Papers by Keyword: Ultrafine Grained Structure

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Authors: Andrzej Rosochowski, Lech Olejnik, Maria W. Richert
Abstract: This paper explains the concept of 3D-ECAP with “in-die rotation” and presents the results of experiments for two sets of tooling with channel passages orientated at 90° and 120°. The results for aluminium 1070 are compared in terms of the process force, billet end effects, mechanical properties and structure of the material.
Authors: G.H. Salimgareeva, Irina P. Semenova, V.V. Latysh, I.V. Kandarov, Ruslan Valiev
Abstract: The paper investigates an innovative technological processing method for fabricating nanostructured materials for structural applications. Severe plastic deformation (SPD) and subsequent thermomechanical treatment, was used to produce high physical and mechanical properties in bulk billets.
Authors: Geoff M. Scamans, Andreas Afseth, George E. Thompson, Y. Liu, Xiao Rong Zhou
Abstract: Over the past ten years a detailed understanding of the dominant factors controlling the corrosion susceptibility of painted aluminium alloy sheet used for architectural and automotive applications has been developed. Work carried out in this field will be reviewed and the different modes of cosmetic corrosion that can occur-, the mechanisms of surface activation, and the role of different thermo-mechanical processing steps on controlling corrosion susceptibility for different alloy systems, including Al-Mn, Al-Mg and Al-Mg- Si-(Cu) will be discussed. The critical role of chemical or electro-chemical cleaning prior to pre-treatment and coating will be highlighted and prospects for meaningful accelerated testing will be discussed.
Authors: Yan Huang, Philip B. Prangnell
Abstract: The feasibility of a novel continuous severe plastic deformation (SPD) technique, continuous frictional angular extrusion (CFAE), for producing ultra-fine grained strip material, has been studied. The CFAE technique takes advantage of facets of rolling and equal channel angular extrusion (ECAE) and is designed to produce bulk ultra-fine grained (UFG) metals with high productivity and low cost. A process setup was established through the modification of a standard rolling mill. CFAE processing of commercially pure aluminium AA1050 sheets was successfully carried out at room temperature, using a 120o die angle. A uniform UFG structure with an average grain size of ~0.6μm was achieved after 10 CFAE passes, at an equivalent strain of ~ 6.6. Evolution of the deformation structure and texture during processing was examined as a function of strain and characterized using high resolution EBSD.
Authors: Diana Yuzbekova, Vladislav Kulitskiy, Anna Mogucheva, Rustam Kaibyshev
Abstract: Influence of friction stir welding (FSW) on microstructure of an Al-4.57Mg-0.35Mn-0.2Sc-0.09Zr (wt. pct.) alloy was studied. Following parameters of FSW were used: the rotation speeds of 500, 650 and 800 rpm, the traverse speed of 75 mm/min and the tilt angle of 2.5°. Defect-free welds were obtained using all these parameters. FSW leads to the formation of fully recrystallized microstructures with average grain sizes less 2 μm and a moderate dislocation density of ~1013 m2 in the stir zone. No evidence for abnormal grain growth was found in the heat affected zone of the weld. The nanoscale Al3(Sc,Zr) dispersoids coarsened to 21 nm but retained coherent interfaces and cube-cube orientation relationship with the matrix.
Authors: Zsolt Kovács, Nguyen Q. Chinh, Janos Lendvai, Z. Horita, Terence G. Langdon
Authors: Rustam Kaibyshev, Daria Zhemchuzhnikova, Anna Mogucheva
Abstract: Aluminium alloys with a chemical compositions of Al–5.8%Mg–0.52%Mn–0.2%Sc–0.07%Zr–0.16%Fe-0.1%Si and Al-5.4%Mg-0.34%Mn-0.2%Sc-0.07%Zr-0.07%Fe-0.02Si (in weight %), denoted as 1570 and 1570C, respectively, were processed by equal-channel angular pressing (ECAP) at 300°C up to strain ε~12. Extensive grain refinement provided the formation of fully recrystallized structure with the average grain sizes of 0.7 and 0.6 μm, respectively. Tensile tests were carried out in the temperature interval 200–550oC at strain rates ranging from 10-4 to 10-1 s-1. Very high tensile elongations (>1000%) were achieved in the both alloys at T350oC and strain rates higher than 10-3 s-1.
Authors: Elena Avtokratova, Oleg Sitdikov, Rustam Kaibyshev, Yoshimi Watanabe
Abstract: 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.
Authors: Jin Guo Li, Minoru Umemoto, Yoshikazu Todaka, Koichi Tsuchiya
Abstract: SUS 304 austenitic stainless steel was processed by HPT at room temperature with different rotation speed. It was found that the microstructure evolution and composed phases along the progress of HPT were sensitive to the strain rate (rotation speed). During deforming with the low strain rate, the deformation-induced dynamic phase transformation (DPT) from austenite (γ) to martensite (α’) occurred and the microstructure is characterized by elongated submicron α’ grains after 10 revolutions. While the euqiaxed nanocrystalline α’ grains were produced after HPT at the continuously alternative low and high strain rate. XRD analyses showed that multiple DPT of γ→α’→γ→α’ took place during HPT at the continuously alternative low and high rotation speed. Based on the experimental results, it was proposed that the euqiaxed ultrafine grained structure were produced by multiple DPT under the high strain and strain gradient.
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