本文關(guān)鍵詞：電磁屏蔽用Mg-Al-Zn合金的制備及組織性能研究　出處：《西安工業(yè)大學(xué)》2016年碩士論文　論文類(lèi)型：學(xué)位論文

  更多相關(guān)文章： Mg-Al-Zn合金 電磁屏蔽效能 β(Mg_(17)Al_(12))相 Al_2Y相 Al_4Ce相

【摘要】：本文以Mg-Al-Zn為基體,添加不同含量的Y和Ce元素,利用普通鑄造法制備出具有優(yōu)良電磁屏蔽效能的Mg-7Al-1 Zn-0.3Mn-0.9Y-0.6Ce新型鎂合金。采用光學(xué)金相顯微鏡(OM)、掃描電子顯微鏡(SEM)、X射線測(cè)試儀(XRD)分析了所制備合金的微觀組織,借助電導(dǎo)率儀、法蘭同軸測(cè)試儀、布氏硬度儀、電子萬(wàn)能試驗(yàn)機(jī)等測(cè)試手段對(duì)所制備的合金進(jìn)行電磁屏蔽性能和力學(xué)性能測(cè)試,研究了Y、Ce元素對(duì)合金微觀組織、力學(xué)性能以及電磁屏蔽效能的影響,優(yōu)化了合金的熱處理工藝。合金中Y或Ce的添加量小于等于0.9wt%時(shí),可顯著改善合金的顯微組織,第二相由較為粗大的枝晶網(wǎng)狀逐漸變成彌散分布的塊狀和顆粒狀,并有方塊狀的A12Y相、針狀的Al4Ce相生成,對(duì)組織產(chǎn)生了明顯的細(xì)化作用。但是當(dāng)合金中Y或Ce的添加量超過(guò)0.9wt%時(shí),會(huì)對(duì)合金組織產(chǎn)生粗化作用。復(fù)合添加Y和Ce對(duì)合金的顯微組織及力學(xué)性能均有較大影響。在Al2Y、Al4Ce稀土相的析出強(qiáng)化、Y和Ce的細(xì)晶強(qiáng)化的共同作用,使合金的力學(xué)性能都得到顯著提高,添加0.9wt%Y-0.6wt%Ce的鑄態(tài)Mg-Al-Zn合金可得到較佳的力學(xué)性能,其抗拉強(qiáng)度達(dá)到218MPa,延伸率達(dá)到了10.5%,布氏硬度達(dá)到69.86HB。添加Y、Ce合金元素的合金可以獲得良好的屏蔽效能,含0.9wt%Y、0.6wt%Ce時(shí)的合金其屏蔽效能為最佳,在測(cè)試頻率(30-1500MHz)范圍內(nèi)、測(cè)試試樣厚度為3mm時(shí),最高屏蔽效能值在25MHz達(dá)到108.3dB,最低屏蔽效能值在1495MHz為87.13dB,滿足軍事領(lǐng)域60-120dB的要求。Y、Ce能夠改善合金的電導(dǎo)率與電磁屏蔽性能主要依賴于合金中新形成的Al2Y、Al4Ce稀土相化合物,降低了A1在Mg基體中的固溶度,細(xì)化了合金組織,從而使合金的電導(dǎo)率與電磁屏蔽效能得到改善。添加過(guò)量的稀土元素的添加會(huì)使形成的化合物數(shù)量增多,晶粒尺寸減小,晶界增多；從而加大了對(duì)電子的散射作用,使合金的電導(dǎo)率下降,影響了電磁屏蔽效能。Mg-7Al-1Zn-0.3Mn-0.9Y-0.6Ce合金經(jīng)固溶后,彌散分布的β-Mg17Al12相發(fā)生溶解。在時(shí)效時(shí),β-Mg17Al12相又析出,當(dāng)在200℃效溫度時(shí)效時(shí),連續(xù)的β-Mg17Al12析出相數(shù)量較150℃效溫度時(shí)多；隨著時(shí)間的延長(zhǎng),β-Mg17Al12析出相的數(shù)量增加,且連續(xù)析出相的比例增多,組織的這種變化使合金的抗拉強(qiáng)度、硬度值逐漸升高,但合金的延伸率有所降低；最終確定鑄造合金最佳熱處理工藝為固溶415℃×12h后在80℃溫水淬火、時(shí)效200℃×12h,空冷。合金的抗拉強(qiáng)度提高到243MPa,布氏硬度達(dá)到75.2HB,延伸率為12.3%,達(dá)到了電控箱體材料的力學(xué)標(biāo)準(zhǔn)。
[Abstract]:In this paper, Y and ce elements with different contents were added in Mg-Al-Zn matrix. A new type of Mg-7Al-1 Zn-0.3Mn-0.9Y-0.6Ce magnesium alloy with excellent electromagnetic shielding efficiency was prepared by ordinary casting method. Optical metallographic microscope was used to fabricate the new magnesium alloy. The microstructure of the alloy was analyzed by means of scanning electron microscope (SEM), SEMU X ray tester (XRD) and Brinell hardness tester (Brinell hardness tester) with the help of conductivity meter, flange coaxial tester and Brinell hardness tester. The electromagnetic shielding properties and mechanical properties of the prepared alloys were tested by means of electronic universal testing machine. The effects of YCe on the microstructure, mechanical properties and electromagnetic shielding efficiency of the alloys were studied. The heat treatment process of the alloy was optimized. When the addition of Y or ce in the alloy was less than 0.9 wt%, the microstructure of the alloy could be improved significantly. The second phase was gradually changed from coarse dendritic network to distributed block and granular, with block A12Y phase and needle-like Al4Ce phase. But when the content of Y or ce in the alloy is more than 0.9 wt%. The composite addition of Y and ce has a great effect on the microstructure and mechanical properties of the alloy. The mechanical properties of Y and ce alloys have been greatly improved by the combined effect of fine grain strengthening. The mechanical properties of the as-cast Mg-Al-Zn alloy with 0.9wt and Y-0.6wt can be obtained. The tensile strength and elongation of the as-cast Mg-Al-Zn alloy are 218MPa and 10.5%, respectively. Brinell hardness reaches 69.86HB.The alloy with YCe alloy can obtain good shielding efficiency, and the alloy containing 0.9wt YCe 0.6wt has the best shielding efficiency. In the test frequency range of 30-1500 MHz, when the thickness of the test sample is 3 mm, the maximum shielding efficiency is 108.3 dB at 25 MHz. The minimum shielding efficiency is 87.13 dB at 1495 MHz, which meets the requirements of 60-120 dB in military field. Ce can improve the electrical conductivity and electromagnetic shielding performance of the alloy mainly depends on the newly formed Al _ 2Y _ 2O _ (4) ce rare earth phase compound, which reduces the solution of Al _ 1 in mg matrix. The structure of the alloy was refined, and the conductivity and electromagnetic shielding efficiency of the alloy were improved. The addition of excess rare earth elements would increase the number of the compounds formed, decrease the grain size and increase the grain boundary. Thus, the scattering of electrons was increased, the conductivity of the alloy decreased, and the electromagnetic shielding efficiency. Mg-7Al-1Zn-0.3Mn-0.9Y-0.6Ce alloy after solid solution. The dispersed 尾 -Mg17Al12 phase dissolves. During aging, the 尾 -Mg17Al12 phase precipitates again, and when aged at 200 鈩，

本文編號(hào)：1367380