scholarly journals Controlling the Formation of Iron-Bearing Intermetallics in Wrought Al Alloys by Melt Conditioned DC (MC-DC) Casting Technology

2015 ◽  
Vol 828-829 ◽  
pp. 43-47 ◽  
Author(s):  
Hu Tian Li ◽  
J.B. Patel ◽  
H.R. Kotadia ◽  
Z. Fan
Keyword(s):  
Corrosion Resistance ◽  
Aluminium Alloys ◽  
Downstream Processing ◽  
Al Alloys ◽  
Grain Refiner ◽  
Casting Technology ◽  
Negative Effect ◽  
Dc Casting ◽  
Primary Aluminium ◽  
Iron Bearing

With the increasing use of recycled aluminium alloys from the end-of-life products more and more iron is accumulated into the compositions of alloys. Sometimes, recycling causes the iron levels to increase beyond the set target levels for down-stream processing. The only way to deal with this impurity currently in industry is to increase the primary aluminium added to the furnace to dilute the melt and re-add all other elements or cast it for re-melting or extrude it for products that is not surface finish critical or required higher corrosion resistance. Formation of small well dispersed spherical a- or small b- Fe-bearing intermetallics, which can be homogenised for shorter times and has no negative effect on downstream processing, would be promising even if the iron levels are above the targeted compositional limits. In the present paper, fine and dispersed Fe-bearing intermetallics have been achieved by Melt Conditioned DC (MC-DC) casting technology, instead of coarser Fe-bearing intermetallics forming network like morphology in the DC castings with grain refiner additions (DC-GR). This suggests feasibility of an increased tolerance of iron levels by melt conditioned DC casting technology.

scholarly journals Corrosion Behaviors of Selective Laser Melted Aluminum Alloys: A Review

Metals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 102 ◽  
Author(s):  
Hongwei Chen ◽  
Chaoqun Zhang ◽  
Dan Jia ◽  
Daniel Wellmann ◽  
Wen Liu
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloys ◽  
High Strength ◽  
Al Alloys ◽  
Good Corrosion Resistance ◽  
Geometrical Complexity ◽  
Negative Effect ◽  
Corrosion Behaviors ◽  
Different Shapes ◽  
Ideal Method

Selective laser melting (SLM) is an ideal method to directly fabricate products with high geometrical complexity. With low density and good corrosion resistance, aluminum alloys are widely used as important structural materials. Microstructures and mechanical properties of SLMed aluminum alloys have been recently widely studied. Corrosion behavior as a vital concern during the service of SLMed aluminum alloy parts has also drawn many attentions. Previous studies have found that SLM-processed aluminum alloys exhibit better corrosion resistance compared to the casted and wrought counterparts for both Al-Si alloys and high strength 2xxx Al alloys, which is mainly due to the unique microstructure features of SLMed Al alloys. For Al-Si alloys, with different shapes of Si networks, the different building planes show discrepant corrosion behaviors. Owing to the rougher surface with relatively larger numbers of defects, the as-printed surface is vulnerable to corrosion than the polished. Heat treatment has a negative effect on corrosion resistance due to the breakup of Si networks. The microstructure features correlated with the corrosion behaviors were also reviewed in this paper. Some suggestions on the future study of corrosion behaviors of SLMed Al alloys were put forward.

scholarly journals Pit nucleation on as-cast aluminiuim alloy AW-5083 in 0.01M NaCl

2011 ◽  
Vol 47 (1) ◽  
pp. 79-87 ◽  
Author(s):  
N. Dolic ◽  
J. Malina ◽  
A. Begic-Hadzipasic
Keyword(s):  
Corrosion Resistance ◽  
Aluminium Alloys ◽  
High Strength ◽  
Al Alloys ◽  
Surface Oxide Layer ◽  
Good Corrosion Resistance ◽  
Weight Saving ◽  
Wide Range ◽  
Pit Nucleation ◽  
Cast Condition

The use of aluminium alloys in a wide range of technical applications is related mostly to the two facts: they facilitate weight saving of final products (if compared to the steel) and they are prone to spontaneous passivity due to the coherent surface oxide layer which impedes further reaction of aluminium with the environment. Among the commercial Al alloys, EN AW-5083 alloy is a representative non-heat treatable Al-Mg based alloy which possesses many interesting characteristics as a structural material, such as low price, moderately high strength, high formability in conjunction with superplasticity and good corrosion resistance in marine atmospheres. Aiming to enhance the knowledge of possible interactions of studied alloy EN AW-5083 in as-cast condition with chloride media, electrochemical measurements were used to follow the pitting behaviour in 0.01 M NaCl. The results of tests have shown that susceptibility of alloy to pitting corrosion is strongly influenced by the microstructural constituents of the alloy in as-cast condition.

