Download or read book Rheological Behavior and Microstructural Evolution of Semi solid Hypereutectic Al Si Mg Cu Alloys Using Rheoforming Process written by Mehand Tebib and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Semi Solid Processing of Alloys and Composites written by Shahrooz Nafisi and published by MDPI. This book was released on 2020-06-18 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semi-solid metal (SSM) processing, as a viable alternative manufacturing route to those of conventional casting and forging, has not yet been fully exploited despite nearly half a century since its introduction to the metal industry. The slow pace of adopting SSM routes may be due to various reasons, including capital costs, profit margins, and, most importantly, the lack of detailed analysis of various SSM processes in open literature to confidently establish their advantages over more conventional routes. Therefore, the SSM community must disseminate their findings more effectively to generate increased confidence in SSM processes in the eyes of our industrial leaders. As such, we have embarked on the task to invite the leaders in SSM research to share their findings in a Special Issue dedicated to semi-solid processing of metals and composites. SSM processing takes advantage of both forming and shaping characteristics usually employed for liquid and solid materials. In the absence of shear forces, the semi-solid metal has similar characteristics to solids, i.e., easily transferred and shaped; by applying a defined force, the viscosity is reduced and the material flows like a liquid. These unique dual characteristics have made SSM routes attractive alternatives to conventional casting on an industrial scale. With the intention of taking full advantage of SSM characteristics, it is crucial to understand SSM processing, including topics such as solidification and structural evolution, flow behavior through modelling and rheology, new processes and process control, alloy development, and properties in general. This Special Issue focuses on the recent research and findings in the field with the aim of filling the gap between industry and academia, and to shed light on some of the fundamentals of science and technology of semi-solid processing.

Download or read book Quantitative Characterization of Microstructural Evolution During Solidification and Ageing of Al Mg Si Alloys with Cu Additions written by Kai Li and published by . This book was released on 2014 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book High Temperature Deformation Behaviour of an Al Mg Si Cu Alloy and Its Relation to the Microstructural Characteristics written by Roger Nicol Carrick and published by . This book was released on 2009 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: The microstructural evolution and mechanical properties at elevated temperatures of a recently fabricated fine-grained AA6xxx aluminium sheet were evaluated and compared to the commercially fabricated sheet of the same alloy in the T4P condition. The behaviour of the fine-grained and T4P sheets was compared at elevated temperatures between 350°C and 550°C, as well as room temperature. Static exposure to elevated temperatures revealed that the precipitate structure of the fine-grained material did not change extensively. The T4P material, however, underwent extensive growth of precipitates, including a large amount of grain boundary precipitation. At room temperature, the T4P material deformed at much higher stresses than the FG material, but achieved lower elongations. Deformation at elevated temperatures revealed that the fine-grained material achieved significantly larger elongations to failure than the T4P material in the temperature range of 350°C-450°C. Both materials behaved similarly at 500°C and 550°C. Above 500°C, the grain size was greatly reduced in the T4P material, and only a slightly increased in the fine-grained material. At temperatures above 450°C, the elongation to failure in both materials generally increased with increasing strain-rate. The poor performance of the T4P material at low temperatures was attributed to the precipitate characteristics of the sheet, which lead to elevated stresses and increased cavitation. The deformation mechanism of both materials was found to be controlled by dislocation climb, accommodated by the self diffusion of aluminium at 500°C and 550°C. The deformation mechanism in the fine-grained material transitioned to power law breakdown at lower temperatures. At 350°C to 450°C, the T4P material behaved similarly to a particle hardened material with an internal stress created by the precipitates. The reduction in grain size of the T4P material after deformation at 500°C and 550°C was suggested to be caused by dynamic recovery/recrystallization. The role of a finer grain-size in the deformation behaviour at elevated temperatures was mainly related to enhanced diffusion through grain boundaries. The differences in the behaviour of the two materials were mainly attributed to the difference in the precipitation characteristics of the materials.

