scholarly journals Precipitation Hardening at Elevated Temperatures above 400 °C and Subsequent Natural Age Hardening of Commercial Al–Si–Cu Alloy

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7155
Author(s):  
Ruoqi Li ◽  
Naoki Takata ◽  
Asuka Suzuki ◽  
Makoto Kobashi ◽  
Yuji Okada ◽  
...  
Keyword(s):  
Artificial Aging ◽  
Elevated Temperatures ◽  
Solution Treatment ◽  
Age Hardening ◽  
Nominal Composition ◽  
Cu Alloy ◽  
Long Duration ◽  
Cast Alloys ◽  
Lower Temperature ◽  
Impurity Elements

The precipitation of intermetallic phases and the associated hardening by artificial aging treatments at elevated temperatures above 400 °C were systematically investigated in the commercially available AC2B alloy with a nominal composition of Al–6Si–3Cu (mass%). The natural age hardening of the artificially aged samples at various temperatures was also examined. A slight increase in hardness (approximately 5 HV) of the AC2B alloy was observed at an elevated temperature of 480 °C. The hardness change is attributed to the precipitation of metastable phases associated with the α-Al15(Fe, Mn)3Si2 phase containing a large amount of impurity elements (Fe and Mn). At a lower temperature of 400 °C, a slight artificial-age hardening appeared. Subsequently, the hardness decreased moderately. This phenomenon was attributed to the precipitation of stable θ-Al2Cu and Q-Al4Cu2Mg8Si6 phases and their coarsening after a long duration. The precipitation sequence was rationalized by thermodynamic calculations for the Al–Si–Cu–Fe–Mn–Mg system. The natural age-hardening behavior significantly varied depending on the prior artificial aging temperatures ranging from 400 °C to 500 °C. The natural age-hardening was found to strongly depend on the solute contents of Cu and Si in the Al matrix. This study provides fundamental insights into controlling the strength level of commercial Al–Si–Cu cast alloys with impurity elements using the cooling process after solution treatment at elevated temperatures above 400 °C.

Consequences of Inappropriate Temperatures of the Solution Heat Treatment in Al-Si-Cu Cast Alloys

2020 ◽  
Vol 405 ◽  
pp. 357-364
Author(s):  
Lenka Kuchariková ◽  
Eva Tillová ◽  
Ivana Švecová
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Solution Heat Treatment ◽  
Solution Treatment ◽  
Age Hardening ◽  
Solution Temperature ◽  
Optimum Conditions ◽  
Cu Alloy ◽  
Cast Alloys ◽  
Casting Industry

Al-Si-Cu alloy systems have a great importance in the casting industry due to their excellent castability, good mechanical properties and wear resistance. Addition of alloying elements, such as Mg and Cu, makes these alloys heat treatable. Improving of their mechanical properties allows their using in new, more demanding applications (e.g. engines, cylinder heads etc.). The most applied heat treatment for this alloy is a T6 (age hardening). Such a heat treatment is required for precipitation of the Al2Cu hardening dispersed phase that increases the mechanical properties of Al alloys. Therefore, the consequences of different solution heat treatment temperatures 505, 515 and 525 °C for AlSi9Cu3 and 515, 525 and 545 °C for AlSi12Cu1Fe cast alloys, with holding times 2, 4, 8, 16 and 32 hours, were investigated in this study. The effect of solution treatment was evaluated based on changes in microstructure (optical microscopy) and mechanical properties (hardness, impact energy and ultimate tensile strength). The study confirms the strengthening of the experimental alloys caused by application of optimum conditions of T6 and melting of the Cu-rich phases with application of inappropriate solution temperature, as well as distortion and changes of the testing bars.

Effect of Mg and Cu Additions on Microstructure and Mechanical Properties of Squeeze Casting Al-Si-Cu-Mg Alloy

2016 ◽  
Vol 850 ◽  
pp. 511-518 ◽  
Author(s):  
Hai Jun Liu ◽  
Lie Jun Li ◽  
Jian Wei Niu ◽  
Ji Xiang Gao ◽  
Chuan Dong Ren
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Artificial Aging ◽  
Squeeze Casting ◽  
Solution Treatment ◽  
Mg Alloys ◽  
Percentage Elongation ◽  
Microstructure And Mechanical Properties ◽  
Content Ratio ◽  
Cast Alloys

The effects of Mg and Cu additions with different contents on the mechanical properties of Al-Si alloy prepared by indirect squeeze casting have been experimentally investigated. The microstructure and mechanical properties of as-cast and T6-treated Al-Si-Cu-Mg alloys were tested by OM, SEM, DSC and tensile measurement, where the samples were produced by artificial aging at 180°C for 8 h after solution treatment at 540°C for 4 h. It has been found that for the as-cast alloys, with increasing contents of Mg and Cu the tensile strength (UTS) and yield strength (YS) increased, while the percentage elongation (El) decreased. And the optimal mechanical properties of Al-Si-Cu-Mg alloys were obtained under the content ratio of Cu/Mg within 4, where the UTS and El reached 426 MPa and 6.3% after T6 treated, respectively.

