• Aghaie, Ermia

Abstract

Aluminum powertrain alloys, such as B319 has attracted a great deal of attention from automotive industries due to their excellent castability, desirable wear resistance, high strength-to-weight ratio, and high recyclability. The B319 Al alloy has distinct phases and intermetallics. However, at the elevated temperatures (250-300 °C), some phases in the alloy may coarsen and partially dissolve in the Al matrix and decrease the strength of the material. Addition of some elements such as Ce, Sr, and Eu to Al alloys has been reported to have a significant effect on improving the high-temperature mechanical properties of the Al alloys.In this thesis, various amounts of Ce (0.1, 0.3, 0.5, and 1.0 wt.%) were added to the B319 alloy though the casting process to improve the mechanical properties of the alloy at room-temperature and high temperatures (250-300 °C). The microstructure and phase analysis of the alloys were evaluated using SEM/EDS and XRD, respectively. The Thermo-Calc-2019 software was employed to estimate the formation temperature and volume fraction of the phases present in the alloys. Hardness of the specimens was measured using the Vickers micro-hardness tester. Tensile strength of the alloys was also assessed at room-temperature and 250 °C. In addition, to evaluate the long-term thermal stability, the alloys were kept at 250 °C and 300 °C each for 10 days, then the microstructure, microhardness, and high-temperature (250 °C) tensile strength of the specimens were assessed. The presence of the Al2Cu, Q-AlCuMgSi, Si, Al15(Fe,Mn)3Si2, and α-Al phases were detected in all alloys; however, by addition of Ce, the AlCeSi2 and Al3Ce4Si6 intermetallics were also formed in the material. Si had the highest volume fraction in the all specimens, and it was found that the addition of Ce suppressed the size of the Si particles. The results of the mechanical tests revealed that, addition of 0.1%Ce to the B319 alloy substantially improved the tensile strength at room temperature and 250 °C. However, further addition of Ce (0.3, 0.5, 1.0 Wt.%Ce) slightly suppressed the mechanical strength due to formation of the long-needle shape Ce phases and increasing the amount of porosity in the material.

Topics

• phase
• scanning electron microscopy
• x-ray diffraction
• aluminium
• wear resistance
• strength
• hardness
• casting
• Energy-dispersive X-ray spectroscopy
• tensile strength
• porosity
• intermetallic
• Cerium