Download or read book Microstructure Evolution and Stress Corrosion Cracking Behavior in Short term Thermomechanically Processed Al Cu Li Alloys written by Jannik Entringer and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Increasing access to space leaves human footprints in orbits closer to the Earth. Today, space debris poses a major risk for in-service missions and on-ground casualties. Reducing the amount of debris is the only way to preserve key orbits. One strategy to avoid future debris is to maneuver spacecraft after mission into the atmosphere where the structure burns up. This strategy is taken into account at early design stages of modern spacecraft. Therefore, material choices must be made to ensure high structural demisability. Titanium, currently used in propellant tanks, is often a large portion, by mass, of the total structure and does not completely ablate during re-entry. Aluminum-copper-lithium alloys are being considered as a substitute for titanium in propellant tanks because they deliver comparable specific material properties at a higher demisability rate. Because the technology of aluminum-copper-lithium alloys in space structures is not as mature as that of titanium, new joining methods must be developed. Friction stir welding features the unique characteristic of joining in the solid state; thus, it is especially attractive for hard-to-weld alloys such as aluminum-copper-lithium. The development of space structures requires a fundamental knowledge of the material behavior, both during processing and during the subsequent exposure to the environment. In recent years, aluminum copper-lithium alloys have rarely been welded by bobbin tool friction stir welding. The underlying microstructure evolution has been described as complex, certain aspects are not fully understood and contradictory results have been reported. Current knowledge on the behavior of welded joints on this specific alloy under stress and exposed to corrosive environments is limited. Therefore, for the possible use in spacecraft structures, a scientific analysis of the stress corrosion behavior of welded joints is necessary. As part of the present work, two modern aluminum-copper lithium alloys were successfully joined by semi-stationary bobbin tool friction stir welding. Identical parameters allowed a detailed comparison of the process response. The welding process imposes a short time, thermomechanical exposure in the base material that leads to severe microstructure modification. Based on the chemical composition of the two alloys, the microstructural evolution is explained, and a precipitation sequence is proposed. Overaged strengthening precipitates and equilibrium phases of several types were identified to form during welding. These modifications led to a reduced mechanical performance of 78 % of the ultimate tensile strength. Stress corrosion analyses were performed on pre-, as- and post-welded samples and were correlated with the modified microstructure. Stress corrosion cracking phenomena were found to result from the short-time, thermomechanical effect induced by the welding process. The mechanism leading to stress corrosion lies in the modified microstructure, where coarse, precipitates accumulate at the grain boundaries. These particles are observed to promote local galvanic reactions, which promote dissolution and the consequent development of a cracking network under stress.

Download or read book Development of Al Si Mg Alloys for Semi solid Processing and Silicon Spheroidization Treatment SST for Al Si Cast Alloys written by Erhard Ogris and published by . This book was released on 2002 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Microstructural Evolution During Aging of an Al Cu Li Ag Mg Zr Alloy written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-08-20 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: Alloys in the Al-Cu-Li Ag-Mg subsystem were developed that exhibit desirable combinations of strength and ductility. These Weldalite (trademark) alloys, are unique for Al-Cu-Li alloys in that with or without a prior cold stretching operation, they obtain excellent strength-ductility combinations upon natural and artificial aging. This is significant because it enables complex, near-net shape products such as forgings and super plastically formed parts to be heat treated to ultra-high strengths. On the other hand, commercial extrusions, rolled plates and sheets of other Al-Cu-Li alloys are typically subjected to a cold stretching operation before artificial aging to the highest strength tempers to introduce dislocations that provide low-energy nucleation sites for strengthening precipitates such as the T(sub 1) phase. The variation in yield strength (YS) with Li content in the near-peak aged condition for these Weldalite (trademark) alloys and the associated microstructures were examined, and the results are discussed. Kumar, K. S. and Brown, S. A. and Pickens, Joseph R. Unspecified Center ...

