG-BASED METALLIC GLASSES IN MG-TM-X ALLOYS (TM-EQUIVALENT-TO-CU OR NI - X-EQUIVALENT-TO-SN, SI, GE, ZN, SB, BIOR IN)

Amorphous Mg-TM-X (TM = Cu or Ni; X = Sn, Si, Ge, Zn, Sb, Bi or In) al loys are produced by a single-roller melt-spinning technique. It is fo und that, by varying the quenching speed, the amorphous phases can rea dily be formed in Mg-TM-Sn alloys and the critical thickness for formi ng complete amorphous ribbons can be expanded to about 150-200 mum. Ca lorimetry studies reveal that the reduced glass temperature T(rg) in M g-TM-Sn metallic glasses is about 0.52, which is quite low compared wi th that of the conventional good glass formers. A fracture tensile str ength as high as 900 MPa is recorded for Mg80Ni15Sn5 metallic glass. w hich is much higher than that of the conventional Mg-based crystalline alloys. Substitution of Sn by Sb, Bi or In in these Mg-based alloys c an also result in metallic glass formation; however a high quenching s peed is needed and the tensile strengths are much reduced. The glass f ormability in these Mg-based alloys is discussed within the framework of current metallic glass formation theories.