Age-Hardening of Rheo-High Pressure Die Cast Al-Alloy 6066

2014 ◽  
Vol 1019 ◽  
pp. 47-54
Author(s):  
Carlien Taute ◽  
Heinrich Möller
Keyword(s):  
High Pressure ◽  
High Performance ◽  
Solution Treatment ◽  
Heat Treatments ◽  
Hot Tearing ◽  
Age Hardening ◽  
Al Alloy ◽  
Artificial Ageing ◽  
One Step ◽  
Semi Solid

Al-Mg-Si-Cu alloy 6066 is a heat-treatable wrought alloy that is commonly used in high performance bicycle frames. Wrought alloys are difficult to cast using conventional liquid casting techniques, as hot tearing can occur. However, a method that effectively reduces that risk is rheo-high pressure die casting (R-HPDC). Casting alloy 6066 using semi-solid metal processing makes it possible to be used for near-net shape forming of components. This study investigates the age-hardening response of R-HPDC alloy 6066. The effects of different solution heat treatments, natural pre-ageing and artificial ageing are studied. The different solution heat treatments investigated are a one-step and a two-step solution treatment. The one-step treatment was performed at 530°C only and the two-step treatment at 530°C followed by 550°C. It is shown that natural pre-ageing has a detrimental effect on the T6 properties and that the longer two-step solution heat treatment is justified due to an increase in hardness and prevention of incipient melting. The Vickers hardness in different temper conditions (F, T4, T5 and T6) were determined and compared to the typical hardness values of the alloy in the wrought condition.

Segregation Characteristics of Rheo-High Pressure Die Cast Al-Alloy 2139 Plates

2015 ◽  
Vol 828-829 ◽  
pp. 100-105 ◽  
Author(s):  
Carlien Taute ◽  
Heinrich Möller
Keyword(s):  
High Pressure ◽  
Die Casting ◽  
Hot Tearing ◽  
Three Dimensions ◽  
Age Hardening ◽  
Al Alloy ◽  
Die Cast ◽  
Near Net Shape ◽  
Net Shape Forming ◽  
Pressure Die Casting

Al-Cu-Mg-Ag alloy 2139 is a wrought alloy that is heat-treatable and used in aerospace constructions. This is mainly due to the addition of silver in the alloy. Hot-tearing is a problem for casting wrought alloys with conventional liquid casting techniques. The risk is reduced by using rheo-high pressure die casting (R-HPDC) to allow the alloy to be used for near-net shape forming of components. This study investigates the segregation characteristics of R-HPDC alloy 2139. The effects of segregation on the age-hardening response as well as the tensile properties are studied. The chemical composition differences across the casting were found to aid in correlation of results. It is found that segregation occurs in three dimensions, namely from the surface to the centre of the casting, as well as across the width and length of the casting.

The Effect of Natural Pre-Ageing on the Mechanical Properties of Rheo-High Pressure Die Cast Aluminium Alloy 2139

2015 ◽  
Vol 828-829 ◽  
pp. 244-249 ◽  
Author(s):  
Levy Chauke ◽  
Pfarelo Daswa ◽  
Heinrich Möller ◽  
Gonasagren Govender
Keyword(s):  
High Pressure ◽  
Aluminium Alloy ◽  
Tensile Properties ◽  
Casting Process ◽  
Hot Tearing ◽  
Age Hardening ◽  
Peak Hardness ◽  
Artificial Ageing ◽  
Significant Difference ◽  
Precipitation Phenomena

Near-net shape casting of wrought aluminium alloys has proven to be difficult due to hot tearing. The Council for Scientific and Industrial Research (CSIR) has successfully processed wrought aluminium alloy 2139 into plate castings using the Rheo-high pressure die casting process (R-HPDC). Alloy 2139 is a Ag-containing aluminium alloy from the Al-Cu-Mg 2xxx series family. The addition of Ag enhances the age hardening response through the formation of co-clusters that act as precursors to the formation of plate-like Ω precipitates. These co-clusters typically form during natural ageing and 12-24 h of natural pre-ageing is normally specified before artificial ageing in Ag-containing Al-Cu-Mg alloys. The T6 hardness and tensile properties of R-HPDC 2139 alloy were investigated with and without natural pre-ageing. It is shown that there is no significant difference in both peak hardness and tensile properties in R-HPDC alloy 2139 with and without natural pre-ageing. The possible precipitation phenomena in both cases are discussed.

