Effects of Changes in Test Temperature and Loading Conditions on Fracture Toughness of a Zr-Based Bulk Metallic Glass
- PDF / 604,216 Bytes
- 9 Pages / 593.972 x 792 pts Page_size
- 80 Downloads / 245 Views
ODUCTION
THE interest in metallic glasses has increased after the development of bulk metallic glasses (BMGs) during the early 1990s.[1–3] Several multicomponent systems such as Zr-Al-Ni,[2] Zr-Al-Cu-Ni,[3] and Zr-Ti-Cu-NiBe[1] have been discovered that exhibit exceptional glass formability. Peker and Johnson[1] reported that Zr-TiCu-Ni-Be forms glass at cooling rates less than 10 K/s, enabling fabrication of fully amorphous rods up to 14 mm in diameter. Some of the BMGs possess strength in excess of structural steel, have greater wear and corrosion[4] resistance, are tougher than ceramics,[5–8] and have greater elasticity. This work is focused on a Zr-Ti-Ni-Cu-Be bulk metallic glass, with tensile strength of 2 GPa[9–12] and density of 6.1 g/cm3.[13,14] This BMG is a possible candidate for structural applications because of its high strength-to-weight ratio[14] and has been used to fabricate golf club heads because of its high strengthto-stiffness ratio.[14] Recent work has begun to investigate the corrosion resistance,[15,16] mechanical strength,[9,11,12,15,17] fatigue behavior,[18,19] and glass formability[3] of these materials. Although metallic glasses exhibit almost zero global plastic tensile strain at failure, the elastic strain at failure approaches 2 pct and high local strains are evident on fracture surfaces. Surprisingly high values for toughness have been HALA A. HASSAN, formerly Fulbright fellow, CWRU, Cleveland, OH 44106, is now Assistant Professor, with Department of Design and Production Engineering, Faculty of Engineering, Ain Shams University, Cairo, Egypt. LASZLO KECSKES, Research Physical Scientist, is with the US Army Research Laboratory, Aberdeen Proving Ground, MD 21005-5069. J.J. LEWANDOWSKI, Leonard Case, Jr. Professor of Engineering, Department of Materials Science and Engineering, CWRU, Cleveland, OH 44106. Contact e-mail: [email protected] Manuscript submitted December 18, 2007. Article published online May 17, 2008 METALLURGICAL AND MATERIALS TRANSACTIONS A
reported at room temperature,[7,8,10] but very little work has been reported on the effects of changes in test temperature up to the glass transition temperature (Tg), or loading conditions, on this property. The objectives of this work are to determine the effects of changes in test temperature, in addition to changes in loading rate under both displacement rate control and loading rate control on the fracture toughness and the failure mechanisms of a Zr-based BMG. Related recent work has reported the significant effects of displacement rate control vs loading rate control on the tensile properties.[20]
II.
EXPERIMENTAL PROCEDURES
A. Materials The zirconium-based bulk metallic glass (BMG) used in this investigation is commercially known as Vitreloy I, or Liquidmetal 1 (LM1) (Liquidmetal Technologies, Lake Forest, CA). The composition of this alloy is Zr41.8Ti12.9Cu12Ni9.5Be23.8 (at. pct). The general processing details have been summarized elsewhere.[1] The material was received in the form of plates with 2.7-mm thickness and is identical
Data Loading...
