scholarly journals Simulation of Primary Particle Development and Their Impact on Microstructural Evolution of Sc-Modified Aluminum Alloys during Additive Manufacturing

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1056
Author(s):  
Mohammad Sadegh Mohebbi ◽  
Vasily Ploshikhin
Keyword(s):  
Aluminum Alloys ◽  
Scanning Speed ◽  
Grain Structure ◽  
Coarse Grained ◽  
2D Simulation ◽  
Fine Grain ◽  
Precipitation Model ◽  
Intermetallic Particles ◽  
Experimental Findings

The microstructures of additively manufactured Sc- and Zr-modified aluminum alloys are significantly influenced by the nucleation role of solid intermetallic particles in undercooled liquid. To replicate such effects, a precipitation model relying on L12-Al3Sc particles is developed. An initiation criterion is proposed based on the precipitation kinetics of primary particles to address solute trapping under high solidification rates. Avrami’s equation is then used to estimate the progress of precipitation. The model is integrated into a cellular automata (CA) analysis to simulate the resulting solidified microstructure, in that the precipitation model is performed implicitly within the CA cells. It is shown that, in accordance with the experimental findings, the proposed simulation approach can predict the distinct fine- (FG) and coarse-grained (CG) zones at the fusion boundary and the meltpool core, respectively. The model can also deliver the reported enhancement of the FG zone under lower scanning speed and higher platform temperatures. These findings are explained in terms of particle number densities at different meltpool regions. Moreover, a semi-2D simulation with a very small cell size is suggested to address the extremely fine grain structure within the FG zone.

Finite Element Simulation of Heat Transfer during Cryogenic Asymmetric Sheet Rolling of Aluminum Alloys

2016 ◽  
Vol 716 ◽  
pp. 692-699 ◽  
Author(s):  
Alexander Pesin ◽  
Denis Pustovoytov
Keyword(s):  
Heat Transfer ◽  
Plastic Deformation ◽  
Aluminum Alloy ◽  
Aluminum Alloys ◽  
Severe Plastic Deformation ◽  
Grain Structure ◽  
Sheet Rolling ◽  
Fine Grain ◽  
Element Simulation ◽  
Alloy 6061

Aluminum and its alloys are widely used as structural materials in aerospace, automotive and other industries due to low density and high specific strength. Efficient way to increase strength and other properties of aluminum alloys is to form an ultra fine grain structure using severe plastic deformation methods. Cryogenic asymmetric sheet rolling under liquid nitrogen temperature is a process of severe plastic deformation that can be used to improve the aluminum alloys structure and properties. Prediction of sheet temperature during plastic deformation is very important. The temperature of sheet is changed due to the conversion of mechanical work of deformation into heat through sliding on contact surfaces. This paper presents the results of the finite element simulation of heat transfer during cryogenic asymmetric sheet rolling of aluminum alloy 6061. The effect of thickness reduction, rolling velocity and friction coefficient on the deformation heating and temperature field of aluminum alloy 6061 was found. The results of investigation could be useful for the development of the optimal treatment process of aluminum alloys by cryogenic severe plastic deformation to obtain the ultra fine grain structure and high strength properties.

Formation of Ultrafine Grained Low Carbon Steels via Martensite Deformation and Annealing

2006 ◽  
Vol 15-17 ◽  
pp. 750-755 ◽  
Author(s):  
H. Azizi-Alizamini ◽  
Matthias Militzer ◽  
Warren J. Poole
Keyword(s):  
Uniform Elongation ◽  
Carbon Steels ◽  
Grain Structure ◽  
Initial Structure ◽  
Low Carbon ◽  
Low Carbon Steels ◽  
Fine Grain ◽  
Ultrafine Grained ◽  
Kinetics Of

Recently, there has been a large interest in the development of low carbon steels with ultra fine grain structure using lean chemistries. Although these steels typically have superior strength, the lack of work hardening capability limits the uniform elongation and thus the formability of these kinds of steels. It has been reported by Tsuji and co-workers (2002) that straining of martensite as an initial structure can yield an ultra fine grain structure with good combination of strength and ductility. However, the detailed mechanism of the grain refinement has not yet been clarified. In the present work, the annealing behavior of a low carbon martensitic structure with and without deformation at room temperature has been systematically studied. It is proposed that the process of concurrent softening due to recovery and recrystallization and precipitation of carbides is different for the deformed and undeformed materials. Further, preliminary results have been found on the role of substitutional alloying elements such as Mo or Cr on the kinetics of the softening processes.

