Mg-Al金属间化合物合金化及其应用特性研究

发布时间：2018-04-02 11:37

本文选题：Mg17Al12金属间化合物　切入点：合金化　出处：《太原理工大学》2015年博士论文

【摘要】：金属间化合物具有高强度、高硬度、抗腐蚀、耐高温等优异的性能，同时具有特殊的声、光、电学性质，可以被用于结构材料也能被用作功能材料。但是，金属间化合物往往具有室温脆性，这极大的影响着它们的应用。因此，改善室温脆性是拓展金属间化合物使用范围的有效途径。目前国内外有关金属间化合物的研究工作主要集中于铝系和硅系。AZ系镁合金的显微组织中常见的第二相Mg17Al12也是一种铝系化合物，近年来，它们在某些方面的性能也受到关注。一是作为防护涂层的制备方法及其耐蚀性，，二是作为储氢合金的吸放氢特性。但Mg-Al金属间化合物的力学特性却较少受到关注。针对这一不足，本文通过合金化方法，研究合金元素对Mg17Al12金属间化合物组织和力学性能的影响，并对其潜在应用进行探索性研究。实验通过添加Er、Y和B，研究合金元素对Mg17Al12金属间化合物显微组织形貌、相组成、硬度、压缩性能、耐腐蚀性能及热稳定性的影响。考虑到Mg17Al12硬度高，但室温脆性大，将其与泡沫Al进行结合，研究Mg17Al12增强泡沫Al的吸能特性。Mg17Al12具有较高的理论储氢量，试验中研究了Y对Mg17Al12金属间化合物储氢性能的影响。研究了Mg-Al-Er涂层对镁合金的防护效果。制备了接近Mg-Mg17Al12共晶组织成分的Mg70Al30合金，并研究了其在酸溶液中的腐蚀行为。最后利用近共晶合金的腐蚀特性成功地制备了具有表面多孔结构的Mg-Al合金。通过研究得到以下主要的结论： (1) Mg-Al-Er合金的显微组织随Er含量的不同而变化。当Er含量低于1.0wt.%时，合金仅由Mg17Al12基体和Al3Er相组成。当Er含量超过3.0wt.%时，基体中除了Al3Er相外还出现了Mg17Al12-Mg共晶组织。和Mg-44.3Al合金（单相Mg17Al12）的硬度相比，含Er合金的硬度都有了较大的提高，结合计算结果表明主要原因为添加Er后引起的晶粒细化。添加Er后，合金的抗腐蚀能力和耐磨损性能都有明显的提高。其中，Mg-43.8Al-1.0Er合金具有最好的耐蚀性和最强的抑制阴极析氢能力，而Mg-42Al-5.0Er合金具有最好的耐磨损性能。当Y含量低于1.0wt.%时，Mg-Al-Y合金由Mg17Al12基体和Al2Y组成。当Y含量超过1.0wt.%时，Mg-Al-Y合金中出现了Mg17Al12-Mg共晶组织。Y含量为2.0wt.%~5.0wt.%时，合金的硬度相差很小为285~290HV。 (2)利用热压烧结法在AZ61镁合金表面制备了Mg-Al-Er金属间化合物涂层。电化学测试和滑动磨损试验结果表明涂层样品的耐蚀性和耐磨性比AZ61镁合金基体有很大的提高，且都好于热扩散涂层。原因在于涂层中形成的高硬度Al3Er第二相使得烧结涂层具有较好的耐磨损性能，而Er还可以抑制涂层的析氢腐蚀。 (3) Mg-xAl-yY(x=44.3,43.8,43; y=0,1.0,3.0)合金在球磨30h内，随着球磨时间的延长没有发生相变，但衍射峰强度降低、峰宽化。添加稀土Y能有效地改善Mg17Al12合金的吸放氢性能，添加Y使合金的吸放氢速率和放氢平台压力显著升高。其中添加1.0wt.%Y合金的吸氢量和放氢量均很高，分别为3.39%和2.84%，且有较宽而平坦的放氢平台压力为1.33MPa。 (4)随着Mg-Al-B合金中B的含量从0.1wt.%增至1.35wt.%，合金的组织由单相树枝晶逐渐向以共晶组织为主过渡。B含量≤1.25wt.%时，合金的显微硬度变化不大，为223HV~229HV。B含量为1.35wt.%时，硬度较低为192HV，但压缩应变和压缩强度极限比Mg-44.3Al合金的分别提高了25%和57%。随着B含量的增加合金的熔点和自腐蚀电位呈单调下降趋势。 (5) Mg70Al30合金的显微组织主要由α-Mg枝晶和Mg-Mg17Al12共晶组织组成。合金在H2SO4和乙酸（HAc）溶液中的腐蚀行为有很大的不同。Mg70Al30合金在pH=1.0的H2SO4溶液中表现为全面腐蚀，而在pH=1.0的HAc溶液中表现为选择性腐蚀。共晶组织中晶粒的取向对合金在HAc溶液的腐蚀行为有较大影响，点状共晶组织具有比羽毛状共晶更好的抗腐蚀剥落能力。晶粒取向对合金在H2SO4溶液中的腐蚀行为影响较小。共晶组织在两种溶液中均具有比α-Mg枝晶组织较好的耐蚀性。Mg-Mg17Al12共晶合金发生选择性腐蚀需要两个条件。一是，两相间具有较大的自腐蚀电位差；二是，耐蚀相在去合金化溶液中具有良好的耐蚀性。 (6)填充金属间化合物Mg17Al12的泡沫铝复合材料具有实心结构，但具有和泡沫铝一样的压缩特性。复合材料的压缩性能比泡沫铝的有很大的提高。平台应力提高1.5倍以上，吸能能力在各应变水平都有大幅提高。在应变小于0.02和0.2~0.6两个区间时，泡沫铝样品的吸能效率低于同直径的泡沫铝复合材料。应变在0.02~0.2范围内时泡沫铝复合材料的吸能效率低于泡沫铝样品。
[Abstract]:Intermetallic compounds with high strength, high hardness, corrosion resistance, high temperature resistance, excellent, and has a special sound, light, electrical properties, can be used for structural materials can also be used as functional materials. However, intermetallic compounds are brittle at room temperature, which greatly affects their applications. Therefore that is to improve the brittleness at room temperature effective method to expand the scope of use of intermetallic compounds. The second phase Mg17Al12 common microstructure research work at home and abroad mainly focus on the intermetallic compounds of aluminum and silicon.AZ magnesium alloy is a kind of aluminum compounds, in recent years, their performance in some areas have also been