Formation, Thermal Stability and Mechanical Properties of Bulk Glassy Alloys with a Diameter of 20 mm in Zr-(Ti,Nb)-Al-Ni-Cu System

Abstract

Bulk glassy alloy rods with a diameter of 20 mm were produced for Zr 61 Ti 2 Nb 2 Al 7:5 Ni 10 Cu 17:5 and Zr 60 Ti 2 Nb 2 Al 7:5 Ni 10 Cu 18:5 by a tilt casting method. The replacement of Zr by a small amount of Ti and Nb caused a distinct increase in the maximum diameter from 16 mm for Zr 65 Al 7:5 Ni 10 Cu 17:5 to 20 mm, accompanying the decrease in liquidus temperature and the increase in reduced glass transition temperature. The primary precipitation phase from supercooled liquid also shows a distinct change, i.e., from coexistent Zr 2 Cu, Zr 2 Ni and Zr 6 NiAl 2 phases for the 65%Zr alloy to an icosahedral phase for the 61%Zr and 60%Zr alloys. These results allow us to presume that the enhancement of the glassforming ability is due to an increase in the stability of supercooled liquid against crystallization caused by the development of icosahedral shortrange ordered atomic configurations. The 60%Zr specimens taken from the central and near-surface regions in the transverse cross section at the site which is 15 mm away from the bottom surface of the cast glassy rod with a diameter of 20 mm exhibit good mechanical properties under a compressive deformation mode, i.e., Young's modulus of 81 GPa, large elastic strain of 0.02, high yield strength of 1610 MPa and distinct plastic strain of 0.012. Besides, a number of shear bands are observed along the maximum shear stress plane on the peripheral surface near the final fracture site. The finding of producing the large scale Zr-based bulk glassy alloys exhibiting reliable mechanical properties is encouraging for future advancement of bulk glassy alloys as a new type of functional material.

Deformation Evolution of a Zr-Based Bulk Metallic Glass under Three-Point Bending Tests

“…In the present work, the deformation evolution and mechanisms of a Zr-based BMG under three-point bending tests are investigated. A Zr 65 Cu 17.5 Ni 10 Al 7.5 BMG is selected for its good glass forming ability, and has also been studied extensively due to its potential engineering applications [17][18][19][20][21].…”

Recent Development and Applications of Bulk Glassy Alloys

“…It was reported that the eutectic Zr 55 Al 10 Cu 30 Ni 5 alloy rods retained a glassy phase in the diameter range up to 30 mm 7,8 in the case of copper mold suction casting and 32 mm using copper mold cap casting 44 . Similarly, the maximum diameter for the hypoeutectic‐type glassy alloys has been reported to be at least 20 mm for Zr 60 Al 10 Ni 10 Cu 20 , Zr 61 Ti 2 Nb 2 Al 7.5 Ni 10 Cu 17.5 , Zr 60 Ti 2 Nb 2 Al 7.5 Ni 10 Cu 18.5 , and Zr 65 Al 7.5 Ni 10 Cu 15.5 Pd 2 (K. S. Son, X. M. Wang, A. Inoue, personal communication) 57 and 16 mm for Zr 65 Al 7.5 Ni 10 Cu 17.5 58 by copper mold tilt casting. We have also confirmed that the thermal stability parameters of T g , T x , and Δ T x (= T x − T g ), static mechanical properties of Young's modulus, yield strength and plastic strain, and deformation and fracture behaviors via shear sliding along the maximum shear stress plane and then catastrophic final rupture are independent of the picking position and the picking angle to the longitudinal direction of the cast alloy rod as well as the rod dimension in the diameter range up to 20 mm 59 .…”