Effect of Multidirectional Forging and Subsequent Annealing to the Microstructure of Al-Mg-Mn Type Alloy

2020 ◽  
Vol 306 ◽  
pp. 23-32
Author(s):  
Anton D. Kotov ◽  
Mikhail Kishchik ◽  
Anastasia V. Mikhaylovskaya
Keyword(s):  
Room Temperature ◽  
Elevated Temperatures ◽  
Shear Bands ◽  
Grain Structure ◽  
Coarse Grained ◽  
Recrystallization Annealing ◽  
Type Alloy ◽  
Rich Phase ◽  
Multidirectional Forging ◽  
Fine Grain

The grain refinement is important to improve both service properties at room temperature and superplasticity at elevated temperatures. This study focuses on the effect of multidirectional forging in isothermal conditions on the microstructure of Al-Mg-Mn-type alloy. The evolution of dislocation and grain structure, and precipitates of Mn-rich phase during multidirectional forging in a temperature range of 200 to 500 °C was studied. Multidirectional forging at temperatures of 200 and 300 °C leads to the formation of shear bands in the deformed grains. The multidirectional forging at 400 and 500 °C leads to the formation of a bimodal grain structure with fine- and coarse-grained areas. Subsequent recrystallization annealing at 500 °C increases the grain size and decreases the fine grains fraction in the samples pre-deformed at 400-500°C, and, on the contrary, annealing leads to formation homogeneous and fine grain structure with size up to 6.5 μm in samples pre-deformed at 200 and 300 °C.

Forging of Articles out of Aluminum Alloys under Superplastic Conditions – Difficulties and Methods of their Overcoming

2012 ◽  
Vol 735 ◽  
pp. 284-288
Author(s):  
Vadim Trifonov
Keyword(s):  
Aluminum Alloys ◽  
Superplastic Deformation ◽  
Hot Forging ◽  
Grain Structure ◽  
Heat Processing ◽  
Corrosion Properties ◽  
Fine Grain ◽  
Mechanical And Corrosion Properties

The manuscript considers the possibility of using of superplastic deformation at hot forging of aluminum alloys. The analysis has been conducted concerning the use of different methods for imparting ultra-fine grain structure to aluminum alloys in terms of their workability. The deformation and heat processing for thermo-strengthened aluminum alloys has been proposed in which superplastic deformation is combined with hardening. The effect of such processing on mechanical and corrosion properties of aluminum alloys is shown. The model processing of a component is demonstrated at forging under superplasticity conditions often surpass the advantages obtained.

scholarly journals Anisotropic Plasticity and Fracture of Three 6000-Series Aluminum Alloys

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 557
Author(s):  
Susanne Thomesen ◽  
Odd Sture Hopperstad ◽  
Tore Børvik
Keyword(s):  
Aluminum Alloys ◽  
Work Hardening ◽  
Failure Strain ◽  
Texture Evolution ◽  
Extrusion Direction ◽  
Extrusion Process ◽  
Deformation Texture ◽  
Grain Structure ◽  
Anisotropic Plasticity ◽  
Experimental Findings

