Microstructural Evolution of 7050 Aluminum Alloy Semisolid Billets Fabricated by RAP Process

2014 ◽  
Vol 217-218 ◽  
pp. 29-36 ◽  
Author(s):  
Ju Fu Jiang ◽  
Zhi Ming Du ◽  
Ying Wang ◽  
Shou Jing Luo
Keyword(s):  
Aluminum Alloy ◽  
Microstructural Evolution ◽  
Ostwald Ripening ◽  
Soaking Time ◽  
Isothermal Temperature ◽  
7050 Aluminum Alloy ◽  
Average Grain Size ◽  
Different Temperatures ◽  
Equiaxed Grains ◽  
Grain Coalescence

In the present study, 7050 supplied in extruded state was heated to different temperatures below solidus or the semisolid state and microstructural evolution and coarsening were investigated. The results showed that complete recrystallisation only occurs after soaking for 5 minutes at 545°C, which is characterised by formation of a lot of fine equiaxed grains. RAP is suitable for fabricating high-quality semisolid billet of 7050 aluminum alloy with an average grain size ranging from 47.4 um to 70.5 um and a roundness ranging from 1.3 to 1.7. Grain growth occurs as the samples were soaked at 610°C and 615°Cfor prolonged soaking time. When the isothermal temperatures were 610°C and 615°C, the coarsening rate constants were 359.5μm3s-1 and 470.5μm3s-1, respectively, indicating an increase of coarsening rate constant (K) with the increasing isothermal temperature. Coarsening tends to occur via Ostwald ripening and coalescence. Ostwald ripening plays an important role during the whole coarsening process, but the grain coalescence only contributes to coarsening after soaking for 12 minutes. 625°C is an optimal temperature to keep cylinder shape of the sample due to collapse of the sample above this temperature, leading to difficult clamping.

Microstructure Evolution and Coarsening Mechanism of 7075 Semi-Solid Aluminum Alloy Pre-Deformed by ECAP Method

2016 ◽  
Vol 256 ◽  
pp. 294-300 ◽  
Author(s):  
Jin Long Fu ◽  
Yu Wei Wang ◽  
Kai Kun Wang ◽  
Xiao Wei Li
Keyword(s):  
Aluminum Alloy ◽  
Solid State ◽  
Ostwald Ripening ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
Angular Pressing ◽  
Average Grain Size ◽  
Semi Solid ◽  
Equiaxed Grains ◽  
Kinetics Of

To investigate the influence of refined grains on the microstructure of 7075 aluminum alloy in semi-solid state, a new strain induced melting activation (SIMA) method was put forward containing two main stages: pre-deformation with equal channel angular pressing (ECAP) method and isothermally holding in the semi-solid temperature range. The breaking up and growth mechanisms of the grains and kinetics of equiaxed grains coarsening during the semi-solid holding were investigated. The results showed that the average grain size after ECAP extrusion decreased significantly, e.g., microstructure with average globular diameter less than 5μm was achieved after four-pass ECAP extrusion. Obvious grain coarsening had been found during isothermal holding in the semi-solid state and the roundness of the grains increased with the increasing holding time. The proper microstructure of 66.8μm in diameter and 1.22 in shape factor was obtained under proper soaking condition (at 590°C for 15 min). Two coarsening mechanisms, namely, coalescence in lower liquid fraction and Ostwald ripening in higher liquid fraction contributed to the grain growth process.

scholarly journals Aging Behavior of Aluminum Alloy 6082 Subjected to Friction Stir Processing

Crystals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 337 ◽  
Author(s):  
Khaled Al-Fadhalah ◽  
Fahad Asi
Keyword(s):  
Grain Size ◽  
Aluminum Alloy ◽  
Aging Time ◽  
Friction Stir Processing ◽  
Aging Temperature ◽  
Friction Stir ◽  
Average Grain Size ◽  
Different Temperatures ◽  
Equiaxed Grains ◽  
Electron Back Scattered Diffraction

The present work examined the effect of artificial aging on the microstructure, texture, and hardness homogeneity in aluminum alloy AA6082 subjected to friction stir processing (FSP). Aging was applied to FSP samples at three different temperatures (150 °C, 175 °C, and 200 °C) for a period of 1 h, 6 h, and 12 h. Microstructure analysis using optical Microscopy (OM) and Electron Back-Scattered Diffraction (EBSD) indicated that FSP produced fine equiaxed grains, with an average grain size of 6.5 μm, in the stir zone (SZ) due to dynamic recrystallization. Aging was shown to result in additional grain refinement in the SZ due to the occurrence of recovery and recrystallization with either increasing aging temperature and/or aging time. An optimum average grain size of 3–4 μm was obtained in the SZ by applying aging at 175 °C. This was accompanied by an increase in the fraction of high-angle grain boundaries. FSP provided a simple shear texture with a major component of B fiber. Increasing aging temperature and/or time resulted in the formation of recrystallization texture of a Cube orientation. In addition, Vickers microhardness was evaluated for the FSP sample, indicating a softening in the SZ due to the dissolution of the hardening precipitates. Compared to other aging temperatures, aging at 175 °C resulted in maximum hardness recovery (90 Hv) to the initial value of base metal (92.5 Hv). The hardness recovery is most likely attributed to the uniform distribution of fine hardening precipitates in the SZ when increasing the aging time to 12 h.

