Download or read book Microstructural Characterization of Superplastic Aluminum lithium Alloys written by Rajasekaran Balasubramanian and published by . This book was released on 1991 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Flow Behavior and Microstructural Evolution During Superplastic Deformation of AA8090 Aluminum lithium Alloy written by and published by . This book was released on 1906 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Superplasticity in AA8090 Al-Li alloy has been a subject of extensive studies, due to its potential for commercial applications since last decade. However, the anisotropy and microstructural gradient existing in this material introduce additional complication in understanding the mechanisms for superplastic deformation and has resulted in a debate about the role of dislocation activity. This has necessitated a more detailed microstructural study, especially texture, than that is commonly required to understand the deformation mechanism in other superplastic materials. Attempt has been made in this investigation to achieve this by means of microstructural characterization of specimens deformed in ten ion by using optical microscopy, TEM, SEM and orientation imaging microscopy (OIM). The microstructural characterization of the as-received material showed that there were three distinct layers in the cross-section of the sheet. Pancake grains in the center layer of about 1/3 thickness with brass-type texture, and nearly equiaxed grains on either side of it of about 1/3 thickness with copper texture. Tensile tests were conducted over a temperature range of $25{-}570\sp\circ$C and a strain rate range of $\rm 1 \times 10\sp{-4}{-}1 \times 10\sp{-2}/s.$ Optimum superplastic conditions were found in a temperature range of 500-530$\sp\circ$C and in a strain rate range of $\rm 1 \times 10\sp{-4}{-}1 \times 10\sp{-3}/s.$ These deformation conditions yielded the maximum value of strain rate sensitivity index $\rm(m \approx 0.5)$ and the minimum value of instability parameter (I). During superplastic deformation, there occurred grain growth, texture weakening and change in grain shape. The disappearance of initial microstructural gradient occurred at a strain of about 1.0. The relationship between grain size (d) and strain $(\varepsilon)$ could be expressed as $\rm d\propto\varepsilon\sp{q}, $ with the value of exponent q ranging from 0.21-0.44 depending on the test temperature. T.
Download or read book Microstructural Characterization of Aluminum Lithium Alloys 1460 And 2195 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 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) techniques were employed to characterize the precipitate distributions in lithium-containing aluminum alloys 1460 and 2195 in the T8 condition. TEM examinations revealed delta prime and T1 as the primary strengthening precipitates in alloys 1460 and 2195 respectively. TEM results showed a close similarity of the Russian alloy 1460 to the U.S. alloy 2090, which has a similar composition and heat treatment schedule. DSC analyses also indicate a comparable delta prime volume fraction. TEM study of a fractured tensile sample of alloy 1460 showed that delta prime precipitates are sheared by dislocations during plastic deformation and that intense stress fields arise at grain boundaries due to planar slip. Differences in fracture toughness of alloys 1460 and 2195 are rationalized on the basis of a literature review and observations from the present study. Wang, Z. M. and Shenoy, R. N. Langley Research Center NAS1-96014; RTOP 242-20-05-05...
Download or read book Flow Behavior and Microstructural Evolution During Superplastic Deformation of AA8090 Aluminum lithium Alloy written by Wenjie Fan and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Microstructural Characterization of Aluminum Lithium Alloys 1460 and 2195 written by Z. M. Wang and published by . This book was released on 1998 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aluminum Lithium Alloys written by K. Satya Prasad and published by Elsevier Inc. Chapters. This book was released on 2013-09-20 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: This chapter reviews the precipitation and precipitate phases that occur during heat treatments in multi-component Al-Li based alloys. It describes aspects related to nucleation, growth, morphology and orientation relationships of the strengthening precipitates δ’ and T1, the toughening precipitate S’ and the recrystallisation-inhibiting precipitate β’. Equilibrium precipitate phases such as T2, which are deleterious to the mechanical and corrosion properties of the alloys, are also described. It is shown that careful alloy chemistry control, two-step homogenization and controlled stretching prior to ageing can be employed to improve the volume fraction and distribution of the precipitate phases. All these processing aspects are necessary to achieve optimum combinations of properties for the alloys.
Download or read book Microstructural Characterization of Aluminium lithium Alloys 1460 Nd 2195 written by Z. M. Wang and published by . This book was released on 1997 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dynamic Microstructural Characterization of High Strength Aluminum Alloys written by William Morgan Lee and published by . This book was released on 2008 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt: Keywords: precipitate, omega, impact, aluminum.
