The Effects of Combined Addition of Ce and Yb on Microstructure and Mechanical Properties of Al-Si-Mg-Cu-Cr Casting Alloy

作者：Qiu, Mingkun; Du, Xiaodong^*; Zhang, Zhen; Chen, Chang; Lei, Xuanxuan

来源：JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE, 2023, 32(8): 3443-3451.

DOI：10.1007/s11665-022-07348-5

• Al-Si casting alloy
• (Ce plus Yb) combined addition
• Ce- and
• or Yb-rich precipitates
• microstructure
• mechanical properties

In the present work, the effects of combined addition of (Ce + Yb) on the heat treatment microstructure and mechanical properties of Al-6Si-0.6 Mg-0.6Cu-0.2Cr casting alloy were investigated. The results indicated that the alpha-Al grains, eutectic Si and beta-Al5FeSi phases were refined and modified simultaneously by (Ce + Yb), which transformed the coarse plate-like eutectic Si into short rod-like and/or granular shape. Furthermore, the heat treatment process facilitated the spheroidization of eutectic Si and the optimum combined addition of (Ce + Yb) was 0.4 wt%. The 0.4 wt% (Ce + Yb) modified alloy was compared with the unmodified alloy, and it was found that the average grain size and SADS of the alpha-Al grains were reduced by 62.9 and 60.6%, and the average aspect ratio and area of eutectic Si decreased by 182.0 and 91.3%, respectively. Most importantly, the combined addition of (Ce + Yb) greatly enhanced the tensile properties of the alloy, especially due to the significant improvement of the microstructure, which resulted in a remarkable increase in the ultimate tensile strength (UTS), yield strength (YS) and elongation (El) of the alloy. Finally, the combined addition of (Ce + Yb) transformed the fracture patterns of the modified alloy from brittle fracture to ductile fracture.