Extra Strain Hardening in High Pressure Die Casting Mg-Al-RE Alloy
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tronger and tougher materials are desired for engineering applications such as automotive industries for higher energy efficiency and better performance.[1] However, higher strength materials are generally accompanied with limited strain hardening ability thus showing brittleness.[2–4] After decades of research, materials with heterogeneous structures, such as gradient structure,[2,5,6] lamellar structure,[3,4,7] and dual-phase structure,[8] are promising to combat this issue. In these materials, different mechanical behaviors between two consecutive domains during deformation lead to the
JIE WEI, QUDONG WANG, LI ZHANG, BING YE, HAIYAN JIANG, and WENJIANG DING are with the National Engineering Research Center of Light Alloy Net Forming and Key State Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China. Contact e-mail: [email protected] DONGDI YIN is with the Key Laboratory of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031, China. HAO ZHOU is with the Nano and Heterogeneous Materials Center, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China. Manuscript submitted September 10, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
mechanical incompatibility, which brings in both strengthening and strain hardening.[1–3,9] Such mechanical behaviors originate from the forceful mutual constraint between neighboring domains, which promotes the accumulation and interaction of dislocations.[2–5,7,9] High pressure die casting (HPDC) is an important technique in preparing light-metal components, since it could economically produce large, thin-walled, and complex castings.[10] One of the intrinsic microstructure characteristics produced during HPDC is the finegrained layer (defined as ‘‘skin’’[11,12]) near the casting surface accompanied with a coarse-grained interior. This character is attributed to the different cooling rates along the depth during solidification.[13] Generally, the casting surface or ‘‘skin’’ displays higher integrity, strength, and ductility than those of the interior, rendering the so-called ‘‘skin effect.’’[11,12] The influence of this effect on the tensile deformation behavior of HPDC materials has been well studied by Yang et al.[11,12,14] and Zhang.[15] In these reports, the strength and the integrated deformation behavior were taken as the weighted average of different layers. However, the mechanical incompatibility in heterogeneous structures often brings a strain hardening, resulting in its strength exceeding the average.[2–4,7] So, for HPDC materials, is there an extra strain hardening originating from such mechanical incompatibility or ‘‘skin effect’’? What is the effect of the intrinsic heterostructure on the strain hardening behaviors? To date, these issues are still neglected in the widely applied HPDC materials. The aim of the p
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