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Study On Preparation And Mechanical Properties Of Mg-li Bulk Amorphous Alloy System

Posted on:2011-02-05Degree:MasterType:Thesis
Country:ChinaCandidate:J ZhangFull Text:PDF
GTID:2191330332460433Subject:Materials science
Abstract/Summary:PDF Full Text Request
In this paper, Mg-Li-Cu-Y bulk amorphous alloys with diameter of 2 mm have been successfully fabricated by copper mold injection-casting method. Whereafter, Mg-Li-Cu-Y-Gd and Mg-Li-Cu-Zn-Y bulk amorphous alloys were prepared by using Gd and Zn to partially substitute for Y and Cu of Mg-Li-Cu-Y alloy system, respectively. The microstructure, glass forming ability (GFA), thermal stability and mechanical properties of Mg-Li bulk amorphous alloy system were systematically investigated by X-ray diffractometry (XRD) and differential scanning calorimetry (DSC), room temperature compression test and scanning electron microscopy (SEM), respectively. The effects of Gd and Zn on the GFA and mechanical properties of Mg-Li-Cu-Y alloy system were discussed.By analyzing the results of XRD and DSC, it was found that the supercooled liquid region temperature (ΔTx) of Mg-Li-Cu-Y, Mg-Li-Cu-Y-Gd and Mg-Li-Cu-Zn-Y alloy system gradually decreased with increasing Li content (3 at.%-8 at.%), thereby leading to the decline of GFA and thermal stability. Compared with Mg-Li-Cu-Y alloy system, the GFA and thermal stability of Mg-Li-Cu-Y-Gd and Mg-Li-Cu-Zn-Y alloy system were observably enhanced. The results of room temperature compression test indicated that the dominant fracture behavior of Mg-Li-Cu-Y, Mg-Li-Cu-Y-Gd and Mg-Li-Cu-Zn-Y alloy system was a typical brittle fracture. The plasticity of Mg-Li-Cu-Y alloy system was not improved when Y was partly replaced by Gd, whereas the fracture strength was decreased. The plasticity of Mg-Li-Cu-Y alloy system was remarkably improved by adding Zn to partly substitute for Cu, and fracture strength was increased. A large number of vein-like patterns were observed in the fracture surface of Mg-Li-Cu-Zn-Y alloy system, illustrating that there existed local plastic flow process during the fracture.In addition, the densities (3.35 g/cm3-3.68 g/cm3) of Mg-Li bulk amorphous alloy system were controlled with the addition of Gd or Zn, which promoted its extensive application as engineer structural materials in aviation and spaceflight fields.
Keywords/Search Tags:Mg-Li alloys, Bulk amorphous alloys, Glass forming ability, Mechanical properties
PDF Full Text Request
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