A Novel Micro-Arc Anodising Process for Aluminium Alloys Containing High Silicon

2009 ◽  
Vol 618-619 ◽  
pp. 279-282
Author(s):  
Zhi Ming Shi ◽  
Ming Xing Zhang
Keyword(s):  
Corrosion Resistance ◽  
High Voltage ◽  
Current Density ◽  
Aluminium Alloys ◽  
Al Alloys ◽  
Alkaline Electrolyte ◽  
Microstructure Examination ◽  
High Silicon ◽  
Highly Porous ◽  
Silicon Particles

Although the anodising process has been widely used in surface treatment of Al alloys, the well known sulphuric acid anodising process produces inhomogeneous and highly porous anodised coatings on Al alloys containing high Si due to the inertness of the silicon particles. The present work reports a novel micro-arc anodising process for such high-silicon aluminium alloys. Uniform and thick anodising coatings can be obtained through an anodising process in an alkaline electrolyte under high voltage and low current density conditions. The microstructure examination in SEM indicates that most pores in the coatings have been sealed during the anodising process, thus post-treatment that is normally needed for the currently used anodising process can be eliminated. The coating is very promising in the improvement of corrosion resistance for cast high-silicon aluminium alloys.

Study through Potentiodynamic Techniques of the Corrosion Resistance of Different Aluminium Base MMC´s with Boron Additions

2010 ◽  
Vol 660-661 ◽  
pp. 203-208 ◽  
Author(s):  
J. Abenojar ◽  
Asuncion Bautista ◽  
S. Guzmán ◽  
Francisco Velasco ◽  
M.A. Martinez
Keyword(s):  
Corrosion Resistance ◽  
Mechanical Alloying ◽  
Boron Carbide ◽  
Aluminium Alloys ◽  
Anodic Polarization ◽  
Sintering Temperature ◽  
Pure Aluminium ◽  
Mechanically Alloyed ◽  
Negative Effect ◽  
Lower Corrosion Rate

This paper compares wrought aluminium with PM aluminum and PM aluminium alloys with boron-base additions, containing boron carbide and Fe/B (obtained by mechanical alloying during 36 hours from a Fe-B 50% mixture by weight). The effect of sintering temperature for the Fe/B containing material and the effect of mechanical alloying for the boron carbide containing aluminium alloy on the corrosion resistance of those materials have been studied. Their behavior is followed through cyclic anodic polarization curves in chloride media. In the Al+20%Fe/B composite, low sintering temperatures (650-950°C) exert a negative effect. However, when the material was sintered at high temperature (1000-1100°C) its behaviour was very similar to the PM pure aluminium. The effect of mechanical alloying studied in aluminium with boron carbide was also important in corrosion resistance, finding a lower corrosion rate in the mechanically alloyed material.

scholarly journals Development of Al–Mg–Si alloy performance by addition of grain refiner Al–5Ti–1B alloy

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042110294
Author(s):  
Khaled Abd El-Aziz ◽  
Emad M Ahmed ◽  
Abdulaziz H Alghtani ◽  
Bassem F Felemban ◽  
Hafiz T Ali ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Corrosion Resistance ◽  
Testing Machine ◽  
Dendritic Structure ◽  
Grain Refiner ◽  
Corrosion Properties ◽  
Average Grain Size ◽  
Structural Applications ◽  
Alloy Addition

Aluminum alloys are the most essential part of all shaped castings manufactured, mainly in the automotive, food industry, and structural applications. There is little consensus as to the precise relationship between grain size after grain refinement and corrosion resistance; conflicting conclusions have been published showing that reduced grain size can decrease or increase corrosion resistance. The effect of Al–5Ti–1B grain refiner (GR alloy) with different percentages on the mechanical properties and corrosion behavior of Aluminum-magnesium-silicon alloy (Al–Mg–Si) was studied. The average grain size is determined according to the E112ASTM standard. The compressive test specimens were made as per ASTM: E8/E8M-16 standard to get their compressive properties. The bulk hardness using Vickers hardness testing machine at a load of 50 g. Electrochemical corrosion tests were carried out in 3.5 % NaCl solution using Autolab Potentiostat/Galvanostat (PGSTAT 30).The grain size of the Al–Mg–Si alloy was reduced from 82 to 46 µm by the addition of GR alloy. The morphology of α-Al dendrites changes from coarse dendritic structure to fine equiaxed grains due to the addition of GR alloy and segregation of Ti, which controls the growth of primary α-Al. In addition, the mechanical properties of the Al–Mg–Si alloy were improved by GR alloy addition. GR alloy addition to Al–Mg–Si alloy produced fine-grained structure and better hardness and compressive strength. The addition of GR alloy did not reveal any marked improvements in the corrosion properties of Al–Mg–Si alloy.

