稀土元素对CuZrAl系块体非晶合金形成能力的影响及力学性能研究

【作者】 张永章；

【导师】 谢致薇；

【作者基本信息】 广东工业大学 ， 材料学， 2006， 硕士

【摘要】 本文采用铜模吸铸法成功制备了一系列的CuZrAl-M系块体非晶合金,采用X射线衍射仪（XRD）、示差扫描量热分析仪（DSC）、扫描电子显微镜（SEM）、显微硬度计以及压缩实验等测试了Cu₄₆Zr_47-xAl₇M_x（M=Ce、Pr、Tb、Gd:x=2,4,5）块体非晶合金的结构、热学性能和力学性能。并分析了稀土元素对CuZrAlM系合金玻璃形成能力及部分性能的影响因素。论文的主要工作包括以下几个方面: （1）通过添加稀土元素替换Zr的方法,分别探讨了不同族稀土元素,不同含量稀土元素对CuZrAlM系合金玻璃形成能力的影响: 合金Cu₅₀Zr₅₀的研究表明,添加6%的Ce、Pr稀土元素替代相同含量的（CuZr）后,并未能提高Cu₅₀Zr₅₀的玻璃形成能力;添加6%的Ti,吸铸直径3mm的(Cu₅₀Zr₅₀)₉₄Ti₆合金试样中以非晶相为主,同时存在少量的晶态相;添加Al制备直径3mm的(Cu₅₀Zr₅₀)_100-x （x=4,6,8）合金,当x=4时,该合金为完全晶态合金,当x增加到6和8时,该合金表现为完全非晶态合金。 合金Cu₄₆Zr₄₇Al₇的研究结果表明,添加Ce、Pr稀土元素替代相同含量的Zr时,随着稀土含量的增加,玻璃形成能力先增大后减小,当添加4%时达到最大,能够制得直径为5mm的Cu₄₆Zr₄₃Al₇M₄（M=Ce,Pr）非晶合金;添加Tb稀土元素时,能够制得直径为5mm的Cu₄₆Zr_47-xAl₇Tb_x（x=2,4,5）非晶合金,表明添加Tb有利于玻璃形成能力的提高,而Tb添加量的变化对玻璃形成能力并无多大影响;对于添加Gd稀土元素的合金,当添加2%和4%时,仅能制得直径为5mm的非晶合金,当Gd含量增加到5%时,玻璃形成能力进一步提高,能制得直径8mm的非晶合金。当其直径增大到10mm时,合金为完全晶态合金。 （2）对块体非晶试样进行DSC热分析,在升温速率为20℃/min时,分析结果表明:添加稀土元素Ce、Pr、Tb、Gd后,合金的晶化起始温度T_x和晶化峰值温度T_p均向低温区移动,且T_x均为480℃左右,T_p均为490℃左右,而玻璃转变温度T_g的变化则较复杂,T_g随着添加元素的不同和含量的变化而变化。整体上看,过冷液相区△T_x均变小。更多还原

【Abstract】 A series of CuZrAl-based bulk metallic glassy（BMG） alloys were prepared by means of copper-mold vacuum suction casting. The glassy structure, thermal stability, glass-forming ability（GFA） and mechanical properties of these alloys with nominal composition of Cu₄₆Zr_47-xAl₇M_x（M=Ce,Pr,Tb,Gd;x=2,4,5） were investigated by differential scanning calorimeter（DSC）, X-ray diffraction（XRD）, scanning electron microscope（SEM）, Vicker’s hardness, compression tests. The results are summarized as follows.（1） A series of Cu₄₆Zr_47-xAl₇M_x（M=Ce, Pr, Tb, Gd;x=2,4,5） amorphous alloy were prepared by using rare-earth elements Ce, Pr, Tb, Gd to substitute the same quantity of Zr in the Cu₄₆Zr₄₇Al₇ system. The maximal BMG dimension(t_max) of the series of alloy added with Ce, Pr, Tb, Gd are 5mm, 5mm, 5mm, 8mm, respectively.The glass-forming ability（GFA） of CuZrAl-based amorphous increase first and then decrease with increasing elements content of Ce and Pr, and the optimal content is 4at.%. The increasing content of Tb affect the GFA of the alloy littlely. When added 5at.% Gd to the alloy, the GFA increases greatly, an amorphous alloy of Cu₄₆Zr₄₂Al₇Gd₅ with a diameter of 8mm is prepared.As to the amorphous alloy Cu₅₀Zr₅₀, when 6at.% Ce or Pr is added to substitute the same quantity of （CuZr）, it can’t improve the GFA of the alloy. When added 6at.% Ti to the alloy, it presents amorphous mainly while v/ith some crystal in the sample of 3mm. When added 4at.% Al, it is difficult to prepare amorphous alloy with 3mm diameter, however, when the content of Al increase to 6at.% and 8at.%, it can be prepared.（2） Thermal stability was examined by DSC at heating rate of 20℃/min. With the addition of Ce, Pr, Tb, Gd to the alloy, the onset crystallization temperature（T_x） and the crystallization peak temperature（T_p） all move to the low temperature, and T_x is about 480 ℃, T_p is about 490 ℃. While the change of T_g is more complex than the above, it changes with the difference of the element and its content. Most of the the supercooled liquid region（△T_x） decrease to less than Cu₄₆Zr₄₇Al₇ except Cu₄₆Zr₄₂Al₇Gd₅.Cu₄₆Zr₄₃Al₇M₄（M=Ce, Pr） and Cu₄₆Zr_47-xAl₇M_x（M=Tb, Gd;x=2,4,5） amorphous alloy allexhibitc large GFA and good thermal stability. The Tg is above 410"C, and the ATX is between 47-77K, all the BMG alloys exhibite only one main exothermic peak. The ATX of Cu46Zr42Al7Gd5 amorphous alloy is 76.8°C, about the same as that of Cu46Zr47Al7 amorphous alloy.（3） The values of activation energy AEg, AEX and AEP for Cu46Zr42Al7Gd5 BMG alloy have been obtained at the heating rate of 12°C/min, 20°C/min and 28°C/min with Kissinger and Ozawa equations as follows: 340.7 kJ/mol, 211.3kJ/mol, 211.3kJ/mol and 334.8kJ/mol, 210.3 kJ/mol, 210.3kJ/mol, respectively.The values obtained with Kissinger equation are just a little higher than those with Ozawa equation, but the vaviation trend of these parameter is consistent greatly.（4） The Vicker’s hardness of the series BMG were investigated. The Vicker’s hardness changes with the difference of rare-earth elements and its content. When added 4at.% Ce, Pr, Tb, Gd, the Vicker’s hardness of Tb alloy exhibites the largest, Hv568, while that of Pr alloy the least, Hv479. The Vicker’s hardness of the alloy added Tb and Gd decrease with the increase of rare-earth content.（5） The compression properties of the series BMG rods were investigated. The fracture strength（ o cf） for Cu46Zr43Al7M4（M=Ce,Gd,Tb） BMG alloy are 407MPa, 712MPa, lOHMPa respectively and their elongation（ e f） are 1.56%, 2.8%, 3.3% respectively. Compressive samples are always fracture or crack nearly parallel to the compressive axis, and the compressive fracture angles are about 0° and all exhibite brittle fracture.更多还原