Formation of Al 15 Mn 3 Si 2 Phase During Solidification of a Novel Al-12%Si-4%Cu-1.2%Mn Heat-Resistant Alloy and Its Th
- PDF / 4,378,101 Bytes
- 11 Pages / 593.972 x 792 pts Page_size
- 25 Downloads / 182 Views
ASM International 1059-9495/$19.00
Formation of Al15Mn3Si2 Phase During Solidification of a Novel Al-12%Si-4%Cu-1.2%Mn Heat-Resistant Alloy and Its Thermal Stability Xiaojing Suo, Hengcheng Liao, Yiyun Hu, Uday S. Dixit, and Pavel Petrov (Submitted October 14, 2016; in revised form December 2, 2017) The formation of Al15Mn3Si2 phase in Al-12Si-4Cu-1.2Mn (wt.%) alloy during solidification was investigated by adopting CALPHAD method and microstructural observation by optical microscopy, SEM–EDS, TEM–EDS/SAD and XRD analysis; SEM fixed-point observation method was applied to evaluate its thermal stability. As-cast microstructural observation consistently demonstrates the solidification sequence of the studied alloy predicted by phase diagram calculation. Based on the phase diagram calculation, SEM– EDS, TEM–EDS/SAD and XRD analysis, as well as evidences on Al-Si-Mn-Fe compounds from the literature, the primary and eutectic Mn-rich phases with different morphologies in the studied alloy are identified to be Al15Mn3Si2 that has a body-centered cubic (BCC) structure with a lattice constant of a = 1.352 nm. SEM fixed-point observation and XRD analysis indicate that Al15Mn3Si2 phase has more excellent thermal stability at high temperature than that of CuAl2 phase and can serve as the major strengthening phase in heat-resistant aluminum alloy that has to face a high-temperature working environment. Results of tension test show that addition of Mn can improve the strength of Al-Si-Cu alloy, especially at elevated temperature. Keywords
heat-resistant aluminum alloy, microstructure, phase evolution, solidification, thermal stability
1. Introduction Al-Si-Cu-based alloys have been extensively used to produce pistons, engine blocks and cylinder heads, due to low density, excellent cast ability, good mechanical properties as well as low cost (Ref 1-3). However, since the main strengthening phases in Al-Si-Cu-based alloys, such as CuAl2 or Mg2Si, usually are very prone to coarsening or even dissolving at above 443 K (170 C), the conventional Al-Si-Cu system heat-resistant alloys cannot sustain or possess good strength at high temperature beyond 523 K (250 C); thus, they cannot meet the increasingly more rigorous requirements of heat resistance for high power density engines (Ref 4-6). A great number of attempts have been made by several researchers to improve these promising alloys for hightemperature application (Ref 7-12). Zheng et al. (Ref 12) reported that the Cu content and Cu/Mg ratio had an considerable influence on the strength and ductility of Al-SiCu-Mg alloy because they affected the formation of primary
Xiaojing Suo, Hengcheng Liao, and Yiyun Hu, School of Materials Science and Engineering, Southeast University, Jiangsu Key Laboratory for Advanced Metallic Materials, 2# Dongnandaxue Road, Nanjing 211189, China; Uday S. Dixit, Department of Mechanical Engineering, IIT Guwahati, Guwahati, Assam 781039, India; and Pavel Petrov, Department of Metal Forming and Metal Forming Machines, University of Mechanical Engineering, M
Data Loading...