is a concern. As a protective coating preparation method and its corrosion resistance is two, as hydrogen storage alloys. But the mechanical properties of Mg-Al intermetallic compound has received less attention. In view of this not In this paper, through the method of foot, alloy, and the effect of alloying elements on mechanical properties of Mg17Al12 intermetallic compound organization, and exploratory research on its potential application. Through the experiment of adding Er, Y and B, the research of alloying elements on Mg17Al12 intermetallic compound microstructure, phase composition, hardness, compressive properties, impact resistance the corrosion resistance and thermal stability of Mg17Al12. Considering the high hardness, but the room temperature brittleness, and the foam Al combines the research of Mg17Al12 reinforced foam Al energy absorption theory of the hydrogen storage capacity of.Mg17Al12 has the characteristics of high, the test studied the effect of Y on hydrogen storage properties of Mg17Al12 intermetallic compound of Mg-Al-Er coating. The protective effect of magnesium alloy. Mg70Al30 alloy to Mg-Mg17Al12 eutectic composition were prepared and studied its corrosion behavior in acid solution. The corrosion properties of near eutectic alloy forming Mg-Al alloys with porous surface structures are prepared. The following main conclusions are obtained.
(1) the different microstructure of Mg-Al-Er alloy with Er content change. When the Er content is lower than 1.0wt.%, the alloy only by Mg17Al12 matrix and Al3Er phase. When the Er content is more than 3.0wt.%, in addition to the Al3Er matrix phase also appeared in the eutectic structure of Mg17Al12-Mg alloy and Mg-44.3Al alloy. The hardness compared (phase Mg17Al12) containing, the hardness of Er alloy are greatly improved, combined with the calculation results show that the main reason for grain refinement caused by the addition of Er. After adding Er, have significantly improved the corrosion resistance of the alloys and abrasion resistance. Among them, the inhibition of cathodic hydrogen evolution of Mg-43.8Al-1.0Er alloy has the best corrosion resistance and the strongest however, the Mg-42Al-5.0Er alloy has the best wear resistance.
When Y content is lower than 1.0wt.%, Mg-Al-Y alloy is made up of Mg17Al12 matrix and Al2Y. When Y content exceeds 1.0wt.%, Mg17Al12-Mg eutectic structure appears in Mg-Al-Y alloy. When.Y content is 2.0wt.%~5.0wt.%, the hardness difference of alloy is very small.
(2) by using hot pressing sintering synthesis of Mg-Al-Er intermetallic compound coating on the surface of AZ61 magnesium alloy. The electrochemical test and wear test results show that the samples coated with corrosion resistance and wear resistance are greatly improved compared with AZ61 magnesium alloy, and are better than the thermal diffusion coating. Because the coating formed in high hardness Al3Er the second phase sintering coating has good abrasion resistant properties, hydrogen corrosion and Er can also inhibit the coating.
