铸造方法对Al-Mg-Mn-Ce合金组织和力学性能的影响
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摘要
采用砂型铸造、金属型铸造和压铸制备了Al-5.0Mg-0.6Mn-0.25Ce合金,研究了不同铸造方法(冷却速率)对合金组织和力学性能的影响。结果表明,随着冷却速率增加,铸态合金中的α-Al枝晶发生等轴化,粗大的第二相发生细化。低冷却速率时,砂型铸造、金属型铸造合金的铸态组织主要由α-Al枝晶和分布在周围的Al_3Mg_2相、Al_6(Fe,Mn)相、Mg_2Si相等第二相组成;高冷却速率时,压铸合金则由α-Al等轴晶和分布在其周围的短棒状含Mn相、针状Mg_2Si相组成。随着冷却速率增加,铸态合金的屈服强度、抗拉强度逐渐增加,而伸长率则呈现先增后减的趋势,这主要是与合金显微组织和内部气孔、缩孔等缺陷有关。冷却速率越高,合金组织越细,并且Mg、Mn固溶在α-Al基体内的含量增多,所以合金强度越高。然而,压铸合金中,组织内存在气孔和针状Mg_2Si相降低了合金的塑性。
The microstructure and mechanical properties of the Al-5.0Mg-0.6Mn-0.25Ce alloys prepared by sand casting,metal casting and die-casting were investigated by OM,SEM,EDS and tensile testing.The results show that with the increase of cooling rate,theα-Al dendrites in the casting alloy are transformed into roundα-Al grains,and the second phase is refined.With a lower cooling rate,the as-cast microstructure of sand casting and metal casting alloy mainly consists ofα-Al dendrite,Al_3Mg_2phase,Al_6(Fe,Mn)phase,Mg_2Si phase.While with a higher cooling rate,the die-casting alloy consists of small equiaxedα-Al grains and short rod-shaped Mn-containing phases as well as needle-shaped Mg_2Si phases distributed around the grain boundaries.With the increase of the cooling rate,the yield strength and tensile strength of the casting alloys are gradually increased,while the elongation rate is increased firstly and then decreased,which is mainly attributed to the microstructure of the alloy and the casting defects such as shrinkage holes.When the cooling rate increases,the microstructure of the casting alloys become finer,and the more Mg and Mn are dissolved into theα-Al-based matrix,leading to the higher strength of the alloys.However,in die-cast alloy,there exists gas hole and needle Mg_2Si phases,which is harmful to the plasticity of the alloy.
The microstructure and mechanical properties of the Al-5.0Mg-0.6Mn-0.25Ce alloys prepared by sand casting,metal casting and die-casting were investigated by OM,SEM,EDS and tensile testing.The results show that with the increase of cooling rate,theα-Al dendrites in the casting alloy are transformed into roundα-Al grains,and the second phase is refined.With a lower cooling rate,the as-cast microstructure of sand casting and metal casting alloy mainly consists ofα-Al dendrite,Al_3Mg_2phase,Al_6(Fe,Mn)phase,Mg_2Si phase.While with a higher cooling rate,the die-casting alloy consists of small equiaxedα-Al grains and short rod-shaped Mn-containing phases as well as needle-shaped Mg_2Si phases distributed around the grain boundaries.With the increase of the cooling rate,the yield strength and tensile strength of the casting alloys are gradually increased,while the elongation rate is increased firstly and then decreased,which is mainly attributed to the microstructure of the alloy and the casting defects such as shrinkage holes.When the cooling rate increases,the microstructure of the casting alloys become finer,and the more Mg and Mn are dissolved into theα-Al-based matrix,leading to the higher strength of the alloys.However,in die-cast alloy,there exists gas hole and needle Mg_2Si phases,which is harmful to the plasticity of the alloy.
引文
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[2]孙景旺,王渠东,丁文江.铸造Al-Mg-Mn合金的显微组织及力学性能[J].特种铸造及有色合金,2012,32(1):85-89.
[3]戴圣龙.铸造手册·第3卷:铸造非铁合金[M].北京:机械工业出版社,2011.
[4] MIKHAYLOVSKAYA A V,MOCHUGOVSKIY A G,LEVCHENKO V S,et al.Precipitation behavior of L12 Al3Zr phase in Al-Mg-Zr alloy[J].Materials Characterization,2018,139:30-37.
[5] BARKOV R Y,POZDNIAKOV A V,TKACHUK E,et al.Effect of Y on microstructure and mechanical properties of Al-Mg-Mn-ZrSc alloy with low Sc content[J].Materials Letters,2018,217:135-138.
[6] OKAYASU M,OHKURA Y,TAKEUCHI S,et al.A study of the mechanical properties of an Al-Si-Cu alloy(ADC12)produced by various casting processes[J].Materials Science and Engineering,2012,A543:185-192.
[7]胡文鑫,姜佳鑫,吴俊子.稀土元素在镁合金及铝合金中的作用及应用[J].稀土信息,2016(7):27-30.
[8] CHE H,JIANG X,QIAO N,et al.Effects of Er/Sr/Cu additions on the microstructure and mechanical properties of Al-Mg alloy during hot extrusion[J].Journal of Alloys and Compounds,2017,708:662-670.
[9]吴健,古文全,薛涛,等.稀土Ce对Al-10Mg合金组织及力学性能的影响[J].特种铸造及有色合金,2014,34(1):89-92.
[10]邢泽炳,聂祚仁,邹景霞,等.冷却速度对Al-4.5Mg-0.7Mn-0.4Er合金固溶度及组织的影响[J].特种铸造及有色合金,2007,27(9):657-659.
[11]徐国富,杨军军,金头男,等.微量稀土Er对Al-5Mg合金组织与性能的影响[J].中国有色金属学报,2006,16(5):768-774.
[12] ZHANG P,LI Z,LIU B,et al.Improved tensile properties of a new aluminum alloy for high pressure die casting[J].Materials Science and Engineering,2016,A651:376-390.
[13]刘永勤.铝合金凝固过程及其结构件的铸造工艺研究[D].西安:西北工业大学,2015.
[14] LIU Y,LUO L,HAN C,et al.Effect of Fe,Si and cooling rate on the formation of Fe-and Mn-rich intermetallics in Al-5Mg-0.8Mn alloy[J].Journal of Materials Science&Technology,2016,32(4):305-312.