Oleg Sitdikov

Effects of Processing Routes on Wear Property of Al-Al3Ti Alloys Severely Deformed by ECAP

Al-Ti alloys, which have Al3Ti platelet particles in Al matrix, were deformed by ECAP with routes A and Bc. With increasing the number of ECAP passes, Al3Ti platelet particles are fragmented and their sizes decrease. The microstructure of ECAPed Al-Ti alloy specimens by route A has a strong alignment of the fragmented Al3Ti particles. On the other hand, ECAPed Al-Ti alloy specimens by route Bc have a relatively homogeneous distribution of Al3Ti particles comparing with the specimen deformed by route A. Based on these results, it was found that ECAPed Al-Ti alloy specimen by route A has highly anisotropic microstructure. However, both ECAPed specimens with routes A and Bc have no anisotropic wear property. That is because the wear property of the Al-Ti alloy specimen depends on the shape of the Al3Ti particle. From these results, it was found that SPD induced by ECAP is an effective processing method to make homogeneous wear property for the metallic material containing platelet solid-particles.

Geometric Dynamic Recrystallization in an AA2219 Alloy Deformed to Large Strains at an Elevated Temperature

The mechanism of new grain evolution during equal channel angular extrusion (ECAE) up to a total strain of ~12 in an Al-Cu-Mn-Zr alloy at a temperature of 475oC (0.75Tm) was examined. It was shown that the new grains with an average size of about 15 µm result from a specific process of geometric dynamic recrystallization (GRX) which can be considered as a type of continuous dynamic recrystallization (CDRX). This process involves three elementary mechanisms. At moderate strains, extensive elongation of initial grains takes place; old grain boundaries become progressively serrated. Upon further ECAE processing, transverse low-angle boundaries (LAB) with misorientation ranging from 5 to 15o are evolved between grain boundary irregularities subdividing the initial elongated grains on crystallites with essentially equiaxed shape. The misorientation of these transverse subboundaries rapidly increases with increasing strain, resulting in the formation of true recrystallized grains outlined by high-angle boundaries from all sides. In the same time, the average misorientation of deformation-induced boundaries remains essentially unchanged during ECAE. It is caused by the fact that the evolution of LABs with misorientation less than 4o occurs continuously during severe plastic deformation. The mechanism maintaining the stability of the transverse subboundaries that is a prerequisite condition for their further transformation into highangle boundaries (HABs) is discussed.

Effect of Processing Temperature on Microstructure Development during ECAP of Al-Mg-Sc Alloy

Microstructural evolution taking place during equal channel angular pressing (ECAP) was studied in a commercial coarse-grained Al-6%Mg-0.4%Mn-0.3%Sc alloy in a temperature interval 200- 450oC (~0.5-0.8 Tm). Samples were pressed using route A to a total strain of 12 and quenched in water after each ECAP pass. Uniform fine-grained microstructures with the average grain sizes of 0.7 and 2.5 0m, are almost fully evolved at high ECAP strains at 250oC and 450oC, respectively, while ECAP at 300oC (~0.6 Tm) leads to the formation of bimodal grain structure with fine grains of around 1 µm and relatively coarse grains of around 8 µm. The latter are developed due to the occurrence of static recrystallization during “keeping” time in the ECAP channel and/or reheating between ECAP passes. The microstructural development under warm-to-hot ECAP conditions is discussed in terms of the large potential for grain boundary migration resulted from an overlapping of accelerated grain boundary mobility at high pressing temperatures and enhanced driving force for recrystallization, which is caused by a strong inhibition of dynamic recovery in a heavily-alloyed Al alloy.

Grain Refinement in the Magnesium Alloy ZK60 During Multi-Step Isothermal Forging

Transformations of hot-pressed partially recrystallized structure of the magnesium alloy ZK60 into ultrafine-grained one with the (sub) grain size of ~1 μm under multi-step isothermal forging were analyzed. The mechanisms of recrystallization, as well as the role of the processing temperature and second phases in the development of new grains are discussed.

