The Thermal Properties of L12 Phases in Aluminum Enhanced by Alloying Elements

Jihang Lan,Jianbo Li,Xiaofang Peng,Linghong Liu,Zhaoqun Chen,Qingzhou Zhang,Mengdong He,Touwen Fan

doi:10.3390/met11091420

Abstract

The L12 type trialuminide compounds Al3M possess outstanding mechanical properties, which enable them to be ideal for dispersed strengthening phases for the high-strength thermally stable Al based alloys. Ab-initio calculations based on the density functional theory (DFT) were performed to study the structural, electronic, thermal, and thermodynamic properties of L12-Al3M (M = Er, Hf, Lu, Sc, Ti, Tm, Yb, Li, Mg, Zr) structures in Al alloys. The total energy calculations showed that the L12 structures are quite stable. On the basis of the thermodynamic calculation, we found that the Yb, Lu, Er, and Tm atoms with a larger atomic radii than Al promoted the thermal stability of the Al alloys, and the thermal stability rank has been constructed as: Al3Yb > Al3Lu > Al3Er > Al3Tm > Al, which shows an apparent positive correlation between the atomic size and thermal stability. The chemical bond offers a firm basis upon which to forge links not only within chemistry but also with the macroscopic properties of materials. A careful analysis of the charge density indicated that Yb, Lu, Er, and Tm atoms covalently bonded to Al, providing a strong intrinsic basis for the thermal stability of the respective structures, suggesting that the addition of big atoms (Yb, Lu, Er, and Tm) are beneficial for the thermal stability of Al alloys.

Highlights

The considerable attention that aluminum alloys have received originates from their excellent physical and chemical properties, such as low density, high specific strength, easy processing and molding, excellent electrical conductivity, thermal conductivity, corrosion resistance, etc
The electron–ion interaction was described by the projector augmented wave (PAW) method
It is worth noting that the narrow f-bands in RE compounds are not adequately described by standard local density approximation (LDA) and the generalized gradient approximation (GGA) [25,26] due to strong electronic correlation effects

Summary

Introduction

The considerable attention that aluminum alloys have received originates from their excellent physical and chemical properties, such as low density, high specific strength, easy processing and molding, excellent electrical conductivity, thermal conductivity, corrosion resistance, etc. The L12 -Al3 M structure phase in Al alloy has received great attention since it was reported to improve the strength, toughness, wear resistance, corrosion resistance, fatigue resistance, and high-temperature resistance properties significantly [5,6].

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