Influence of β-Mg17Al12 Phase on Initial Pitting Process of AZ91D Magnesium Alloy

2016 ◽  
Vol 879 ◽  
pp. 1895-1898 ◽  
Author(s):  
Masahiro Kaido ◽  
Kenta Imai ◽  
Masahiko Hatakeyama ◽  
Satoshi Sunada
Keyword(s):  
Magnesium Alloy ◽  
Corrosion Behavior ◽  
Az91d Alloy ◽  
Az91d Magnesium Alloy ◽  
Β Phase ◽  
Α Phase ◽  
Before And After ◽  
Sem Micrograph ◽  
Chloride Environment ◽  
Z Contrast

AZ91D magnesium alloy for casting is significantly corroded in chloride environment. In addition, Al-rich-α phase, which is formed during cooling process around β-Mg17Al12 phase, is one of the important factors on corrosion behavior in AZ91D. It is expected that pitting formation is dominant in the corrosion behavior in magnesium alloys. To clarify the influence of the Al-rich-α phase to pitting formation and corrosion behavior in AZ91D alloy, we have investigated the relationship between Microstructure and pitting formation in this study. We have carried out polarization curve measurement and scanning electron microscope (SEM) observation before and after the corrosion-tests. SEM micrograph of as-cast samples showed AZ91D alloy consist of α phase, Al-rich-α phase which shows bright Z-contrast due to high Al contents and β phase. Al-rich-α phase formed around β phase. After the corrosion examination, holes were observed at Al-rich-α phase around the β phase, and it is thought that small pits grow up to be holes, because β phase is remained, while the Al-rich-α phase around the β phase preferentially dissolves with time. The result indicates that Al-rich-α phase around β phase enhance the formation of pitting and preferentially dissolve it in initial stage of corrosion in AZ91D alloy.

Influence of Cl- on Corrosion Behavior of AZ91 Magnesium Alloy in Simulating Acid Rain

2011 ◽  
Vol 686 ◽  
pp. 181-185
Author(s):  
Wan Qiu Zhou ◽  
Wei Tang ◽  
Da Yong Shan ◽  
En Hou Han ◽  
Wei Ke
Keyword(s):  
Magnesium Alloy ◽  
Acid Rain ◽  
Corrosion Behavior ◽  
Localized Corrosion ◽  
Passive State ◽  
Nacl Solution ◽  
Az91 Magnesium Alloy ◽  
Β Phase ◽  
Α Phase ◽  
Az91 Magnesium

Initial corrosion behavior of AZ91 magnesium alloy in simulating acid rain containing Cl-is investigated by SEM/EDX and electrochemical method. The results show that corrosion of magnesium alloy in diluted NaCl solution was localized corrosion, and the attack only occurred around the scattered AlMn particle which induced the departure of AlMn from metal matrix. HSO3-in acid rain induced the dissolution of corrosion in α phase, β phase was not be corroded and presented in passive state. The corrosion of magnesium alloy in simulating acid rain containing Cl-was mainly induced by HSO3-, and the existence of Cl-accelerated the corrosion process.

CORROSION MECHANISM AND MODEL OF ANODIZED FILM ON AZ91D MAGNESIUM ALLOY

2010 ◽  
Vol 24 (15n16) ◽  
pp. 3077-3082 ◽  
Author(s):  
LINA LI ◽  
JIANGANG QIAN ◽  
ZHAOZHONG LU ◽  
ZHONGWU SUN
Keyword(s):  
Magnesium Alloy ◽  
Immersion Time ◽  
Immersion Test ◽  
Corrosion Mechanism ◽  
Nacl Solution ◽  
Az91d Magnesium Alloy ◽  
Β Phase ◽  
Α Phase ◽  
Corrosion Reaction ◽  
Neutral Aqueous Solution

The corrosion behavior of anodized film on AZ91D magnesium alloy in 3.5% neutral NaCl solution was investigated by saline immersion test. The results show that new corrosion points seldom occur on the surface of the said anodized film during the immersion time in 3.5% NaCl neutral aqueous solution after the first macroscopic corrosion point appears on the anodized film, while the previous corrosion point extends vertically or horizontally and turns into a corrosion pit which is in form of "strip". Moreover, the corrosion occurs firstly on α phase rather than β phase, when the corrosion of anodized film reaches the Mg alloy substrate. The corrosion products of anodized film on AZ91D magnesium alloy in neutral immersion solution were analyzed by XRD. A possible corrosion reaction and model about the corrosion of anodized film on AZ91D magnesium alloy in NaCl solution based on the experimental results is proposed.