Effect of Processing Route on Microstructure and Texture Development in ECAP of Al-Ti Alloy

Microstructure and texture evolution during equal channel angular pressing (ECAP) of Al-5 mass%Ti alloy are investigated for up to 8 passes via routes A and BC. Platelet-shaped Al3Ti particles in the Al-5mass%Ti alloy are cracked severely with repetitive ECAP passes, and the mean size of the Al3Ti particles is decreased with increasing the number of ECAP passes. Microstructural observation showed that an Al–Ti supersaturated solid solution is formed during the ECAP process. It is also found that the Al-Ti alloy after ECAP by route A and route Bc methods have very different microstructures. Namely, after ECAP by route Bc, the fine Al3Ti particles are homogeneously dispersed in Al matrix, while the microstructure has highly anisotropic distribution after ECAP by route A.

New Grain Formation in a Coarse-Grained 7475 Al Alloy during Severe Hot Forging

Strain-induced grain refinement in a coarse-grained 7475Al alloy was studied by means of multidirectional forging (MDF) carried out at T = 490oC under a strain rate of 3 x 10-4 s-1. Integrated flow curves exhibit significant work softening just after yielding, followed by steady-state-like behavior at high strains. The evolution of new fine grain structure during deformation can be assisted by grain-boundary sliding, resulting in frequent formation of high strain gradients and subsequently microshear bands in grain interiors. Microshear bands developed in various directions are intersected with each other, subdividing original grains into misoriented small domains. The number and the misorientation angle of microshear bands progressively increase during deformation, finally followed by their transformation into high-angle boundaries. It is concluded that grain refinement under hot MDF conditions occurs by a series of deformation-induced continuous reactions; that is essentially similar to continuous dynamic recrystallization.

Fatigue-Crack-Growth Behavior of Ultrafine-Grained Al-Mg-Sc alloy Produced by ECAP

Fatigue-crack-growth in an ultrafine-grained (UFG) Al-6%Mg-0.3%Sc alloy is investigated in conjunction with a precise analysis of the fracture surface. The comparison of the crack growth behavior of the UFG and ordinary polycrystalline materials has shown that the fatigue crack growth rate in the UFG alloy is higher than that in the coarse-grained material only in the near-threshold region. In the intermediate fatigue stage, propagation of the fatigue-crack in the UFG structure becomes insensitive to the grain size. At larger stress-intensity-factor-increments, K, the crack resistance of the UFG material is better than that of un-ECAPed specimen. Analysis of the surface features indicates that such inhibition of the crack growth in the UFG structure upon increasing K may be related to the gradual transition from intergranular- to transgranular mode of fatigue fracture.

Microstructural Evolution in a Commercial Al-Mg-Sc Alloy during ECAP at 300°C

Microstructural evolution taking place during equal channel angular pressing (ECAP) was studied in a commercial coarse-grained Al-6%Mg-0.4%Mn-0.3%Sc alloy at a temperature of 300oC (~0.6Tm). Samples were pressed using route A to a total strain of 12 and quenched in water after each ECAP pass. ECAP at moderate-to-high strains leads to the formation of a bimodal grain structure with grain sizes of around 1 and 8 μm and volume fractions of 0.3 and 0.6, respectively. The development of new-grained regions has been shown to result from a concurrent operation of continuous dynamic recrystallization that occurs during deformation and static recrystallization that occurs during each ECAP cycle by the exposure of the as-deformed material in the die kept at 300oC for around 1.5 minutes. The microstructural development during warm-to-hot ECAP is discussed in terms of the enhanced driving force for recrystallization, resulting from the evolution of high-density dislocation substructures due to the localization of plastic flow and inhibition of recovery in the present alloy.

Strain Rate Effect on Fine-Grain Development in 7475 Al Alloy during Hot Multidirectional Forging