The influence of microstructure on plasticity and fracture of three 6000-series aluminum alloys is studied with emphasis on the anisotropy caused by the extrusion process. Tension tests on smooth and notched specimens are performed in different directions with respect to the extrusion direction, where the stress and strain to fracture are based on local measurements inside the neck or notch. The microstructure of the alloys, i.e., grain structure, crystallographic texture and size distribution of constituent particles, is characterized and used to explain the experimental findings. The experiments show considerable differences in the directional variation of the yield stress, the plastic flow, the work hardening, and the failure strain between alloys exhibiting recrystallization texture and deformation texture. The alloys with recrystallized microstructure exhibited substantial anisotropic work hardening caused by texture evolution and a stronger notch sensitivity of the failure strain than the alloy with deformed, non-recrystallized microstructure. Comparisons are made with previous experiments on the same alloys in the cast and homogenized condition, and the effects of the microstructural changes caused by the extrusion process on the macroscopic response are discussed.

scholarly journals The Effects of Chemical Etching and Ultra-Fine Grain Structure of Titanium on MG-63 Cells Response

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 510
Author(s):  
Denis Nazarov ◽  
Elena Zemtsova ◽  
Vladimir Smirnov ◽  
Ilya Mitrofanov ◽  
Maxim Maximov ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Chemical Etching ◽  
Grain Structure ◽  
Coarse Grained ◽  
Etching Time ◽  
Force Microscopy ◽  
Flight Mass Spectrometry ◽  
Fine Grain ◽  
Atomic Force ◽  
Ultrafine Grained

In this work, we study the influence of the surface properties of ultrafine grained (UFG) and coarse grained (CG) titanium on the morphology, viability, proliferation and differentiation of osteoblast-like MG-63 cells. Wet chemical etching in H2SO4/H2O2 and NH4OH/H2O2 solutions was used for producing surfaces with varying morphology, topography, composition and wettability. The topography and morphology have been studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The composition was determined by time of flight mass-spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS). The results showed that it is possible to obtain samples with different compositions, hydrophilicity, topography and nanoscale or/and microscale structures by changing the etching time and the type of etching solution. It was found that developed topography and morphology can improve spreading and proliferation rate of MG-63 cells. A significant advantage of the samples of the UFG series in comparison with CG in adhesion, proliferation at later stages of cultivation (7 days), higher alkaline phosphatase (ALP) activity and faster achievement of its maximum values was found. However, there is no clear benefit of the UFG series on osteopontin (OPN) expression. All studied samples showed no cytotoxicity towards MG-63 cells and promoted their osteogenic differentiation.

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

2004 ◽  
Vol 467-470 ◽  
pp. 421-428 ◽  
Author(s):  
Oleg Sitdikov ◽  
Tetsuo Sakai ◽  
Alexandre Goloborodko ◽  
Hiromi Miura ◽  
Rustam Kaibyshev
Keyword(s):  
Grain Refinement ◽  
Hot Forging ◽  
Grain Boundary Sliding ◽  
Grain Structure ◽  
Coarse Grained ◽  
Al Alloy ◽  
Continuous Dynamic Recrystallization ◽  
Multidirectional Forging ◽  
Fine Grain ◽  
Continuous Dynamic

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.

scholarly journals Investigation of the Intermetallic Compounds Fragmentation Impact on the Formation of Texture during the as Cast Structure Thermomechanical Treatment of Aluminum Alloys

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 507
Author(s):  
Evgenii Aryshenskii ◽  
Jurgen Hirsch ◽  
Sergey Konovalov
Keyword(s):  
Aluminum Alloys ◽  
Intermetallic Compounds ◽  
Hot Rolling ◽  
Texture Evolution ◽  
Intermetallic Particle ◽  
Grain Structure ◽  
Deformation Degree ◽  
Cast Material ◽  
Cast Structure ◽  
Intermetallic Particles

