scholarly journals Effect of retrogression and re-ageing heat treatment on microstructure and microhardness of aluminium 7010 alloy

2018 ◽  
Vol 144 ◽  
pp. 02003
Author(s):  
M. S. Nandana ◽  
K. Udaya Bhat ◽  
C. M. Manjunatha
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Microstructural Characterization ◽  
Treatment Results ◽  
Time Intervals ◽  
Optimum Time ◽  
Transmission Electron ◽  
The Matrix ◽  
Peak Aged ◽  
Resistance To Stress

Aluminium alloy 7010 is subjected to retrogression and re-ageing (RRA) heat treatment to study the influence of microstructural changes on hardness. Retrogression is performed at 190 °C for different time intervals ranging from 10 to 60 minutes. Optimum time for retrogression treatment is estimated based on the retrogression time that result with equivalent mechanical properties as that of peak aged (T6) condition. Retrogression performed for 30 minutes resulted with micro hardness of 203 HV, which is equivalent to that obtained by following T6 treatment. Microstructural characterization done with the help of transmission electron microscope (TEM) indicates RRA treatment results with the coarsened and discontinuous precipitates along the grain boundary which is similar to over aged (T7) condition, where as fine and densely populated precipitates in the matrix similar to T6 condition. Coarse and discontinuous grain boundary precipitates (GBP’s) improves resistance to stress corrosion cracking. Fine and dense precipitates in the matrix ensures hardness equivalent to that of T6.

Retrogression and Re-aging Heat Treatment: AA7XXX Aluminum Alloys

2019 ◽  
Author(s):  
V. Anil Kumar ◽  
S. Arjun ◽  
R.K. Gupta ◽  
P.V. Venkitakrishnan
Keyword(s):  
Heat Treatment ◽  
Aluminum Alloys ◽  
Industrial Applications ◽  
Age Hardening ◽  
Large Cross Section ◽  
Structural Applications ◽  
The Matrix ◽  
Peak Aged ◽  
Aged Temper ◽  
Short Time

Retrogression and re-aging (RRA) treatment was introduced to increase the stress corrosion cracking (SCC) resistance while retaining the strength attainable in T6 (peak aged) temper. Retrogression is a short-term heat treatment at an elevated temperature wherein a partial dissolution of metastable precipitates occurs, which are responsible for the hardening. During the next step, the material is re-aged in the regime of typical age hardening parameters to restore the strength with improved ductility. Response of RRA treatment has been reported on AA7XXX series Aluminum alloys such as AA7075, AA7050, AA7150, AA7049, and AA7010. Studies have been done on the effect of RRA on microstructure, mechanical properties such as tensile and hardness, corrosion, exfoliation corrosion, and SCC resistance by various researchers. The key characteristic of RRA is retrogression, which makes the re-precipitation in the matrix and coarsening of grain boundary precipitates such as MgZn2, η′. The retrogression treatment however requires high temperature and a short time, which limits the industrial application of RRA, especially in the heat treatment of the components with large cross section, due to the inherent thermal conductivity limitations. Hence, further work needs to be done in this area to apply this specialized heat treatment for industrial applications. This article brings out a comprehension of the changes in microstructure, tensile properties, and corrosion resistance of the various commonly used AA7XXX Aluminum alloys in structural applications with RRA heat treatment. The future scope of the work in RRA heat treatment is also discussed in this article.

Effect of Heat-Treatment Time on Microstructure and Mechanical Properties of Mg-5Gd-2Y-2Zn-0.5Zr Alloy

2012 ◽  
Vol 482-484 ◽  
pp. 1384-1389 ◽  
Author(s):  
Ling Gang Meng ◽  
Can Feng Fang ◽  
Peng Peng ◽  
Nai Pu Li ◽  
Qiong Zhu ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Treatment Time ◽  
Time Range ◽  
Lpso Phase ◽  
High Temperature Heat Treatment ◽  
Lpso Structure ◽  
The Matrix ◽  
New Type ◽  
The Stability

Microstructure evolution of Mg-5Gd-2Y-2Zn-0.5Zr alloy during high temperature heat-treatment at 500°C in the time range 10-70h was investigated. The results show that after adding the element Y, the as-cast Mg-5Gd-2Y-2Zn-0.5Zr alloy forms the Mg12Zn(Y,Gd) phase with 18R-LPSO structure at the grain boundary. During heat-treatment at 500°C, the stability of 18R-LPSO structure is weakened by Gd atoms, parts of LPSO phases dissolve gradually into the matrix with time prolonged and a new type Mg(Y,Gd)Zn phase come into being. LPSO phase in the grain boundary can ensure the ultimate tensile strength and elongation of the alloy, and effect of dissevering on the LPSO phase by Mg(Gd,Y)Zn phase results the decrease of UTS and elongation.