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>

Aging Behavior of Al-Li-Cu-Mg Alloy Processed by High-Pressure Torsion

2010 ◽  
Vol 654-656 ◽  
pp. 1243-1246 ◽  
Author(s):  
Seung Won Lee ◽  
Daichi Akama ◽  
Z. Horita ◽  
Tetsuya Masuda ◽  
Shoichi Hirosawa ◽  
...  
Keyword(s):  
High Pressure ◽  
High Pressure Torsion ◽  
Solution Treatment ◽  
Aging Treatment ◽  
Rolling Process ◽  
Mg Alloy ◽  
Age Hardening ◽  
Subsequent Aging ◽  
Solid Solution Treatment ◽  
Conventional Rolling

This study presents an application of high-pressure torsion (HPT) to an Al-Li-Cu-Mg alloy (2091). The alloy was subjected to solid solution treatment at 505oC for 30 minutes and was processed by HPT under 6 GPa for 5 revolutions at room temperature. The hardness increased with straining and saturated to a constant level at 225 Hv. Aging was undertaken on the HPT-processed alloy at 100, 150 and 190oC for the total periods up to 9.3 days. The aging treatment led to a further increase in the hardness to ~275 Hv. It is shown that the simultaneous strengthening of the alloy due to grain refinement and age hardening was successfully achieved by application of HPT and subsequent aging treatment. The enhancement of the strength is prominent when compared with the application of a conventional rolling process.

Effects of Natural Ageing on T6 Heat Treated Rheocasts of 319S Aluminum Alloy

2016 ◽  
Vol 256 ◽  
pp. 58-62 ◽  
Author(s):  
Kang Du ◽  
Qiang Zhu ◽  
Da Quan Li
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Aluminium Alloys ◽  
Solution Treatment ◽  
Treatment Temperature ◽  
Solution Treatment Temperature ◽  
Artificial Ageing ◽  
Natural Ageing ◽  
T6 Heat Treatment ◽  
Semi Solid

T6 heat treatment is an effective method to improve the comprehensive properties of Al-Si-Cu-Mg series aluminium alloys. Solution treatment temperature and time, quench process and media, as well as artificial ageing temperature and time are the key factors to determine mechanical properties. Besides these factors, natural ageing, i.e. the holding time between quenching and the starting of artificial treatment at ambient temperature was observed to be significant affect mechanical properties of the aluminium alloys. This effect on semi solid processed aluminium alloys was lack of investigations as the semi solid process produces T6 treatable and weldable components. The present paper focuses on the change regularity of hardness and precipitate behaviour of semi-solid 319S aluminium alloy under different natural ageing (NA) treatment additional to standard T6. Density and morphology of hardening precipitates are analysed using TEM, and the influence mechanism of NA during T6 heat treatment will be discussed. The results show that NA has a positive influence on mechanical properties of the rheo-cast 319S alloy.

Microstructure Evolution during Solution Heat Treatment of Semisolid Cast 2024 Aluminum Alloy

2011 ◽  
Vol 339 ◽  
pp. 714-717 ◽  
Author(s):  
Siriwan Pannaray ◽  
Sirikul Wisutmethangoon ◽  
Thawatchai Plookphol ◽  
Jessada Wannasin
Keyword(s):  
Heat Treatment ◽  
Aluminum Alloy ◽  
Solution Heat Treatment ◽  
Solution Treatment ◽  
Treatment Temperature ◽  
Grain Structure ◽  
Al Alloy ◽  
Solution Treatment Temperature ◽  
2024 Aluminum Alloy ◽  
Semi Solid

The aim of this study is to determine the appropriate solution treatment temperature and time of semi solid 2024 Al alloy. Solution heat treatment at 450°C and 480 °C for various times, from 4 hours to 16 hrs, were applied followed by artificial aging at 220 °C for 1 hr. Microstructure of the semi solid cast 2024 aluminum alloy mainly showed globular grain structure which consisted of matrix-α (Al) and grain boundary (GB) - eutectic phases (α+Al2CuMg/Al2Cu). Eutectic GB phases was found to completely dissolved after solution heat treatment at 480°C for 14 hrs while sample solution treated at 450°C for the same time showed the existence of remaining GB phases. Prolonging heat treatment after 14 hrs at both temperatures resulted in the formation of coarse black particles at the grain boundaries which were identified as Mg2Si phases. Therefore the suitable solution treatment of the alloy in this study was at 480°C for 14 hrs.

