Title:	Understanding of elastic and plastic behaviors of metals and alloys under extreme conditions
DNr:	SNIC 2014/1-277
Project Type:	SNIC Medium Compute
Principal Investigator:	Börje Johansson <borje.johansson@fysik.uu.se>
Affiliation:	Kungliga Tekniska högskolan
Duration:	2014-10-01 – 2015-05-01
Classification:	20506
Keywords:

Abstract

In general, metals show two different mechanical behaviors, elastic and plastic deformations. The stacking fault energy (SFE) is very essential factor to understand plastic deformation of metals. According to our previous results, universal scale of SFE, consisted with stable SFE and unstable SFE, well describe the plastic deformation activations of pure metals under zero temperature and pressure. To extend our knowledge, we will apply the universal scaled models to other cases, such as highly disordered alloy, high temperature, and high pressure. In this part, we will use EMTO-CPA and VASP methods. In principles, we need large super cells along <111> direction, at least 12 layers, to calculate simple SFE and large number of systems should be considered to obtain highly accurate results. In normal metals, the elastic strain is limited to 0.2%. Elastic limitation can be increased up to 10%, so-called 'super-elasticity, on the occurrence of a thermo-elastic martensitic phase transformation. Fe-based shape memory alloys have long been investigated, because of their better workability and low cost. They are commercially more attractive than NiTi-based SMAs. The invention of ferrous shape memory alloy Fe-28Ni-17Co-11.5Al-2.5Ta-0.05B by Y. Tanaka et. al is a breakthrough, in which alloy the elastic strain reaches ~13%. We will perform the calculations about phase stability, Bain-transformation, interface energy, and magnetic properties using the ab-initio calculation based on density functional theory (DFT). In this calculation, we will use VASP with super-cell method to describe chemical effect on elastic properties, and about 500 atoms will be considered in a cell. In summary, we will investigate the elastic and plastic deformation behaviors of metals and alloys depending on various conditions such as, external pressure, temperature and chemical compositions. This study will be very helpful to survey origin of mechanical deformations in metals, and provide extending potentials of application for usefulness of metals.