Effects of T6 Age Hardening on Microstructure and Mechanical Properties of Al-Si-Cu Cast Aluminium Alloy

2013 ◽  
Vol 770 ◽  
pp. 88-91
Author(s):  
Amporn Wiengmoon ◽  
Pattama Apichai ◽  
John T.H. Pearce ◽  
Torranin Chairuangsri
Keyword(s):  
Electron Microscopy ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Aging Time ◽  
Artificial Aging ◽  
Solution Treatment ◽  
Hot Water ◽  
Age Hardening ◽  
Solution Treated ◽  
Cast Condition

Effects of T6 artificial aging heat treatment on microstructure, microhardness and ultimate tensile strength of Al-4.93 wt% Si-3.47 wt% Cu alloy were investigated. The T6 age hardening treatment consists of solution treatment at 500±5°C for 8 hours followed by quenching into hot water at 80°C and artificial aging at 150, 170, 200 and 230°C for 1-48 hours followed by quenching into hot water. Microstructure was characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). XRD and SEM revealed that the microstructure in the as-cast condition consists of primary dendritic α-Al, acicular-plate and globular forms of eutectic Si and intermetallic phases including globular Al2Cu and a flake-shape Al5FeSi. By T6 aging hardening, some intermetallics were dissolved and spheroidized. The volume fraction of eutectic phases in the as-cast, solution-treated, and solution-treated plus aging at 170°C for 24 hours is 17%, 12% and 10%, respectively. TEM results showed that precipitates in under-aging condition at 170° C for 6 hours are in the form of disc shape with the diameter in the range of 7-20 nm. At peak aging at 170°C for 24 hours, thin-plate precipitates with about 3-10 nm in thickness and 20-100 nm in length were found, lengthening to about 30-200 nm at longer aging time. The microhardness and ultimate tensile strength were increased from 71 HV0.05 and 227 MPa in the as-cast condition up to 140 HV0.05 and 400 MPa after solution treatment plus aging at 170°C for 24 hours, and decreased at prolong aging time.

Characterization of Precipitation Evolution in a Zn-Added Al-Mg-Si-Cu Alloy during Artificial Aging at 170 °C

2018 ◽  
Vol 941 ◽  
pp. 961-966
Author(s):  
Shang Zhu ◽  
Zhi Hui Li ◽  
Li Zhen Yan ◽  
Xi Wu Li ◽  
Shu Hui Huang ◽  
...  
Keyword(s):  
Artificial Aging ◽  
Age Hardening ◽  
Peak Hardness ◽  
Aging Condition ◽  
Β Phase ◽  
Cu Alloy ◽  
Zn Concentration ◽  
The Matrix ◽  
Small Clusters

A Zn-added Al-Mg-Si-Cu alloy during aging at 170 °C up to 34 h exhibits an interesting age-hardening effect. Small clusters, enriched in Mg and Si, are present in the sample after 0.25 h aging. The β′′ phase is dominant with the peak hardness of 135 HV after aging of 8 h. A decrease in hardness of the alloy occurs with the aging time increasing to 34 h, due to the coarsening of β′′ phase. It is also found that the Cu-containing L phase co-exists with the β′′ phase at this aging condition. The quantitative solute concentrations of the matrix show that the formation of clusters is consistent with the slight lower contents of Mg, Si and Cu compared with the alloy chemical composition, and the present of β′′ and L phase is associated with the further partitioning of Mg, Si and Cu from the Al matrix into the precipitates. No Zn-rich clusters and precipitates are observed and the Zn concentration in matrix has no significant change during aging for up to 34 h. This result means that the major of Zn remains in the matrix as aging continues.

