BOCCACCINI, in, 2005 3.6 Impact of fabrication on microstructure and propertiesThe microstructure and composition of a material determines many of its physical, and all of its mechanical, properties. The microstructure is determined by the processing conditions and the composition.

• Properties Of Concrete Pdf

The evolution of the microstructure during processing (for example, densification during sintering) may limit the processing operations that can be performed. Alternatively, microstructures that may result in poor properties of the finished component may form in the work piece. The complex interaction between fabrication, microstructure, mechanical properties and external factors (e.g. Temperature, environment conditions) is given in Fig. Figure 24.11 shows typical microstructures of as-built Ti6Al4V alloy from various AM processes. Corresponding tensile properties (UTS and YS) are also plotted as a function of elongation to show the effect of microstructure on mechanical properties.

Clearly, laser-based technologies offer higher strength and lower ductility because of the formation of α’-martensite as a result of fast cooling. Electron beam processed material exhibit α-β microstructure due to slower cooling in vacuum atmosphere and results in lower tensile strength and higher ductility. In comparison, microstructure morphology is coarser in the as-cast material and wrought material has equiaxed α-β microstructure. Arc-processed material (wire and arc AM WAAM) offers a microstructure similar to cast structure, though finer in length scale. The effect of these various microstructures is well demonstrated in their tensile behavior. Figure 24.12 shows microstructure of as-built material using DMD process and after subsequent HIPing (hot isostatic pressing) and aging.

The as-built microstructure shows the typical martensitic structure expected for Ti-6Al-4V cooled rapidly from the beta phase field, while the HIPed and aged material shows the expected grain boundary alpha and intergranular coarse alpha plates. This microstructural transition from as-deposited to HIPed-aged condition is also reflected through their tensile properties. While UTS and YS is a little lower after HIPing and aging, ductility improves significantly (see below) as a result of the microstructure changing from martensitic to transformed beta (precipitated alpha) structure.

In practice, the gap between the components to be joined often has to, for thick steels, be filled by a sequence of several weld deposits. These multirun welds have a complicated microstructure ( Fig. The deposition of each successive layer heat treats the underlying microstructure. Some of the regions of original primary microstructure are reheated to temperatures high enough to cause the reformation of austenite, which during the cooling part of the thermal cycle transforms into a different microstructure. Other regions may simply be tempered by the deposition of subsequent runs. The microstructure of the reheated regions is called the reheated or secondary microstructure. Microstructure measures describe the amount of each phase, its distribution, and its composition using descriptors of size, shape, and relations between the phases.

Properties Of Concrete Pdf

Liquid phase sintering is a normalization process. Although the starting point depends on the green body, the sintered microstructure converges to common characteristics during sintering. For most systems, porosity declines, smaller pores are annihilated first, and the mean pore size increases while grain shape accommodation and solid skeletal densification release liquid to fill the smaller pores first. In spite of large differences in starting conditions the sintered material often is the same. Table 9.2 compares features from liquid phase sintered microstructures to illustrate some combinations. System (wt.%)W-8Mo-7Ni-3FeWC-8CoFe-50CuW-7NiMo-46CuSintering Cycle1480°C2 h1400°C1 h1200°C1 h1540°C1 h1400°C1 hLiquid, vol.%Porosity, vol.%0.4010212Grain size, µm173383510Dihedral angle, deg.Contiguity0.520.39–––Connectivity––0.90.23.2Interfacial energies guide microstructure evolution. These change when the first liquid forms and are sensitive to segregation and temperature, so they vary during sintering 47.

Thus, the microstructure depends on processing conditions and will be different with location within the sintered body. Curiously, controversies arise with regard to these factors without proper vetting of the processing conditions. Proper understanding comes from freezing the microstructure to avoid temperature-dependent shifts in solubility or interfacial energy. Otherwise, reports on the microstructure are only valid with respect to the “sintered” condition and do not represent the conditions existing during “sintering.” This is frequently seen in disagreements over grain boundary films. Slow cooling induces decreasing solubility and segregation to heterogeneous sites, resulting in precipitation of liquid-like compositions segregated on grain boundaries. Slow cooling results in a grain boundary layer while quenching finds the grain boundaries free of matrix (liquid). Without proper processing there is poor rationalization of the conditions during liquid phase sintering.

Kitagawa, in, 2005 Abstract:Microstructure control for joining advanced stainless steel SAF2507 was carried out on weld simulations. The toughness of the bond region in the heat affected zone (HAZ) of SAF2507 stainless steel was much lower than that of the base metal. In order to improve the toughness of the bond region, microstructure control by varying cooling time from 1673K to 1073K was carried out. The ferrite grain size increased with increasing cooling time from 1673K to 1473K (Δt 16–14). The amount of austenite increased with increasing the cooling time from 1473K to 1073K (Δt 14–10).

When the cooling time of Δt 16–14 is below 29s, the absorbed energy was kept almost constant because of the combination effect of ferrite grain growth and austenite reformation. When the cooling time becomes longer the absorbed energy decreased. The equations describing the change of microstructure in the bond region were also presented. The microstructures play three essential roles: (1)The first, and the most important role, is determining the resistances to cleavage microcracking. In criteria (5.1)–(5.3) the parameters representing the resistances σ f, ε pc even T c all are determined by the material microstructures.

The involved factors such as effective surface energy γ p, the length of the critical event “ c,” and the factors affecting the critical plastic strain and the critical stress triaxiality are closely related to the microstructure.On one hand, the fine microstructures with smaller length of the critical event, “ c,” offer stronger resistance. Those with smaller second-phase particles offering higher ε pc and σ f(c) and those with finer grains offering higher σ f( σ f(f)) to resist cleavage microcracking, will make the cleavage fracture more difficult and improve the toughness. Refining the microstructures in the material plays a positive role in improving the global toughness.On the other hand, in an existing material (even with a fine microstructure), among the components in its microstructure, the weakest are those with the coarsest particles or the coarsest grains, on which microcracking is triggered with the lowest resistance.