(3) Mg-xAl-yY (x=44.3,43.8,43; y=0,1.0,3.0) in 30h alloy milling, with the increase of milling time did not change, but the intensity of the diffraction peaks decreased and the peak width. Rehydrogenation properties of rare-earth Y can effectively improve Mg17Al12 alloy, adding Y to the hydrogen generation rate and hydrogen absorbing alloy platform pressure increased significantly the amount of hydrogen absorption. The addition of 1.0wt.%Y alloy and hydrogen volume were high, respectively 3.39% and 2.84%, and the plateau pressure is wide and flat on 1.33MPa.
(4) with the content of Mg-Al-B alloy in B from 0.1wt.% to 1.35wt.%, the microstructure of the alloy by single phase dendrite to eutectic transition.B content is less than 1.25wt.%, the microhardness of the alloy changes little, 223HV~229HV.B content is 1.35wt.%, lower hardness is 192HV, but the compression strain and compressive strength limit ratio Mg-44.3Al alloy were increased by 25% and 57%. with the increase of B content the melting point of the alloy and the corrosion potential decreased monotonously.
(5) the microstructure of Mg70Al30 alloy is mainly composed of alpha -Mg dendrite and eutectic phases. Mg-Mg17Al12 alloy in H2SO4 and acetic acid (HAc) with different.Mg70Al30 alloy in H2SO4 solution pH=1.0 greatly in the performance of the overall corrosion behavior in solution, and in the HAc pH=1.0 solution is in the form of orientation selective corrosion. Crystal in the alloy have a greater impact on the corrosion behavior of HAc eutectic point solution, than a feather shaped eutectic organization has better resistance to corrosion and exfoliation. Little effect of grain orientation on the corrosion behavior of the alloy in H2SO4 solution. The eutectic microstructure in two kinds of solution are better than the corrosion resistance of.Mg-Mg17Al12 alpha -Mg dendrite eutectic alloy selective corrosion requires two conditions. One is that the two phases have large self corrosion potential difference; two, corrosion resistance has good corrosion resistance in dealloy solution.
(6) aluminum foam filled Mg17Al12 intermetallic compound composite material with solid structure, but with the same aluminum foam compression properties. The compressive strength of the composites than the aluminum foam is greatly improved. The plateau stress increased more than 1.5 times, the energy absorption ability has greatly improved the level of each strain in strain is less than. 0.02 and 0.2~0.6 two range, energy absorption efficiency is lower than the diameter of the aluminum foam with composite aluminum foam samples. The strain in the energy absorption efficiency is lower than the aluminum foam samples range of 0.02~0.2 foam aluminum composite material.

【学位授予单位】：太原理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG113;TG174.4

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