scholarly journals Assessment of Mechanisms for Particle Migration in Semi-Solid High Pressure Die Cast Aluminium-Silicon Alloys

2020 ◽  
Vol 4 (2) ◽  
pp. 51
Author(s):  
Madeleine Law ◽  
Christopher Neil Hulme-Smith ◽  
Taishi Matsushita ◽  
Pär G. Jönsson
Keyword(s):  
High Pressure ◽  
Die Casting ◽  
Particle Migration ◽  
Silicon Alloys ◽  
High Pressure Die Casting ◽  
Die Cast ◽  
Semi Solid ◽  
Pressure Die Casting ◽  
Saffman Lift Force ◽  
Externally Solidified Crystals

In semi-solid metal high pressure die casting and in conventional high pressure die casting, it is common to find a defect band just below the surface of the component. The formation of these bands is not fully understood. However, there are several theories as how they occur, and it has been suggested that segregation is caused by the migration of aluminium-rich externally solidified crystals. In the present work the formation of these bands is investigated theoretically by reviewing suitable potential mechanisms for the migration of such crystals. Two mechanisms are identified as the most probable: Saffman lift force and the Mukai-Lin-Laplace effect. However, it was not possible to identify which of these two mechanisms acted in the case studies. Further testing is required to identify the mechanism that is causing the migration of the aluminium globules and suitable tests are proposed.

Corrosion Behaviour of the Anodised A356 Aluminium Alloy Produced by the Rheo-High Pressure Die Casting Process

2014 ◽  
Vol 1019 ◽  
pp. 67-73 ◽  
Author(s):  
Levy Chauke ◽  
Kalenda Mutombo ◽  
Gonasagren Govender
Keyword(s):  
High Pressure ◽  
Aluminium Alloy ◽  
Corrosion Behaviour ◽  
Die Casting ◽  
Casting Process ◽  
Optical Microscope ◽  
High Pressure Die Casting ◽  
Semi Solid ◽  
Pressure Die Casting ◽  
A356 Aluminium Alloy

<span><p>Semi-solid metal forming of aluminium alloys has demonstrated the capability to produce near net shaped high integrity components. Anodising of these components for aesthetic and/or improved corrosion resistance is specified by some designers or users of this technology. The corrosion behaviour of fully anodised and partially anodised A356 aluminium alloy plates produced using the CSIR Rheo-High Pressure Die Casting (CSIR-RHPDC) process was investigated using immersion testing in a 3.5% NaCl solution with pH = 7. Optical microscope equipped with image analysis software and scanning electron microscope (SEM) equipped with Energy Dispersive X-ray Spectroscopy (EDS) were used to evaluate the behaviour of the corroded samples. The fully anodised sample showed that the anodised surface displayed some surface degradation. This degradation was more severe on the anodised surface with surface liquid segregation (SLS), but provided sufficient protection to prevent corrosion of the base metal. The partially anodised sample showed severe corrosion of the based metal with the corrosion concentrated in the silicon rich eutectic and SLS regions.</p> <span style="font-family: Times New Roman; font-size: medium;" face="Times New Roman" size="3"> </span>

Fusion Welding of Rheocast Semi-Solid Metal (SSM) Processed Aluminium Alloy 7017

2012 ◽  
Vol 192-193 ◽  
pp. 161-166 ◽  
Author(s):  
Madeleine du Toit ◽  
Patronica Letsoalo ◽  
Heinrich Möller
Keyword(s):  
Mechanical Properties ◽  
High Pressure ◽  
Aluminium Alloy ◽  
Die Casting ◽  
Solid Metal ◽  
Hot Tearing ◽  
High Pressure Die Casting ◽  
Near Net Shape ◽  
Semi Solid ◽  
Pressure Die Casting

Near-net shape casting of wrought aluminium alloys has proven to be difficult due to a tendency towards hot tearing during cooling. Rheocasting, or semi-solid metal (SSM) processing followed by high pressure die casting (HPDC), has recently been shown to be an effective alternative to conventional die casting, yielding near-net shape wrought aluminium alloy castings with less risk of hot tearing. This casting process involves pouring the liquid metal into a processing cup, which is then transferred into a coil for induction stirring and simultaneous forced air cooling. When the metal reaches the semi-solid casting temperature, the resultant slurry is transferred to a high pressure die casting machine and cast to near-net shape. This modifies the as-cast microstructure, yielding a more globular primary phase and results in mechanical properties in the -T6 condition closely approaching those of wrought material in the same condition. Little information is currently available on the response of SSM-HPDC material to welding. This project investigated the influence of autogenous laser and gas tungsten arc welding on the microstructure and mechanical properties of aluminium 7017 after rheocasting. It is possible to successfully weld this material without solidification or liquation cracking. The effect of welding on the rheocast microstructure in the heat-affected zone and weld metal was shown, and the hardness and tensile properties of the resulting joints in the as-welded condition were tested and related to the microstructures achieved.

Support for Ingate Design by Analysing the Geometry of High Pressure Die Cast Geometries Using Dijkstra’s Shortest Path Algorithm

2016 ◽  
Vol 1140 ◽  
pp. 400-407
Author(s):  
Florian Heilmeier ◽  
Daniel Goller ◽  
Daniel Opritescu ◽  
Christopher Thoma ◽  
Frank Rieg ◽  
...  
Keyword(s):  
High Pressure ◽  
Die Casting ◽  
Shortest Paths ◽  
Casting Process ◽  
Product Development Process ◽  
Analysis Tool ◽  
High Pressure Die Casting ◽  
Die Cast ◽  
Die Casting Process ◽  
Pressure Die Casting

A new approach for the analysis of high pressure die casting geometries concerning form filling is introduced. It enables the reduction of simulation cycles needed in the product development process, as they are highly time and cost intensive. Therefore, we developed an analysis tool, which uses shortest paths from each part of the geometry to the chosen ingate surfaces. This way, and by evaluating the information given by basic filling simulations, we can evaluate the usability of a given geometry for a high pressure die casting process and are able to suggest useful strategies to place ingates and to design a filling system.

A Development of Virtual Manufacturing System for Magnesium High Pressure Die Casting Processes

Materials ◽  
2003 ◽  
Author(s):  
Weilong Chen
Keyword(s):  
High Pressure ◽  
Magnesium Alloys ◽  
Die Casting ◽  
Virtual Manufacturing ◽  
Mold Design ◽  
High Pressure Die Casting ◽  
Molten Magnesium ◽  
Pressure Die Casting ◽  
Soft And Hardware ◽  
Free Magnesium

In recent years, high-pressure die-casting magnesium components have been gaining currency worldwide because of the excellent properties that magnesium alloys can offer to meet new product requirements. With the increasing application of magnesium parts worldwide, many research and development projects have been carried out to advance HPDC technology. However, truly optimized mold design and production of defect free castings remains a challenge for die casters. For many HPDC magnesium products, especially those specified for porosity-free and high cosmetic requirement, the challenge not only comes form a lack of a deeper understanding of how molten magnesium alloys fill the mold cavity and form defects, but also from improper preliminary part design. This study proposes a virtual prototyping system that integrates several effective soft and hardware tools for both the part and mold-design engineer to evaluate part manufacturability. Also, investigated in this study are the major causes of those defects that are the predominant cause of rejection of thin walled, leak-free magnesium parts requiring highly cosmetic finishes.

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