Mohsen Esmaily

Corrosion behavior of alloy AM50 in semi-solid cast and high pressure die cast states in cyclic conditions

The atmospheric corrosion behavior of the Mg-Al alloy AM50 produced by high-pressure die casting (HPDC) and a semisolid metal (SSM) technique was studied under alternating wet-dry conditions for up to 672 hours. Alloy AM50 in the SSM state was fabricated using rheocasting (RC) technique in which the slurry was prepared by the newly developed RheoMetal process. To simulate the real-world atmospheric environment, the exposure program included a 6 hour wet phase (including rain with 0.5% NaCl), a 2.5 hour transition phase, followed by a 15.5 hour dry phase at 50°C and 70% relative humidity. The results showed that the RC alloy was substantially less prone to corrosion than the HPDC material in the cyclic wet-dry atmosphere. Based on the gravimetric results and microstructural characterization studies, this was attributed to a lower fraction of porosity and to the barrier role of β phase particles in the RC.

On the capability of in-situ exposure in an environmental scanning electron microscope for investigating the atmospheric corrosion of magnesium

The feasibility of environmental scanning electron microscope (ESEM) in studying the atmospheric corrosion behavior of 99.97% Mg was investigated. For reference, ex-situ exposure was performed. A model system was designed by spraying few salt particles on the metal surface and further promoting the corrosion process using platinum (Pt) deposition in the form of 1×1×1 µm(3) dots around the salt particles to create strong artificial cathodic sites. The results showed that the electron beam play a significant role in the corrosion process of scanned regions. This was attributed to the irradiation damage occurring on the metal surface during the ESEM in-situ experiment. After achieving to a reliable process route, in a successful attempt, the morphology and composition of the corrosion products formed in-situ in the ESEM were in agreement with those of the sample exposed ex-situ.

Corrosion of Magnesium-Aluminum (Mg-Al) Alloys-An Interplay Between Al Content and CO2

In course of their practical applications, magnesium-aluminum (Mg–Al) alloys are frequently exposed to the ambient atmospheric, and thus, are susceptible to environmental degradation. In this study, we exposed several Mg–Al alloys (including AM20, AZ31, AM50, and AZ91) with different Al content to atmospheric environment to examine the effect of most important environmental factor, i.e., carbon dioxide (CO2) and its relation to the alloys’ Al content. The surface films formed on alloys at two temperatures (−4 and 22 °C) were examined using auger electron spectroscopy (AES). The results show that CO2 inhibits long-term atmospheric corrosion behavior of the alloys and that the thickness of the carbon-rich layer in the surface film increases with increasing Al content. We suggest that; (a) the inhibitive effect of CO2 on the atmospheric corrosion behavior of Mg–Al systems, and (b) the positive influence of Al content on the corrosion performance of Mg–Al alloys are partly linked to the occurrence of compounds that exhibit characteristics close to that of the layered double hydroxides (LDHs).

Technical note: A major loss in tensile strength of friction stir welded aluminum alloy joints resulting from atmospheric corrosion

The effect of corrosion on the mechanical properties of aluminum alloy (AA6005-T6) joints produced by friction stir welding is investigated. The tensile strength of the weldments was analyzed after...

Effects of cold working and heat treatment on microstructure and wear behaviour of Cu–Be alloy C17200

The effects of cold work process between aging and solution heat treatment on the microstructure, hardness and the tribologic behaviour of a copper–beryllium (Cu–Be) alloy C17200 were investigated. The wear behaviour of the alloys was studied using ‘pin on disc’ method under dry conditions. The results show that the formation of fine grained structure and γ phase particles enhances the mechanical properties of the alloy; nonetheless, they do not reduce the wear rate. This is attributed to the capability of the softer specimens to maintain oxygen rich compounds during the dry sliding test.