Microstructural Evolution and Mechanical Properties of Ultrafine Grained Commercially Pure 1100 Aluminum Alloy Processed by Accumulative Roll-Bonding (ARB)

2004 ◽  
Vol 449-452 ◽  
pp. 625-628 ◽  
Author(s):  
Yong Suk Kim ◽  
T.O. Lee ◽  
Dong Hyuk Shin
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloy ◽  
Microstructural Evolution ◽  
Sliding Wear ◽  
Al Alloy ◽  
Commercially Pure ◽  
Transmission Electron ◽  
Ultrafine Grained ◽  
Average Grain Size ◽  
Accumulated Strain

The ARB process has been carried out up to seven cycles on a commercial purity 1100 aluminum alloy to obtain ultra-fine grains with the average grain size of 500 nm. Microstructural evolution of the ARB processed aluminum alloy was examined by a transmission electron microscopy as a function of accumulated total strain. Mechanical properties including hardness, tensile property, and sliding wear characteristics of the severely deformed Al alloy were also investigated. Grain boundaries of the ARB processed alloy were diffusive and poorly defined after the initial ARB cycles, however they changed to well-defined high angle boundaries with the increase of the accumulated strain. Though hardness and strength of the ARB processed alloy were enhanced significantly, wear resistance of the processed alloy hardly increased. The mechanical properties were discussed in connection with the microstructure.

Softening Behavior of Ti6Al4V Alloy during Hot Deformation

2015 ◽  
Vol 828-829 ◽  
pp. 407-412 ◽  
Author(s):  
Paul Micheal Souza ◽  
Hossein Beladi ◽  
Bernard Rolfe ◽  
Rajkumar Singh ◽  
Peter D. Hodgson
Keyword(s):  
Strain Rate ◽  
Microstructural Evolution ◽  
Volume Fraction ◽  
Softening Behavior ◽  
Strain And Strain Rate ◽  
Measured Activation Energy ◽  
Average Grain Size ◽  
Measured Activation ◽  
Equiaxed Grains ◽  
Good Agreement

The effect of strain rate and strain on the hot compression behaviour of Ti6Al4V has been analysed to understand the microstructural evolution and restoration behaviour. Cylindrical samples with partially equiaxed grains were deformed in the α+β region at different thermo-mechanical conditions. EBSD has been used to study the microstructural behaviour and the restoration mechanisms. The microstructural evolution showed a complex restoration behaviour, where both fragmentation and nucleation of new grains have been observed. The volume fraction of the equiaxed grains increased with an increase in the strain, but oppositely decreased with the strain rate. At the same time the average grain size of the equiaxed grains decreased with an increase in both the strain and strain rate. The measured activation energy for deformation revealed a good agreement with reported values in the literature.

Study on Microstructures and Components Uniformity of 7050 Aluminum Alloy with Annulus Electromagnetic Stirring Casting

2016 ◽  
Vol 850 ◽  
pp. 716-721
Author(s):  
Ya Bao Wang ◽  
Zhen Lin Zhang ◽  
Bao Li ◽  
Zhi Hua Gao ◽  
Zhi Feng Zhang ◽  
...  
Keyword(s):  
Grain Size ◽  
Aluminum Alloy ◽  
Shape Factor ◽  
Grain Shape ◽  
Chemical Component ◽  
Electromagnetic Stirring ◽  
High Chemical ◽  
Globular Structure ◽  
7050 Aluminum Alloy ◽  
Average Grain Size

7050aluminum alloy billets processed by semi-continuous casting were studied using conventional casting (N-EMS), conventional electromagnetic stirring casting (EMS) and annulus electromagnetic stirring casting (AEMS), respectively. Adopting the method of mathematical statistics, Zn, Mg, Cu chemical component uniformity and the microstructure of 7050 aluminum alloy billets were analyzed. The results showed that the high chemical component uniformity of the AEMS billets were obtained compared with N-EMS and EMS. The Zn, Mg, Cu element component variance was reduced 26% compared with EMS. And the A-EMS process exhibited superior grain refinement and remarkable structure homogeneity, which mainly consisted of rosaceous and nearly globular structure. The average grain size for AEMS sample was 42μm, and the grain shape factor was about 0.68.

