泡沫镁的宏微观结构表征及压缩性能
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摘要
针对熔体发泡法制备泡沫镁存在的困难,使用包覆发泡剂及改进工艺成功制得泡孔均匀的泡沫镁试样。利用OM、SEM、EDS及XRD等分析手段对试样进行宏微观结构表征。结果表明:泡沫镁试样宏观孔以典型的闭孔结构为主,但也存在一些连通孔及少量大孔,它们多是宏观裂纹的产生及扩展位置。泡孔内壁存在一些褶皱缺陷,且弥散分布着许多反应产生的MgO和CaO颗粒,压缩变形过程中,这些部位易产生应力集中,促进微裂纹的形成与扩展。孔壁上主要分布着碳化硅颗粒及生成的Mg_2Ca相。测试分析了孔隙率和孔径对泡沫镁压缩力学性能和能量吸收性能的影响,并深入研究其压缩破坏机理。研究发现:随着孔隙率的降低,泡沫镁弹性变形增大,屈服强度升高;随着孔径的增大,泡沫镁屈服强度及平台应力明显减小,表现出显著的孔径效应。随着孔隙率的升高或孔径的增大,泡沫镁的能量吸收性能显著降低。泡沫镁的破坏为解理脆性断裂,这与孔壁组织及镁基体性质有很大的关系。
Magnesium foams were fabricated by a melt foaming method using coated CaCO_3 as a blowing agent. Macro-micro structure characteristics of the magnesium foams were investigated by OM, SEM, EDS and XRD. The results show that the macro pores of the pores are dominated by closed-cell structure. Meanwhile there are also some communicated pores and big pores, where macro cracks usually initiate and propagate during compression. Fold defects and reaction products MgO and CaO particles diffusely distribute on the pore inner walls, and they easily create stress concentration and cause micro cracks. Pore walls are mainly composed of SiC particles introduced at the thickening stage and second phases Mg_2Ca. Furthermore, compressive properties and energy absorption performances were tested and the fracture mechanism was studied. Elastic deformation and yield strength increase with decreasing porosity. Yield strength and plateau stress decline dramatically with increasing pore size, namely magnesium foam shows an evident aperture effect. Besides, energy absorption performances significantly decrease with increasing porosity or pore size. And magnesium foam exhibits cleavage fracture during compression due to the micro structure of pore walls and the characteristic of magnesium substrate.
Magnesium foams were fabricated by a melt foaming method using coated CaCO_3 as a blowing agent. Macro-micro structure characteristics of the magnesium foams were investigated by OM, SEM, EDS and XRD. The results show that the macro pores of the pores are dominated by closed-cell structure. Meanwhile there are also some communicated pores and big pores, where macro cracks usually initiate and propagate during compression. Fold defects and reaction products MgO and CaO particles diffusely distribute on the pore inner walls, and they easily create stress concentration and cause micro cracks. Pore walls are mainly composed of SiC particles introduced at the thickening stage and second phases Mg_2Ca. Furthermore, compressive properties and energy absorption performances were tested and the fracture mechanism was studied. Elastic deformation and yield strength increase with decreasing porosity. Yield strength and plateau stress decline dramatically with increasing pore size, namely magnesium foam shows an evident aperture effect. Besides, energy absorption performances significantly decrease with increasing porosity or pore size. And magnesium foam exhibits cleavage fracture during compression due to the micro structure of pore walls and the characteristic of magnesium substrate.
引文
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[2]Xie Xiangyun(谢香云),Zuo Xiaoqing(左孝青),Wang Yingwu(王应武)et al.Rare Metal Materials and Engineering(稀有金属材料与工程)[J],2013,42(8):1649
[3]Banhart J,Baumeister J,Weber M.Materials Science and Engineering A[J],1996,205(1-2):221
[4]Feng Yi(凤仪),Zheng Haiwu(郑海务),Zhu Zhengang(朱振刚)et al.The Chinese Journal of Nonferrous Metals(中国有色金属学报)[J],2004,14(1):33
[5]Nakajima H.Progress in Materials Science[J],2007,52(7):1091
[6]Ashby M F,Evans A G.Metal Foams:A Design Guide[M].San Diego:Butterworth-Heinemann,2000:1
[7]Gibson L J,Ashby M F.Cellular Solids:Structure and Properties[M].Cambridge:Cambridge University Press,1997:1
[8]Yamamura S,Shiota H,Murakami K et al.Materials Science and Engineering A[J],2001,318(1-2):137
[9]Mondal D P,Goel M D,Bagde N et al.Materials&Design[J],2014,57:315
[10]Xue X,Wang L,Wang M et al.Transactions of Nonferrous Metals Society of China[J],2012,22:188
[11]Liu Peisheng(刘培生),Luo Jun(罗军),Chen Yiming(陈一鸣).Rare Metal Materials and Engineering(稀有金属材料与工程)[J],2012,41(S2):50
[12]Li Jing(李婧),Yang Hailin(杨海林),Ruan Jianming(阮建明)et al.Rare Metal Materials and Engineering(稀有金属材料与工程)[J],2013,42(5):1023
[13]Zahrani M M,Meratian M,Kabiri Y.Materials Letters[J],2012,85:14
[14]Zhang Y H,Song C H,Ren H P et al.Transactions of Nonferrous Metals Society of China[J],2011,21(9):2099
[15]Yang D H,Hur B Y,Yang S R.Journal of Alloys and Compounds[J],2008,461(S1-2):221
[16]Shen Jian(沈剑),Feng Yi(凤仪),Wang Songlin(王松林)et al.Metallic Functional Materials(金属功能材料)[J],2006,13(03):9
[17]Yuan L,Yanxiang L,Jiang W et al.Materials Science and Engineering:A[J],2005,402(1-2):47
[18]Zhou Quan(周全),Chen Leping(陈乐平).Special Casting&Nonferrous Alloys(特种铸造及有色合金)[J],2009,29(3):224
[19]Lu G,Hao H,Wang F et al.Transactions of Nonferrous Metals Society of China[J],2013,23(6):1832
[20]Yang Donghui(杨东辉),He Deping(何德坪),Yang Shangrun(杨上闰).The Chinese Journal of Nonferrous Metals(中国有色金属学报)[J],2009,19(11):1934
[21]Hull D.Fractography:Observing,Measuring and Interpreting Fracture Surface Topography[M].Cambridge:Cambridge University Press,1999:158