The Influence of Nd on the High-cycle Fatigue of Die Cast AZ91 Magnesium Alloy

　　The Influence of Nd on the High-cycle Fatigue of Die Cast AZ91 Magnesium Alloy
　　Magnesium alloys have been widely used to reduce the car in automotiveindustry, so it becomes a focus in the field of material science due to their lowdensity. This paper have studied the high cycle fatigue property and thecorrelative mechanical properties of AZ91 die-casting magnesium alloys withthe addition of different content rare earth Nd(0.5%,1.0% and 1.5%). The resultof this research has evaluated the properties of the three kinds of materialobjectively. It also has practical value on industrial production.At first,we reviewed the current status of magnesium alloys application inmost related field and the gap of it between other developed country and us.
　　The superiority on property and the potential Ball Neodymium Magnets of magnesium alloys are alsodescribed. Fatigue property of materials in modern industrial applicationemphasized in this paper.This paper has observed the phase microstructure and analyzed the newphase by energy chart and XRD, tested the regular mechanical property of thethree kinds of alloys comparatively and obtained S-N curve and the fatiguelimit by using “small sample” and “group” method. In order to understand themicrostructure and the mechanism of high cycle fatigue, we studied themicrostructure and fatigue fracture by scanner electron microscope andtransmission electron microscope. And then discussed the reasons of influenceon the fatigue property and the influence of RE on fatigue property.The study indicates that because the strengthening effect of the secondphrase Al11Nd3, the rigidity of material enhances within a small range as theaddition of RE . When the content of Nd is 1.0%, the material has the bestfatigue property and correlative mechanical property. But σb,σ0.2,δ and even thefatigue limit of the three kinds of material decreases to different extent when Ndis kept adding. That is the result of the http://www.chinamagnets.biz increase of the second phrase which willproduce to be thicker then divide the microstructure. From SEM and TEManalysis of the high cycle fatigue fractures, we can observe differentmicrostructure character at different moment of crack propagation. The crack isused to initiate from the flaws like cavities, impurities or second phase on ornear to the surface of the samples. Fatigue stripes, fatigue steps and microcracks are observed in the area of crack propagation. When the content of Nd is0.1%, the fatigue stripes distribute most obviously and regularly.This paper has tested the mechanical property and high cycle fatigueproperty of the three kinds of alloys across-the-board and analyzed the effect ofRE Nd on the properties of alloys by changing the microstructure. The result ofresearch indicate that the mechanical property can be enhanced by adding RE.