热处理及轧制对ecap加工az91镁合金腐蚀行为的影响.doc

2万字             54页

 

摘  要

    近年来，镁合金因其具有比重小、比强度和比刚度高、导电导热性能好、阻尼减振效果好和电磁屏蔽性能好等优点，在航空航天、军事、交通和3C产品等领域的应用受到广泛的关注。然而，由于镁合金的绝对强度、耐蚀性和耐热性等性能较低，不能满足产品的需求，在很大程度上制约了镁合金的应用进程。利用等通道转角挤压（Equal-Channel Angular Pressing, ECAP）组合后续轧制工艺可获得超细晶镁合金板材，使镁合金组织均匀化，消除轧制变形基面织构的不利影响，获得较高的强度及塑性,而该组合工艺对镁合金耐蚀性的影响尚不清晰。在ECAP前对合金试样进行预固溶工艺可以加速合金的晶粒细化，提高组织均匀性，提高合金的力学性能及耐蚀性。因此，本文设计了针对AZ91镁合金的固溶-ECAP-轧制复合工艺，借助预固溶及ECAP加工制备出超细晶镁合金，继而对其进行轧制，以期获得新型高耐蚀性镁合金制备与加工复合技术。

    研究结果表明：AZ91镁合金经多道次等通道转角挤压后，晶粒被显著细化，挤压流纹明显，在100℃下进行轧制具有较好的成型能力，固溶+16道次ECAP试样从1.46mm轧成0.80mm，总变形量达到了45.21%，成材率较好。固溶+16道次ECAP+轧制的试样显微硬度可以达到112.1HV，与初始铸态相比提高了38.3HV。ECAP后的试样耐蚀性变差，经固溶处理的试样耐蚀性略有提高，而轧制处理后的试样耐蚀性变差。

关键词：AZ91镁合金；ECAP加工；轧制；显微组织；硬度；耐蚀性

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