Elastic constants of oriented Ti3AlC2 and Ti3SiC2 obtained via coherent inelastic neutron scattering

Abstract

Effort has gone into understanding the properties of MAX phases and their archetypes, Ti3SiC2,and Ti3AlC2, is as these materials exhibit a desirable combination of metallic and ceramic properties [1]. Single crystal elastic constants(SEC), usually obtained using ab-initio calculations in combination with crystallographic information, indicate the materials to be isotropic [2]. While it is difficult to obtain single crystals it is possible to produce highly textured specimens. Using a method developed by Buchenau [3] allows using coherent inelastic neutron scattering to obtain an estimation of the SEC, and such an experiment was performed using the three-axis spectrometer TAIPAN at ANSTO [4]. Results for Ti3AlC2 agree with ab-initio calculations and the assumption of isotropy. For Ti3SiC2 experimental results of c44 = 402.7 GPa do not support isotropic values obtained from ab-initio calculations. Molecular dynamics simulations combined with inelastic neutron scatteringexperiments support the initial diffraction experiment and hence themicromechanical model that was used [5]. We present here a self-consistentdescription of the mechanical properties of the MAX phases Ti3SiC2and Ti3AlC2. [1] M. W. Barsoum et al. Annual Rev.Mat. Res. 41(2011); [2] M. F. Cover et al., J. Phys.Conds. Matt., 21(2009) 305403; [3] U. Buchenau, Sol. St. Comm.,Vol.32(12), 1979 ; [4] V. Gray et al.. J. Am. Ceram. Soc.1-6, 2016; [5] E.H. Kisi et al, J. of Phys.: Cond.Matter 22 (2010) 162202