Methods of deforming metals to large strains are reviewed and the process of equal channel angular extrusion is analysed in detail. The development of microstructure during large strain deformation is discussed, and it is concluded that the main criterion for the formation of a sub–micron grain structure is the generation of a sufficiently large fraction (> 0.7) of high–angle grain boundary during the deformation process. For aluminium alloys, it is found that a low–temperature anneal is required to convert the deformed microstructure into an equi–axed grain structure. The material, microstructural and processing factors that influence the formation of such fine–grain microstructures are discussed, and the stability of these microstructures at elevated temperatures is considered.

Developing stable fine-grain microstructures by large strain deformation - Discussion

A new dynamic recrystallization kinetics model for a Nb containing Ni-Fe-Cr-base superalloy considering influences of initial δ phase

A review of hot deformation behavior and constitutive models to predict flow stress of high-entropy alloys

Thermal mechanisms of microstructural refinement in steels were reviewed. These include thermal cycling, martensite process, and static recrystallization (SRX), in which the dominant stage of microstructural refinement is governed by an annealing treatment of a deformed or an undeformed material. Recent progress in grain refinement by thermal cycling for the body-centered cubic, face-centered cubic, and dual phase (DP) steels was introduced. The application of the cold rolling and subsequent annealing of a martensite starting structure (martensite process) for grain refinement of low-carbon and DP steels was reviewed. The formation and reversion of strain-induced martensite in metastable austenitic stainless steels and their effects on the microstructural evolutions were critically discussed. Moreover, the repetition of the martensite process and its limitations were explained. Important findings on the SRX of ferrite and austenite for grain refinement as well as the recrystallization kinetics were presented. Finally, the concepts of controlled rolling for grain refinement and the interaction of austenite recrystallization and strain-induced precipitation in microalloyed steels during thermomechanical processing were also reviewed. This short overview presents the opportunities that the conventional and innovative processing routes can offer for grain refinement of steels.

Thermal Mechanisms of Grain Refinement in Steels: A Review

The machining induced material microstructure evolution path is determined from the temperature and mechanical loading history Inversely, the machining forces and machined part surface integrity are dependent on the material microstructure attributes Most of the previous research work with a microstructure consideration in machining stays largely on the experimental observation stage A comprehensive thermal-mechanical-microstructure coupled machining process modeling framework is still missing This paper reviews the recent research work on the material microstructure evolution in the context of machining components The material microstructure property change on the workpiece material in the machining process are analyzed The effects of material microstructure evolution on workpiece mechanical properties and surface integrity are investigated It is concluded that a physical based material microstructure affected machining model is needed for the machining process optimization

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Material microstructure affected machining: a review

In the present study, friction stir processing was adopted for surface treatment of Al5083 by incorporation of CNT and Al2O3 nanoparticles. Microstructural, mechanical and tribological properties o...

Fabrication of Al5083 surface hybrid nanocomposite reinforced by CNTs and Al2O3 nanoparticles using friction stir processing

Deformation of metals and alloys at temperatures above 0.5 Tm is a complex process in which mechanical working interacts with various metallurgical processes such as dynamic restoration including recovery and recrystallization, and phase transformation for polymorphous materials. The understanding of these processes, however, enables the behavior of the metals and alloys. Recent developments have been described in several review papers. These reviews were in agreement that metals and alloys having relatively low values of stacking fault energy (SFE) could recrystallize dynamically, whereas those of high SFE including bcc metals and alloys which behave in a manner similar to fcc metals of high SFE recovered dynamically only during high temperature deformation. So that, according to microstructural evolutions, material response can principally be divided into two categories in hot deformation: dynamic recovery (DRV) type and dynamic recrystallization (DRX) type.

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Mathematical Modeling of Single Peak Dynamic Recrystallization Flow Stress Curves in Metallic Alloys

A comparative study was carried out on GTAW AISI 316 welds fabricated by three different filler metals including ER-317M, ER-316 and ER-308. Filler metals were selected in a way to induce varying Molybdenum (Mo) concentrations in the weld metal, so that the effect of Mo on the microstructural, mechanical and corrosion behavior of the welds was investigated. Microstructural studies revealed that as Mo concentration increased in the weld metal, the dendritic morphology of this zone gradually was changed from cellular dendritic to columnar dendritic and a noticeable amount of austenitic phase and precipitations were formed. Mo-containing ER-316 and ER-317M welds showed appreciable amount of Mo- and Cr-rich carbides such as (Fe,Cr)23C6 which formed at the grain boundaries of δ-ferrite phase resulting in increased the hardness and strength of welded samples. The highest microhardness value of 188 HV and yield strength of 330 MPa belonged to ER-317M welds containing the highest Mo concentration. Also, corrosion resistance of the welds significantly improved by increasing Mo concentration and a minimum corrosion rate of 4.178 mm/year was accounted for ER-317M welds in which, the formation of passive film was more facilitated due to the higher concentration of Mo.

On the role of molybdenum on the microstructural, mechanical and corrosion properties of the GTAW AISI 316 stainless steel welds

A New Constitutive Equation to Predict Single Peak Flow Stress Curves

Study and selection of most appropriate filler rod for GTAW of S32750 super duplex steel joints: A comprehensive study on microstructural, mechanical and corrosion properties

Ehsan Shafiei

Papers

Fabrication of Al5083 surface hybrid nanocomposite reinforced by CNTs and Al2O3 nanoparticles using friction stir processing

Mathematical Modeling of Single Peak Dynamic Recrystallization Flow Stress Curves in Metallic Alloys

On the role of molybdenum on the microstructural, mechanical and corrosion properties of the GTAW AISI 316 stainless steel welds

A New Constitutive Equation to Predict Single Peak Flow Stress Curves

Study and selection of most appropriate filler rod for GTAW of S32750 super duplex steel joints: A comprehensive study on microstructural, mechanical and corrosion properties