High cycle fatigue behavior of different regions in a low-pressure sand-cast GW103K magnesium alloy component
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Wencai Liua) National Engineering Research Center of Light Alloy Net Forming and State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China; and Shanghai Light Alloy Net Forming National Engineering Research Center Co., Ltd, Shanghai 201615, China
Yanlei Li, Guohua Wu, and Wenjiang Ding National Engineering Research Center of Light Alloy Net Forming and State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China (Received 14 May 2014; accepted 22 August 2014)
Different parts of a casting may receive different microstructures during cooling particularly for the large scale casting, which can affect the fatigue behavior. In the present study, in consideration of the safety and reliability, the microstructures, tensile properties, and high cycle fatigue behaviors of different regions in a low-pressure sand-cast Mg–10Gd–3Y–0.5Zr (GW103K) magnesium alloy component with large scale and complicated structure were investigated. The results showed that the tensile properties particularly ultimate tensile strength (UTS) and elongation (EL) varied with regions and the fatigue strength varied in a range from 100 to 115 MPa. In addition, crack initiation, crack propagation, and fracture behavior of the studied alloys after tensile test and high cycle fatigue test were also investigated systematically.
I. INTRODUCTION
Magnesium alloys are replacing aluminum alloys as construction materials in many applications, particularly in the aerospace, aircraft, and automotive industries due to comparable strength and price, but lower density. Magnesium alloys with rare earth (RE) metals are quite interesting for scientific investigations because of their good mechanical properties.1–4 It has been reported that the recently developed Mg–Gd–Y–Zr magnesium alloys showed considerable precipitation strengthening, leading to improved specific strength at both room and elevated temperatures, and better creep resistant than conventional Al and Mg alloys.5–7 Thanks to the high performance of Mg–Gd–Y–Zr magnesium alloys, much attention is paid to produce complicated structures by these alloys in a sand mold. Different parts of a casting may receive different chemical compositions, heat treatments, and microstructures during cooling especially for the large scale castings whose size is up to meters, which can affect the tensile strength and fatigue strength.1,8 In consideration of the
safety and reliability, the fatigue properties of different regions of these castings need to be studied. Horstemeyer 9 studied the high cycle fatigue properties of a die cast AZ91E-T4 magnesium alloy. Specimens from different locations were tested. It is indicated that the dimensions of the casting dictated the total cooling rate, which in turn produced a geometry dependent dendrite cell size and porosity level. Therefore, different locations showed varied fatigue behavior. Lu et al.8,10 inv
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