Formation, Thermal Stability and Mechanical Properties of Ca-Based Bulk Glassy Alloys

Abstract

New bulk glassy alloys were formed in the Ca-Mg-Cu system by the copper mold casting method. The maximum rod diameter (d max ) for the formation of a glassy phase was 2 mm for Ca 67 Mg 19 Cu 14 and above 4 mm for Ca 57 Mg 19 Cu 24 . The glass transition temperature (T g ), crystallization temperature (T x ), supercooled liquid region (∆T x = T x − T g ) and reduced glass transition temperature (T g /T m ) are 387 K, 407 K, 20 K and 0.60, respectively, for the former alloy and 404 K, 440 K, 36 K and 0.64, respectively, for the latter alloy. There is a tendency for d max to increase with increasing ∆T x and T g /T m . Young's modulus (E) and compressive fracture strength are 38 GPa and 545 MPa, respectively, for the Ca 57 Mg 19 Cu 24 alloy rod with a diameter of 2 mm. The success of synthesizing bulk glassy alloys in the simple metal (Ca) base system makes it important as a basic alloy system for examining fundamental chemical and physical properties of bulk glassy alloys.

Development and Characterization of Low-Density Ca-Based Bulk Metallic Glasses: An Overview

“…[5] and [6], k 1 and k 2 are, respectively, linear and parabolic oxidation-rate constants, and c 1 and c 2 are constants, which reflect the abrupt oxidation of juvenile surfaces during early stages of the oxidation experiment or a change in the mechanism of oxidation (for example, from a linear to a parabolic one). The values of these constants are given in Figure 9 near the corresponding oxidation curves.…”

“…[5]) is an indication that the ratedetermining step for the oxidation reaction is a gasmetal interface reaction. [57,58] This situation generally occurs when the surface oxide has a volume much different than the volume of the alloy from which it forms, and, therefore, it is unable to form a continuous passive layer and suppress further oxidation of the substrate alloy.…”

Development of Low Density Ca-Mg-Al-Based Bulk Metallic Glasses

“…[1][2][3][4][5][6][7][8][9][10] In particular, these metallic glasses have the lowest density ($2000 kgÁm À3 ) among all known amorphous metallic alloys. They also have low Young's modulus ($20{35 GPa) 11) comparable to the modulus of human bones, low glass transition temperature (T g $ 100{150 C) and a wide temperature range of super-cooled liquid (ÁT x ¼ T x À T g $ 30{70 C, where T x is the crystallization temperature).…”

Corrosion Properties of Ca Based Bulk Metallic Glasses

“…The first successful synthesis of Cabased bulk metallic glasses (Ca BMGs) produced Ca 57 Mg 19 -Cu 24 and Ca 60 Mg 20 Ag 20 in amorphous cylinders with diameters up to 4 mm 1) and Ca 60 Mg 20 Ag 10 Cu 10 with a maximum diameter of 7 mm.…”