Mechanical Properties and Microstructural Evolution of Yb-Modified Al-20%Si Alloy
- PDF / 5,845,709 Bytes
- 10 Pages / 593.972 x 792 pts Page_size
- 101 Downloads / 282 Views
ÓASM International 1059-9495/$19.00
Mechanical Properties and Microstructural Evolution of Yb-Modified Al-20%Si Alloy Qinglin Li, Jinbao Li, Binqiang Li, Yuqian Zhu, Dexue Liu, Yefeng Lan, and Shu Wang (Submitted January 5, 2018; in revised form April 18, 2018) In the study, the mechanical properties and microstructural evolution of hypereutectic Al-20%Si-xYb alloys (x = 0, 0.1, 0.3, 0.5 and 0.7 wt.%) were studied. The as-prepared samples were characterized by scanning electron microscopy, optical microscope, x-ray diffraction (XRD) and electron probe microanalysis. The characterization results showed with the addition amount of Yb increasing to 0.5%, the eutectic Si structure was gradually modified from coarse needle-like/platelet-like structure into fine coral-like fibrous structure and the primary Si phases were gradually converted from coarse platelet-like/star-like/polygonal shape into fine blocky shape. In particular, according to the results of WDS and XRD analyses, the Yb-rich intermetallic phase in the Al-20%Si alloy is Al3Yb. Tensile test was carried out to study the mechanical properties of Al-20%Si-x%Yb alloys, and results showed that the elongation and ultimate tensile strength increased by 73.6% and 64.5%, respectively. Keywords
eutectic Si, hypereutectic Al-20%Si alloy, mechanical properties, primary Si, rare earth Yb
1. Introduction Hypereutectic aluminum–silicon (Al-Si) casting alloys, with mass percentage of silicon in aluminum larger than 12.6%, have been widely used in piston production because of high corrosion resistance, good cast ability and high strength-toweight ratio (Ref 1-6). As we know that the microstructure of hypereutectic Al-Si alloys usually consists of coarse primary Si crystals and eutectic mixture structure of (a-Al + Si), Si is a faceted phase forming complex morphology during the process of conventional casting, such as acicular/flake eutectic Si and star-like, plate-like/star-like/polygonal primary Si. The brittleness of the primary and eutectic Si leads to the poor properties of Al-Si alloys in certain degree as stress concentration results in crack initiation and fracture in tensile test (Ref 7, 8). On this basis, it is necessary to refine or modify coarse Si phases into fine Si phases with desirable tensile properties. In order to modify the primary and eutectic Si phases, scholars have developed many methods including chemical modification, rapid solidification, mechanical vibration (Ref 914). Among them, chemical modification is regarded as one of the most effective and simple methods for the refinement and
Qinglin Li, Jinbao Li, Binqiang Li, Yuqian Zhu, Dexue Liu, Yefeng Lan, and Shu Wang, School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050, PeopleÕs Republic of China; and State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, Lanzhou University of Technology, Lanzhou 730050, PeopleÕs Republic of China. Contact e-mail: [email protected].
Journal of Materials Engineering and Performance
modification of
Data Loading...