Microstructural and Vickers Microhardness Evolution of Heat Treated Secondary Aluminium Cast Alloy

2013 ◽  
Vol 586 ◽  
pp. 137-140 ◽  
Author(s):  
Lenka Hurtalová ◽  
Eva Tillová ◽  
Mária Chalupová
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Artificial Aging ◽  
Vickers Microhardness ◽  
Cast Alloy ◽  
Solution Treatment ◽  
Holding Time ◽  
Age Hardening ◽  
Structural Components ◽  
Heat Treated

Secondary aluminium alloys are made out of aluminium scrap and aluminium-processable waste by recycling. These alloys contain different alloying elements such as Al, Cu, Fe, Si and Mg that form intermetallic phases in aluminium matrix and influence on the microstructure, basic mechanical properties and microhardness evolution in aluminium cast alloy. As experimental material was used secondary aluminium cast alloy AlSi9Cu3. Material was subjected to heat treatment (age-hardening) consisting of a solution treatment at temperature 515 °C with holding time 4 hours, than water quenching at 40 °C and artificial aging by different temperature 130 °C, 150 °C and 170 °C with different holding time (2, 4, 8, 16 and 32 hours). The age-hardening led to changes in the morphology of structural components, but also leads to precipitation of finer hardening phases in the material substructure. As optimal age-hardening mode for secondary aluminium cast alloy AlSi9Cu3 was determined mode consisting of solution treatment at temperature 515 °C with holding time 4 hours and artificial aging at temperature 170 °C with holding time 16 hours. After this heat treatment cast alloy shows the best changes in microstructure and mechanical properties. These changes are comparable with changes by primary AlSi9Cu3 cast alloy.

Effect of Sm on the Microstructure and Mechanical Property of Mg-xSm-0.4Zn-0.3Zr Alloys

2013 ◽  
Vol 747-748 ◽  
pp. 238-244 ◽  
Author(s):  
Xin Su ◽  
De Jiang Li ◽  
Yan Cai Xie ◽  
Xiao Qin Zeng ◽  
Wen Jiang Ding
Keyword(s):  
Tensile Strength ◽  
Yield Strength ◽  
Volume Fraction ◽  
Cast Alloy ◽  
Solution Treatment ◽  
Age Hardening ◽  
Second Phase ◽  
Gravity Casting ◽  
Cast Alloys ◽  
Microstructure And Mechanical Property

The effect of Sm content (2, 4, 6, 8wt.%) on the microstructures and mechanic properties of gravity casting Mg-xSm-0.4Zn-0.3Zr alloys were investigated. The results showed that the cast alloy mainly consists of α-Mg matrix and Mg41Sm5 phase distributed at the grain boundaries, and the amount of the second phase increased with the rise of Sm content. After the solution treatment (T4), the second phase disappeared, however small amount of cuboid-like phase were found inside the grain, and its volume fraction also increases with the rise of Sm content. It is found in the age hardening curves of the alloys at 175, 200, and 225 °C that the alloys with various components almost showed the same trend of age hardening. While the higher the Sm content, the harder the alloy. With the Sm content increases, the yield strength (TYS) of cast alloys (F state) were obviously improved, however the tensile strength (UTS) became lower because of the quick drop of the elongation. The elongations of solid solution (T4) and aging (T6) alloy became lower, while the yield strength and tensile strength increased at first and then decreased. The optimized component is Mg-4Sm-0.4Zn-0.3Zr, which the mechanic properties at T6 state are: TYS=131MPa; UTS=261MPa; δ=6.8%.

Effect of Pre-Straining and Natural Aging on the Hardening Response during Artificial Aging of EN AW 6082 and Lead Free EN AW 6023 Aluminium Alloys

2019 ◽  
Vol 952 ◽  
pp. 82-91
Author(s):  
Martin Fujda ◽  
Miloš Matvija ◽  
Peter Horňak
Keyword(s):  
Aluminium Alloys ◽  
Artificial Aging ◽  
Solution Treatment ◽  
Natural Aging ◽  
Age Hardening ◽  
Aging Effects ◽  
Β Phase ◽  
Transmission Electron ◽  
Negative Effect ◽  
Microscopy Characterization

In order to study the pre-straining and natural aging effects on the age-hardening response of EN AW 6082 and EN AW 6023 aluminium alloys during artificial aging at 170°C, the pre-straining by 5% was performed immediately after solution treatment of alloys at 550°C and subsequent quenching. The age-hardening response during artificial aging applied after various natural aging time (from 0.1 to 5 000 hours) was investigated using Vickers microhardness measurements and transmission electron microscopy characterization. It was found that pre-straining of quenched alloys state caused a dislocation density increasing in solid solution, which resulted in an immediate microhardness increase of alloys. During the subsequent natural aging of EN AW 6082 alloy, its microhardness increased right after alloy quenching and pre-straining, but only to the values obtained for the unstrained alloy state. On the contrary, the hardness of pre-straining EN AW 6023 alloy that is alloyed by Sn did not increase either after 10 hours of natural aging. This phenomenon is attributed to the effect of Sn on suppression of the strengthening clusters formation. The hardness of alloys increased greatly during artificial aging after pre-straining and natural aging due to accelerating the formation of coherent β″-phase particles. The negative effect of natural aging on the maximum age-hardening response obtained during alloys artificial aging had been observed for most of the pre-strained and naturally aged alloys states, with exception of EN AW 6023 alloy states that were pre-strained and shortly naturally aged (up to 100 hours).