(ΙΙΗΦΩ ΡΙ ςΩΥ∆ΛΘ Υ∆ΩΗ ΡΘ θΥ∆ΛΘ ΥΗΙΛΘΗΠΗΘΩ Ζ∆ς ςΩΞΓΛΗΓ ΛΘ ΠΞΟΩΛΓΛΥΗΦΩΛΡΘ∆Ο ΙΡΥθΛΘθ (0∋)) ΡΙ ∆ ΦΡ∆ΥςΗ-θΥ∆ΛΘΗΓ 7475 ∃Ο ∆ΟΟΡ∴ ∆Ω 490 Ρ & ΞΘΓΗΥ ςΩΥ∆ΛΘ Υ∆ΩΗς ΡΙ 3 υ 10 ς ∆ΘΓ 3 υ 10 ς. ∃Ω ∆ ςΩΥ∆ΛΘ Υ∆ΩΗ ΡΙ 3 υ 10 ς, ΩΚΗ ςΩΥΗςς ± ςΩΥ∆ΛΘ (ς -Η) ΕΗΚ∆ΨΛΡΥ ςΚΡΖς ςΛθΘΛΙΛΦ∆ΘΩ ΖΡΥΝ ςΡΙΩΗΘΛΘθ ΜΞςΩ ∆ΙΩΗΥ ∴ΛΗΟΓΛΘθ ∆ΘΓ ∆ ςΩΗ∆Γ∴-ςΩ∆ΩΗ ΙΟΡΖ ∆Ω ΚΛθΚΗΥ ςΩΥ∆ΛΘς. 7ΚΗ ςΩΥΞΦΩΞΥ∆Ο ΦΚ∆ΘθΗς ∆ΥΗ ΦΚ∆Υ∆ΦΩΗΥΛ]ΗΓ Ε∴ ΓΗΨΗΟΡΣΠΗΘΩ ΡΙ ΓΗΙΡΥΠ∆ΩΛΡΘ Ε∆ΘΓς ∆Ω Η∆ΥΟ∴ ςΩ∆θΗς ΡΙ ΓΗΙΡΥΠ∆ΩΛΡΘ, ΙΡΟΟΡΖΗΓ Ε∴ ΙΡΥΠ∆ΩΛΡΘ ΡΙ ∆ ΙΛΘΗ-θΥ∆ΛΘ ςΩΥΞΦΩΞΥΗ ΛΘ ΚΛθΚ ςΩΥ∆ΛΘ ΛΘ ΩΚΗ ΖΚΡΟΗ Π∆ΩΗΥΛ∆Ο. 7ΚΗ ΨΡΟΞΠΗ ΙΥ∆ΦΩΛΡΘ ΡΙ ΘΗΖ θΥ∆ΛΘς ΛΘΦΥΗ∆ςΗς ΖΛΩΚ ςΩΥ∆ΛΘ ∆ΘΓ ∆ΣΣΥΡ∆ΦΚΗς ∆ Ψ∆ΟΞΗ ΡΙ ∆ΕΡΞΩ 0.85 ΡΨΗΥ ∆ ςΩΥ∆ΛΘ ΡΙ 3. ∃Ω ∆ ΚΛθΚΗΥ ςΩΥ∆ΛΘ Υ∆ΩΗ ΡΙ 3 υ 10 ς, ΛΘ ΦΡΘΩΥ∆ςΩ, ∆ ςΩΗ∆Γ∴-ςΩ∆ΩΗ ΙΟΡΖ ΙΡΟΟΡΖΛΘθ ςΠ∆ΟΟ ΙΟΡΖ ςΡΙΩΗΘΛΘθ ∆ΣΣΗ∆Υς ∆Ω ∆ ΥΗΟ∆ΩΛΨΗΟ∴ ΟΡΖ ςΩΥ∆ΛΘ. 1ΗΖ θΥ∆ΛΘς ∆ΥΗ ΙΡΥΠΗΓ ΓΞΥΛΘθ ςΩΗ∆Γ∴ ςΩ∆ΩΗ ΙΟΡΖ ∆ΟΡΘθ ΡΥΛθΛΘ∆Ο θΥ∆ΛΘ ΕΡΞΘΓ∆ΥΛΗς ∆ΘΓ ΩΚΗ ΨΡΟΞΠΗ ΙΥ∆ΦΩΛΡΘ ΥΗ∆ΦΚΗς ΕΗΟΡΖ 0.2 ΗΨΗΘ ∆Ω ∆ ςΩΥ∆ΛΘ ΡΙ 6.3. 7ΚΗ ΡΦΦΞΥΥΗΘΦΗ ΦΡΘΓΛΩΛΡΘς ∆ΘΓ ΩΚΗ ΠΗΦΚ∆ΘΛςΠς ΡΙ θΥ∆ΛΘ ΥΗΙΛΘΗΠΗΘΩ ∆ΥΗ ΓΛςΦΞςςΗΓ ΛΘ ΓΗΩ∆ΛΟ. Introduction 0ΗΩ∆ΟΟΛΦ Π∆ΩΗΥΛ∆Ος ΖΛΩΚ ΙΛΘΗ-θΥ∆ΛΘΗΓ ΠΛΦΥΡςΩΥΞΦΩΞΥΗς Κ∆ΨΗ Π∆Θ∴ ∆ΓΨ∆ΘΩ∆θΗς ΡΙ ΩΚΗ ΦΚΗΠΛΦ∆Ο, ΣΚ∴ςΛΦ∆Ο ∆ΘΓ ΠΗΦΚ∆ΘΛΦ∆Ο ΣΥΡΣΗΥΩΛΗς >1≅. ∃Ω ΣΥΗςΗΘΩ ΩΛΠΗ, ςΗΨΗΥ∆Ο ΠΗΩΚΡΓς ∆Ψ∆ΛΟ∆ΕΟΗ ΙΡΥ ΣΥΡΓΞΦΛΘθ ΡΙ ΕΞΟΝ Π∆ΩΗΥΛ∆Ος ΦΡΠΣΡςΗΓ ΡΙ ∆ ΙΛΘΗ-θΥ∆ΛΘΗΓ ςΩΥΞΦΩΞΥΗ ∆ΥΗ Ε∆ςΗΓ ΠΡςΩΟ∴ ΡΘ ςΗΨΗΥΗΟ∴ Ο∆ΥθΗ ΣΟ∆ςΩΛΦ ΓΗΙΡΥΠ∆ΩΛΡΘ >1,2≅. 2ΘΗ ΡΙ ΩΚΗΠ Λς ΠΞΟΩΛΓΛΥΗΦΩΛΡΘ∆Ο ΙΡΥθΛΘθ (0∋)), ΖΚΛΦΚ Λς ΩΚΗ Η∆ςΛΗςΩ ΠΗΩΚΡΓ ΖΛΩΚΡΞΩ ∆Θ∴ ςΣΗΦΛΙΛΦ ΓΗΨΛΦΗ ∆ΘΓ Κ∆ς ∆ θΥΗ∆Ω ΣΡΩΗΘΩΛ∆ΟΛΩ∴ ΙΡΥ ΣΥΡΓΞΦΛΘθ ΡΙ ΥΗΟ∆ΩΛΨΗΟ∴ Ο∆ΥθΗ ΖΡΥΝΣΛΗΦΗ ΩΚ∆Ω Φ∆Θ ΕΗ ΞςΗΓ ΛΘ Π∆ςς ΣΥΡΓΞΦΩΛΡΘ. 7ΚΗ ΣΥΛΘΦΛΣΟΗ ΡΙ 0∋) Λς ΦΡΠΣΥΗςςΛΡΘ ΣΥΡΦΗςς ΥΗΣΗ∆ΩΗΓ ΖΛΩΚ ΦΚ∆ΘθΗ ΛΘ ΩΚΗ ΓΛΥΗΦΩΛΡΘ ΡΙ ΩΚΗ ∆ΣΣΟΛΗΓ ςΩΥ∆ΛΘ (i.e. x ο y ο z ο x ...) ∆Ω Η∆ΦΚ ςΩΗΣ. 6ΛΘΦΗ ∆ ΖΡΥΝΣΛΗΦΗ ΓΡΗς ΘΡΩ ΦΚ∆ΘθΗ ΛΩς ςΚ∆ΣΗ ΞΘΓΗΥ 0∋) ΦΡΘΓΛΩΛΡΘς, Ο∆ΥθΗ ΣΟ∆ςΩΛΦ ςΩΥ∆ΛΘ Φ∆Θ ΕΗ ΛΘΩΥΡΓΞΦΗΓ ΛΘΩΡ Π∆ΩΗΥΛ∆Ο ΓΞΥΛΘθ ΥΗΣΗ∆ΩΗΓ ΦΡΠΣΥΗςςΛΡΘ ∆Ω ∆ΠΕΛΗΘΩ ΩΡ ΗΟΗΨ∆ΩΗΓ ΩΗΠΣΗΥ∆ΩΞΥΗς. ,Ω Κ∆ς ΕΗΗΘ ςΚΡΖΘ ΥΗΦΗΘΩΟ∴ >3-7≅ ΩΚ∆Ω ςΞΦΚ ςΩΥ∆ΛΘ ∆ΦΦΞΠΞΟ∆ΩΛΡΘ ∆ΦΦΡΠΣ∆ΘΛΗΓ ΖΛΩΚ Ψ∆ΥΛΡΞς ςΩΥ∆ΛΘ Σ∆ΩΚς Λς ΨΗΥ∴ ΛΠΣΡΥΩ∆ΘΩ ΙΡΥ ΓΗΨΗΟΡΣΠΗΘΩ ΡΙ ΗΤΞΛ∆[Λ∆Ο ΙΛΘΗ θΥ∆ΛΘς, i.e. θΥ∆ΛΘ ΥΗΙΛΘΗΠΗΘΩ. ∃Ω ΩΚΗ ς∆ΠΗ ΩΛΠΗ, θΥ∆ΛΘ ΥΗΙΛΘΗΠΗΘΩ ΓΞΥΛΘθ 0∋) Φ∆Θ ΕΗ ΦΡΘΩΥΡΟΟΗΓ ΘΡΩ ΡΘΟ∴ Ε∴ ΩΡΩ∆Ο ςΩΥ∆ΛΘ ∆ΦΦΞΠΞΟ∆ΩΗΓ ∆ΘΓ ςΩΥ∆ΛΘ ΣΗΥ Η∆ΦΚ Σ∆ςς, ΕΞΩ ∆ΟςΡ ςΩΥ∆ΛΘ Υ∆ΩΗ ∆ΘΓ ΩΗΠΣΗΥ∆ΩΞΥΗ. 7ΚΗΥΗ ∆ΥΗ, ΚΡΖΗΨΗΥ, ∆ ΙΗΖ Η[ΣΗΥΛΠΗΘΩ∆Ο Γ∆Ω∆ ΡΘ ΩΚΗ Ο∆ΩΩΗΥ∂ς ΗΙΙΗΦΩ ΞΘΓΗΥ 0∋) ΦΡΘΓΛΩΛΡΘς. 