Effect of Two-Stage Aging on Microstructure and Properties of Al-Mg-Si Alloys

2022 ◽  
Vol 905 ◽  
pp. 51-55
Author(s):  
Li Wang ◽  
Ya Ya Zheng ◽  
Shi Hu Hu
Keyword(s):  
Growth Rate ◽  
Grain Boundary ◽  
Tensile Properties ◽  
Tensile Testing ◽  
Diffusion Rate ◽  
Two Stage ◽  
Precipitated Phase ◽  
Transmission Electron ◽  
The Matrix ◽  
Microstructure Characteristic

The effects of two-stage aging on the microstructures, tensile properties and intergranular corrosion (IGC) sensitivity of Al-Mg-Si alloys were studied by tensile testing and IGC experiments and transmission electron microscope (TEM). The results show that the two-stage aging (180°C, 2h+160°C, 120h) can reduce the IGC sensitivity without decrease the tensile properties. The grain is distributed with high-density β′′ phases, and the grain boundary phases are spherical and intermittently distributed. The formation of the microstructure characteristic is due to the lower re-aging temperature, which results in a decline differences in the diffusion rate between the matrix and grain boundaries. As a result, the pre-precipitated phase can maintain a better strengthening effects due to the slower growth rate. The pre-precipitated phase of the grain boundary presents a spherical and intermittent distribution due to the fast coarsening speed.

Microstructural Studies of High Coercivity Nd15Fe77B8 Sintered Magnets

1987 ◽  
Vol 96 ◽  
Author(s):  
M. H. Ghandehari ◽  
J. Fidler
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Transmission Electron Microscopy ◽  
Grain Boundary ◽  
Electron Microprobe ◽  
Boundary Phase ◽  
High Coercivity ◽  
Transmission Electron ◽  
Microstructural Studies ◽  
Domain Reversal

ABSTRACTMicrostructures of Nd15−xDyxFe77B8 prepared by alloying with Dy, and by using Dy2O3 as a sinl'ken adidive, have been determined using electron microprobe and transmission electron microscopy. The results have shown a higher Dy concentration near the grain boundaries of the 2–14–1 phase for magnets doped with Dy2O 3, as compared to the Dy-alloyed magnets. A two-step post sintering heat treatment was also studied for the two systems. The resultant concentration gradient of Dy in the 2–14–1 phase of the oxide-doped magnets is explained by the reaction of Dy2O3 with the Nd-rich grain boundary phase and its slow diffusion into thg 4–14–1 phase. Increased Dy concentration near the grain boundary is more effective in improving the coercivity, as domain reversal nucleation originates at or near this region.

Mechanical Stress, Grain-boundary Relaxation, and Oxidation of Sputtered CuNi(Mn) Films

1999 ◽  
Vol 14 (4) ◽  
pp. 1286-1294 ◽  
Author(s):  
W. Brückner ◽  
W. Pitschke ◽  
S. Baunack ◽  
J. Thomas
Keyword(s):  
Grain Boundary ◽  
Microstructural Characterization ◽  
Excess Vacancy ◽  
X Ray Diffraction ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Boundary Relaxation ◽  
20 Nm ◽  
Atomic Rearrangement

This paper focuses on understanding stress development in CuNi42Mn1 thin films during annealing in Ar. In addition to stress-temperature measurements, resistance-temperature investigations and chemical and microstructural characterization by Auger electron spectroscopy, scanning and transmission electron microscopy, x-ray diffraction, and atomic force microscopy were also carried out. The films are polycrystalline with a grain size of 20 nm up to 450 °C. To explain the stress evolution above 120 °C, atomic rearrangement (excess-vacancy annihilation, grain-boundary relaxation, and shrinkage of grain-boundary voids) and oxidation were considered. Grain-boundary relaxation was found to be the dominating process up to 250–300 °C. A sharp transition from compressive to tensile stress between 300 and 380 °C is explained by the formation of a NiO surface layer due to reaction with the remaining oxygen in the Ar atmosphere. This oxidation is masking the inherent structural relaxation above 300 °C.

Effect of Heat Treatment on Fracture during Bending in AA6016 Aluminium Alloy Sheets

2011 ◽  
Vol 488-489 ◽  
pp. 521-524
Author(s):  
Aleksandar Davidkov ◽  
Roumen H. Petrov ◽  
Peter De Smet ◽  
Leo Kestens
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Volume Fraction ◽  
Boundary Structure ◽  
Homogeneous Distribution ◽  
Fracture Mechanisms ◽  
Al Alloy ◽  
Technological Parameters ◽  
The Matrix ◽  
Strengthening Phases

The bending properties of high strength precipitation-hardening AA6016-type Al alloy thin sheets in pre-aged T4P temper state were studied in this work. Microstructural features like grain boundary particles distribution and volume fraction of the matrix strengthening phases were considered as factors controlling the mechanical properties and the fracture of this grade. Remarkable decrease in ductility, accompanied by severe deterioration of bendability occurred when coarse precipitates were found into the grain boundaries. The in-situ fracture sequence investigations as well as the post-failure surfaces observations indicated that grain boundary ductile fracture mechanisms were involved in the propagation of the cracks during bending. Heat treatment simulations were carried out and the results showed that the precise control of the technological parameters during production of these sheets is the key factor responsible for obtaining an appropriate combination of strength and bendability. Only by providing both, homogeneous distribution of the matrix strengthening phases and a favourable grain boundary structure, the severe and often contradictory requirements for the functional properties of these alloys can be successfully satisfied.

Aging and Precipitation Behavior in Supersaturated Al-2%Fe Alloy Produced by High-Pressure Torsion

2014 ◽  
Vol 794-796 ◽  
pp. 766-771 ◽  
Author(s):  
Jorge M. Cubero-Sesin ◽  
Masashi Watanabe ◽  
Makoto Arita ◽  
Zen Ji Horita
Keyword(s):  
High Pressure ◽  
High Pressure Torsion ◽  
Xrd Analysis ◽  
Aged Condition ◽  
Subsequent Aging ◽  
Transmission Electron ◽  
Fe Content ◽  
Average Grain Size ◽  
The Matrix ◽  
Peak Aged

The aging behavior of a cast Al-2 wt.% Fe alloy processed by High-Pressure Torsion (HPT) at room temperature was studied by subsequent aging treatments at 200 °C. Observations by Transmission Electron Microscopy (TEM) revealed that the microstructure after HPT processing reached an ultrafine-grained level with an average grain size in the Al matrix of ~120 nm. The initial eutectic structures were fragmented into particles with sizes of less than 400 nm and partially dissolved in the matrix up to a supersaturated Fe content of ~1% as confirmed by X-Ray Diffraction (XRD) analysis. The peak-age condition was achieved within 0.25 h of aging, which provides the maximum hardness of ~200 HV. Analyses by high-resolution S/TEM show that round particles of Al6Fe with sizes of ~5-10 nm and semi-coherent with the matrix are the dominant precipitates in the peak-aged condition. The hardness increases by aging for 12 h above the as-HPT-processed level of 185 HV. The dominant precipitate phase transforms to Al3Fe in the over-aged condition with a loss of coherency during growth. Enhanced precipitation kinetics was observed because of high density of lattice defects induced by the HPT processing, which were also confirmed by significant recovery in the electrical conductivity of the samples after aging.

Laves Phase Formation in the Fe20Co18W Alloy Annealed at 800°C

2011 ◽  
Vol 172-174 ◽  
pp. 517-522 ◽  
Author(s):  
Paolo Galimberti ◽  
Sabine Lay ◽  
Annie Antoni-Zdziobek
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Transmission Electron Microscopy ◽  
Orientation Relationship ◽  
Phase Formation ◽  
Laves Phase ◽  
Transmission Electron ◽  
Precipitation Behaviour ◽  
The Matrix

The precipitation behaviour of the Fe20Co18W (wt%) alloy was studied by transmission electron microscopy during aging treatments at 800°C. The decomposition of the matrix produces the C14 phase. At the beginning of the heat treatment, the observation at the atom scale indicates that the structure of the precipitates does not coincide exactly with the Laves phase. Using the orientation relationship between the Fe based matrix and the precipitates it is shown that simple atomic shifts can lead to the transformation from the bcc matrix to the C14 Laves phase.

Development of Mechanical Stress in Cuni(mn) Films During Temperature Ramping: Related Mechanisms

1997 ◽  
Vol 505 ◽  
Author(s):  
W. Brückner ◽  
St. Baunack ◽  
W. Pitschke ◽  
J. Thomas
Keyword(s):  
Grain Boundary ◽  
Microstructural Characterization ◽  
Biaxial Stress ◽  
Stress Evolution ◽  
X Ray Diffraction ◽  
Sharp Transition ◽  
X Ray ◽  
Transmission Electron ◽  
Boundary Relaxation ◽  
Atomic Rearrangement

ABSTRACTThis paper focusses on the development of biaxial stress in Cu0.57Nio.42Mno.ol thin films during annealing in Ar and, for comparison, in vacuum. Besides stress-temperature measurements also resistance-temperature investigations as well as chemical and microstructural characterization by Auger electron spectroscopy, scanning and transmission electron microscopy, and X-ray diffraction were carried out. To explain the stress evolution, atomic rearrangement (excessvacancy annihilation, grain-boundary relaxation, and shrinkage of grain-boundary voids) and oxidation were considered. Up to 250 - 300 °C grain-boundary relaxation was found to be the dominating process. A sharp transition from compressive to tensile stress between 300 °C and 380 °C is explained by the formation of a NiO surface layer

Grain Boundary Transformations in Bi-Doped Copper

1991 ◽  
Vol 238 ◽  
Author(s):  
Elsie C. Urdaneta ◽  
David E. Luzzi ◽  
Charles J. McMahon
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Treatment Time ◽  
High Resolution Electron Microscopy ◽  
Transmission Electron ◽  
Resolution Electron

ABSTRACTBismuth-induced grain boundary faceting in Cu-12 at ppm Bi polycrystals was studied using transmission electron microscopy (TEM). The population of faceted grain boundaries in samples aged at 600°C was observed to increase with heat treatment time from 15min to 24h; aging for 72h resulted in de-faceting, presumably due to loss of Bi from the specimen. The majority of completely faceted boundaries were found between grains with misorientation Σ=3. About 65% of the facets of these boundaries were found to lie parallel to crystal plane pairs of the type {111}1/{111]2- The significance of these findings in light of recent high resolution electron microscopy experiments is discussed.

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