Download or read book Aluminum Lithium Alloys written by S. Balasivanandha Prabu and published by Elsevier Inc. Chapters. This book was released on 2013-09-20 with total page 51 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the late 1950s, lithium is being used as an alloying element in aluminum. Their excellent ductility, which allows superplastic forming, along with their ability to decrease the density, makes aluminum-lithium alloys a primary choice for many structural applications in aerospace industry. This chapter initially discusses the processes and mechanisms that give rise to significant plasticity/Superplasticity in these alloy systems. The superplastic behavior of Al-Li alloys and their applications in forming are then discussed. The thickness variation during superplastic forming strongly depends on the peak strain rate sensitivity index (m) of the material, and an increase in the m value reduces the thickness variation in the formed component. The factors that help increase the value of m are enumerated. Superplastic forming is carried out at temperatures ≥ 0.5 Tm (Tm is the absolute melting temperature), often closer to 0.7 − 0.8 Tm. Significant cavitation and grain growth are present at such high temperatures. This has ushered in low temperature superplastic forming by the production of ultra-fine grain sizes via dispersion strengthening and severe plastic deformation (SPD). The promise of superplastic forming of Al-Li alloys for the future and the factors including cost that limit the use of Al-Li alloys are also discussed.
Download or read book Dynamic Microstructural Characterization of High Strength Aluminum Alloys written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effects of Alloy Chemistry on Superplastic Forming of Rapid Solidification Processed Aluminum Lithium Alloys written by RJ. Lederich and published by . This book was released on 1986 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: The superplastic forming characteristics of rapid-solidification-processed (RSP) Al-3Li-based alloys containing varying amounts of copper, magnesium, cobalt, and zirconium and processed by different thermomechanical sequences were investigated. Their final microstructures were strongly dependent on the processing treatment and alloy composition. All the zirconium-containing alloys were processed to have a fine subgrain microstructure. These alloys deform predominantly by dislocation glide and climb processes and by subgrain boundary motion, and they exhibit up to 400% elongation, which is sufficient for many commercial forming applications. Cavitation was suppressed, and the mechanical properties were not affected by forming. A thermomechanical processing sequence was established that develops a completely recrystallized fine grain microstructure in the Al-Li-Cu-Zr alloys. The alloys with this recrystallized microstructure have excellent formability.
Download or read book Aluminum Lithium Alloys written by N. Eswara Prasad and published by Elsevier Inc. Chapters. This book was released on 2013-09-20 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: The low cycle fatigue (LCF) and high cycle fatigue (HCF) properties of Al–Li alloys are influenced by alloy composition, microstructural characteristics, tensile stretching prior to artificial aging, and crystallographic texture. In general the fatigue properties, notably the notched HCF resistances, of Al–Li alloys are similar to those of conventional aerospace aluminium alloys. Alloy development programs on newer Al–Li alloys aim to study further the effects of minor alloying additions (rare earths, beryllium, silver and TiB); various thermomechanical treatments; alloy microstructure, notably crystallographic texture and grain size; and the fatigue load history and environment on the mechanical behavior, including the fatigue properties. It is important to note that the occurrence of bilinearity in LCF life-dependence on strain amplitude in most Al–Li alloys engenders the overestimation of the LCF lives in both the hypo-transition (lower strain amplitudes; longer fatigue lives) and hyper-transition (higher strain amplitudes; shorter fatigue lives) regions if the lives are estimated by extrapolation from either of these regions. Further, in cases such as in Al-Li alloys where there are large differences in strength-based (Basquin-like) and plastic strain – based (Coffin-Manson) power-law relationships, it is appropriate to develop an alloy design philosophy based on either plastic strain energy per cycle (Halford-Morrow) or fatigue toughness (total plastic strain energy to fracture). All of these aspects are discussed in detail in this chapter.
