【作者】 王宁；

【导师】 陈刚；

【作者基本信息】 江苏大学 ， 材料加工工程， 2005， 硕士

【摘要】 镁基非晶合金的玻璃形成能力强,在Mg-Ln-TM系的合金中,Mg₆₅Cu₂₅Y₁₀合金具有最大的△T_x（=T_x-T_g,T_x为晶化转变温度,T_g为玻璃转变温度）和最高的GFA。笔者在现有镁基大块非晶合金的基础上研究成本低、室温塑性好、玻璃形成能力强的新型非晶合金材料。通过对不同合金元素的影响进行系统分析,对玻璃形成能力、室温力学性能等进行研究,实现了低成本制备新型镁基大块非晶合金。 在Mg-Cu-Y体系及相关范围探索添加其它金属元素对合金玻璃形成能力的影响,制备临界尺寸更大的镁基非晶合金。实验过程中,使用钨极磁控电弧炉熔炼Cu-Y-M（M为添加其它元素）中间合金,再用此中间合金与纯镁在氩气保护气氛下于电阻炉中熔炼Mg-Cu-Y-M（M为添加其他元素）最终合金,最后使用铜模浇铸大块Mg-Cu-Y-M非晶合金。使用高真空单辊旋淬系统制备各种成分的Mg-Cu-Y-M非晶合金条带。将制得非晶合金以及非晶合金条带进行X射线衍射分析确定其相组成。使用差热扫描量热仪绘制Mg-Cu-Y-M非晶合金DSC曲线,确定其玻璃化温度和晶化温度,根据热分析结果分析其形成大块非晶合金的能力。将制得的Mg-Cu-Y-M非晶合金条带在一定温度区间进行热处理,对热处理前后条带进行弯曲实验判断其室温塑性,并进行拉伸实验判断其拉伸强度。利用光镜,扫描电镜对条带试样的组织进行分析,并对条带断口形貌进行观察和分析。 实验结果表明,使用Nd元素部分代替Y元素不影响合金的非晶形成能力,并且Nd的价格大大低于Y的价格。添加Ni部分代替Cu,在不影响其非晶形成能力条件下,大大改善了大块非晶合金的室温塑性。对比分析添加元素的含量以及元素种类对非晶形成能力的影响。并综合分析了Mg-Cu-Y-M（M为添加其它元素）非晶的力学性能。结合力学性能测试结果和断口照片分析了时效处理对Mg₆₅Cu₂₅Y₁₀、Mg-Cu-Y-Nd和Mg₆₅Cu₂₃Ni₂Y₁₀非晶条带、大块非晶合金的室温塑性、力学性能影响,提出了一种提高条带室温塑性的方法,对非晶合金的晶化过程做了初步探讨。更多还原

【Abstract】 The glass forming ability （GFA） of magnesium based bulk amorphous alloy is strong. Among Mg-Ln-TM alloy systems, Mg₆₅Cu₂₅Y₁₀ alloy has the largest value of ΔT_x （=T_x-T_g, where T_x is the crystallization point, T_g is the glass transition temperature） and supreme GFA. In the present paper, new Mg-based bulk amorphous alloys with low cost, fine room-temperature plasticity and strong glass forming ability are researched on based on the Mg-based bulk amorphous alloy now available. According to the systematic analysis about effects of different alloy elements on the glass forming ability, room-temperature mechanical properties, new Mg-based bulk amorphous alloys with low cost have been developed.Effects of adding other alloy elements into Mg-Cu-Y and the related alloy systems on the glass forming ability were studied and new Mg-based bulk amorphous alloy with larger critical glass forming size was then fabricated. In the present work, arc-melting furnace with magnetism-controlled tungsten electrode was employed to melt Cu-Y-M （M is the added element） master alloy. The master alloy is then smelted with pure magnesium in an electricity resistance furnace under the protection of argon atmosphere to get Mg-Cu-Y-M final alloy. Mg-Cu-Y-M bulk amorphous alloys were then prepared by casting the above alloy in a traditional copper mould. Melt-spinning machine with high vacuum was employed to prepare Mg-Cu-Y-M amorphous alloy ribbons of different composition. X-ray diffractometer was utilized to determine the phase constitution of the bulk amorphous alloys and the amorphous ribbons. DSC curves of Mg-Cu-Y-M bulk amorphous alloy were obtained by using the differential scanning calorimerter, and the glass transition temperatures and crystallization temperatures were confirmed. The glass forming ability was then analysed based on the differential scanning calorimeter curves. Mg-Cu-Y-M amorphous ribbons were heat treated in certain temperature range, and bending was carried out to determine the room-temperature plasticity of amorphous ribbons both before and after heat treatment, while tensile experiment was carried out to judge their strength. Utilizing optical microscope and scanning electron microscope, microstructures and the fracture morphology of ribbon sample were then observed.The experimental result shows that there will be no influence of the replacement of neodymium （Nd） by yttrium （Y） in the alloy on the glass forming ability. During thisprocess, Y was partly replaced by Nd, remembering that the price of Nd is much lower than that of Y. The room-temperature plasticity of Mg-based bulk amorphous alloys was improved as copper （Cu） was partly replaced by nickel （Ni）, without influencing the glass forming ability. Then, the influence on the glass forming ability was discussed by comparing the contents and types of the addition elements. Mechanical properties of Mg-Cu-Y-M （M is the adding alloy element） bulk amorphous alloys were also examined systimatically. Influence of aging treatment on the room-temperature plasticity and mechanical properties of Mg65Cu2sYio, Mg-Cu-Y-Nd , Mg6sCu23Ni2Yio bulk amorphous alloys was discussed according to the results of mechanical examination and fracture morphology. A method to improve the room-temperature plasticity was then suggested. The crystallization of the amorphous alloy was also analyzed briefly.更多还原