scholarly journals Aging Response and Precipitation Behavior after 5% Pre-Deformation of an Al-Mg-Si-Cu Alloy

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1422 ◽  
Author(s):  
Shuoxun Jin ◽  
Tungwai Ngai ◽  
Liejun Li ◽  
Shian Jia ◽  
Tongguang Zhai ◽  
...  
Keyword(s):  
Yield Strength ◽  
Artificial Aging ◽  
Natural Aging ◽  
Negative Influence ◽  
Peak Hardness ◽  
Cu Alloy ◽  
Transmission Electron ◽  
Peak Aging ◽  
Peak Aged ◽  
Deformation Treatment

In this study, Al-1.00 Mg-0.65 Si-0.24 Cu alloy was solution heat-treated, water-quenched, and then pre-deformed for 5% before aging. The peak hardness and yield strength of the pre-deformed sample with subsequent artificial aging were similar to that of a T6 condition sample. It was also found that the pre-deformation treatment could inhibit the negative influence of natural aging to some degree. After seven days of natural aging, the pre-deformed sample obtained better peak hardness and yield strength upon artificial aging than the sample without pre-deformation. In addition, the pre-deformation treatment could reduce 50% of the artificial aging time to reach the peak aging condition compared with T6 treatment. For the peak aged condition in the pre-deformed sample, transmission electron microscopy (TEM) observation found two types of precipitates exhibited along the dislocations besides the β″ precipitates in the Al matrix. Both precipitates had disordered atomic arrangements on the ordered subcell (Si network). The disordered precipitates occupied a number of Mg and Si atoms, resulting in less β″ precipitates formed during artificial aging at 180 °C.

scholarly journals T4 and T6 Treatment of 6061 Al-15 Vol. % SiCP Composite

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
S. Rajasekaran ◽  
N. K. Udayashankar ◽  
Jagannath Nayak
Keyword(s):  
Room Temperature ◽  
Artificial Aging ◽  
Brinell Hardness ◽  
Natural Aging ◽  
Aging Treatment ◽  
Temperature History ◽  
Peak Hardness ◽  
Aging Behavior ◽  
Hardness Variation ◽  
Peak Aging

Aging temperature history has profound effect on the mechanical and corrosion behavior of 6061 Al/SiC composite. In order to understand the effect of aging on the corrosion resistance, the natural and artificial aging behavior of 15 vol. % 6061 Al-SiCP composites was studied using the aging treatment and the Brinell hardness measurements. The aging curves for the composite (T6 treated) were determined at various aging temperatures such as room temperature, 140, 160, 180, 200, 220, and 240°C. According to the peak hardness variation with temperature profile, it is found that the composite is underaged at 140°C and 160°C. Peak aging takes place at 180°C. Overaging takes place at 200°C, 220°C, and 240°C. The natural aging characteristics of the composite (T4 treated) are also studied using the Brinell hardness measurements.

HRTEM Observation of Precipitates at Early Stage of Aging in Mg-Gd-Zr Alloy

2007 ◽  
Vol 561-565 ◽  
pp. 303-306 ◽  
Author(s):  
Tokimasa Kawabata ◽  
Toshiyuki Matsuno ◽  
Kenji Matsuda ◽  
Shigeharu Kamado ◽  
Yo Kojima ◽  
...  
Keyword(s):  
Early Stage ◽  
Peak Hardness ◽  
Aged Specimen ◽  
Β Phase ◽  
Transmission Electron ◽  
Hrtem Observation ◽  
Peak Aging ◽  
Peak Aged ◽  
Aging Stage ◽  
Zr Alloy

High resolution transmission electron microscopy（HRTEM）observation was performed to clarify morphology of precipitates at early stage of aging in Mg-Gd-Zr alloy. In the specimen aged at 423K, monolayer was observed on {1100}Mg planes. With increasing aging time, the monolayer and β” phase grew along the <1120>Mg directions. Arrangement of bright dots corresponding to {020}β’ except for the monolayer and β” phase was observed before peak aging stage. β’ phases formed at the same aging stage. Thus, these precipitates co-existed before peak aging stage. The monolayer, β” phase and β’ phase still co-existed in the peak aged specimen. The β’ phase was dominated in the peak hardness. It is revealed that the monolayer lying on {1100}Mg act as precursor of β” phase and β’ phase.

