Effects of Cu Addition on the Precipitation Process of Al-9Zn-4Mg-xCu (wt. %) Alloys at 130°C

Aluminium is a light-weight material and possesses high corrosion resistance, so that it is widely used in manufacturing industries. The Al-Zn series have the highest strength compared to other aluminium alloys. To further increase the strength of Al-Zn alloys, Mg and Cu are added and age hardening treatment is applied. This research studied the precipitation process in Al-9Zn-4Mg (wt. %) alloys with Cu content of 0, 1, 3 and 5 wt.%. The alloys were produced through investment casting taking the shape of turbine impeller. The samples were solution treated at 460 °C for 2 hours and then aged at 130 °C. The characterization included hardness testing to observe response of age hardening, microstructural observation and Differential Scanning Calorimetry (DSC) testing. Microstructural observation was conducted by optical microscope and Scanning Electron Microscope (SEM) which was combined with Energy Dispersive Spectroscopy (EDS). The results showed that addition of Cu initially decreased the hardness during early ageing (2 hours) due to segregation of Cu-V complexes toward the grain boundaries which then decreased the hardness and enlarged the grain boundary phases. However, the peak hardness of the alloys was not affected by the increase in Cu content. due to high concentration of Zn and Mg. Exothermic reactions of formation of GP zones, η", η' and η (MgZn2) were found during precipitation process while endothermic reaction were observed due to dissolution of the phases. Presence of MgZn2 and Al7Cu2Fe second phases were observed in grain boundaries.

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Effects of Cu Addition on Age Hardening Response of Al-7Si-4Mg Alloys at 130 °C

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.833.74 ◽

2020 ◽

Vol 833 ◽

pp. 74-79

Author(s):

Inas M. Jauhari ◽

Danny Taufik Bahar ◽

Syarah Khayrun Nisa ◽

Bondan Tiara Sofyan

Keyword(s):

Thermal Analysis ◽

Simultaneous Thermal Analysis ◽

Hardness Test ◽

Optical Microscope ◽

Age Hardening ◽

Peak Hardness ◽

X Rays ◽

Microstructural Observation ◽

Solution Treated ◽

Scanning Electron

The effects of Cu addition of 0.38, 3.82, and 6 wt. % in Al-7Si-4Mg alloy on hardness and age hardening response were discussed. Samples were solution treated at 495 °C for 2 h, quenched, and aged at 130 °C for 0 to 498 h. Characterization included hardness test, microstructural observation by an optical microscope (OM) and Scanning Electron Microscope (SEM) combined with Energy Dispersive X-Rays Spectroscopy (EDX), as well as Simultaneous Thermal Analysis (STA) testing. The results showed an increased in as-cast hardness along with addition of Cu. Peak hardness increased to 64.47, 65.8, and 70.1 HRB by addition of 0.38, 3.82, and 6 wt. % Cu, respectively. The addition of Cu promoted the formation of Al2Cu and Al5Cu2Mg8Si6 which contributed to higher as-cast hardness. Formation of GP-zone, θ”, and θ’ was observed after ageing at 48, 240, and 290 °C, respectively and no effects of Cu was detected on the formation temperatures of the precipitates.

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Optimization of Ageing Parameters of a Low Nickel Maraging Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.636-637.471 ◽

2010 ◽

Vol 636-637 ◽

pp. 471-477 ◽

Cited By ~ 1

Author(s):

M. Cabeza ◽

G. Castro ◽

P. Merino ◽

G. Pena ◽

M. Román ◽

...

Keyword(s):

Maraging Steel ◽

Structural Changes ◽

Precipitation Hardening ◽

Age Hardening ◽

Scanning Calorimetry ◽

Hardening Treatment ◽

Depth Study ◽

Final Selection ◽

Selection Of

In the present work the age hardening parameters of a 14Ni (200) maraging steel are studied in order to optimize mechanical properties of the steel. The initial characterization of the as received solution annealed steel has been carried out by optical and scanning electron microscopy (LOM and SEM), and hardness measurements. To identify the structural changes during ageing, differential scanning calorimetry (DSC) tests were performed. Different time-temperature combinations were considered for the precipitation hardening treatment of as-quenched material samples. After hardness measurements, three of these treatments were selected for an in depth study. The obtained microstructure at the maximum hardness peaks then analysed (LOM, SEM and TEM) and mechanical behaviour (strength, toughness and wear resistance) was studied for the final selection of the age hardening conditions.

