摘要
采用扫描电镜（SEM）、X射线衍射仪（XRD）和高温蠕变试验机等实验手段研究了碱土元素Ca，Sr对AM80镁合金显微组织和力学性能的影响．结果表明：在AM80合金中复合添加0．2％Sr和0．5％～2．5％Ca，Ca、Sr元素可逐步细化合金的铸态组织，Ca原子与Al原子优先结合在晶界处生成了高熔点相Al2Ca，抑制了低熔点相β-Mg17Al12的形成．AM80合金在高温蠕变过程中，β-Mg17Al12相在晶界处存在连续析出和非连续析出2种形式．β-Mg17Al12相非连续析出并且垂直于晶界，造成合金蠕变性能较差．当在合金中复合添加Ca，Sr后，高熔点相Al2Ca是主要的晶界强化相，替代低熔点的β-Mg17Al12相，从而减少β-Mg17Al12相的非连续析出，抑制了晶界滑动，改善了合金的高温蠕变性能．当Ca质量分数增加到2．5％时，合金的高温蠕变性能最优．
The effects of alkaline elements Ca and Sr additions on the microstructure and mechanical properties of AM80 magnesium alloy were investigated by using scanning electron microscopy（SEM）, X- ray diffraction（XRD） and creep properties testing at elevated temperature. The results show that the microstructures of the as--cast alloys are refined by adding 0.2 % Sr and 0.5 % - 2.5 % Ca. A high-melting point AI2Ca phase dispersedly formed at the grain boundaries in the AM80 alloy due to the priority combination of Ca and A1, thus the formation of 13-Mg17 Al12 phase was reduced. The mechanical properties of the alloys were also improved due to the existence of the addition of Ca and St. The β-Mg17Al12 phase had two kinds of precipitation forms, which were non-continuous precipitation and continuous precipitation during creep process. The non-continuous β-Mg17Al12 phase precipitated at the grain boundaries and was perpendicular to the grain boundaries, decreasing the creep properties of AM80 magnesium alloy. The elevated temperature creep properties of the alloys were greatly improved because the low-melting point β-Mg17Al12 phase was replaced by high-melting point Al2Ca phase, which prevented the grain boundaries sliding. The creep mechanism was best when the mass fraction of Ca was 2.5%.
出处
《湖南大学学报（自然科学版）》
EI
CAS
CSCD
北大核心
2010年第4期46-52,共7页
Journal of Hunan University:Natural Sciences
基金
科技部国际合作重点资助项目(2008DFA50990)
湖南省杰出青年基金资助项目(09JJ1007)
重庆市科技攻关计划资助项目(CSTC
2007AA4008)
湖南大学汽车车身先进设计制造国家重点实验室自主课题资助项目(60870005)
教育部长江学者与创新团队发展计划资助项目(531105050037)
关键词
钙
锶
显微组织
AM80镁合金
蠕变性能
Calcium
Strontium
microstructure
AM80 magnesium alloys
creep properties
