The Fatigue Properties Of The Mg-6wt%Zn-1wt%Y-0.6wt%Ce-0.6wt%Zr Alloy Fabricated By Rapid Solidification And Forward Extrusion

The microstructures and phase compositions of Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr(wt%) alloy prepared by rapid solidification and reciprocating extrusion were studied by optical microscope,scanning electronic microscope.Mechanical properties at room temperature of the alloy as well as the fatigue behavior were tested.The fatigue fracture morphologies of the alloy were analyzed.The conclusions are as follows:1.Compared with conventionally solidified Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr alloy,the microstructures of the Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr alloy prepared by rapid solidification and reciprocating extrusion are much finer,and the secondary phases distribute more uniform.The hardness HV₅,tensile strength and elongation of the alloy are 88.0 kgf/mm², 348MPa and 20%,respectively.2.The fatigue limit of the alloy is 159.2MPa with 10⁶ cycles.The ratio of fatigue limit to tensile strength of the alloy is 46%,which is higher than other magnesium alloys.3.The fatigue cracks originate from surface of the alloy generally.Secondary phases, inclusions and defects at surface and subsurface can become the fatigue initiative nucleus easily. It could not be observed that the inclusions or secondary phases in the interior of the fatigue sample become fatigue source or influence the crack direction of propagation obviously. Fatigue crack extended section is composed of small planar cross-sections,whereas fatigue striations were not observed.The character of instant failure section is similar to tensile fracture with dead-load.4.The grains of the alloy is fine.Zn,Zr dissolved in the matrix can strengthen the alloy by solution strengthening.Meanwhile,the alloy is strengthened with secondary phases by dispersion strengthening.As a result,the fatigue resistance of the alloy is improved effectively.