本文選題：Mg17Al12金屬間化合物　切入點：合金化　出處：《太原理工大學(xué)》2015年博士論文

【摘要】：金屬間化合物具有高強度、高硬度、抗腐蝕、耐高溫等優(yōu)異的性能，同時具有特殊的聲、光、電學(xué)性質(zhì)，可以被用于結(jié)構(gòu)材料也能被用作功能材料。但是，金屬間化合物往往具有室溫脆性，這極大的影響著它們的應(yīng)用。因此，改善室溫脆性是拓展金屬間化合物使用范圍的有效途徑。目前國內(nèi)外有關(guān)金屬間化合物的研究工作主要集中于鋁系和硅系。AZ系鎂合金的顯微組織中常見的第二相Mg17Al12也是一種鋁系化合物，近年來，它們在某些方面的性能也受到關(guān)注。一是作為防護涂層的制備方法及其耐蝕性，，二是作為儲氫合金的吸放氫特性。但Mg-Al金屬間化合物的力學(xué)特性卻較少受到關(guān)注。針對這一不足，本文通過合金化方法，研究合金元素對Mg17Al12金屬間化合物組織和力學(xué)性能的影響，并對其潛在應(yīng)用進(jìn)行探索性研究。實驗通過添加Er、Y和B，研究合金元素對Mg17Al12金屬間化合物顯微組織形貌、相組成、硬度、壓縮性能、耐腐蝕性能及熱穩(wěn)定性的影響。考慮到Mg17Al12硬度高，但室溫脆性大，將其與泡沫Al進(jìn)行結(jié)合，研究Mg17Al12增強泡沫Al的吸能特性。Mg17Al12具有較高的理論儲氫量，試驗中研究了Y對Mg17Al12金屬間化合物儲氫性能的影響。研究了Mg-Al-Er涂層對鎂合金的防護效果。制備了接近Mg-Mg17Al12共晶組織成分的Mg70Al30合金，并研究了其在酸溶液中的腐蝕行為。最后利用近共晶合金的腐蝕特性成功地制備了具有表面多孔結(jié)構(gòu)的Mg-Al合金。通過研究得到以下主要的結(jié)論： (1) Mg-Al-Er合金的顯微組織隨Er含量的不同而變化。當(dāng)Er含量低于1.0wt.%時，合金僅由Mg17Al12基體和Al3Er相組成。當(dāng)Er含量超過3.0wt.%時，基體中除了Al3Er相外還出現(xiàn)了Mg17Al12-Mg共晶組織。和Mg-44.3Al合金（單相Mg17Al12）的硬度相比，含Er合金的硬度都有了較大的提高，結(jié)合計算結(jié)果表明主要原因為添加Er后引起的晶粒細(xì)化。添加Er后，合金的抗腐蝕能力和耐磨損性能都有明顯的提高。其中，Mg-43.8Al-1.0Er合金具有最好的耐蝕性和最強的抑制陰極析氫能力，而Mg-42Al-5.0Er合金具有最好的耐磨損性能。 當(dāng)Y含量低于1.0wt.%時，Mg-Al-Y合金由Mg17Al12基體和Al2Y組成。當(dāng)Y含量超過1.0wt.%時，Mg-Al-Y合金中出現(xiàn)了Mg17Al12-Mg共晶組織。Y含量為2.0wt.%~5.0wt.%時，合金的硬度相差很小為285~290HV。 (2)利用熱壓燒結(jié)法在AZ61鎂合金表面制備了Mg-Al-Er金屬間化合物涂層。電化學(xué)測試和滑動磨損試驗結(jié)果表明涂層樣品的耐蝕性和耐磨性比AZ61鎂合金基體有很大的提高，且都好于熱擴散涂層。原因在于涂層中形成的高硬度Al3Er第二相使得燒結(jié)涂層具有較好的耐磨損性能，而Er還可以抑制涂層的析氫腐蝕。 (3) Mg-xAl-yY(x=44.3,43.8,43; y=0,1.0,3.0)合金在球磨30h內(nèi)，隨著球磨時間的延長沒有發(fā)生相變，但衍射峰強度降低、峰寬化。添加稀土Y能有效地改善Mg17Al12合金的吸放氫性能，添加Y使合金的吸放氫速率和放氫平臺壓力顯著升高。其中添加1.0wt.%Y合金的吸氫量和放氫量均很高，分別為3.39%和2.84%，且有較寬而平坦的放氫平臺壓力為1.33MPa。 (4)隨著Mg-Al-B合金中B的含量從0.1wt.%增至1.35wt.%，合金的組織由單相樹枝晶逐漸向以共晶組織為主過渡。B含量≤1.25wt.%時，合金的顯微硬度變化不大，為223HV~229HV。B含量為1.35wt.%時，硬度較低為192HV，但壓縮應(yīng)變和壓縮強度極限比Mg-44.3Al合金的分別提高了25%和57%。隨著B含量的增加合金的熔點和自腐蝕電位呈單調(diào)下降趨勢。 (5) Mg70Al30合金的顯微組織主要由α-Mg枝晶和Mg-Mg17Al12共晶組織組成。合金在H2SO4和乙酸（HAc）溶液中的腐蝕行為有很大的不同。Mg70Al30合金在pH=1.0的H2SO4溶液中表現(xiàn)為全面腐蝕，而在pH=1.0的HAc溶液中表現(xiàn)為選擇性腐蝕。共晶組織中晶粒的取向?qū)辖鹪贖Ac溶液的腐蝕行為有較大影響，點狀共晶組織具有比羽毛狀共晶更好的抗腐蝕剝落能力。晶粒取向?qū)辖鹪贖2SO4溶液中的腐蝕行為影響較小。共晶組織在兩種溶液中均具有比α-Mg枝晶組織較好的耐蝕性。Mg-Mg17Al12共晶合金發(fā)生選擇性腐蝕需要兩個條件。一是，兩相間具有較大的自腐蝕電位差；二是，耐蝕相在去合金化溶液中具有良好的耐蝕性。 (6)填充金屬間化合物Mg17Al12的泡沫鋁復(fù)合材料具有實心結(jié)構(gòu)，但具有和泡沫鋁一樣的壓縮特性。復(fù)合材料的壓縮性能比泡沫鋁的有很大的提高。平臺應(yīng)力提高1.5倍以上，吸能能力在各應(yīng)變水平都有大幅提高。在應(yīng)變小于0.02和0.2~0.6兩個區(qū)間時，泡沫鋁樣品的吸能效率低于同直徑的泡沫鋁復(fù)合材料。應(yīng)變在0.02~0.2范圍內(nèi)時泡沫鋁復(fù)合材料的吸能效率低于泡沫鋁樣品。
[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.

【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TG113;TG174.4

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