Behaviour of Artificial Aging in 6066 Alloy Using Microhardness and Nuclear Techniques

2010 ◽  
Vol 305-306 ◽  
pp. 15-22
Author(s):  
Emad A. Badawi ◽  
M.A. Abdel-Rahman ◽  
Alaa El-Deen A. El-Nahhas ◽  
M. Abdel-Rahman
Keyword(s):  
Heat Treatment ◽  
Vickers Hardness ◽  
Artificial Aging ◽  
Solution Treatment ◽  
Natural Aging ◽  
Careful Consideration ◽  
Age Hardening ◽  
Solution Temperature ◽  
Precipitate Size ◽  
Precipitation Heat

Many Aluminum-based alloys are strengthened by using a heat-treatment process known as age-hardening. The aim of this work was to produce a high-strength 6xxx-series Aluminum alloy by adjusting the processing conditions, namely solutionizing and artificial aging. It consists of heating the alloy to a temperature at which the soluble constituents will form an homogeneous mass via solid diffusion, holding the mass at that temperature until diffusion takes place, then quenching the alloy rapidly to retain the homogeneous condition. In the quenched condition, heat-treated alloys are supersaturated solid solutions that are comparatively soft and workable, and unstable, depending upon the composition. After solution treatment and quenching, hardening is achieved either at room temperature (natural aging) or via a precipitation heat treatment at a suitable temperature (artificial aging). Precipitation heat treatments are generally low-temperature, long-term processes. Temperatures range from 115 to 190C; times vary from 5 to 48 h. The choice of time-temperature cycles for precipitation heat treatment should receive careful consideration. The objective is to select the cycle that produces an optimum precipitate size and distribution pattern. The mechanical characterization of heat-treatable 6xxx (Al-Mg-Si-Cu based) 6066 wrought aluminum alloys was studied. Their effects were investigated in terms of microstructure using positron annihilation lifetime techniques and monitoring the mechanical properties by mean of Vickers hardness measurements. The hardness is the resistance of a material to plastic deformation, and gives it the ability to resist deformation when a load is applied. The greater the hardness of the material, the greater resistance it has to deformation. The Vickers hardness of 6066 alloy has its maximum value (98) when aged for (10) hours at (175C) after quenching at 530C; so this temperature is the solution temperature of this alloy .The hardness conformed to reference values.

Deviations from Ideal Decagonal Symmetry in Electron Diffraction Patterns of the “Decagonal” Phase in the Al-Co-Cu Alloy System

1991 ◽  
Vol 49 ◽  
pp. 914-915
Author(s):  
Atul S. Ramani ◽  
Earle R. Ryba ◽  
Paul R. Howell
Keyword(s):  
Electron Microscope ◽  
Alloy System ◽  
Nominal Composition ◽  
Dimensional Lattice ◽  
3 Dimensional ◽  
Decagonal Phase ◽  
Cu Alloy ◽  
Transmission Electron ◽  
Lattice Periodicity ◽  
Diffraction Patterns

The “decagonal” phase in the Al-Co-Cu system of nominal composition Al65CO15Cu20 first discovered by He et al. is especially suitable as a topic of investigation since it has been claimed that it is thermodynamically stable and is reported to be periodic in the dimension perpendicular to the plane of quasiperiodic 10-fold symmetry. It can thus be expected that it is an important link between fully periodic and fully quasiperiodic phases. In the present paper, we report important findings of our transmission electron microscope (TEM) study that concern deviations from ideal decagonal symmetry of selected area diffraction patterns (SADPs) obtained from several “decagonal” phase crystals and also observation of a lattice of main reflections on the 10-fold and 2-fold SADPs that implies complete 3-dimensional lattice periodicity and the fundamentally incommensurate nature of the “decagonal” phase. We also present diffraction evidence for a new transition phase that can be classified as being one-dimensionally quasiperiodic if the lattice of main reflections is ignored.

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