The Effect of Pre-Ageing and Addition of Copper on the Precipitation Behaviour in Al-Mg-Si Alloys

2006 ◽  
Vol 519-521 ◽  
pp. 543-548 ◽  
Author(s):  
A.I. Morley ◽  
M.W. Zandbergen ◽  
Alfred Cerezo ◽  
George D.W. Smith
Keyword(s):  
Aluminium Alloys ◽  
Deleterious Effect ◽  
Atom Probe ◽  
Artificial Ageing ◽  
Strengthening Effect ◽  
Natural Ageing ◽  
Aged Material ◽  
3 Dimensional ◽  
Precipitation Behaviour ◽  
6Xxx Series

Hardness measurements and 3-dimensional atom probe analysis have been used to characterise the precipitation behaviour in two 6xxx series aluminium alloys, one Cu-free alloy (Al-0.78at%Mg- 0.68at%Si) and one Cu-containing alloy (Al-0.78at%Mg-0.68at%Si-0.30at%Cu). The heat treatments consisted of either natural ageing or pre-ageing at 353K followed by a paint-bake treatment at 453K. Natural ageing was seen to increase the hardness, and hence reduce formability compared to pre-ageing. In addition, the strengthening effect of artificial ageing was less after natural ageing than after pre-ageing. In the Cu-free alloy, needle-like β″ was observed to form only after a pre-ageing treatment during the first 60 minutes of a paint-bake treatment. In the Cucontaining alloy, needle-like β″ formed during paint bake in both the naturally-aged and pre-aged material, although it is formed more rapidly after pre-ageing. This was accompanied by an increase in strength over the Cu-free alloy and indicates that Cu reduces the deleterious effect of natural ageing.

Effect of Pre-Ageing on the Artificial Ageing Response of Al-Mg-Si(-Cu) Alloys

2010 ◽  
Vol 654-656 ◽  
pp. 918-921 ◽  
Author(s):  
Ling Fei Cao ◽  
Paul A. Rometsch ◽  
Hao Zhong ◽  
Barry C. Muddle
Keyword(s):  
Early Stage ◽  
Solution Treatment ◽  
Atom Probe ◽  
Artificial Ageing ◽  
Natural Ageing ◽  
Scanning Calorimetry ◽  
Short Delay ◽  
3 Dimensional ◽  
Cu Alloys ◽  
Short Time

The effect of different pre-ageing treatments on the subsequent artificial ageing response of Al-Mg-Si(-Cu) alloys have been investigated using hardness, tensile and electrical conductivity testing. The microstructural evolution was characterised by differential scanning calorimetry (DSC) and 3-dimensional atom probe (3DAP) analysis. Pre-ageing treatments were carried out at 160-250°C for short times. Results show that the early stage artificial ageing response after 30 minutes at 170°C is strongly influenced by the pre-ageing and natural ageing conditions. A pre-ageing treatment performed for a short time at a high temperature and within a short delay after solution treatment and quenching was found to give a promising hardening response during subsequent artificial ageing. The mechanisms by which pre-ageing can reduce the detrimental effect of natural ageing on the artificial ageing response will be discussed in relation to the formation and distribution of clusters, GP zones and/or precipitates.

A Combined TEM and Atom Probe Approach to Analyse the Early Stages of Age Hardening in AA 6016

2016 ◽  
Vol 877 ◽  
pp. 231-236 ◽  
Author(s):  
Olaf Engler ◽  
C. Schäfer ◽  
Henk Jan Brinkman ◽  
Calin D. Marioara ◽  
Masaya Kozuka ◽  
...  
Keyword(s):  
Atom Probe ◽  
Age Hardening ◽  
Artificial Ageing ◽  
Phase Decomposition ◽  
Number Density ◽  
Early Stages ◽  
Transmission Electron ◽  
Different Types ◽  
6Xxx Series ◽  
Insight Into

In this study we aim at combining the results from transmission electron microscopy (TEM) and atom probe tomography (APT) to study the early stages of phase decomposition in the age hardening alloy AA 6016. Samples are subjected to different periods of natural ageing or artificial pre-ageing at elevated temperature in order to produce different types of clusters and early stages of precipitation before age hardening commences. APT is utilized to detect clusters and identify their compositions, whereas TEM is applied to analyse and quantify number density and sizes of the particles during artificial ageing at 185°C. It is shown that the two techniques, TEM and APT, are complementary and a combined approach yields more detailed insight into the early stages of phase decomposition in age hardening 6xxx series alloys than possible by the sole use of either technique individually.

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.

The Effect of Intermediate Storage Temperature and Time on the Age Hardening Response of Al-Mg-Si Alloys

2006 ◽  
Vol 519-521 ◽  
pp. 239-244 ◽  
Author(s):  
Jostein Røyset ◽  
Tore Stene ◽  
Jan Anders Sæter ◽  
Oddvin Reiso
Keyword(s):  
Storage Temperature ◽  
Age Hardening ◽  
Artificial Ageing ◽  
Natural Ageing ◽  
Aged Material ◽  
Delayed Onset ◽  
Heat Treated ◽  
Before And After ◽  
Different Temperatures ◽  
Intermediate Storage

Specimens of three Al-Mg-Si alloys, 6060, 6005 and 6082, were solution heat treated, stored at different temperatures for different time, and artificially aged. Properties were measured before and after artificial ageing. The natural ageing response of the alloys is dependent on the storage temperature. Decreasing storage temperature leads to a delayed onset of natural ageing, but also to a higher strength after prolonged ageing, particularly for lean alloys such as 6060. The temperature and time of intermediate storage between solution heat treatment and artificial ageing has a significant effect on the strength of the artificially aged material. For the 6005 and 6082 alloys the processes that take place during natural ageing lead to a reduced strength after artificial ageing.

