【作者】 彭彪林；

【导师】 陈学定；

【作者基本信息】 兰州理工大学 ， 材料学， 2006， 硕士

【摘要】 本文以Mg合金为基础,利用稀土元素La,Tb,Gd分别替代非晶形成能力较强的Mg₆₅Cu₂₅Y₁₀中的Y,用真空吹铸法制备出了直径2mm的Mg₆₅Cu₂₅Y_10-xLa_x（x=0,0.35,1,2）,Mg₆₅Cu₂₅Y_10-xTb_x（x=0,2,4,6,8,10）、Mg₆₅Cu₂₅Y₆Gd₄以及Mg₆₅Cu₂₅Gd₁₀块体非晶合金棒。 采用X射线衍射分析（XRD）、差热分析（DTA）分别对块体非晶合金Mg₆₅Cu₂₅Y_10-xLa_x（x=0,0.35,1,2,3,4）的结构和玻璃形成形成能力（GFA）进行了研究。结果表明:x=2时,合金具有最高的GFA（Trg=0.5872）;当x=0.35时,也就是当原子半径参数λ=0.18时,不但没得到共晶点的成分,反而其GFA比Mg₆₅Cu₂₅Y₁₀还差;当x=3,4时,此时在非晶基体中已经出现晶体相,说明其GFA显著降低。 对于块体非晶合金Mg₆₅Cu₂₅Y_10-xTb_x（x=0,2,4,6,8,10）的研究,结果表明:此合金系全为非晶合金,随着合金元素Tb含量的增加其GFA逐渐增强,当x=8时,合金的GFA最强,当x=10时,有所下降;通过对Mg₆₅Cu₂₅Y_10-xTb_x合金系的电负性差（△x）与原子尺寸参数6的计算,认为产生这一现象的原因可能是由于Mg₆₅Cu₂₅Y_10-xTb_x（x=0,2,4,6,8,10）合金的电负性差的变化所引起的。当x=6,8时,合金的GFA较强,DTA图显示其成分可能属于共晶点成分或其附近,同时通过计算得出此两种非晶合金的λ值与由原子团簇模型推导而出的参数λ=0.18值相差较大,说明原子结构参数λ并不完全适用于Mg₆₅Cu₂₅Y_10-xTb_x（x=0,2,4,6,8,10）合金系中的两种共晶点成分或其附近的非晶合金。利用Kissinger方程研究了Mg₆₅Cu₂₅Y₂Tb₈合金的玻璃转变动力学行为,结果表明:Mg₆₅Cu₂₅Y₂Tb₈非晶合金的玻璃转变和晶化行为均具有明显的动力学效应。 研究了Mg₆₅Cu₂₅Y₆Gd₄、Mg₆₅Cu₂₅Gd₁₀块体非晶合金的结构和GFA及其玻璃转变动力学,结果表明:玻璃转变表观激活能与频率因子V0越小,玻璃转变处Lasocka关系的B值越大,则对于同一合金系表现出GFA越强。经分析得出这一现象是由于大块非晶合金独特的结构特点所引起的。 由于Mg₆₅Cu₂₅Gd₁₀合金具有较强的GFA,利用真空吹铸法成功地制备了长宽厚分别为80mm、20mm、3mm的Mg₆₅Cu₂₅Gd₁₀块体非晶合金。系统地分析了其在不同的退火温度与时间的非晶晶化行为。结果表明:Mg₆₅Cu₂₅Gd₁₀块体非晶合金与传统非晶合金相比在0.5Tm处退火不能析更多还原

【Abstract】 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.更多还原