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Understanding Solid Solution Strengthening at Elevated Temperatures in a Creep-Resistant Dilute Mg-Gd-Ca Alloy

39 Pages Posted: 26 Aug 2019 Publication Status: Accepted

See all articles by Ning Mo

Ning Mo

University of Queensland - School of Mechanical and Mining Engineering

Ingrid McCarroll

The University of Sydney - School of Aerospace Mechanical and Mechatronic Engineering; The University of Sydney - Australian Centre for Microscopy & Microanalysis

Qiyang Tan

University of Queensland - School of Mechanical and Mining Engineering

Anna Ceguerra

University of Queensland - School of Mechanical and Mining Engineering

Ying Liu

The University of Sydney - Australian Centre for Microscopy & Microanalysis; The University of Sydney - School of Aerospace Mechanical and Mechatronic Engineering

Julie Cairney

The University of Sydney - Australian Centre for Microscopy & Microanalysis; The University of Sydney - School of Aerospace Mechanical and Mechatronic Engineering

Hajo Dieringa

MagIC-Magnesium Innovation Centre

Yuanding Huang

MagIC-Magnesium Innovation Centre

Bin Jiang

Chongqing University - College of Material Science and Engineering

Fusheng Pan

Chongqing University - College of Material Science and Engineering

Michael Bermingham

University of Queensland - School of Mechanical and Mining Engineering

Ming-Xing Zhang

University of Queensland - School of Mechanical and Mining Engineering

Abstract

The present work studies the strengthening mechanisms of a low-cost creep-resistant Mg-0.5Gd-1.2Ca (at.%) alloy at both room and elevated temperatures. Although peak-ageing (T6) at 180°C for 32 h led to a significant increase in room temperature strength due to the precipitation strengthening by three types of precipitates (Mg2Ca, Mg5Gd on prismatic planes and a new type of Mg-Gd-Ca intermetallic compound on the basal plane), the as-solid solution treated (T4) alloy exhibited better resistance to temperature softening during compression and to stress relaxation at 180°C and better creep resistance at 210°C/100 MPa. The Gd-Ca co-clusters with short-range order in the Mg solid solution, which was verified, at the first time, by atom probe tomography (APT) analysis and atomic-resolution high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM), were responsible for the solid solution hardening, offering a more effective strengthening effect through local order-strengthening. Such solid solution strengthening increased the thermal stability of the alloy structure at elevated temperatures, at least at early stage of the creep. Subsequently, dynamic precipitation started contributing to the creep resistance due to the formation of higher density of precipitates. However, in the T6 alloy, creep testing at elevated temperatures, particularly at 210°C that was higher than the ageing temperature, led to coarsening of the precipitates, which acted as over ageing. As a result of such over ageing, the resistance of the T6 alloy to heat-induced softening was weakened, leading to lower creep resistance than the T4 alloy.

Keywords: Magnesium alloy, Mechanical properties, Atom-probe tomography, STEM HAADF

Suggested Citation

Mo, Ning and McCarroll, Ingrid and Tan, Qiyang and Ceguerra, Anna and Liu, Ying and Cairney, Julie and Dieringa, Hajo and Huang, Yuanding and Jiang, Bin and Pan, Fusheng and Bermingham, Michael and Zhang, Ming-Xing, Understanding Solid Solution Strengthening at Elevated Temperatures in a Creep-Resistant Dilute Mg-Gd-Ca Alloy. Available at SSRN: https://ssrn.com/abstract=3441466 or http://dx.doi.org/10.2139/ssrn.3441466

Ning Mo (Contact Author)

University of Queensland - School of Mechanical and Mining Engineering

St Lucia
Brisbane, Queensland 4072
Australia

Ingrid McCarroll

The University of Sydney - School of Aerospace Mechanical and Mechatronic Engineering

Sydney
Australia

The University of Sydney - Australian Centre for Microscopy & Microanalysis

Sydney
Australia

Qiyang Tan

University of Queensland - School of Mechanical and Mining Engineering

St Lucia
Brisbane, Queensland 4072
Australia

Anna Ceguerra

University of Queensland - School of Mechanical and Mining Engineering

St Lucia
Brisbane, Queensland 4072
Australia

Ying Liu

The University of Sydney - Australian Centre for Microscopy & Microanalysis

Sydney
Australia

The University of Sydney - School of Aerospace Mechanical and Mechatronic Engineering

Sydney
Australia

Julie Cairney

The University of Sydney - Australian Centre for Microscopy & Microanalysis

Sydney
Australia

The University of Sydney - School of Aerospace Mechanical and Mechatronic Engineering

Sydney
Australia

Hajo Dieringa

MagIC-Magnesium Innovation Centre

Germany

Yuanding Huang

MagIC-Magnesium Innovation Centre

Germany

Bin Jiang

Chongqing University - College of Material Science and Engineering

Chongqing 400044, Chongqing 400030
China

Fusheng Pan

Chongqing University - College of Material Science and Engineering

Chongqing 400044, Chongqing 400030
China

Michael Bermingham

University of Queensland - School of Mechanical and Mining Engineering

St Lucia
Brisbane, Queensland 4072
Australia

Ming-Xing Zhang

University of Queensland - School of Mechanical and Mining Engineering ( email )

St Lucia
Brisbane, Queensland 4072
Australia

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