摘要
对Mg-5Ca合金在不同气氛下生成的表面膜形貌结构及阻燃机理进行了研究。结果表明,740℃保温2h后,合金在普通工业氮气(99.5%)中生成的表面膜呈淡黄色且平整连续;高纯氮气(99.995%)中表面由大量颗粒堆积而成,存在破裂的现象;大气中表面呈菜花状,结构疏松,开裂变形非常严重。阻燃机理分析表明,Mg-5Ca合金在普通工业氮气下形成了表层由CaO、MgO和Mg3N2、Ca3N2组成,里层由CaO和MgO组成的双层复合膜;其中Ca元素在膜表面褶皱、杂质、裂纹处以及膜与基体的交界处存在明显聚集的现象。这种特殊的双层复合膜填补了单一膜中的疏松和孔洞,阻止了镁合金的燃烧;而高纯氮气下合金表面只能形成一层很薄的Mg3N2和Ca3N2,不能完全覆盖表面,其阻燃效果相对较差;大气中形成的表面膜非常厚,导致膜所受的压力过大而产生破裂,故其表面质量最差。
In order to understand the influence of different atmospheres on the ignition-proof behavior of spraying deposited magnesium alloy,the morphology,structure and the ignition-proof mechanism of the Mg-5Ca alloy surface film formed under different atmospheres were observed.The results indicate that,after heated at 740 ℃ for 2 h,the surface film formed under commercial nitrogen atmosphere（99.5%）on the alloy exhibits smooth and continuous,while under high-purity nitrogen atmosphere（99.995%）,the surface film formed is composed of a large number of irregular particles with observed crack.Meanwhile,the surface film formed in air shows loose structure with cauliflower-like appearance,and the crack and deformation are very serious.Ignition-proof mechanism reveals that,under nitrogen atmosphere,a protective film is composed of the mixed structure of CaO,MgO,and Mg3N2、Ca3N2 at the outer surface and CaO and MgO at the inner layer,where Ca element aggregated on the folds,impurities,cracks and the junction of surface and substrate.The dense structure compensate the loose hole,which is beneficial for preventing the Mg-5Ca alloy from burning.However,the film under high-purity nitrogen is only composed of Mg3N2 and Ca3N2,and it is very thin,so that it can not cover the surface entirely,resulting in the low ignition-proof efficiency.Film formed in air is composed of mixed structure of CaO and MgO with mostly CaO at the free surface,and it is too thick to bear the pressure,so that the film is broken and the surface quality is the worst.
出处
《特种铸造及有色合金》
CAS
CSCD
北大核心
2012年第9期871-875,共5页
Special Casting & Nonferrous Alloys
基金
国家自然科学基金资助项目(50904035)
广东省教育部产学研结合项目(2009B090300148
2010B090400244)