Effects of Heat Treatment on a High-Pressure Die-Cast Mg-La-Y Alloy

2011 ◽  
Vol 690 ◽  
pp. 210-213 ◽  
Author(s):  
Serge Gavras ◽  
Su Ming Zhu ◽  
Mark A. Easton ◽  
Mark A. Gibson ◽  
Jian Feng Nie
Keyword(s):  
Heat Treatment ◽  
High Pressure ◽  
Creep Resistance ◽  
Solution Treatment ◽  
Dislocation Motion ◽  
Heat Treatments ◽  
Dimensional Changes ◽  
Heat Treated ◽  
Die Cast ◽  
Solute Atoms

In this study effects of heat treatments on the creep resistance at 177°C/90MPa of a high-pressure die-cast Mg-2.70La-1.50Y (wt.%) alloy were examined. It was found that ageing at 160°C for 24 h (T5) or a solution treatment at 520°C for 1 h (T4) improved creep resistance and caused no blistering on the surface or dimensional changes to the die-cast specimens. TEM was used to characterize the microstructures of heat-treated samples. Improvements to creep resistance might be attributed to the pinning or otherwise retarding of dislocation motion by precipitates and/or solute atoms during creep.

scholarly journals Prior Solutionising Deformation Consequence on the Aging Characteristics of Steel Powder Reinforced Al 7075 Composites

2019 ◽  
Vol 8 (2S11) ◽  
pp. 2256-2261
Keyword(s):  
Aluminum Alloy ◽  
Strain Hardening ◽  
Cold Deformation ◽  
Solution Treatment ◽  
Steel Powder ◽  
Heat Treatments ◽  
Age Hardening ◽  
Peak Hardness ◽  
Alloy Matrix ◽  
Al 7075

Globally, in the application of structural materials, aluminum composites are emerging as pioneer materials due to balanced properties like ductility, strength, hardness and weight to volume ratio. It is obvious that addition of harder steel powder reinforcements to the softer aluminum alloy matrix will yield in larger benefits as energy efficient method, durability and recyclability for the composite. Infact, improvement in hardness levels at low temperatures in softer matrix aluminium alloys is the order of the day for wear related applications. Aluminum alloy composites especially Al 7075 matrix containing solid state soluble elements like copper, zinc and silicon with or without wetting agents like magnesium are heat treatable and got medium strength. The alloy matrix dispersed with solid reinforcements like carbides, oxides, flyash and steel powder contribute for the property improvement by tailoring the suitable heat treatment with flexibility in process parameters. Cold deformation assisted heat treatments, prior to or post solutionising challenge conventional heat treatments like age hardening or precipitation hardening. When the cold deformation is provided before solution treatment increases hardness by strain hardening with increased nucleation sites for phase transformation. When partial solutionising is given to the cold deformed composite retains the partial strain hardening effect on the specimen compared to complete solutionising. The retention of partial strain hardening followed by further aging develops complex interaction effect of strain hardening coupled with controlled precipitation of intermetallics on the composite for drastic uplift in hardness property. During conventional age hardening hardness and strength of the samples increase. Reduction in peak hardness value with increasing aging temperature is the renowned behaviour of age hardenable composites. The obtained peak hardness value is further increasing when cold deformation is supported with prior intentional deformation. Considering these features, it is proposed to perform prior solutionising deformation followed by subsequent aging on the stir cast Al 7075 –steel powder reinforced composite and analyse the microstructure and hardness distribution pattern by varying the steel powder quantity (0, 3 and 6 wt%), deformation density (10 and 20%) and aging temperatures (100 and 180oC)

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.

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