Grain Refinement Of Materials Research Articles

Displacement field measurements in traditional and rotational diamond anvil cells

A digital image correlation-based method has been developed to measure the displacement field during compression in a traditional diamond anvil cell (DAC) and torsion in rotational DAC (RDAC) employing ruby fluorescence microscopy imaging. The optical arrangements for these measurements are adaptable at any commercial or customized micro-confocal system used for in situ high-pressure Raman or ruby fluorescence spectroscopy. In this paper, we describe details of the setup developed at Iowa State University along with a few demonstrative measurements for a zirconium sample. In particular, under compression in DAC, no adhesion zone is found, and relative sliding increases almost linearly along the radius. During torsion in RDAC, actual angular displacement of the material is found to be 5 times smaller than the rotation angle of an anvil, which is routinely used in the definition of the plastic shear for the determination of stress–strain curves and plastic strain-induced kinetics of phase transformations and grain refinement in materials. Obtained displacements can be used as the boundary conditions for finite element method (FEM) simulations of processes in DAC and RDAC instead of hypothetical friction conditions. After iterative fitting of FEM simulations and all measured fields from x-ray diffraction and absorption experiments, this will allow us to more precisely determine contact friction conditions and material parameters in the constitutive equations for elastoplastic flow and strain-induced phase transformations.

Deformation analysis of Al Alloy AA2024 through equal channel angular pressing for aircraft structures

ABSTRACT Equal Channel Angular Pressing (ECAP) is one of the most innovative Severe Plastic Deformation (SPD) methods used for grain refinement of materials up to ultra-fined or Nano structured level which leads to superior mechanical properties. Computer simulation is one of the best alternative of actual ECAP deformation to know the influence of each processing parameters on end results. In the present work, AA2024 alloys is used, which is a demanding material in aircraft structure and automotive applications. To understand the process/die design parameter, 3D FEM simulation is done on ECAP process using DEFORM-3D software. Simulation was done on different channel angles such as 90º, 105º, 120º and 135º and corner angles such as 0º, 10º, 20º and 30º. The ECAP process was simulated for a single ECAP pass. The results concern to the extrusion load, developed stresses, effectivestrain and temperature variation on the processed material were noted obtained. From the observed results, it was found that the minimum channel angle produces the maximum temperature profile on the material, develop maximum stress and strain at deformation zone. Additionally, the outcome acquired by such computational technique illustrate that the shear strain decrease with increase in channel and corner angle.

Surface strengthening and grain refinement of AZ31B magnesium alloy by ultrasonic cavitation modification

Ultrasonic cavitation modification (UCM) employs cavitation effect to induce strong plastic deformation on the material surface and improve surface properties. To explore the surface strengthening and grain refinement of materials by UCM, the UCM orthogonal experiments of AZ31B magnesium alloy were carried out in water and kerosene, respectively. The effects of ultrasonic amplitude, distance from the sample, and processing time on Vickers hardness and grain size of the material were studied. The results showed that the Vickers hardness of samples increased to 1.5–3 times after UCM in water, which was 23.77–48.19% higher than that in kerosene. The metallographic observation indicated the grains on the surface of AZ31B were refined after UCM. The maximum fluctuation of grain size on the material surface was not more than 10 μm after UCM in water, and most of them were concentrated between 1.5 μm and 2.5 μm, while the former was more than 40 μm and the latter were concentrated between 2 μm and 10 μm in kerosene. This reflected that the grain refinement effect of UCM in water was better than that in kerosene. Ultrasonic cavitation can be used as a benign means to improve the surface properties of materials.

Deformation and strain analysis for grain refinement of materials processed through equal channel angular pressing

Abstract Among the various metal forming forms ECAP is one method in which nano crystalline and ultrafine grain metal and amalgams are formed. This method is used for high strain super plasticity in the material by grain refinement to the nano or submicron level, without changing the dimensions of work piece. In this process metal is forced to pass repeatedly through the specially designed channel die with intersectional channel for different angels. The modeling of the die and the billet was done through SOLIDWORKs 2017 and quantitative analysis was done through ANSYS workbench 15.0 software. The result was compared with practical results for different channel angle and it was observed that the ideal parameters for most extreme homogeneity in strain can be accomplished with channel angle Φ = 90 0 , corner angle Ψ = 15 0 and coefficient of friction μ = 0.25.

Can zinc alloys be strengthened by grain refinement? A critical evaluation of the processing of low-alloyed binary zinc alloys using ECAP

In this work, the effect of equal channel angular pressing (ECAP) on the microstructure and mechanical properties of zinc and zinc alloys with Ag, Cu, and Mn additions (0.5 at%) was investigated. Four passes of ECAP Route BC was performed at room temperature for each material. Properties of investigated materials after ECAP were compared to their coarse grained counterparts obtained via indirect hot extrusion at 300 °C. Highest strengthening effect was observed for alloy containing the Mn addition. Grain refinement in materials after ECAP was obtained, mean grain diameter is equal to 20 µm in the case of pure zinc, and less than 3.2 µm for alloys. Strain rate dependent plasticity increase was observed for all fine grained materials, with maximum elongation of 510% measured for Zn-Cu alloy after ECAP. Grain refinement did not result in increased yield and ultimate tensile strength of alloys after ECAP. In all investigated materials tensile properties after ECAP were 20 ~ 60% lower than in hot extruded samples. Based on the tensile properties, microstructure and texture analysis, the changes in the main deformation mechanisms were considered. It was presented that the crystallographic texture and grain size are the main factors affecting twinning, slip and non-slip deformation mechanisms resulting in large differences in observed mechanical properties.

Effects of die profile on grain refinement in Al–Mg alloy processed by repetitive corrugation and straightening

It is shown that a proper selection of corrugation die profile and die parameters is essential for achieving homogeneous grain refinement in materials subjected to repetitive corrugation and straightening (RCS). An Al–Mg (AA 5083) alloy was subjected to the RCS process using three different corrugation die profiles (V-groove, Flat groove, and Semi-circular groove), followed by straightening to determine the allowable maximum number of passes prior to surface cracking/fracture. Mechanical properties, i.e., hardness and tensile strength of the RCS samples were measured and compared as functions of corrugation die profiles and number of passes and the changes in microstructure. Grain refinement was studied using Electron Back Scattered Diffraction (EBSD) analysis and Transmission Electron Microscopy (TEM).