Microstructures and Hardness Prediction of an Ultrafine-Grained Al-2024 Alloy

Chen Chen,Starink Starink,Hu Hu,Gao Gao,Zhang Zhang,Tang Tang

doi:10.3390/met9111182

Chen Chen, Starink Starink + Show 4 more

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https://doi.org/10.3390/met9111182

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Abstract

High-pressure torsion (HPT) is a high efficiency processing method for fabricating bulk ultrafine-grained metallic materials. This work investigates microstructures and evaluates the corresponding strengthening components in the center of HPT disks, where effective shear strains are very low. An Al-4.63Cu-1.51Mg (wt. %) alloy was processed by HPT for 5 rotations. Non-equilibrium grain and sub-grain boundaries were observed using scanning transmission electron microscopy in the center area of HPT disks. Solute co-cluster segregation at grain boundaries was found by energy dispersive spectrometry. Quantitative analysis of X-ray diffraction patterns showed that the average microstrain, crystalline size, and dislocation density were (1.32 ± 0.07) × 10−3, 61.9 ± 1.4 nm, and (2.58 ± 0.07) × 1014 m−2, respectively. The ultra-high average hardness increment was predicted on multiple mechanisms due to ultra-high dislocation densities, grain refinement, and co-cluster–defect complexes.

Highlights

IntroductionHigh-pressure torsion (HPT) is a type of advanced severe plastic deformation processing (SPD)
High-pressure torsion (HPT) is a type of advanced severe plastic deformation processing (SPD)that can fabricate bulk metallic materials with ultrafine-grained microstructures and a high dislocation density [1,2]
Compared to other SPD techniques, HPT has a higher efficiency for grain refinements and a good potential to improve the strength of metallic materials

Summary

Introduction

High-pressure torsion (HPT) is a type of advanced severe plastic deformation processing (SPD). That can fabricate bulk metallic materials with ultrafine-grained microstructures and a high dislocation density [1,2]. HPT produces heterogeneous microstructures across the radius of the discs [2,3]. Compared to other SPD techniques, HPT has a higher efficiency for grain refinements and a good potential to improve the strength of metallic materials. The hardness evolution, dislocation behavior, and grain refinement during HPT processing of Al-2024 alloys have been recently investigated [6]. Grain refinement to nano scales with high angle misorientations leading to superplastic deformation through boundary sliding has been reported [7]

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