Numerical Simulations of Microstructural Evolution of Lamellar Alloys: Applications to Pb-Sn Solder

2002 ◽  
Vol 731 ◽  
Author(s):  
Rifa J. El-Khozondar ◽  
Vitcheslav S. Solomatov ◽  
Veena Tikare
Keyword(s):  
Microstructural Evolution ◽  
Lamellar Structure ◽  
Ostwald Ripening ◽  
Morphological Changes ◽  
Lamellar Spacing ◽  
Eutectic System ◽  
Initial Structure ◽  
Lamellar Structures ◽  
Power Law Function ◽  
Equiaxed Grains

AbstractUnderstanding the morphological changes of Pb-Sn solder alloys helps to improve their performance in electronic applications. The focus of our study is degeneration of lamellar structures at high temperatures. Microstructural evolution of the Pb-Sn eutectic lamellar structure is modeled numerically using Monte Carlo Potts approach. The initial structure consists of alternating layers of Pb-rich and Sn-rich phases, simulating the lamellar array in a near eutectic system. Faults are introduced to destabilize the system. After a short incubation period the shape of lamellae become irregular. The perturbations grow with time and eventually break the lamellae into nearly equiaxed grains. The grain size of the degenerated structure is 2-3 times the original lamellar spacing weakly depending on the spacing between the faults. This is consistent with the experimental observation of degeneration of Pb-62 wt% Sn solder. The duration of degeneration processes is comparable with the time it would take Ostwald ripening to produce grains of the same size. Eventually grain growth reaches the asymptotic regime of coarsening described by a power-law function of time.

Remelting Technology and Microstructural Evolution of Semi-Solid Al-7Si-2RE Alloy

2010 ◽  
Vol 33 ◽  
pp. 1-5
Author(s):  
Shi Kun Xie ◽  
Rong Xi Yi ◽  
Xiu Yan Guo ◽  
Xiao Liang Pan ◽  
Xiao Qiu Zheng
Keyword(s):  
Aluminum Alloy ◽  
Microstructural Evolution ◽  
Temperature Control ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
Control Program ◽  
Holding Time ◽  
Α Phase ◽  
Semi Solid ◽  
Equiaxed Grains

In semi-solid remelting process, the various stages of reheating temperature and isothermal holding time must be accurately controlled in order to obtain the uniformly distributed and small equiaxed grains microstructure. In this paper, a temperature control program was developed and the remelting process for Al-7Si-2RE aluminum alloy was carried out. The results showed that with the raise of reheating temperature and the extension of isothermal holding time, the liquid fraction increases, α-phase grain grows and becomes rounding in the process of Al-7Si-2RE alloy semi-solid remelting. The most reasonable process parameter of reheating temperature is at 585~590°C and its appropriate isothermal holding time are about 10~15min for the semi-solid Al-7Si-2RE alloy.

Microstructural Evolution of ZL104 Aluminum Alloy Semi-Solid Billet Fabricated by RAP Process

2019 ◽  
Vol 285 ◽  
pp. 234-239
Author(s):  
Yong Fei Wang ◽  
Sheng Dun Zhao ◽  
Chao Chen ◽  
Peng Dong ◽  
Peng Zhang
Keyword(s):  
Aluminum Alloy ◽  
Ostwald Ripening ◽  
Isothermal Holding ◽  
Isothermal Treatment ◽  
Liquid Droplets ◽  
Microstructural Coarsening ◽  
Average Grain Size ◽  
Cold Rolled ◽  
Semi Solid ◽  
Holding Temperature

In this study, ZL104 aluminum alloy supplied in cold rolled state was introduced in recrystallization and partial melting (RAP) process to fabricate semi-solid billets. During the RAP process, samples cut from cold rolled ZL104 aluminum plate were heated to different semi-solid temperatures, and the effects of isothermal treatment parameters on the microstructures of semi-solid billets were investigated. Results showed that, with the increase of isothermal holding temperature and time, both the average grain size and the shape factor were increased. Namely, the shape of solid grain was more and more spherical, but the size of solid grain was larger and larger, which may be not suitable for semi-solid forming. The size of liquid droplets was increased while the number of liquid droplets was decreased with increasing the isothermal holding temperature and time. Microstructural coarsening of solid grain were attributed to coalescence and Ostwald ripening mechanisms, however, the latter one played a more and more important role with the increase of isothermal holding time and temperature. Additionally, The optimal isothermal holding temperature and time are 570 °C and 5 min, respectively, and the coarsening rate constant is 1357.2 μm3/s at 570 °C.

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