Investigations on the fatigue property of the high-strength and toughness 211Z casting aluminium alloy

摘要

211Z is a new type of high strength and toughness Al-Cu-Mn casting aluminum alloy. With the aid of GPS-100 high-cycle fatigue testing machine and DDL100 multifunction tensile testing machine, conventional mechanics performance tests and high-cycle fatigue tests were carried out in this paper. The conventional mechanical property results show that the tensile strength is 477.5 MPa, the theory yield strength is 397.5 MPa and the elongation is 6.625%. Fatigue experiments were performed with load control at room temperature and R = -1 in ambient air. The tensile and compression fatigue strength is 130 MPa under ten million times fatigue test, and S-N fatigue life curve of this alloy was also given in the investigations. 211Z casting aluminum alloy possessing high fatigue strength can be attributed to the fact that it owns high strength and good plasticity simultaneously. The microstructure analysis of fatigue fracture appearance shows that, the fatigue crack initiation behavior of this aluminium alloys depends mainly on the region possessing defects under the surface, there has only one crack source, which means it is belongs to low nominal stress unidirectional bending. In the crack growth stage, the width of fatigue striations decreases with the increase of stress, and a few secondary cracks were found in this stage. When cracks finally loosed stability, an instantaneous fracture occurred in the investigated samples. Shear lips and dimples were found in the fracture appearance and the final fracture is belongs to ductile fracture.