An Investigation on Precipitation Behaviour of Cu-Rich Phase in Super304H Heat-Resistant Steel by Three Dimensional Atom Probe

2010 ◽  
Vol 654-656 ◽  
pp. 110-113
Author(s):  
Cheng Yu Chi ◽  
Jian Xin Dong ◽  
Wen Qing Liu ◽  
Xi Shan Xie
Keyword(s):  
Aging Time ◽  
Power Plants ◽  
Three Dimensional ◽  
Atom Probe ◽  
Strengthening Effect ◽  
Resistant Steel ◽  
Heat Resistant Steel ◽  
Rich Phase ◽  
Heat Resistant ◽  
Precipitation Behaviour

Super304H, a Cu-containing 18Cr-9Ni-3CuNbN heat-resisting steel is wildly used as an superheater/reheater tube material for ultra-super-critical (USC) power plants all over the world. It is recognized that the Cu-rich phase is an important strengthening phase for Super304H. However, the detail precipitation behaviour and its strengthening effect are still not very clear. Investigated material was taken from routine production and was aged at 650°C for different times. The precipitation of Cu-rich phase in Super304H was studied by three dimensional atom probe (3DAP) and TEM. Experimental results show that Cu-rich clusters have been formed at very early stage of 650°C aging. The Cu-rich particle images have been clearly caught just after 650°C aging for 5h. The Cu atoms gradually concentrate to Cu-rich particles and the other elements (such as Cr, Ni etc) diffuse away from Cu-rich particles to γ-matrix with the increasing of aging time. The Cu-rich particle size and its density have been determined as a function of aging time. Cu-rich particles still keep nano-size and distribute homogenously in grains even after long time (1,000h) aging, which is one of the most important reasons for keeping good strength of Super304H heat-resistant steel at high temperatures.

Investigation and Constitutive Modelling of High Strength 6xxx Series Aluminium Alloy: Precipitation Hardening Responses to FAST (Fast Light Alloys Stamping Technology) and Artificial Ageing

2018 ◽  
Vol 941 ◽  
pp. 814-820 ◽  
Author(s):  
Qun Li Zhang ◽  
Saksham Dhawan ◽  
Xi Luan ◽  
Qiang Du ◽  
Jun Liu ◽  
...  
Keyword(s):  
High Temperature ◽  
Aluminium Alloy ◽  
Aluminium Alloys ◽  
Precipitation Hardening ◽  
High Strength ◽  
Temperature Deformation ◽  
Artificial Ageing ◽  
Light Alloys ◽  
Fast Light ◽  
6Xxx Series

FAST (Fast light Alloys Stamping Technology) has recently been developed to efficiently and economically manufacture lightweight, high strength structural components from aluminium alloys sheet. Post-form strength prediction of 6xxx series aluminium alloy (AA6xxx) after FAST and multiple stage heat treatments has been a challenge. This is due to the effect of pre-existing dislocations induced via high temperature plastic deformation in the forming process. In the present research, a new PFS (post-form strength) model has been proposed to predict the age-hardening response of AA6xxx alloys undergoing FAST and subsequent thermal cycles. The model incorporates two sub-models, for simulating viscoplastic flow and predicting strength evolution respectively. The first sub-model incorporates a set of constitutive equations, developed to model the stress-strain curve of AA6xxx during FAST. The second sub-model employs precipitation-hardening and dislocation-hardening theories to simulate the evolution of microstructure and, as a consequence, strength of alloys undergoing artificial ageing cycles. This is calculated by considering the intrinsic resistance of the alloy to dislocation movement due to solute atoms and precipitates. The strength was computed accurately via the internal state variables method, in which dislocation density, volume fraction of precipitates, solute concentration and radii of precipitates were correlated. Furthermore, the model was validated by comparing results with transmission electron microscope (TEM) images as well as hardness measurements. Hence, the model performs as a powerful and comprehensive tool to simulate post-form strength of 6xxx series aluminium alloys that undergo complicated thermomechanical processes including high temperature deformation and post-form heat treatment, with less than 5% deviation between measured and predicted values.

Interaction between Cu and Sn in the Early Stages of Ageing of Al-1.7at.%Cu-0.01at.%Sn

2006 ◽  
Vol 519-521 ◽  
pp. 495-500 ◽  
Author(s):  
Laure Bourgeois ◽  
Timothy Wong ◽  
X.Y. Xiong ◽  
Jian Feng Nie ◽  
Barry C. Muddle
Keyword(s):  
Three Dimensional ◽  
Atom Probe ◽  
Age Hardening ◽  
Peak Hardness ◽  
Artificial Ageing ◽  
Natural Ageing ◽  
Number Density ◽  
Transmission Electron ◽  
Hardening Treatment ◽  
Significant Acceleration

The interaction between vacancies and Sn and Cu solute atoms in an Al-1.7at.%Cu- 0.01at.%Sn alloy was investigated by exploring the effect of incorporating natural ageing into conventional age hardening treatment. It was found that provided the artificial ageing temperature does not exceed a critical value between 160°C and 200°C, a narrow window of natural ageing (3-100 h) will result in a significant acceleration of the age hardening response and no decrease in peak hardness. Transmission electron microscopy showed that this effect reflects a large and rapid increase in number density of Cu GP(I) zones, and, to a lesser extent, of θ". The distribution and number density of θ' are essentially unaffected. Three-dimensional atom probe provided strong evidence that refinement of GP(I) zone distribution is not due to clustering of Cu atoms onto pre-existing Sn clusters. Instead it appears to be caused by a subtle interaction between vacancies, Sn and Cu atoms.

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