AL-LA-CU AMORPHOUS-ALLOYS WITH A WIDE SUPERCOOLED LIQUID REGION

Amorphous Al-La-Cu alloys exhibiting a wide supercooled liquid region and a high reduced glass transition temperature (Tg/Tm) were formed over a compositional range from 25 to 85 at% La and 0 to 60%Cu by melt spinning. The temperature span ΔTx (= Tx-Tg) between Tg and crystallization temperature (Tx) reaches as large as 59 K for Al20La55Cu25. The Tg/Tm is also as high as 0.68 for Al20La55Cu25 and the Al-La-Cu alloys are concluded to have a high glass-forming ability. The Tx and hardness (Hv) increase with increasing Al and Cu contents in the range from 430 to 575 K and 140 to 300 and the tensile strength also has a similar compositional dependence in the range of 535 to 880 MPa. The compositional effect on Tx and Hv was presumed to originate from the variation of the atomic configuration which reflects the compounds of La3Al, La(Al, Cu) and La(Al, Cu)2. The high stability of the supercooled liquid against the precipitation of crystalline phases in the vicinity of the stoichiometric composition Al1La2Cu1, i.e., large ΔTx and high Tg/Tm, seems to result from an optimum bonding state of the constituent atoms for the stoichiometric alloy. © 1990, The Japan Institute of Metals. All rights reserved.