Effects of Test Temperature and Loading Conditions on the Tensile Properties of a Zr-Based Bulk Metallic Glass

Abstract

The effects of changes in test temperature (20°C, 260°C, 330°C, and 380°C), strain rate (10 -5 to 10 -1 s -1 ), and loading conditions (displacement control vs loading-rate control) on the tensile behavior of Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 (LiquidMetal 1 (LM1)), a bulk metallic glass (BMG), have been determined. Significant effects of the test temperature, strain rate, and loading condition were observed on the strength, ductility/elongation, and mechanisms of failure (shear, ductile rupture, etc.). This material exhibited extensive elongation (i.e., >100 pct) prior to failure when tested near the glass transition temperature (T g % 375°C) at sufficiently low strain rates, while higher strain rates or lower test temperatures produced shear fracture at low elongation. The flow and fracture behavior was also significantly affected by the loading condition (i.e., displacement vs loading-rate control). The effective strain rate necessary to cause failure in shear without significant global flow was several orders of magnitude lower in loadingrate control than in displacement control. Samples exhibiting high elongation tested in displacement control gently and convexly drew to a near point (i.e., ductile rupture). Samples tested at the same temperature exhibiting high elongation in loading-rate control rapidly and concavely necked, followed by drawing to a constant diameter ''wire'' (i.e., ductile drawing), eventually failing by nearly pure ductile rupture. All samples that displayed significant elongation did so inhomogeneously, and were characterized by non-Newtonian global flow.

Effects of Changes in Test Temperature and Loading Conditions on Fracture Toughness of a Zr-Based Bulk Metallic Glass

“…[20] The present work further shows that the toughness and macroscopic fracture mode at high temperature strongly depends on the loading rate (i.e., local strain rate). Wang et al [36] established a deformation mechanism map that delineated the boundaries between distinctly different failure modes in tension.…”

“…[1] The material was received in the form of plates with 2.7-mm thickness and is identical in composition, including oxygen analyses, to our previous works on this material. [7,8,11,12,[20][21][22] …”

“…These temperatures were selected based on the expected softening that will occur near T g , shown via hot hardness studies, [28] and from tension tests reported elsewhere. [20] The DSC measurements of T g for this material are also reported elsewhere. [29] The chamber's heating rate was about 0.2 K/s enabling these temperatures to be reached within 1 to 2 hours and controlled within ±1 K. When the chamber reached the desired temperature, the sample was left to equilibrate for 20 to 25 minutes before running the test, which was monitored and recorded by the LABVIEW program (National Instruments, Austin, TX).…”

“…Related recent work has reported the significant effects of displacement rate control vs loading rate control on the tensile properties. [20] II. EXPERIMENTAL PROCEDURES…”

Deformation and fracture of a Zr-Al-Cu metallic glass ribbon under tension near glass transition temperature

“…The tensile strength at room temperature for the present test is much lower than that reported by other researchers [23,24] whose results of about 2,000 MPa were based on a compression test. This may be attributed to lower stress state softening parameter of tensile testing and high stress concentration caused by the raw rough state of test ribbons.…”