Synthesis and mechanical behavior of nanocomposite Mg-based bulk metallic glasses

Abstract

Nanocomposites can be produced by partial crystallization of bulk metallic glasses (BMG). The introduction of such nanocrystals in an amorphous matrix can sharply change the mechanical behavior of the glass at room temperature. In the present study, the effect of crystals in Mg-based BMG is studied by partial crystallization of the Mg65Cu25Gd10 and addition of 3 at.% of iron. Various techniques (DSC, DRX, TEM) are used to get data about the nature, the volume fraction or the average size of the crystals. Mechanical properties at room temperature are investigated in compression. The fracture stress is enhanced by iron addition, but no favorable effect of partial crystallization is observed for the Mg65Cu25Gd10 BMG. These results are discussed in relation with the associated microstructures

Viscoplastic Forming of Mg Bulk Metallic Glasses in the Supercooled Liquid Region

“…Whatever the extent of crystallization, it has been shown that these crystallites maintained a relatively constant size. [29] The nature of the crystals (Mg 2 Cu and Cu 2 Gd) was confirmed by XRD and is in agreement with the results obtained by Men et al [30] The presence of both sphere-shaped and rod-shaped particles in the Mg 65 Cu 25 Gd 10 BMG during crystallization is expected to affect the value of F max vol in Relation [2]. However, this possible variation is particularly difficult to estimate quantitatively, and it is the reason why predicted reinforcement factors as a function of F vol have been drawn for various values of F max vol in Figure 10.…”

Large plastic stability in magnesium alloys: crystalline vs. amorphous alloys

“…The master alloy was re-melted several times to assure homogeneity. Amorphous Mg 65 Cu 25 Gd 10 rods of 4 mm diameter were obtained by copper mould casting in argon atmosphere [3]. XRD patterns taken from the cross-section of the rod confirmed the amorphous structure of the as-cast alloys (i.e.…”

Effect of silver on the glass forming ability of MgCuGdY bulk metallic glasses

“…At room temperature, Mg-based BMG exhibit generally brittle behavior in both compressive and tensile conditions. In previous experiments on MgCuGd(Fe) glasses tested in compression [16], maximum stresses between 650 and 800 MPa were measured with Young's modulus close to 45-50 GPa. Such fracture stresses are significantly larger than those generally obtained for conventional Mg alloys (Mg-Y-RE alloys = 300 MPa with Young's modulus = 45 GPa).…”

“…Improvement of GFA has been reported in Mg 65 Cu 25 Y 10 alloys where Cu is partially substituted with transition metals such as Ni, Zn, Ag, Pd [2,[5][6][7][8] and in Mg 65 Cu 25 Gd 10 alloys by the same metal substitutions [9][10][11][12][13] and samples with D c of 14 mm were produced in MgCuNiAgZnYGd alloys. Recently in the search for high GFA in magnesium alloys Ma et al have proposed alloys with various Mg/Cu composition ratios and D c of 16 and 25 mm were obtained on Mg 54 Cu 28 Ag 7 Y 11 and Mg 54 Cu 26.5 Ag 8.5 Gd 11 , respectively [14], and D c ≥ 10 mm for mixed Y-Gd alloys also with various Mg/Cu composition ratios but without silver addition [15,16]. In this paper, we have studied the effects of silver addition on the alloys produced in these previous studies, looking particularly to their stability upon crystallization and their mechanical properties in compression.…”