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.

scholarly journals Effects of Mg Addition and Pre-Aging on the Age-Hardening Behavior in Al-Mg-Si

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1046 ◽  
Author(s):  
JaeHwang Kim ◽  
Jiwoo Im ◽  
Minyoung Song ◽  
Insu Kim
Keyword(s):  
Early Stage ◽  
Natural Aging ◽  
Age Hardening ◽  
Number Density ◽  
Hardening Behavior ◽  
Transmission Electron ◽  
Alloy Hardness ◽  
Peak Aged ◽  
Mg Addition ◽  
Cluster 2

Two types of nanoclusters, Cluster (1) and Cluster (2), formed at around room temperature and 100 °C, respectively, affect the age-hardening behavior in Al-Mg-Si alloys. Formation of Cluster (1) during natural aging (NA) is more accelerated in the high-Mg (9M10S) alloy than in the low-Mg (3M10S) alloy. Hardness at the early stage of two-step aging at 170 °C is not increased for the natural aging samples. On the other hand, hardness is directly increased for the pre-aged (PA) specimens. Furthermore, the formation of Cluster (1) during natural aging is suppressed by the formation of Cluster (2) during pre-aging at 100 °C. To understand the effects of heat treatment histories and Mg contents on the microstructure, transmission electron microscopy (TEM) was utilized. All the images were obtained at (001) plane, and peak aged samples with different heat treatments were used. Lower number density of precipitates is confirmed for the natural aging samples compared with the single-aged and pre-aged specimens. A higher number density of precipitates is confirmed for 9M10S in comparison to 3M10S. Hardness results correspond well to the TEM images.

Improvement of Stress Corrosion Cracking (SCC) Resistance of a 7150 Al-Zn-Mg-Cu Alloy by Retrogression and Reageing (RRA) Treatment

2014 ◽  
Vol 984-985 ◽  
pp. 529-535 ◽  
Author(s):  
Prasanta Kumar Rout ◽  
M.M. Ghosh ◽  
K.S. Ghosh
Keyword(s):  
Electron Microscope ◽  
Grain Boundary ◽  
Transmission Electron Microscope ◽  
Stress Corrosion Cracking ◽  
Peak Hardness ◽  
Slow Strain Rate Test ◽  
Cu Alloy ◽  
Transmission Electron ◽  
Crack Morphology ◽  
Rate Test

A 7150 Al-Zn-Mg-Cu alloy is artificially aged at 120 oC for varying time. The peak hardness (T6 temper) is obtained at about 24 h at that temperature. Further, the T6 temper is subjected to retrogression and reageing (RRA) treatment. Slow strain rate test (SSRT) has been carried out on the T6 and RRA tempers. SSRT results indicated that the RRA temper have higher resistance to SCC compared to that of T6 temper. SCC behaviour of the alloy tempers have been explained with the help of microstructural features studied by transmission electron microscope (TEM). The large, discrete and discontinuous grain boundary precipitates observed in the microstructure of the RRA temper are believed to be the responsible factor for achieving higher SCC resistance. Further, SEM fractographs and crack morphology have also been analyzed to evaluate the SCC behaviour of the alloy tempers.

Isochronal Aging Hardening of the Mg-8Gd-3Y-0.5Zr Alloy after Cold Rolling

2013 ◽  
Vol 747-748 ◽  
pp. 333-339
Author(s):  
Yan Cai Xie ◽  
De Jiang Li ◽  
Xiao Qin Zeng ◽  
Xin Su ◽  
Wen Jiang Ding ◽  
...  
Keyword(s):  
Cold Rolling ◽  
Heating Rate ◽  
Aging Process ◽  
Room Temperature ◽  
Peak Hardness ◽  
Heating Rates ◽  
Hardening Law ◽  
Transmission Electron ◽  
Peak Aging ◽  
Aging Hardening

By transmission electron microscopy (TEM) and optical microscopy (OM), the isochronal aging hardening law and microstructure have been studied for the Mg-8Gd-3Y-0.5Zr alloy after cold rolling. During isochronal aging process (heated from room temperature to 500 with the heating rate of 1/min), there are two peak hardness temperature points, which are corresponding to the large number of precipitation of β and β phases, and the peak aging time of the alloy substantially decreased with the increase of deformation reduction. The β phases started to precipitate at temperatures of 145, 134, 127 and 124 in the alloy after cold rolling with the reduction of 0%, 8%, 15% and 22%. The heating rate greatly affected the starting precipitation of metastable phases. β phases started to precipitate at temperatures of 109 and 124 with the reduction of 22% and with the heating rates of 3 /min and 30 /min.