Download or read book Microstructural Evolution and Strengthening Mechanisms in Al Sc and Al Mg Sc Alloys written by Emmanuelle A. Marquis and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Examination of Microstructure Development in Al Si and Al Cu Alloys microform written by Nurhan Apaydin and published by National Library of Canada. This book was released on 1989 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Microstructural Evolution of an Al Cu Zr Si Alloy During Concurrent Straining and Annealing written by Douglas Brooks and published by . This book was released on 1991 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Microstructural Evolution of Al Cu Zr Alloys During Thermochemical Processing written by E. M. Cullen and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Microstructural Evolution of Al Cu Zr Alloys During Thermomechanical Processing written by Elaine M. Cullen and published by . This book was released on 1996 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Solidification Growth Mechanisms and Associated Properties of Al Si and Magnesium Lightweight Casting Alloys written by and published by . This book was released on 2010 with total page 315 pages. Available in PDF, EPUB and Kindle. Book excerpt: Continually rising energy prices have inspired increased interest in weight reduction in the automotive and aerospace industries, opening the door for the widespread use and development of lightweight structural materials. Chief among these materials are cast Al-Si and magnesium-based alloys. Utilization of Al-Si alloys depends on obtaining a modified fibrous microstructure in lieu of the intrinsic flake structure, a process which is incompletely understood. The local solidification conditions, mechanisms, and tensile properties associated with the flake to fiber growth mode transition in Al-Si eutectic alloys are investigated here using bridgman type gradient-zone directional solidification. Resulting microstructures are examined through quantitative image analysis of two-dimensional sections and observation of deep-etched sections showing three-dimensional microstructural features. The transition was found to occur in two stages: an initial stage dominated by in-plane plate breakup and rod formation within the plane of the plate, and a second stage where the onset of out-of-plane silicon rod growth leads to the formation of an irregular fibrous structure. Several microstructural parameters were investigated in an attempt to quantify this transition, and it was found that the particle aspect ratio is effective in objectively identifying the onset and completion velocity of the flake to fiber transition. The appearance of intricate out-of-plane silicon instability formations was investigated by adapting a perturbed-interface stability analysis to the Al-Si system. Measurements of silicon equilibrium shape particles provided an estimate of the anisotropy of the solid Si/liquid Al-Si system and incorporation of this silicon anisotropy into the model was found to improve prediction of the instability length scale. Magnesium alloys share many of the benefits of Al-Si alloys, with the added benefit of a 1/3 lower density and increased machinability. Magnesium castings often contain additions of heavier elements, such as zinc, zirconium, and rare earth elements, which significantly improve high temperature performance. However, additions of these elements can lead to macrosegregational effects in castings, which are detectable by radiographic scans. The effect of these flow-line indications on alloy mechanical properties is not well quantified. An examination of these flow-line indications and their effects on mechanical properties in three magnesium-based casting alloys was performed here in order to determine the best practice for dealing with affected castings. Preliminary results suggest the flow-lines do not measurably impact bulk material properties. Three additional methods of characterizing three-dimensional material structures are also presented: a minimum spanning tree analysis is utilized to quantify local structure in Cu-Zr liquid phase simulations obtained from molecular dynamics; the radial distribution function is applied to directionally solidified Al-Si structures in an attempt to extract local spacing data; and the critical diameter measurement is also defined and applied to irregular eutectic Al-Si structures.

Download or read book Effect of Composition in As Cast and Homogenized Al Si Cu Alloys written by Ashrafi Ehsan Ahmed and published by LAP Lambert Academic Publishing. This book was released on 2014-08-04 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aluminium alloys with a wide range of properties are used in engineering structures. These properties can be largely modified by changing the alloy composition and by cold working. Si, Cu, Zn and Mg are the most commonly used alloying elements in aluminium, which have sufficient solid solubility. The as-cast microstructure of cast aluminium alloys normally displays significant segregation and supersaturation. For this, homogenization of aluminium alloys is often done to improve workability and mechanical properties. This book is based on the research about influence of Cu content, cold working and homogenization in Al-Si alloys. The effects were analysed using microstructure study, phase-property modelling, image analysis and hardness measurement. This work should help researchers and metallurgists who are working on modification of alloy properties. Also it will help students who have keen interest in study of microstructure, modelling and image analysis.