Effects of the Duration of Potentiostatic Anodizing on the Corrosion Resistance and Surface Morphology of Films Formed on Mg-Al Alloys

2005 ◽  
Vol 486-487 ◽  
pp. 125-128 ◽  
Author(s):  
Seong Jong Kim ◽  
Seok Ki Jang ◽  
Jeong Il Kim
Keyword(s):  
Corrosion Resistance ◽  
Surface Morphology ◽  
Anodic Oxide ◽  
Al Alloys ◽  
Anodic Film ◽  
Al Alloy ◽  
Active Dissolution ◽  
Dissolution Reaction ◽  
Alloy Az91 ◽  
Morphology Of Films

The effects of the duration of potentiostatic anodizing on the corrosion resistance and surface morphology of anodic oxide films formed on Mg-Al alloy (AZ91) in 1 M NaOH were investigated. With the formation of an anodic film, the current density decreased gradually, started to stabilize at 300 s, and was relatively constant at 600 s. These results may be related to the increased time for catalysis of the active dissolution reaction, which not only enlarges the area covered by the anodic film, but also produces a more coherent, thicker film. The reference corrosion potentials of the anodic oxide film for AZ91 shifted in the noble direction with time. In general, the corrosion resistance characteristics were improved with anodizing time.

Grain Refinement and Hot Tearing of Aluminium Alloys - How to Optimise and Minimise

2009 ◽  
Vol 630 ◽  
pp. 213-221 ◽  
Author(s):  
Mark Easton ◽  
David H. StJohn ◽  
Lisa Sweet
Keyword(s):  
Grain Refinement ◽  
Aluminium Alloys ◽  
Hot Tearing ◽  
Key Factors ◽  
Grain Refiner ◽  
Factors Affecting ◽  
Equiaxed Grains

Grain refinement and hot tearing are important key factors affecting the quality of castings. There have been substantial advances in the understanding of both of these phenomena over the last two decades. The paper discusses strategies for obtaining the lowest cost grain refiner addition and provides an explanation for how the refinement of equiaxed grains leads to a reduction in hot tear susceptibility. However, it also provides a warning that adding more grain refiner may not be better for reducing hot tear susceptibility. Alloy factors affecting hot tearing are also discussed. Finally, a list of six key considerations is provided to help casthouse and foundry engineers when trying to optimise grain refinement and reduce hot tearing.

Plasma Surface Treatment: Effects on Mechanical and Corrosion Protection Properties of Hybrid Sol–Gel Coatings

2019 ◽  
Author(s):  
R. Subasri
Keyword(s):  
Mechanical Properties ◽  
Corrosion Resistance ◽  
Surface Treatment ◽  
Corrosion Protection ◽  
Sol Gel ◽  
Surface Cleaning ◽  
Al Alloys ◽  
Plasma Surface ◽  
Wet Chemical ◽  
Pre Treatment

Surface cleaning and activation of substrates are two critical processes that affect the mechanical and corrosion resistance properties of protective coatings when deposited on the substrates. Surface cleaning removes the contaminants, for example, grease on the substrate, and surface activation introduces active bonds on the substrate thereby increasing the surface free energy. Conventionally, surface cleaning and activation of aluminum and its alloys are carried out by a wet chemical technique. A convenient and safe alternate to the wet chemical cleaning/activation would be to use plasma for the same purpose. Plasma surface pre-treatment greatly improves adhesion of coatings deposited, which is very vital for good corrosion protection and mechanical properties such as scratch and abrasion resistance. Cold and atmospheric air plasma treatments have been the most widely studied pre-treatments for Al alloys. This article will discuss the advancements in the use of plasma treatment on Al/Al alloys and its effect on corrosion resistance and mechanical properties of coatings deposited after the surface treatment.

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