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Nanocluster Formation and Two-Step Aging Behavior of Rapid Hardening Al-Mg-Cu(-Ag) Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.794-796.996 ◽

2014 ◽

Vol 794-796 ◽

pp. 996-1001 ◽

Cited By ~ 4

Author(s):

Mami Mihara ◽

Equo Kobayashi ◽

Tatsuo Sato

Keyword(s):

Electrical Resistivity ◽

Base Alloy ◽

Resistivity Measurement ◽

Hardness Measurement ◽

Age Hardening ◽

Peak Hardness ◽

Electrical Resistivity Measurement ◽

Scanning Calorimetry ◽

Aging Response ◽

Two Stages

The characteristic age-hardening response of Al-3.0Mg-1.0Cu (mass%) alloys with and without Ag addition has been investigated by the hardness measurement, differential scanning calorimetry (DSC) and electrical resistivity measurement. The alloy compositions locating in the (α+S+T) phase field of the Al-Mg-Cu phase diagram are known to be effective to harden in two stages separated by a distinct and often prolonged hardness plateau. The first stage of hardening occurs very rapidly (e.g. within 60 s at 443 K) and contributes to increase hardness as much as 50 % of the total age-hardening. In the Ag-added alloy, the hardness change during the first stage of hardening is larger and the plateau stage is shortened as a result of the fast arrival at the second stage of hardness. Small amount of Ag changes the age hardening response of the Base alloy dramatically. In the low temperature aging, the incubation stage at which no clear hardness and electrical resistivity increase appears for a long period before the first stage of hardening. After the pre-aging at this incubation period, a characteristic two-step aging response is observed. The peak hardness dramatically changes in the Al-3.0Mg-1.0Cu alloy, while no clear change in the Ag-added alloy.

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Influence of Pre-Straining and Pre-Ageing on the Age-Hardening Response of Al-Mg-Si Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.794-796.903 ◽

2014 ◽

Vol 794-796 ◽

pp. 903-908 ◽

Cited By ~ 9

Author(s):

Yong Yan ◽

Ze Qin Liang ◽

John Banhart

Keyword(s):

Differential Scanning Calorimetry ◽

Cluster Formation ◽

Age Hardening ◽

Peak Hardness ◽

Artificial Ageing ◽

Natural Ageing ◽

Scanning Calorimetry ◽

Negative Effect ◽

Kinetics Of ◽

Positive Effect

The effect of pre-straining and pre-ageing on the age hardening response of Al-0.6%Mg-0.8%Si alloy is studied by Vickers hardness and differential scanning calorimetry (DSC). It is found that pre-ageing can suppress the formation of unwanted clusters and keeps the structure stable for a certain time. A pre-ageing treatment can effectively reduce or avoid the negative effect of natural ageing on artificial ageing and even produce a positive effect. Cluster formation can also be reduced by pre-straining, but the kinetics of clustering is still similar to that of the as-quenched condition. In contrast, after pre-straining, the peak positions of β and β move to lower temperatures and peak hardness is achieved in a shorter time, indicating that the formation of β and β is accelerated by pre-straining. However, the negative effect of natural ageing still persists after pre-straining. Pre-straining before pre-aging can take advantage of both techniques and produce a positive strength response. For pre-straining after pre-aging, pre-straining tends to destabilize the structure created by pre-ageing and can reactivate the clustering process, which has negative effect on subsequent artificial ageing.

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Effect of Combined Pre-Straining and Pre-Aging on the Precipitation Behavior and Age Hardening Response for Al-Mg-Si Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1026.74 ◽

2021 ◽

Vol 1026 ◽

pp. 74-83

Author(s):

Guan Jun Gao ◽

Xi Wu Li ◽

Li Zhen Yan

Keyword(s):

Electron Microscopy ◽

Natural Aging ◽

Hardness Test ◽

Age Hardening ◽

Precipitation Behavior ◽

Strengthening Phase ◽

Scanning Calorimetry ◽

Transmission Electron ◽

Hardening Treatment ◽

Cluster 2

Pre-strain (PS) and pre-aging (PA) treatments are often applied during the preparation of Al-Mg-Si automotive aluminum alloy. In this study, the effect of combined PS and PA on the precipitation behavior and age hardening response for Al-Mg-Si alloys was investigated through scanning electron microscopy (SEM), transmission electron microscopy (TEM), tensile test, Vickers hardness test, and differential scanning calorimetry (DSC). It was found that the dislocations introduced by PS treatment and the cluster (2) formed during PA treatment effectively inhibited the cluster (1), which further strengthened the inhibition of natural aging hardening at room temperature (RT). The strength increment of the alloys was kept below 10.0 MPa during two weeks RT storage. The dislocations provided heterogeneous nucleation for the precipitates forming and the cluster (2) transformed into β″ strengthening phase during bake hardening treatment. With the acceleration response of the dislocations and the cluster (2), the age hardening response of Al-Mg-Si alloys obviously improved with the denser and larger β″ strengthening phase formed.

