The Influence On The Glass Forming Ability Of Mg-base Bulk Amorphous Alloys By The Replacement Of The Rare Elements And The Research On Crystallization Kinetics Behavior

2mm diameter rods of Mg₆₅Cu₂₅Y_10-xLa_x ( x=0, 0.35, 1, 2 ), Mg₆₅Cu₂₅Y_10-xTb_x(x=0, 2, 4, 6, 8, 10), Mg₆₅Cu₂₅Y₆Gd₄ and Mg₆₅Cu₂₅Gd₁₀ bulk amorphous were prepared with vacuum copper mold casting method by substitute Y element of Mg₆₅Cu₂₅Y₁₀ amorphous alloy, which have strong glass forming ability, with some Rare Earth elements as La, Tb, and Gd.The structure and glass forming ability of the Mg₆₅Cu₂₅Y_10-xLa_x (x=0, 0.35, 1, 2, 3, 4) bulk amorphous alloys were studied by X-ray diffraction analysis (XRD) and differential thermal analysis method (DTA) respectively. It is shown that a new bulk amorphous alloy has a largest glass-forming ability (T_rg=0.5872) when x=2;The glass forming ability of Mg₆₅Cu₂₅Y_9.65La_0.35 amorphous alloy is not better than that of Mg₆₅Cu₂₅Y₁₀ amorphous alloy when x=0.35, namely as atomic radius criterion λ=0.18, moreover the bulk Mg₆₅Cu₂₅Y_9.65 amorphous alloy is not near eutectic composition. It is found that some crystalline phases appear in the matrix of the amorphous alloys when x=3 and x=4, indicating that the glass-forming ability of which decreases markedly.2 mm diameter rods of bulk Mg₆₅Cu₂₅Y_10-xTb_x (x=0, 2, 4, 6, 8, 10) amorphous alloys were prepared by copper mold casting method. The structure and glass forming ability of the alloys were analyzed by X-ray diffraction (XRD) and differential thermal analysis (DTA) respectively. It is shown that Mg₆₅Cu₂₅Y_10-xTb_x (x=0, 2, 4, 6, 8, 10) alloys all can be prepared into bulk amorphous alloys, the glass forming ability of the alloys become more and more stronger with the increment of Tb in the Mg₆₅Cu₂₅Y_10-xTb_x (x=0, 2, 4, 6, 8, 10) alloys. The glass forming ability of the Mg₆₅Cu₂₅Y_10-xTb_x (x=0, 2, 4, 6, 8, 10) amorphous alloy is the most strongest when x=8, and then drops when x=10, the phenomenon can be explained reasonably by calculating the electro-negativity difference (Ax) and the atomic size parameter of the Mg₆₅Cu₂₅Y_10-xTb_x (x=0, 2, 4, 6, 8, 10) alloys. The single smooth melting peak in the DTA pattern indicates that the alloys with stronger glass forming ability may be eutectic composition when x=6,8. The value of the λ of the two amorphous alloys is far from 0.18 which is deduced from the atom cluster model. Crystallization process ofMg65Cu25Yio-xTbx (x=0, 2, 4, 6, 8, 10) alloy was studied by use of Kissinger equation. It is shown that the dynamics effect exists in the glass transformation and crystallization behavior.The kinetics property during the glass transition process of Mg65Cu25YeGd4 and Mg65Cu2sGdio amorphous alloys was systematically investigated by differential thermal analysis method. The results reveal that the smaller the activation energy and the frequency factor and the bigger B value of Lasocka function are, the stronger the glass-forming ability of bulk amorphous alloys are, as the result of the special structure characteristics.Mg6sCu25Gdio bulk amorphous with 3mm thickness were prepared by vacuum copper mold casting method for its elegant glass forming ability. The crystallization behavior of the alloy annealing after different temperatures and times was researched. It is shown that Mg6sCu25Gdio bulk amorphous does not precipitate nanocrystalline phases at 0.5Tm with contrast to conditional amorphous alloys but undergo structure relaxation for the reason that which does not precipitate nanocrystalline under lower temperature by non-thermal growth mode. Mg6sCu25Gdio bulk amorphous only precipitate hcp-Mg and hcp-Mg2Cu nanocrystallines under isothermal annealing according to the law of continuous nucleus and parabolic curve growth kinetics. The ideal amorphous/nanocrystalline or nanocrystalline materials can be obtained by the control of isothermal annealing temperature and time.The phenomenon that the GFA of Mg6sCu25REio alloys initially increases with the increase of the atomic numbers and reaches a maximum for Gd and then decreases with the further increase of the atomic number is researched from the view of the single electronic number of the RE3+4f orbit. It is shown that the single electronic number of the RE3+4f orbit leads to the forming of the phenomenon.