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对常规压铸(DC)和真空压铸(VDC)Al-Mg-Si-Mn合金平板铸件的微观组织、力学性能和疲劳性能进行研究,并且用SEM和EDS等手段分析了断口形貌。结果表明:Al-Mg-Si-Mn合金的微观组织主要由初生α-Al,[Al+Mg2Si]共晶区以及Al15(Fe,Mn)3Si2颗粒构成。常规压铸试样和真空压铸试样的抗拉强度(Rm)、屈服强度(Rp 0.2)、弹性模量(E)和伸长率(A)分别为321 MPa,205 MPa,54 MPa和3.9%,以及331 MPa,210 MPa,55 MPa和4.4%。真空压铸试样的裂纹扩展速率曲线斜率(2.824)低于常规压铸试样(3.693),因而真空压铸试样的抗疲劳性能较好。试样的拉伸断口显示出大量脆性断裂特点即解理平面,而疲劳断口则可清晰观察到疲劳条纹和撕裂棱。
The microstructure, mechanical properties and fatigue properties of flat castings of conventional DC-DC and VDC Al-Mg-Si-Mn alloy were investigated. The fracture morphology was analyzed by SEM and EDS. The results show that the microstructure of Al-Mg-Si-Mn alloy is mainly composed of primary α-Al, [Al + Mg2Si] eutectic and Al15 (Fe, Mn) 3Si2 particles. The tensile strength (Rm), yield strength (Rp 0.2), elastic modulus (E) and elongation (A) of conventional and vacuum die-cast samples were 321 MPa, 205 MPa, 54 MPa and 3.9% And 331 MPa, 210 MPa, 55 MPa and 4.4%. The slope of the crack growth rate curve (2.824) of the vacuum die-cast samples is lower than that of the conventional die-cast samples (3.693), so the vacuum die-cast samples show better fatigue resistance. Tensile fracture specimens show a large number of brittle fracture characteristics that cleavage plane, while the fatigue fracture can be clearly observed fatigue stripes and tearing edge.