Optimized Combination of Strength and Electrical Conductivity of Al-Mg-Si Alloy Processed by ECAP with Two-Step Temperature.

Nannan Zhao,Chunyan Ban,Jianzhong Cui,Hongfei Wang

doi:10.3390/ma13071511

Abstract

The mechanical properties and electrical conductivity of 6063 aluminum alloy subjected to equal-channel angular press (ECAP) at room temperature (RT), 200 °C, and two-step temperature schedule (TST) have been investigated in this study. The TST refers to one pass at 200 °C followed by further successive pressing at RT. It is shown that this method is effective in obtaining the combination of high strength and electrical conductivity. After two passes, the higher strength can be achieved in TST condition (328 MPa yield strength and 331 MPa ultimate tensile strength), where the changing parameter is processing temperature from the first pass at 200 °C to the second pass at RT, as compared to two passes in RT condition (241 MPa yield strength and 250 MPa ultimate tensile strength) and two passes in 200 °C condition (239 MPa yield strength and 258 MPa ultimate tensile strength). This performance could be associated with grain refinement and nanosized precipitates in TST condition. Moreover, in contrast to RT condition, a higher electrical conductivity was observed in TST condition. It reveals that high strength and electrical conductivity of 6063 aluminum alloy can be obtained simultaneously by ECAP processing in TST condition because of ultrafine-grained microstructure and nanosized precipitates.

Highlights

Severe plastic deformation (SPD) techniques, such as equal-channel angular pressing (ECAP) and high-pressure torsion (HPT), are effective in refining grain size down to submicron-meter or nanometer range through inducing intense shear strain, and lead to high strength [1]
The effect of ECAP processing temperature on the microstructures, mechanical and electrical properties were investigated in 6063 aluminum alloy, and the major findings are summarized as follows: (1)
Both grain refinement and precipitation are extremely dependent on ECAP processing temperature and strain

Summary

Introduction

Severe plastic deformation (SPD) techniques, such as equal-channel angular pressing (ECAP) and high-pressure torsion (HPT), are effective in refining grain size down to submicron-meter or nanometer range through inducing intense shear strain, and lead to high strength [1]. Pure metals and non-heat-treatable alloys in ultrafine-grained (UFG) structure through SPD processing can obtain high strength, which could be associated with grain refinement and high dislocation density [4,5]. The combination effect of grain refinement, dislocation entanglements, and precipitations on the strength has attracted considerable attention. Dynamic precipitation assisted by high density of dislocations and vacancies during SPD processing at elevated temperature can impede coarsening of grains [9,10]. Most previously reported studies on SPD of heat-treatable alloys usually employ an invariable temperature during consecutive SPD processing, and it is a lack of research on the effect of two-step temperature during processing on the microstructure and strength

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