Effect of cerium addition on improvement of mechanical properties of B319 powertrain aluminum alloy

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.Applied Science, Faculty ofEngineering, School of (Okanagan)Graduat

Tribological behavior of ZK60Gd alloy reinforced by SiC particles after precipitation hardening

In this research, the effect of precipitation hardening on the tribological behavior of the ZK60Gd/SiC composite was studied. For this purpose, ZK60Gd alloy containing with 5 and 10 wt% SiC were produced with stir casting method. The microstructure characterization of the samples showed the wide distributions of Mg7Zn3 and Gd(Mg0.5Zn0.5) precipitates were formed during casting. The results of hardness measurement after precipitation hardening at different temperatures showed that the hardness peck was obtained at 175 °C. The wear tests with different loads (10, 40, 60, 90, and 120 N) and velocities (0.1, 0.3, 0.6, and 0.9 m/s) were performed on the as-cast and heat treated sample at 125, 175, and 225 for 12 h. Between the different precipitation hardening conditions, the precipitation hardened samples at 175 °C had the highest hardness values and least wear rate. The sample containing 10% reinforcement had the least wear rate between the unreinforced alloy and the composites. The results showed that abrasive, adhesive, delamination, MML, and fatigue wear mechanisms were the dominant wear mechanisms for the composite samples. In contrast, the dominant wear mechanism for the unreinforced samples was abrasive, adhesive, delamination, MML, and plastic deformation

Effect of Tricalcium Magnesium Silicate Coating on the Electrochemical and Biological Behavior of Ti-6Al-4V Alloys.

In the current study, a sol-gel-synthesized tricalcium magnesium silicate powder was coated on Ti-6Al-4V alloys using plasma spray method. Composition of feed powder was evaluated by X-ray diffraction technique before and after the coating process. Scanning electron microscopy and atomic force microscopy were used to study the morphology of coated substrates. The corrosion behaviors of bare and coated Ti-6Al-4V alloys were examined using potentiodynamic polarization test and electrochemical impedance spectroscopy in stimulated body fluids. Moreover, bare and coated Ti-6Al-4V alloys were characterized in vitro by culturing osteoblast and mesenchymal stem cells for several days. Results demonstrated a meaningful improvement in the corrosion resistance of Ti-6Al-4V alloys coated with tricalcium magnesium silicate compared with the bare counterparts, by showing a decrease in corrosion current density from 1.84 μA/cm2 to 0.31 μA/cm2. Furthermore, the coating substantially improved the bioactivity of Ti-6Al-4Valloys. Our study on corrosion behavior and biological response of Ti-6Al-4V alloy coated by tricalcium magnesium silicate proved that the coating has considerably enhanced safety and applicability of Ti-6Al-4V alloys, suggesting its potential use in permanent implants and artificial joints

Equivalent circuit of EIS curves of the bare (a) and coated (b) Ti-6Al-4V alloys.

<p>Equivalent circuit of EIS curves of the bare (a) and coated (b) Ti-6Al-4V alloys.</p

Nyquist (a) and Bode (b) plots of the bare Ti-6Al-4V alloy and theTi-6Al-4V alloy coated with tricalcium magnesium silicate.

<p>Nyquist (a) and Bode (b) plots of the bare Ti-6Al-4V alloy and theTi-6Al-4V alloy coated with tricalcium magnesium silicate.</p

Cell morphology after cell growth of cultures with the bare Ti-6Al-4V alloy (a), the coated Ti-6Al-4V alloy (b), and the culture media (c) after 72 h.

<p>Cell morphology after cell growth of cultures with the bare Ti-6Al-4V alloy (a), the coated Ti-6Al-4V alloy (b), and the culture media (c) after 72 h.</p

SEM (a), AFM (b), and cross-section SEM (c) images of the tricalcium magnesium silicate coating.

<p>SEM (a), AFM (b), and cross-section SEM (c) images of the tricalcium magnesium silicate coating.</p

Composition of SBF fluid [35].

<p>Composition of SBF fluid [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0138454#pone.0138454.ref035" target="_blank">35</a>].</p