轻质高熵合金的研究

发布时间：2018-06-08 17:29

本文选题：热力学 + 高熵合金　；参考：《沈阳航空航天大学》2015年硕士论文

【摘要】：高熵合金是近些年来受到研究领域关注的一类新型合金。现有的高熵合金主要是选择密度较大的Co，Cr，Fe，Ni，Mn等过渡族金属元素作为主元素。本文选择Al，Mg，Ti，Ca，Li等密度较小的金属元素作为主元素，尝试制备高比强度的轻质高熵合金。本文根据已有的高熵合金固溶体形成理论设计了8组合金的配方，采用真空感应炉熔炼，并用直径为20mm的钢模和直径为5mm的铜模分别铸造两种冷却速度不同的试样用以对比。通过XRD，SEM和EDS对合金的相组成与组织结构进行了分析，并利用万能试验机对合金的力学性能进行测试，利用阿基米德法测定合金的密度，计算其比强度，对合金的成分进行化学成分分析以验证成分设计理论的准确性。研究结果表明，Al-Mg-Zn-Sn-Cu系合金中Mg元素与Sn元素首先结合生成Mg2Sn相，多余的Sn元素在晶间富集。Al，Cu，Zn三种元素在原子含量相差不大时，会生成Al4.2Cu3.2Zn0.7相，但当相差太多时，会生成更稳定的金属间化合物，如CuAl2等。高熵效应使合金获得了较好的力学性能。其中，Al7MgSnCu4.6Zn6.4合金的强度与硬度均较高，它比强度达到2.245×105(N/m2)/(kg/m3)，而冷却速度较快的试样的硬度为270.75HV。对于Al-Mg-Zn-Sn-Cu-Ti系合金， Mg和Ti不共存于同一相中。其中，Al7Mg3.6Cu1.2Zn7Ti1.2合金由一种HCP相和两种FCC相组成。它的比强度很高，达到1.491×105(N/m2)/(kg/m3)，而密度仅为3.84g/cm3。合金的硬度也很高，在冷却速度较慢的试样中，达到434.3HV。对于Al-Mg-Ca-Li-M系合金，由于其主要成分都是一些轻质金属，所以合金的密度较低。AlMgCa0.5LiCu合金的密度为2.63g/cm3，而AlMgCa0.5LiZn合金的密度为2.65g/cm3，它们都接近于Al合金的密度。其中，，AlMgCa0.5LiCu合金具有较高的比强度，为1.15×105(N/m2)/(kg/m3)。通过上述结果的分析认为，设计高熵合金的成分时，不仅要考虑合金总体的混合焓值，还要考虑到合金中各组分之间的混合焓值以及各元素的原子半径大小，这样可以避免过多的金属间化合物生成或者大量的成分偏析。
[Abstract]:High entropy alloy is a new kind of alloy which has attracted much attention in recent years. The existing high-entropy alloys are mainly composed of transition metal elements such as Co-Cr-Fe, Ni, mn and so on, which are selected as the main elements. In this paper, the light weight and high entropy alloy with high specific strength is prepared by selecting the metal elements with low density, such as Al _ 2O _ 3, mg, Ti, Ca, Li, as main elements. According to the theory of solid solution formation of high-entropy alloy, the formula of eight combinations of gold is designed and melted by vacuum induction furnace. The steel die with diameter 20mm and copper die with diameter of 5mm were cast two kinds of specimens with different cooling rate respectively. The phase composition and microstructure of the alloy were analyzed by XRDX SEM and EDS. The mechanical properties of the alloy were tested by universal testing machine. The density of the alloy was measured by Archimedes method and the specific strength was calculated. The chemical composition analysis of the alloy was carried out to verify the accuracy of the composition design theory. The results showed that the mg element and Sn element in the Al-Mg-Zn-Sn-Cu system alloy first combined to form Mg2Sn phase. The superfluous Sn element in the intergranular enrichment. The three elements, Al4.2Cu3.2Zn0.7 phase, will form when the atomic content is not different, but when the difference is too much, it will produce more stable intermetallic compounds, such as CuAl2 and so on. The high entropy effect makes the alloy obtain better mechanical properties. The strength and hardness of Al-7MgSnCu4.6Zn6.4 alloy are both high, and its specific strength is 2.245 脳 10 ~ 5 N / m ~ (2 / m ~ (-2) / kg 路m ~ (3), while the hardness of the sample with faster cooling rate is 270.75 HV. For Al-Mg-Zn-Sn-Cu-Ti alloy, mg and Ti do not coexist in the same phase. The Al _ 7mg _ (3.6) Cu _ (1.2) Zn _ (7) Ti _ (1.2) alloy consists of one HCP phase and two FCC phases. Its specific strength is very high, reaching 1.491 脳 10 ~ 5 N / m ~ (2) / m ~ (2) 路kg ~ (-3) 路m ~ (3), but the density is only 3.84 g / cm ~ (3). The hardness of Al-Mg-Ca-Li-M alloy is also very high, and the hardness of Al-Mg-Ca-Li-M alloy is 434.3 HV in the sample with slow cooling rate. For Al-Mg-Ca-Li-M alloy, the main composition is some light metal, So the density of AlMgCa0.5LiCu alloy is 2.63g / cm ~ 3, and that of AlMgCa0.5LiZn alloy is 2.65g / cm ~ 3, which is close to that of Al alloy. AlMgCa0.5LiCu alloy has a high specific strength of 1.15 脳 10 ~ (5) N / m ~ (2) / m ~ (2) 路kg ~ (-3) 路m ~ (3). Through the analysis of the above results, it is concluded that not only the total enthalpy value of the alloy should be taken into account in designing the composition of the high-entropy alloy, but also the total enthalpy of the alloy should be considered. The enthalpy of each component in the alloy and the atomic radius of each element can be taken into account in order to avoid the formation of too many intermetallic compounds or the segregation of a large number of components.
【学位授予单位】：沈阳航空航天大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG132

【参考文献】