Tribological behavior of AZ91D magnesium alloy composite: effect of hybrid WC – SiO2 nanoparticles

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mohammed Fahad ◽  
Bavanish B.
Keyword(s):  
Magnesium Alloy ◽  
Wear Rate ◽  
Az91d Alloy ◽  
Hybrid Particles ◽  
Wear Properties ◽  
Sliding Speed ◽  
Composite Effect ◽  
Content Type ◽  
Climate Conditions ◽  
Az91d Magnesium Alloy

Purpose Aviation field requires a material with greater tribological characteristics to withstand the critical climate conditions. Hence, it is of paramount importance to enhance the wear resistance of material. AZ91D magnesium alloy is a light weight material used in the aviation field for the construction work. The purpose of this study is to augment the wear properties of AZ91D alloy by reinforcing with hard particles such as tungsten carbide (WC) and silicon dioxide (SiO2). Design/methodology/approach In this work, three types of composites were fabricated, namely, AZ91D – WC, AZ91D – SiO2 and AZ91D – (WC + SiO2) by ball milling method, and the tribological properties were analyzed using pin-on-disc apparatus. Findings Results showed that the hardness of AZ91D alloy was greatly improved due to the reinforcing effects of WC and SiO2 particles. Wear study showed that wear rate of AZ91D alloy and its composites increased with the increase of applied load due to ploughing effect and decreased with the increase of sliding speed owing to the formation of lubricating tribolayer. Further, the AZ91D – (WC + SiO2) composite exhibited the lower wear rate of 0.0017 mm3/m and minimum coefficient of friction of 0.33 at a load of 10 N and a sliding speed of 150 mm/s due to the inclusion of hybrid WC and SiO2 particles. Hence, the proposed AZ91D – (WC + SiO2) composite could be a suitable candidate to be used in the aviation applications. Originality/value This work is original which deals with the effect of hybrid particles, i.e. WC and SiO2 on the wear performance of the AZ91D magnesium alloy composites. The literature review showed that none of the studies focused on the reinforcement of AZ91D alloy by the combination of carbide and metal oxide particles as used in this investigation.

Transformation between localized and general corrosion behavior of die‐cast AZ91D magnesium alloy in 3.5 wt% NaCl aqueous solutions

2019 ◽  
Vol 70 (12) ◽  
pp. 2303-2310 ◽  
Author(s):  
Shaohua Zhang ◽  
Lifeng Hou ◽  
Huayun Du ◽  
Huan Wei ◽  
Baosheng Liu ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Aqueous Solutions ◽  
Corrosion Behavior ◽  
General Corrosion ◽  
Az91d Magnesium Alloy ◽  
Die Cast

Effect of Heat Treatments on the Bio-Corrosion Resistance of Magnesium Alloy Mg-8.0Al-1.0Zn-xGd

2011 ◽  
Vol 213 ◽  
pp. 497-501
Author(s):  
Lei Li ◽  
Rui He ◽  
Guo Jie Huang ◽  
Shui Sheng Xie
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Annealing Treatment ◽  
Microstructure Analysis ◽  
Β Phase ◽  
Α Phase ◽  
Treatment Procedures ◽  
Human Fluid

In order to improve the bio-corrosion resistance of magnesium alloy Mg-8.0Al-1.0Zn-xGd in the simulated human fluid, different heat treatment procedures were studied. Results showed that annealing treatment lowered the alloy’s corrosion resistance and hardness, while T6 treatment (solid solution+ aging) improved the alloy’s corrosion resistance and hardness. Microstructure analysis showed that the β phase dissolved into α phase after the annealing treatment. Hence, annealing treatment decreased the alloy’s corrosion resistance. However, lots of β-phases were precipitated in the T6 heat treatment, and they impeded the corrosion extending.

Corrosion Resistance of the Ceramic Coating Formed by Micro-Plasma Arc Oxidation on AZ91D Alloy

2007 ◽  
Vol 336-338 ◽  
pp. 2451-2453
Author(s):  
Shu Hua Li ◽  
Fu Chi Wang
Keyword(s):  
Magnesium Alloy ◽  
Ceramic Coating ◽  
Ceramic Coatings ◽  
Az91d Alloy ◽  
Plasma Arc ◽  
X Ray Diffraction ◽  
Compact Layer ◽  
Az91d Magnesium Alloy ◽  
Loose Layer ◽  
Salt Fog

The ceramic coating was formed by micro-plasma arc oxidation (MPAO) on AZ91D magnesium alloy. The surface and section morphology of coatings were observed using scanning electron microscopy. The phase composition of coatings was analyzed by X-ray diffraction. The method of salt fog experimental was carried out to proof-test performances of anti-corrosion of material. The results showed that the ceramic coating was composed by loose layer and compact layer. The coating surface has a large number of grains with various sizes. In addition, there is also a lot of pore in the loose layer, but the compact layer is tighter than the loose layer. Compact layer has a good combination with substrate magnesium alloy. The MPAO coating is mainly composed of silica oxide (MgAl2Si3O12 and β-Mg2SiO4 and (Mg4Al14) (Al4Si2)O20) and composite oxide of Mg and Al (δ-MgAl28O4). The performance of resistant corrosion of AZ91D coved by ceramic coating is higher than AZ91D magnesium alloy. The corrosion ratio of AZ91D alloy coved by ceramic coatings to AZ91D alloy is 1:8.61.

Corrosion Performance of Anodized AZ91D Magnesium Alloy: Effect of the Anodizing Potential on the Film Structure and Corrosion Behavior

2013 ◽  
Vol 23 (2) ◽  
pp. 593-603 ◽  
Author(s):  
Mara Cristina Lopes de Oliveira ◽  
Viviam Serra Marques Pereira ◽  
Olandir Vercino Correa ◽  
Renato Altobelli Antunes
Keyword(s):  
Magnesium Alloy ◽  
Corrosion Behavior ◽  
Film Structure ◽  
Corrosion Performance ◽  
Az91d Magnesium Alloy ◽  
Alloy Effect
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