Mg-based bulk glassy alloys with high strength above 900 MPa and plastic strain
- PDF / 933,617 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 107 Downloads / 186 Views
Cunling Qin Japan Science and Technology Agency, Sendai 980-8577, Japan
Akihisa Inoue Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan (Received 5 August 2004; accepted 26 October 2004)
Bulk metallic glasses with a maximum diameter of 2.5–5 mm were formed in Mg75Cu5Ni10Gd10, Mg70Cu15Ni5Gd10, and Mg65Cu20Ni5Gd10 systems by copper mold casting. There is a clear tendency for glass-forming ability (GFA) to increase with increasing solute content. These bulk glassy alloys exhibit a large supercooled liquid region (⌬Tx) of 44–64 K, indicating high thermal stability of the supercooled liquid. The Young’s modulus, fracture strength, elastic elongation limit, and plastic strain are in the range of 54–59 GPa, 854–904 MPa, 1.50–1.55%, and 0.10–0.20%, respectively. The Mg65Cu20Ni5Gd10 alloy exhibited the highest values of Young’s modulus and strength, while the largest plastic strain was obtained for the Mg75Cu5Ni10Gd10 alloy. The bulk Mg–Cu–Ni–Gd-based metallic glasses exhibited distinct enhanced corrosion resistance compared to Mg65Cu25Gd10 glassy alloy in NaCl aqueous solutions. The fabrication of the Mg-based bulk glassy alloys exhibiting a high strength level of about 900 MPa and plastic strains of ∼0.2%, in conjunction with good corrosion resistance, indicates that the Mg-based bulk glassy alloys may be used as a new generation of structural material.
I. INTRODUCTION
In recent years, much effort has been devoted to change the structure from the crystalline periodic atomic configuration to the disordered random state for Mgbased alloys, with the aim of developing a glassy Mgbased alloy with much higher strength. A large supercooled liquid region of over 50 K before crystallization was found in the Mg–Ln–(Ni,Cu) (Ln ⳱ lanthanide metal) system in 1988,1 and the high stability of supercooled liquid against crystallization resulted in the formation of Mg-based bulk glassy alloys by copper mold casting.2 Subsequently, a large number of Mg-based bulk metallic glasses (BMG) have been developed by modifying the Mg–Ln–(Ni,Cu) base system. As modified alloy systems of bulk glassy alloys, one can list Mg–Cu– Y–Ag,3 Mg–Cu–Y–Pd–Ag,4 Mg–Cu–Y–Pd–Ag–Ni,5 and Mg–Cu–Gd6 systems. The maximum diameter of these Mg-based bulk glassy alloys has reached 13–15 mm.4,5
a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2005.0044 394
http://journals.cambridge.org
J. Mater. Res., Vol. 20, No. 2, Feb 2005 Downloaded: 14 Mar 2015
With respect to mechanical properties, tensile deformation tests have been made only for Mg80Cu10Y10 bulk alloy sheets produced by high-pressure die casting.2 The tensile fracture strength and Young’s modulus have been reported to be 630 MPa and 35 GPa at room temperature. The compressive fracture strength for Mg65Cu15Ag5Pd5Y10 BMG was reported to be 770 MPa.7 Little is known about ductility of Mg-based bulk glassy alloys produced by conventional copper mold casting. One should note that low ductility of the bulk metallic glasses at room temperature would
Data Loading...
