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.

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>

Effect of Excess Mg on the Microstructure and Mechanical Properties of Al-Mg2Si High Pressure Die Casting Alloys

2013 ◽  
Vol 765 ◽  
pp. 64-68 ◽  
Author(s):  
Feng Yan ◽  
Shou Xun Ji ◽  
Zhong Yun Fan
Keyword(s):  
Mechanical Properties ◽  
High Pressure ◽  
Mechanical Performance ◽  
Eutectic Reaction ◽  
Die Casting ◽  
High Strength ◽  
Primary Phase ◽  
High Pressure Die Casting ◽  
Excess Mg ◽  
Pressure Die Casting

In this work we found that the addition of excess Mg can significantly improve the mechanical properties of pseudo-binary Al-Mg2Si alloys after high pressure die casting (HPDC). Al-8Mg2Si-6Mg alloy offered an excellent combination of high strength and reasonable ductility. Excess Mg lowers the Mg2Si content in the eutectic reaction and promotes the formation of Mg2Si as the primary phase, and this is believed to be the origin of improved mechanical performance.

Al-Mg-Si-(Cu) 6xxx Series Alloy Selection for Rheo-High Pressure Die Casting

2014 ◽  
Vol 1019 ◽  
pp. 61-66
Author(s):  
Heinrich Möller ◽  
Pfarelo Daswa ◽  
Gonasagren Govender
Keyword(s):  
High Pressure ◽  
Selection Process ◽  
Die Casting ◽  
Solution Treatment ◽  
Hot Tearing ◽  
Incipient Melting ◽  
Negative Effects ◽  
High Pressure Die Casting ◽  
Pressure Die Casting ◽  
6Xxx Series

<span><span style="font-family: Times New Roman;" face="Times New Roman"><span style="font-family: Times New Roman;" face="Times New Roman"></span></span> <p><span style="font-family: Times New Roman;" face="Times New Roman">This paper investigates the selection process of Al-Mg-Si-(Cu) 6xxx series alloys when used specifically for rheo-high pressure die casting (R-HPDC). The 6xxx series alloys have been developed as wrought alloys and certain factors must be taken into consideration when utilising them for semi-solid metal processing. It is shown that chemical composition has a significant effect on the solution treatment parameters that should be employed i.e. high Cu and excess Si levels necessitate the use of a two-step solution treatment to reduce incipient melting. This incipient melting is especially severe in areas within the component where liquid segregation occurs, which is a common phenomenon in R-HPDC. However, high Cu and excess Si levels also have advantages: it results in higher T6 strength and Cu-additions have been shown to minimise the negative effects of natural pre-ageing. Therefore, the composition of the alloy must be selected in such a way as to achieve acceptable strength without the dangers of incipient melting in liquid segregated areas. Another important modification of 6xxx series alloys used for R-HPDC that is presented is the addition of Ti to minimise hot tearing. </span></p> <p align="LEFT"><span style="font-family: Times New Roman; font-size: medium;" face="Times New Roman" size="3"> </span></p>

Rheocasting of Al-Cu Alloy A201 with Different Silver Contents

2008 ◽  
Vol 141-143 ◽  
pp. 151-156 ◽  
Author(s):  
E.P. Masuku ◽  
Gonasagren Govender ◽  
L. Ivanchev ◽  
Heinrich Möller
Keyword(s):  
Mechanical Properties ◽  
High Pressure ◽  
Grain Boundaries ◽  
Die Casting ◽  
Solution Treatment ◽  
Cast Material ◽  
High Pressure Die Casting ◽  
Cu Alloy ◽  
Pressure Die Casting ◽  
Better Than

Rheocasting of alloys A206 and A201 was investigated in this study. Conical bars with different silver contents were produced using CSIR rheoprocess technology, together with high pressure die casting. The results showed that addition of Ag to alloy A206 increased the mechanical properties of the alloy. However, the addition of Ag also resulted in Cu-rich phases to precipitate at the grain boundaries of the as-cast material. The solution treatment used in this study was unable to dissolve all of this phase, especially in the 1.12%Ag-containing alloy. This resulted in slightly decreased mechanical properties compared to the 0.63%Ag-containing alloy. The T6 mechanical properties (strength and elongation) obtained in this study for rheocast A206 and A201 are better than those reported for permanent mould castings of alloy A206 and A201.

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