In this work, the influence of the intermetallic particle fragmentation during hot rolling of the as cast structure on the evolution of textures in aluminum alloys 8011, 5182 and 1565 was investigated. For this purpose, laboratory multi-pass rolling of the cast material was carried out. At various degrees of hot rolling deformation, the process was stopped, and the metal was quenched and sent for optical and electron microscopy to investigate the large intermetallic particles. In addition, the grain structure was studied and an X-ray analysis was carried out in order to determine the main texture components. Some of the samples were held at a temperature above the recrystallization threshold and then cooled in air; the grain structure and texture composition were also studied. In addition, the simulation of the texture evolution was carried out under various modes of rolling of aluminum alloys, taking into account the process of fragmentation of intermetallic particles. The investigation showed that intermetallic compounds with a deformation degree of 1.8, on average, decrease the particle size by 5–7 times. The large eutectic particles remaining after homogenization are drawn out in the direction of deformation and are crushed, increasing their number accordingly. Therefore, the most favorable stage for the formation of recrystallization nuclei on particles is the moment when they are already numerous and their sizes are much larger than subgrains. Simulation of hot rolling of the investigated alloys showed that considering the factor of fragmentation of intermetallic particles during hot deformation of the as-cast structure significantly increases the accuracy of the results.

scholarly journals Controlling the high temperature deformation behavior and thermal stability of ultra-fine-grained W by re alloying

2021 ◽  
Author(s):  
Johann Kappacher ◽  
Oliver Renk ◽  
Daniel Kiener ◽  
Helmut Clemens ◽  
Verena Maier-Kiener
Keyword(s):  
High Temperature ◽  
Peierls Stress ◽  
Coarse Grained ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Fine Grained ◽  
Boundary Interaction ◽  
Kink Pair ◽  
Fine Grain

Abstract Due to their outstanding properties, ultra-fine-grained tungsten and its alloys are promising candidates to be used in harsh environments, hence it is crucial to understand their high temperature behavior and underlying deformation mechanisms. Therefore, advanced nanoindentation techniques were applied to ultra-fine-grained tungsten–rhenium alloys up to 1073 K. A continuous hardness decrease up to 0.2 $$T_{\text{m}}$$ T m is rationalized by a still dominating effect of the Peierls stress. However, the absence of well-established effects of Rhenium alloying, resulting in a reduced temperature dependence of strength for coarse-grained microstructures, was interpreted as an indication for a diminishing role of kink-pair formation in ultra-fine-grained metals with sufficiently fine grain size. Despite slight grain growth in W, dislocation–grain boundary interaction was identified as the dominating deformation mechanism above 0.2 $$T_{\text{m}}$$ T m . Interaction and accommodation of lattice dislocations with grain boundaries was affected by a reduced boundary diffusivity through alloying with Re. Graphic abstract

Microstructure Development in a High Current Density NbTi Superconducting Composite

1985 ◽  
Vol 43 ◽  
pp. 186-189
Author(s):  
P. J. Lee ◽  
D. C. Larbalestier
Keyword(s):  
Current Density ◽  
High Current Density ◽  
Cold Drawing ◽  
Heat Treatments ◽  
Grain Structure ◽  
Fine Grain ◽  
Boundary Film ◽  
Quantitative Basis ◽  
Cold Worked ◽  
Very High

Several features of the metallurgy of superconducting composites of Nb-Ti in a Cu matrix are of interest. The cold drawing strains are generally of order 8-10, producing a very fine grain structure of diameter 30-50 nm. Heat treatments of as little as 3 hours at 300 C (∼ 0.27 TM) produce a thin (1-3 nm) Ti-rich grain boundary film, the precipitate later growing out at triple points to 50-100 nm dia. Further plastic deformation of these larger a-Ti precipitates by strains of 3-4 produces an elongated ribbon morphology (of order 3 x 50 nm in transverse section) and it is the thickness and separation of these precipitates which are believed to control the superconducting properties. The present paper describes initial attempts to put our understanding of the metallurgy of these heavily cold-worked composites on a quantitative basis. The composite studied was fabricated in our own laboratory, using six intermediate heat treatments. This process enabled very high critical current density (Jc) values to be obtained. Samples were cut from the composite at many processing stages and a report of the structure of a number of these samples is made here.

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