Study On Mg-Based Bulk Amorphous Preparation And The Toughening Of Carbon Nanotube Composites

Mg-based amorphous alloy with the vast development potential and prospects for the advantages of a lightweight, high strength, high elastic limit and low price. Compared to other Mg-based amorphous material, Mg-Ni based amorphous alloy have excellent mechanical properties, high hydrogen storage capacity and high corrosion resistance and so on. Presently, Mg-Ni-based bulk metallic glass has two major drawbacks which hinder their development and application:①Mg-Ni based alloy have lower GFA, the current study found that the largest diameter of the amorphous size is only 3mm.②Poor toughness. The fracture is a significant form of brittle fracture,the general displacement of compression experiment in a maximum of 1%. The work is based on the Mg-Ni-Gd ternary alloy system, hope that get a group of good GFA of alloy composition by changing the alloy composition ratio. On the other hand, take carbon nanotubes as a second phase to improving the toughness and the the Mg-Ni amorphous matrix fracture properties. Taking into account the addition of carbon nanotubes have the possible negative effects on the glass forming ability, good glass forming ability of the alloy composition is the basis of toughening mechanisms of carbon nanotubes. The main results obtained from the experiment are as follows:(1)Gd content have significant impact on the Mg-Ni-Gd ternary alloys glass forming ability, ₁₀at.% of Gd in the formation of amorphous alloys have the best ability to optimize the GFA; by changing the ratio of atomic number,we could found that the Mg-Ni-Gd alloy system have the best glass forming ability in the composition of point Mg₇₅Ni₁₅Gd₁₀, whose amorphous critical size of 3mm. The other way, the strong crystalline phase GdNi₃ have a significant effect on the GFA of Mg-Ni-Gd ternary system.(2)Ag partial substitution Mg in the Mg₇₅Ni₁₅Gd₁₀ alloy have a significant impact on the glass forming ability, the best alternative to alloy composition is Mg₆₉Ni₁₅Gd₁₀Ag₆, with the critical diameter of the amorphous size 6mm. By positioning components in the Pseudo ternary phase diagram, have obtained an excellent group of glass forming ability components. Five component points have the critical size of diameter 6mm, respectively Mg₇₀Ni_14.3Gd₁₀Ag_5.7, Mg₆₉Ni₁₅Gd₁₀Ag₆, Mg₆₈Ni_15.7Gd₁₀Ag_6.3, Mg₆₄Ni_18.6G-d₁₀Ag_7.4, and Mg₆₃Ni_19.3Gd₁₀Ag_7.7。By the rare earth doped method, have obtained the five-component Mg₆₉Ni₁₅Ag₆Gd₇Pr₃, which with excellent glass forming ability of critical diameter of glass forming size 8mm. It's the maximum size of the amorphous Mg-Ni based alloys as far as we know.(3)Milling process can release the agglomeration of carbon nanotubes, in the milling progress, part of carbon nanotubes will be interrupted and short. The compressive stress and strain displacement of CNTs-Mg₆₉Ni₁₅Ag₆Gd₇Pr₃ bulk amorphous composites will improve with the increase of volume content of carbon.The volume fraction of 2% reached the highest value of respectively 925MPa and 2.26%. It's 198MPa and 0.74% increased than haven't add Carbon nanotubes. The pattern of the context increased significantly in the amorphous matrix which is the characterization of toughness in the composite materials by observation of fracture morphology.