Download or read book Optimisation of the Heat Treatment Cycles of CSIR Semi solid Metal Processed Al 7Si Mg Alloys A356 7 written by Heinrich Moller and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Conventional casting alloys Al-7Si-Mg A356/7 contain between 6.5 and 7.5% Si, together with 0.25-0.7% Mg and are used for critical castings in the automotive and aerospace industries. These alloys are also the most popular alloys used for semi-solid metal (SSM) forming due to good castability and fluidity imparted by the large volumes of the Al-Si eutectic. Despite their industrial importance, there is a lack of detailed research work revealing precipitate micro- and nanostructural evolution during aging of these alloys compared with the Al-Mg-Si 6000 series wrought alloys. This study characterises the heat treatment response of SSM-processed Al-7Si-Mg alloys in comparison with conventionally liquid cast alloys (investment casting and gravity die casting). It is shown that, provided that the maximum quantity of the alloy's Mg is placed into solid solution during solution treatment, and that the alloy's Fe content is within specification, the response to age hardening of Al-7Si-Mg alloys is independent of the processing technique used. The nanostructural evolution of Al- 7Si-Mg alloys after artificial aging with and without natural pre-aging has been characterized using transmission electron microscopy and atom probe tomography and correlated with hardness and mechanical tensile properties. The number densities and Mg:Si ratios of solute clusters, GP zones and ;?-needles were determined. The heat treatment response of SSM-processed casting alloys A356/7 alloys are also compared with SSM-processed Al-Mg-Si 6000 series wrought alloys, with the advantage of having similar globular microstructures. The high Si-content of the casting alloys compared to the wrought alloys offers several advantages, including a faster artificial aging response (shorter T6 aging cycles), higher strength for comparable Mg contents and less sensitivity to prior natural aging on peak strength. Finally, an age-hardening model was developed for the Al-7Si-Mg alloys, including a method of incorporating the effects of changes in Mg-content on the aging curves.

Download or read book Euromat 99 Microstructures Mechanical Properties and Processes written by Yves Bréchet and published by John Wiley & Sons. This book was released on 2000-07-13 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: The relation between microstructures and mechanical properties has always been a challenge for materials science. Modelling the formation, properties and long term stability of microstructures is one of the most impressive and promising advances of modern materials science. This book presents recent advances and challenges in this fast evolving cross disciplinary field. It addresses applications of classical physical metallurgy, and the need for new modelling approaches, both on the analytical viewpoint and on the simulation side.

Download or read book The Influence of Sc and Zr Additions on the Microstructure and Mechanical Behavior of Ultrafine Grained Al Mg Alloys Processed by Powder Metallurgy written by Tammy Jeanne Harrell and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Additions of Sc and Zr to an Al-Mg matrix were investigated, paying particular attention to the influence of Al3Sc precipitates and other dispersoids, as well as grain size, on mechanical behavior. Prior studies have shown that Sc and Zr significantly increase the strength of coarse-grained Al-Mg alloys. Prompted by these findings, we hypothesized that it would be of fundamental and technological interest to study the behavior of Sc additions to an ultra-fine-grained (UFG) microstructure (e.g., 100's nm). Accordingly, we investigate the microstructural evolution and mechanical behavior of four powder metallurgy UFG Al-Mg-Sc-(Zr) compositions and compared the results to those of equivalent fine-grained (FG) compositions - Al-5Mg-0.1Sc, Al-3Mg-0.5Sc, Al-5Mg-0.4Sc and Al-5Mg-0.2Sc-0.2Zr (wt.%). Experimental materials were consolidated by hot isostatic pressing (HIP'ing) followed by extrusion or dual mode dynamic (DMD) forging. Under identical processing conditions, UFG ternary Al-5Mg-0.4Sc materials generate large Al3Sc precipitates with an average diameter of 154 nm and spaced approximately 1 - 3 [mu]m apart, while precipitates in the FG materials have an average diameter of 24 nm and are spaced 50 - 200 nm apart. The strengthening mechanisms are quantitatively evaluated for all materials and it is determined that the greatest strengthening contributions for the UFG and FG materials are dispersion strengthening due to the presence of Mg-rich oxides/nitrides and precipitate strengthening, respectively. Preliminary results suggest that replacing 0.2 wt% Sc with Zr results in higher strength, lower ductility and a change in precipitate distribution.