scholarly journals Microstructure development during thermomechanical treatment of Al-Mg-Si alloy

2002 ◽  
Vol 38 (3-4) ◽  
pp. 153-162 ◽  
Author(s):  
Z. Martinova ◽  
G. Zlateva
Keyword(s):  
Electrical Conductivity ◽  
Thermomechanical Treatment ◽  
Artificial Aging ◽  
Cold Deformation ◽  
Natural Aging ◽  
Tensile Tests ◽  
Prolonged Storage ◽  
Recovery Processes ◽  
Transmission Electron ◽  
Lower Aging Temperature

The effect of natural aging and 95% cold deformation on the microstructure evolution and aging characteristics in commercial Al - 1 mass % Mg2Si alloy subjected to thermomechanical treatment (TMT) was examined. Transmission electron microscopy observations, tensile tests and electrical conductivity measurements were carried out in order to correlate microstructural features to properties on each TMT step. It was established that pre-aging at room temperature affected the morphology of dislocation structure induced by next cold deformation. The observed transition from cellular to homogenous dislocation distribution was explained by the different stability of zones produced by pre-aging of different duration. Natural aging suppressed recovery processes during post-deformation artificial aging, especially after prolonged storage after quenching and at lower aging temperature. It influenced the morphology of precipitates produced by post deformation artificial aging also. The overall effect of TMT involving prior-deformation natural aging in the scheme, on hardness, tensile properties and electrical conductivity is discussed based on experimental microstruture observations.

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).

scholarly journals Strengthening Al-Zn-Mg Alloys via Ultra-Fine Lamella Structures Containing a High Density of Dislocations and Clusters

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 140 ◽  
Author(s):  
Yonggui Qin ◽  
Sicong Lin ◽  
Shenbao Jin ◽  
Jizi Liu
Keyword(s):  
Electron Microscope ◽  
Yield Strength ◽  
High Density ◽  
Mechanical Processing ◽  
X Ray Diffraction ◽  
X Ray ◽  
Density Of Dislocations ◽  
Transmission Electron ◽  
Peak Aged ◽  
Fractographic Features

A new method of thermo-mechanical processing has been designed by introducing pre-aging before general cold rolling for an Al-Zn-Mg alloy. This process results in an increase of 200 MPa in yield strength compared to that of the peak-aged samples. The microstructures were examined by transmission electron microscope and X-ray diffraction. It has been found that the enhanced strength is mainly contributed to by ultra-fine lamella structures containing a high density of dislocations pinned by nanoprecipitates. Extra strength is provided by the “interlocking” of precipitates and dislocations. Fractographic features analysis shows that crack propagation along the interface of the lamella structures is the direct reason for resulting in fracture, due to intra-granular strength exceeding grain boundary cohesion.

Microstructural Evolution and Mechanical Properties of Powder Hot Extruded Al-Zn-Mg-Cu Alloy

2009 ◽  
Vol 79-82 ◽  
pp. 2015-2018 ◽  
Author(s):  
Shao Qing Wang ◽  
Hua Shun Yu ◽  
Zhen Ya Zhang ◽  
Guang Hui Min ◽  
Hui Yu
Keyword(s):  
Electron Microscopy ◽  
Compositional Analysis ◽  
Hot Extrusion ◽  
Major Constituent ◽  
Cu Alloy ◽  
Transmission Electron ◽  
Heat Treated ◽  
Peak Aging ◽  
Mean Size ◽  
Al Matrix

In this study, an ultrastrength Al-10Zn-3.2Mg-2.3Cu alloy was fabricated by powder hot extrusion technique. The microstructures of powder, extruded and subsequently heat treated rods were investigated by means of X-ray diffractometer (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS) for compositional analysis. During extrusion, more MgZn2 compounds were precipitated from the supersaturated Al matrix and observed on the grain boundaries and in the grain interiors. The microstructure of as-extruded alloy is composed of Al matrix and MgZn2 phases in different shapes. After solution treating, the MgZn2 phases were mostly dissolved into matrix and the major constituent are Al7Cu2Fe phase as well as oxides. The mean size of grains was controlled to 2.5μm, and the major precipitates were GP zones and/or η’(MgZn2) phases in the Al matrix after peak-aging (T6) treatment (120°C for 20h). The ultimate tensile strength (σb), yield strength (σ0.2) and elongation (δ) are 745Mpa, 690MPa and 9.0%, respectively.

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