Synthesis of new bulk metallic glassy Ti60Al15Cu10W10Ni5 alloy by hot-pressing the mechanically alloyed powders at the supercooled liquid region

Abstract

The mechanical alloying method has been used to fabricate multicomponent Ti60Al15Cu10W10Ni5 glassy alloy powders, using a low-energy ball-milling technique. The glassy powders that were obtained after 720 ks of milling have a sphere-like morphology with an average particle size of 0.38 µm in diameter. This new glassy alloy exhibits a glass transition temperature (Tg) at 733 K. It crystallizes at a crystallization temperature (Tx) of 804 K through a single sharp exothermic peak, with an enthalpy change of crystallization (ΔHx) of −5.20 kJ/mol. The supercooled liquid region before crystallization ΔTx of the obtained glassy powders shows a large value (71 K). The reduced glass transition temperature (ratio betweenTg and liquidus temperatures,T1(TG/T1) was found to be 0.46. The synthetic glassy powders were uniaxial hot-pressed into consolidated round objects with large dimensions (20 mm in diameter × 30 mm in height) in an argon gas atmosphere at several temperatures with a pressure of 936 MPa. The samples that were consolidated at the temperature range of 755 to 775 K (within the ΔTx region) are fully dense (∼99.85 pct) and maintain the chemically homogeneous glassy structure. These hot-pressed glassy samples exhibit excellent mechanical properties for Ti-base metallic glasses. They have high Vickers microhardness values, in the range between 8.0 and 8.2 GPa. They also show high fracture strength (2.28 GPa) with an extraordinarily high Young’s modulus of 153 GPa. Neither yielding stress nor plastic strain could be detected for this glassy alloy, which shows an elastic strain of 1.39 pct.