Fatigue Properties of Cast Magnesium Wheels
- PDF / 6,378,422 Bytes
- 19 Pages / 593.972 x 792 pts Page_size
- 43 Downloads / 198 Views
TRODUCTION
REDUCING the weight of large components such as automotive wheels is critical to control fuel consumption and to reduce emissions. If magnesium alloy materials can endure the cyclical loading during wheel operations, by introducing magnesium wheels to replace cast aluminum wheels will apparently improve fuel efficiency and specific power output.[1] Current commercial magnesium alloys such as AZ91 and AM60, can hardly undergo the wheel running stresses and also do not have sufficient fatigue strength for wheel applications due to the existence of shrinkage porosity.[2–4] As a recently developed magnesium alloy, Mg-Nd-Zn-Zr (NZK) with higher tensile properties[5–7] and fatigue performance[8–11] as good as corrosion resistance[12–14] is very attractive for powertrain and structural application. It has been reported that T6-treated Mg-2.85Nd-0.18Zn-0.45Zr (actual chemical compositions in wt pct except otherwise stated) alloy engine blocks prepared by low-pressure sand casting (average grain size d 100 lm) exhibited high yield ZHENMING LI, Postdoctor, is with the National Engineering Research Center of Light Alloys Net Forming and State Key Laboratory of Metal Matrix Composite, School of Mechanical Engineering, Shanghai Jiao Tong University, 200240 Shanghai, P.R. China, and also with the Suzhou Institute for Nonferrous Metals Research Co., Ltd., 215026 Suzhou, P.R. China. Contact e-mail: [email protected] ALAN A. LUO, Professor, is with the Ohio State University, Columbus, OH 43210. QIGUI WANG, Professor, is with General Motors, Global Propulsion System, Pontiac, MI 48340. LIMING PENG, Professor, and PENG ZHANG, Ph.D. Student, are with the National Engineering Research Center of Light Alloys Net Forming and State Key Laboratory of Metal Matrix Composite, School of Mechanical Engineering, Shanghai Jiao Tong University. Manuscript submitted November 8, 2015. Article published online May 20, 2016 METALLURGICAL AND MATERIALS TRANSACTIONS A
strength [~160 MPa at room temperature of ~293 K (20 C) and ~140 MPa at engine running temperature of 423 K (150 C)] and fatigue strength [~87 MPa at ~293 K (20 C) and ~70 MPa at 423 K (150 C)].[15] Shanghai Jiao Tong University and General Motors have also developed a new process of low-pressure permanent mold casting and used NZK alloy for making magnesium wheels. The increasing use of cast magnesium components such as wheels under cyclic loading has drawn considerable interest in their fatigue properties and fracture behavior.[16–18] For the castings, both fatigue properties and deformation behavior are mainly dependent on casting defects (such as porosity, oxide films, and inclusions)[19–25] and microstructural characteristics (including grain size, second-phase particles, solid solution matrix, and precipitates).[26–31] For magnesium alloy castings, most of fatigue cracks originated from the flaws near or close to the free surface during fatigue test. The fatigue life of those castings is strongly controlled by the maximum flaw as stress concentration site.[23] In the ab
Data Loading...