Download or read book Aluminum Lithium Alloys written by N Eswara Prasad and published by Butterworth-Heinemann. This book was released on 2013-09-20 with total page 596 pages. Available in PDF, EPUB and Kindle. Book excerpt: Because lithium is the least dense elemental metal, materials scientists and engineers have been working for decades to develop a commercially viable aluminum-lithium (Al-Li) alloy that would be even lighter and stiffer than other aluminum alloys. The first two generations of Al-Li alloys tended to suffer from several problems, including poor ductility and fracture toughness; unreliable properties, fatigue and fracture resistance; and unreliable corrosion resistance. Now, new third generation Al-Li alloys with significantly reduced lithium content and other improvements are promising a revival for Al-Li applications in modern aircraft and aerospace vehicles. Over the last few years, these newer Al-Li alloys have attracted increasing global interest for widespread applications in the aerospace industry largely because of soaring fuel costs and the development of a new generation of civil and military aircraft. This contributed book, featuring many of the top researchers in the field, is the first up-to-date international reference for Al-Li material research, alloy development, structural design and aerospace systems engineering. - Provides a complete treatment of the new generation of low-density AL-Li alloys, including microstructure, mechanical behavoir, processing and applications - Covers the history of earlier generation AL-Li alloys, their basic problems, why they were never widely used, and why the new third generation Al-Li alloys could eventually replace not only traditional aluminum alloys but more expensive composite materials - Contains two full chapters devoted to applications in the aircraft and aerospace fields, where the lighter, stronger Al-Li alloys mean better performing, more fuel-efficient aircraft
Download or read book Aluminum Lithium Alloys written by G. Jagan Reddy and published by Elsevier Inc. Chapters. This book was released on 2013-09-20 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mechanical working of Al–Li alloys is primarily concerned with aerospace alloy rolled products (sheet and plate), extrusions, and to a lesser extent forgings. These products are fabricated by hot working with intermittent and final heat treatments. This thermomechanical processing (TMP) can be rather complex for the modern 3rd generation Al-Li alloys, but is necessary to obtain optimum combinations of properties. This Chapter is in two parts. Part 1 discusses the ‘workability’ of metals and alloys and the hot deformation characteristics of Al–Li alloys, leading to the concept of Process Maps. A comprehensive Process Map for a binary Al–Li alloy illustrates the usefulness of these Maps for defining temperature–strain rate regions for safe and unsafe hot working, recrystallization and recovery, and superplastic behaviour Part 2 provides some general considerations about processing Al–Li alloy products, followed by a review and discussion of the currently available information for 3rd generation alloys. It is concluded that their complex TMP schedules may make it difficult to obtain optimum combinations of properties for thicker products.
Download or read book Microstructural Characterization of Nanostructured Aluminum Extrusions written by William Hahn and published by . This book was released on 2016 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanostructured aluminum alloys are advantageous for their high strength properties and low density due to the presence of not only multiple material components, but also the presence of nanocrystalline grains that increase strength through grain boundary strengthening. Microstructural analysis is a crucial step in understanding alloy mechanical properties. The alloys observed in this research were analyzed through transmission electron microscope (TEM) observation and grain analysis to determine the average grain size of each nanocrystalline alloy and determine the distribution of grain sizes through each alloy. Average grain sizes for the alloys, found through number fraction analysis, ranged from 44nm to 624nm. Each alloy had a distribution of grain sizes, where the alloy contained high concentrations of grains close their respective average grain sizes with lower concentrations of grains further from the average size.
Download or read book Superplastic Formability of Al Cu Li Alloy Weldalite Tm 049 written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-16 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: Extensive research during the past decade shows that several aluminum lithium alloys can be processed to attain a microstructure that enables superplasticity. The high tensile stress of Al-Cu-Li alloy Weldalite (TM) 049 in the T4 and T6 tempers offers tremendous potential for attaining exceptional post-SPF (superplastic formability) properties. The used SPF material is Weldalite, which was shown to induce SPF behavior in other Al-Cu-Li alloys. The superplastic behavior and resulting post-SPF mechanical properties of this alloy, which was designed to be the next major structural alloy for space applications, were evaluated. The results indicate that Weldalite alloy does indeed exhibit excellent superplasticity over a wide range of temperatures and strain rates and excellent post-SPF tensile strength at various potential service temperatures. Ma, Bao-Tong and Pickens, Joseph R. Unspecified Center...
Download or read book Microstructural and Superplastic Characteristics of Friction Stir Processed Aluminum Alloys written by Indrajit Charit and published by . This book was released on 2004 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Friction stir processing (FSP) is an adapted version of friction stir welding (FSW), which was invented at The Welding Institute (TWI), 1991. It is a promising solid state processing tool for microstructural modification at localized scale. Dynamic recrystallization occurs during FSP resulting in fine grained microstructure. The main goal of this research was to establish microstructure/superplasticity relationships in FSP aluminum alloys."--Synopsis, p. iv.