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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.519-521.495 ◽

2006 ◽

Vol 519-521 ◽

pp. 495-500 ◽

Cited By ~ 7

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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Crystal Transition and Drug-excipient Compatibility of Clarithromycin in Sustained Release Tablets

Current Pharmaceutical Analysis ◽

10.2174/1573412915666190328234326 ◽

2020 ◽

Vol 16 (7) ◽

pp. 950-959

Author(s):

Yu Li ◽

Xiangwen Kong ◽

Fan Hu

Keyword(s):

Sustained Release ◽

Powder Diffraction ◽

Magnesium Stearate ◽

Influential Factor ◽

High Concentration ◽

Scanning Calorimetry ◽

X Ray ◽

Sustained Release Tablets ◽

Crystal Transition ◽

Excipient Compatibility

Background: Clarithromycin is widely used for infections of helicobacter pylori. Clarithromycin belongs to polymorphic drug. Crystalline state changes of clarithromycin in sustained release tablets were found. Objective: The aim of this study was to find the influential factor of the crystal transition of clarithromycin in preparation process of sustained-release tablets and to investigate the possible interactions between the clarithromycin and pharmaceutical excipients. Methods and Results: The crystal transition of active pharmaceuticals ingredients from form II to form I in portion in clarithromycin sustained release tablets were confirmed by x-ray powder diffraction. The techniques including differential scanning calorimetry and infrared spectroscopy, x-ray powder diffraction were used for assessing the compatibility between clarithromycin and several excipients as magnesium stearate, lactose, sodium carboxymethyl cellulose, polyvinyl-pyrrolidone K-30 and microcrystalline cellulose. All of these methods showed compatibilities between clarithromycin and the selected excipients. Alcohol prescription simulation was also done, which showed incompatibility between clarithromycin and concentration alcohol. Conclusion: It was confirmed that the reason for the incompatibility of clarithromycin with high concentration of alcohol was crystal transition.

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Crystallization Behavior and Mechanical Properties of Poly(ε-caprolactone) Reinforced with Barium Sulfate Submicron Particles

Materials ◽

10.3390/ma14092368 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2368

Author(s):

Hegoi Amestoy ◽

Paul Diego ◽

Emilio Meaurio ◽

Jone Muñoz ◽

Jose-Ramon Sarasua

Keyword(s):

Barium Sulfate ◽

Thermal Studies ◽

Polarized Light ◽

Optical Microscope ◽

Submicron Particles ◽

Degree Of Crystallinity ◽

Scanning Calorimetry ◽

Nucleation Effect ◽

Crystal Fraction ◽

Light Optical Microscope

Poly(ε-caprolactone) (PCL) was mixed with submicron particles of barium sulfate to obtain biodegradable radiopaque composites. X-ray images comparing with aluminum samples show that 15 wt.% barium sulfate (BaSO4) is sufficient to present radiopacity. Thermal studies by differential scanning calorimetry (DSC) show a statistically significant increase in PCL degree of crystallinity from 46% to 52% for 25 wt.% BaSO4. Non-isothermal crystallization tests were performed at different cooling rates to evaluate crystallization kinetics. The nucleation effect of BaSO4 was found to change the morphology and quantity of the primary crystals of PCL, which was also corroborated by the use of a polarized light optical microscope (PLOM). These results fit well with Avrami–Ozawa–Jeziorny model and show a secondary crystallization that contributes to an increase in crystal fraction with internal structure reorganization. The addition of barium sulfate particles in composite formulations with PCL improves stiffness but not strength for all compositions due to possible cavitation effects induced by debonding of reinforcement interphase.

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High-Tribological-Performance Polymer Nanocomposites: An Approach Based on the Superlubricity State of the Graphene Oxide Agglomerates

Polymers ◽

10.3390/polym13142237 ◽

2021 ◽

Vol 13 (14) ◽

pp. 2237

Author(s):

Eder H. C. Ferreira ◽

Angela Aparecida Vieira ◽

Lúcia Vieira ◽

Guilhermino J. M. Fechine

Keyword(s):

Graphene Oxide ◽

High Viscosity ◽

Tribological Performance ◽

Multilayer Graphene ◽

High Concentration ◽

Scanning Calorimetry ◽

Mechanical Reinforcement ◽

Transmission Electron ◽

Twin Screw ◽

Mechanical Tensile

Here, nanocomposites of high-molecular-weight polyethylene (HMWPE) and HMWPE-UHMWPE (80/20 wt.%) containing a low amount of multilayer graphene oxide (mGO) (≤0.1 wt.%) were produced via twin-screw extrusion to produce materials with a higher tribological performance than UHMWPE. Due to the high viscosity of both polymers, the nanocomposites presented a significant concentration of agglomerates. However, the mechanical (tensile) and tribological (volumetric loss) performances of the nanocomposites were superior to those of UHMWPE. The morphology of the nanocomposites was investigated using differential scanning calorimetry (DSC), microtomography, and transmission electron microscopy (TEM). The explanation for these results is based on the superlubricity phenomenon of mGO agglomerates. It was also shown that the well-exfoliated mGO also contained in the nanocomposite was of fundamental importance as a mechanical reinforcement for the polymer. Even with a high concentration of agglomerates, the nanocomposites displayed tribological properties superior to UHMWPE’s (wear resistance up to 27% higher and friction coefficient up to 57% lower). Therefore, this manuscript brings a new exception to the rule, showing that agglomerates can act in a beneficial way to the mechanical properties of polymers, as long as the superlubricity phenomenon is present in the agglomerates contained in the polymer.

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