Thus, the weakest components decrease the toughness, and play a detrimental role; they should be avoided. (2)The second role is putting vital effects on the driving forces that trigger cleavage microcracking and present in terms on the left side in criteria for cleavage fracture.

The driving force of normal tensile stress σ yy is closely related to the yield strength σ y, which is determined by material microstructure. The driving forces of the plastic strain and the stress triaxiality are also closely related to material microstructure, such as the mechanical mismatching between different phases. The driving forces for cleavage fracture are mainly provided by the mechanical constraint, which is produced by the specimen with various defects. However, the role of microstructure should be accounted for.The dilemma caused by effects of the microstructure on both the resistance and the driving force for cleavage fracture is solved by seeking the factor combining both effects to strike a balance, such as the critical stress intensification factor Q c = σ f /σ y. (3)The third key role is defining the critical event for cleavage fracture. The critical event is defined as the most difficult among the three stages in the microcracking process, which is determined by comparing the relevant criteria. The effect of microstructures on the critical event is based on roles played in affecting both the material resistance and the driving force.

Various microstructures make different criteria the most difficult and make different stages the critical event.Based on these three effects on cleavage fracture, material microstructures exert dominant influence on the fracture toughness of materials.The effects of the material microstructure have been discussed for their prominance in the attended events such as the effects on the critical event and the effects on the local cleavage fracture stress σ f. In the following sections, the effects are viewed from the microstructural elements one by one and systematically summarized for main phases and components composing the material microstructure.

Chronakis, in, 2015 AbstractMicro- and nano-structures such as micro- and nano-fibers and micro- and nano-particles based on polymers (synthetic and natural) can be processed by electrospinning. Electrospun micro- and nano-structures are an exciting class of novel materials due to several unique characteristics, including their micro- and nano-meter diameter, the extremely high surface area per unit mass, the very small pore size, and their tunable surface properties. To this may be added their cost-effectiveness. Significant progress has been made in this field in the past few years, and the resultant micro- and nano-structures may serve as a highly versatile platform for a broad range of applications in areas such as medicine, pharmacy, sensors, catalysis, filter, composites, ceramics, packaging, electronics, and photonics.

Some latest developments in the processing and applications of micro- and nano-structured polymers by electrospinning are presented. Clifton, Geoffrey Frohnsdorff, in, 2001 Microstructural Models.The microstructure of cement-based materials is controlled by their constituents, the mixture proportions, processing (e.g., mixing, consolidation, and curing), and degree of hydration. The properties of the hardened cement-based materials are dependent on their microstructure; the capillary pore structure, which includes the transition zone between the cement paste and aggregates, usually governs the transport properties of concrete, while larger voids reduce the strength of concrete. Therefore, microstructure characterization and modeling have come to make a major contribution to understanding the performance of cement-based materials. The progress of microstructure modeling has been comprehensively reviewed in two parts by Jennings, et al. 9 27 Part 1 deals with historical developments and provides a general overview, while Part 2 addresses recent developments. In Part 1, models of the microstructure of cement-based materials and of shrinkage and creep are described, while Part 2 describes models linking microstructure with flow properties, moisture capacity, and shrinkage and creep.

Garboczi and Bentz reported on the state-of-the-art of fundamental computer simulation models for cement-based materials 8 and with Martys, reviewed 28 relationships between transport properties and the microstructure of cement-based materials. Van Breugel 29 used simulation models to link microstructural development with hydration kinetics of cement-based materials.The reviews by Jennings, et al., were contributions to the proceedings of a NATO Advanced Research Workshop on the Modeling of Microstructure and Its Potential for Studying Transport Properties and Durability, held in 1994. 30 The contents of the proceedings are:Part I: Modeling Pore Structure.

0 of 0 people found the following review helpful. Best Textbook IOwnBy RaymundoMy professor co-authored this book and I must saythere's absolutely nothing wrong with this text. All examples,concepts and esoteric language is explained and it makes you dreamabout Concrete (it did for me).My suggestion is try to make a verysimple way to identify key terms in each chapter and write that inthe front of the chapter.

For example, for strength chapter, writedown the terms: w/c, ITZ, Agg size and grade, Agg Elastic Modulus,porosity and relate these terms to strength of concrete.1 of 1people found the following review helpful. Complete book on thetopic concrete made by scientists from.By MaurizioComplete bookon the topic concrete made by scientists from Berkeley EngineeringSchool the most important in the USA. A book to be owned byconcrete technologists.0 of 0 people found the following reviewhelpful. Five StarsBy ammnicGreat reference. THE MOST COMPREHENSIVE AND CURRENT GUIDE TO THE PROPERTIES,BEHAVIOR, AND TECHNOLOGY OF CONCRETE This thoroughly updatededition contains new information on: Recently built constructionprojects worldwide Shrinkage-reducing admixtures Self-consolidatingconcrete, pervious concrete, internal curing, and othercutting-edge innovations Modeling of ice formation andalkali-aggregate reaction in concrete Environmental impact ofconcrete Each chapter begins with a preview of the contents andends with a self-test and a guide for further reading. More than300 drawings and photographs illustrate the topics discussed inthis definitive text on concrete. Comprehensive coverage includes:Microstructure of concrete Strength Dimensional stabilityDurability Hydraulic cements Aggregates Admixtures Proportioningconcrete mixtures Concrete at early age Nondestructive methodsProgress in concrete technology Advances in concrete mechanicsGlobal warming and concrete in the future.