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摘  要

    近年來，鎂合金因其具有比重小、比強(qiáng)度和比剛度高、導(dǎo)電導(dǎo)熱性能好、阻尼減振效果好和電磁屏蔽性能好等優(yōu)點(diǎn)，在航空航天、軍事、交通和3C產(chǎn)品等領(lǐng)域的應(yīng)用受到廣泛的關(guān)注。然而，由于鎂合金的絕對(duì)強(qiáng)度、耐蝕性和耐熱性等性能較低，不能滿足產(chǎn)品的需求，在很大程度上制約了鎂合金的應(yīng)用進(jìn)程。利用等通道轉(zhuǎn)角擠壓（Equal-Channel Angular Pressing, ECAP）組合后續(xù)軋制工藝可獲得超細(xì)晶鎂合金板材，使鎂合金組織均勻化，消除軋制變形基面織構(gòu)的不利影響，獲得較高的強(qiáng)度及塑性,而該組合工藝對(duì)鎂合金耐蝕性的影響尚不清晰。在ECAP前對(duì)合金試樣進(jìn)行預(yù)固溶工藝可以加速合金的晶粒細(xì)化，提高組織均勻性，提高合金的力學(xué)性能及耐蝕性。因此，本文設(shè)計(jì)了針對(duì)AZ91鎂合金的固溶-ECAP-軋制復(fù)合工藝，借助預(yù)固溶及ECAP加工制備出超細(xì)晶鎂合金，繼而對(duì)其進(jìn)行軋制，以期獲得新型高耐蝕性鎂合金制備與加工復(fù)合技術(shù)。

    研究結(jié)果表明：AZ91鎂合金經(jīng)多道次等通道轉(zhuǎn)角擠壓后，晶粒被顯著細(xì)化，擠壓流紋明顯，在100℃下進(jìn)行軋制具有較好的成型能力，固溶+16道次ECAP試樣從1.46mm軋成0.80mm，總變形量達(dá)到了45.21%，成材率較好。固溶+16道次ECAP+軋制的試樣顯微硬度可以達(dá)到112.1HV，與初始鑄態(tài)相比提高了38.3HV。ECAP后的試樣耐蝕性變差，經(jīng)固溶處理的試樣耐蝕性略有提高，而軋制處理后的試樣耐蝕性變差。

關(guān)鍵詞：AZ91鎂合金；ECAP加工；軋制；顯微組織；硬度；耐蝕性

ABSTRACT

Magnesium and magnesium alloys have many advantage such as low density, high specific strength, high specific  stiffness, good thermal conductivity , high damping effect and good electro-magnetic shielding performance. In recent years, these alloys have received lots of attention for  the potential application in the areas of aerospace,  military,  transportation and 3C products. However, their products cannot meet the practical requirement  due to low strength,  poor corrosion resistance and heat resistance . At present,  there are many methods to control the corrosion of Mg alloys. However, the report about corrosion behaviors of Mg alloy prepared by  equal-channel angular pressing(ECAP) plus rolling is still limited. Using  ECAP can gain  bulk ultrafine-grained magnesium alloy with better  mechanical properties. Rolling after ECAP can eliminate the anisotropy of Mg alloy, making its homogenized and further improving its corrosion resistance. In the present work,  ultrafine-grained AZ91Mg alloy was obtained by ECAP process and thus rolling to  develop the new preparation  processing of high corrosion-resistant Mg alloy.

The results indicated that after multi-pass ECAP , grains of AZ91 magnesium alloy were greatly refined and the extrusion flow was obvious. The ECAP-fabricated alloy has good rolling performance at 100 ℃. The SS+16P sample was rolled from 1.46 mm to 0.80 mm with the  deformation rate of 45.21%. It means the product rate of the ultrafine-grained alloy after rolling will be high . The micro-hardness of the SS+16P sample  reach 112.1HV, with an increase of 38.3HV compared to the initial case. The corrosion resistance of the samples after ECAP reduced, but the solid solution treatment before ECAP slightly improved the corrosion resistance of the ECAPed sample. The corrosion resistance of the rolled samples reduced.

Keywords:AZ91D Mg alloy; Equal-Channel Angular Pressing; Rolling; 

  Microstructure; Hardness; Corrosion resistance