7ΚΗ Π∆ΛΘ ∆ΛΠ ΡΙ ΩΚΗ ΣΥΗςΗΘΩ ΖΡΥΝ Ζ∆ς ΩΡ ςΩΞΓ∴ ΗΙΙΗΦΩ ΡΙ ∆ΣΣΟΛΗΓ ςΩΥ∆ΛΘ Υ∆ΩΗ ΡΘ ΙΛΘΗ-θΥ∆ΛΘΗΓ ςΩΥΞΦΩΞΥΗ ΙΡΥΠ∆ΩΛΡΘ ΛΘ ∆ ΦΡ∆ΥςΗ-θΥ∆ΛΘΗΓ 7475 ∃Ο ∆ΟΟΡ∴ ΓΞΥΛΘθ ΚΡΩ 0∋). 7ΚΗ ΠΗΦΚ∆ΘΛςΠς ΡΙ ΚΡΩ ΓΗΙΡΥΠ∆ΩΛΡΘ, ΠΛΦΥΡςΩΥΞΦΩΞΥ∆Ο ΓΗΨΗΟΡΣΠΗΘΩ ΓΞΥΛΘθ 0∋) ∆ΘΓ ΩΚΗΛΥ ΛΘΩΗΥΥΗΟ∆ΩΛΡΘςΚΛΣ ∆ΥΗ ΓΛςΦΞςςΗΓ. Materials Science Forum Online: 2006-01-15 ISSN: 1662-9752, Vols. 503-504, pp 505-510 doi:10.4028/www.scientific.net/MSF.503-504.505

Nanostructuring of 2xxx Aluminum Alloy under Cryorolling to High Strains

The structure transformations in the D16 (2024) aluminum alloy caused by isothermal rolling with effective strain up to e ~3.5 at a temperature of liquid nitrogen were investigated. It is shown that under straining to e ~2.0 the dislocation structure containing cells of the nanometric size is formed. At higher strains the dynamic recovery and continuous recrystallization result in the development of a mixed nano(sub) grain structure, which after e ~3.5 is characterized by the size and volume fraction of grains ~ 150 nm and 40-45%, respectively. Nature of the alloy structure transformations is discussed.