Analysis of the cracks formation on surface of extruded magnesium rod based on numerical modeling and experimental verification
来源期刊：Acta Metallurgica Sinica2009年第5期
论文作者：Mingbo YANG Hongjun HU Fusheng PAN Dingfei ZHANG
Key words：Extrusion; Finite element; Magnesium alloy; Cracks; Experimental validation;
Abstract: To reduce the surface cracks of extrusion rod for AZ31 magnesium caused by nonho-mogeneous metal flow in extrusion process, 3D computer finite element (FE) simulations of extruding a wrought magnesium alloy AZ31 into rods have been performed and the results have been verified in extrusion experiments under identical conditions. The tendency to generate the dead zone is decreased by employing the die angle 60° at the cone-shaped die comparing with the die angle 180°. The surface additional tensile stresses of the rod at the die exit are decreased greatly so that the surface cracks caused are avoided by using the die angle 60°. The extrusion die with die angle 180° would increase the higher temperature rise and possibility of crack formation on the rod surface that caused by die angle 60° and temperature rise decrease tensile strength of the AZ31 rod. The experimental results show that die angle 180° could cause continuous cracks on the surface of the extruded rod. The extrusion force required is reduced approximately 15 ton by employing the die angle 60°. Theoretical results obtained by the Deform~(TM)-3D simulation agreed well with the experiments. The obtained results provide the fundamental and also practical guidelines for the design and correction of dies to produce magnesium rod with good surface quality.
Mingbo YANG1，Hongjun HU1，Fusheng PAN1，Dingfei ZHANG1
(1.College of Materials Science and Engineering, Chongqing University, Chongqing 400045, China;
2.College of Material Science and Engineering, Chongqing University of Technology, Chongqing 400050, China;
3.National Engineering Research Center for Magnesium Alloys, Chongqing 400044, China)
Abstract:To reduce the surface cracks of extrusion rod for AZ31 magnesium caused by nonho-mogeneous metal flow in extrusion process, 3D computer finite element (FE) simulations of extruding a wrought magnesium alloy AZ31 into rods have been performed and the results have been verified in extrusion experiments under identical conditions. The tendency to generate the dead zone is decreased by employing the die angle 60° at the cone-shaped die comparing with the die angle 180°. The surface additional tensile stresses of the rod at the die exit are decreased greatly so that the surface cracks caused are avoided by using the die angle 60°. The extrusion die with die angle 180° would increase the higher temperature rise and possibility of crack formation on the rod surface that caused by die angle 60° and temperature rise decrease tensile strength of the AZ31 rod. The experimental results show that die angle 180° could cause continuous cracks on the surface of the extruded rod. The extrusion force required is reduced approximately 15 ton by employing the die angle 60°. Theoretical results obtained by the Deform~(TM)-3D simulation agreed well with the experiments. The obtained results provide the fundamental and also practical guidelines for the design and correction of dies to produce magnesium rod with good surface quality.
Key words:Extrusion; Finite element; Magnesium alloy; Cracks; Experimental validation;
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