Influence of size and distribution of W phase on strength and ductility of high strength Mg-5.1Zn-3.2Y-0.4Zr-0.4Ca alloy processed by indirect extrusion
来源期刊：JOURNAL OF MATERIALS SCIENCE TECHNOLOG2018年第2期
论文作者：Hansi Jiang Xiaoguang Qiao Chao Xu Shigeharu Kamado Kun Wu Mingyi Zheng
文章页码：277 - 283
摘 要：A high strength Mg-5.1Zn-3.2Y-0.4Zr-0.4Ca（wt%） alloy containing W phase（Mg3Y2Zn3） prepared by permanent mold direct-chill casting is indirectly extruded at 350?C and 400?C, respectively. The extruded alloys show bimodal grain structure consisting of fine dynamic recrystallized（DRXed） grains and unrecrystallized coarse regions containing fine W phase and β2’ precipitates. The fragmented W phase particles induced by extrusion stimulate nucleation of DRXed grains, leading to the formation of fine DRXed grains, which are mainly distributed near the W particle bands along the extrusion direction. The alloy extruded at 350?C exhibits yield strength of 373 MPa, ultimate tensile strength of 403 MPa and elongation to failure of 5.1%. While the alloy extruded at 400?C shows lower yield strength of 332 MPa,ultimate tensile strength of 352 MPa and higher elongation to failure of 12%. The mechanical properties of the as-extruded alloys vary with the distribution and size of W phase. A higher fraction of DRXed grains is obtained due to the homogeneous distribution of micron-scale broken W phase particles in the alloy extruded at 400?C, which can lead to higher ductility. In addition, the nano-scale dynamic W phase precipitates distributed in the un DRXed regions are refined at lower extrusion temperature. The smaller size of nano-scale W phase precipitates leads to a higher fraction of un DRXed regions which contributes to higher strength of the alloy extruded at 350?C.
Hansi Jiang1，Xiaoguang Qiao1，Chao Xu2，Shigeharu Kamado2，Kun Wu1，Mingyi Zheng1
1. School of Materials Science and Engineering, Harbin Institute of Technology2. Department of Mechanical Engineering, Nagaoka University of Technology
摘 要：A high strength Mg-5.1Zn-3.2Y-0.4Zr-0.4Ca（wt%） alloy containing W phase（Mg3Y2Zn3） prepared by permanent mold direct-chill casting is indirectly extruded at 350?C and 400?C, respectively. The extruded alloys show bimodal grain structure consisting of fine dynamic recrystallized（DRXed） grains and unrecrystallized coarse regions containing fine W phase and β2’ precipitates. The fragmented W phase particles induced by extrusion stimulate nucleation of DRXed grains, leading to the formation of fine DRXed grains, which are mainly distributed near the W particle bands along the extrusion direction. The alloy extruded at 350?C exhibits yield strength of 373 MPa, ultimate tensile strength of 403 MPa and elongation to failure of 5.1%. While the alloy extruded at 400?C shows lower yield strength of 332 MPa,ultimate tensile strength of 352 MPa and higher elongation to failure of 12%. The mechanical properties of the as-extruded alloys vary with the distribution and size of W phase. A higher fraction of DRXed grains is obtained due to the homogeneous distribution of micron-scale broken W phase particles in the alloy extruded at 400?C, which can lead to higher ductility. In addition, the nano-scale dynamic W phase precipitates distributed in the un DRXed regions are refined at lower extrusion temperature. The smaller size of nano-scale W phase precipitates leads to a higher fraction of un DRXed regions which contributes to higher strength of the alloy extruded at 350?C.
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