Thermomechanical processing of an ultralight Mg-14Li-1Al alloy
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ORIGINAL ARTICLE
Thermomechanical processing of an ultralight Mg-14Li-1Al alloy Rezawana Islam 1 & Amir Hadadzadeh 2 & Mary Wells 3 & Meysam Haghshenas 4 Received: 17 April 2020 / Accepted: 1 September 2020 / Published online: 21 September 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract In the present work, isothermal hot pressing of a Mg-14Li-Al (wt%) alloy, considered as the lightest metallic alloy, is studied through microstructure, hot compression flow stress curve, and indentation load/displacement plots. The main objective is to correlate the microstructure with the small-scale properties and processing parameters (i.e., thermomechanical parameters like temperature and strain rate). The thermomechanical cycle consists of uniaxial compression tests at temperatures of 250 °C, 350 °C, and 450 °C and strain rates of 1, 0.1, 0.01, and 0.001/s using a Gleeble® 3500 thermal-mechanical simulation testing system. True stress-true strain curves plotted from the thermomechanical tests were used to assess the working behavior of the materials and to analyze and to understand the microstructure evolution which reflects intrinsic mechanical properties. Finally, a comparison has been done in between our previously published article Mg-3.5Li-Al (International Journal of Lightweight Materials and Manufacture 2 (2019) 217–226) and the current work on Mg-14Li-Al alloy in terms of the microstructural changes, hot compression stress-strain curves, and the nanoindentation load/displacement response. Keywords Hot compression . Thermomechanical processing . Ultralight Mg . Mg-14Li-1Al . Nanoindentation
1 Introduction The critical fact associated with greenhouse gas emissions and fuel consumption rate in the automotive and aerospace industries demands lightweight vehicles which brings the transition from high-strength steels to lower density materials like magnesium [1–3]. However, the plasticity of wrought is very limited at the ambient (room) temperature [4–6]. Therefore, alloys with very low density and good formability are developed by adding lithium to magnesium which response excellently to high
* Meysam Haghshenas [email protected] 1
Materials Science & Engineering, Virginia Tech, Blacksburg, VA, USA
2
Department of Mechanical Engineering, University of Memphis, Memphis, TN, USA
3
College of Engineering and Physical Sciences, University of Guelph, Guelph, Canada
4
Micro/Nano-Mechanics Laboratory, Department of Mechanical, Industrial and Manufacturing Engineering, University of Toledo, Toledo, OH, USA
formability and can potentially be formed at room temperature [7–9]. Lithium possesses a favorable effect on the deformability of magnesium alloys replacing the hardly deformable hexagonal α-Mg (hcp) lattice with a body-centered cubic β-Li lattice (bcc) [9–11]. Even it is possible to obtain a Mg-Li alloy with the density lower even than 1 g/cm3 [12]. Conventional Mg-Li alloys normally relied upon large Li additions that change the hexagonal closed pack (HCP) structure of Mg to BCC [1
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