ICAMS / Interdisciplinary Centre for Advanced Materials Simulation

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Mechanical property prediction of additively manufactured metals by micromechanical modelling

Date: 11.12.2019
Time: 12:15
Place: Materials Science and Technology of Additive Manufacturing (MSTAM) Bremen, Germany

Napat Vajragupta
Abhishek Biswas
Mahesh Ramaswamy Guru Prasad
Alexander Hartmaier

Additive manufacturing (AM) has recently come into focus for manufacturing complex metallic structures. Because of the complex thermal cycles the material undergoes, the microstructure of the AM metal is rather complex, of which unique microstructural features including texture, columnar grains, pores, etc. can be observed. To understand the influence of these microstructural features on the mechanical properties of AM metals, which is vital for designing new materials, large series of experiments are typically employed, which is economically rather inefficient. In this context, micromechanical modeling supports the material design process, by predicting the mechanical behavior of materials through microstructure-based simulations. This work aims to demonstrate the possibility of using micromechanical modeling to understand the influence of microstructural features on the mechanical behavior of AM metals. In this context, we present three selected studies from our research group, focusing on 316L stainless steel produced by selective laser melting (SLM). Firstly, because of the importance of texture on anisotropic mechanical behavior, we developed a method to reconstruct the orientation distribution function (ODF) and the misorientation distribution function (MDF). This method is applied to predict anisotropic mechanical behavior during uniaxial tensile testing in different directions. Furthermore, the influence of misorientation distribution function on strain hardening is presented. Secondly, the influence of grain size and shape on strain hardening of AM metal is investigated. To study these size and geometry effects, an in-house software package is applied to generate digitalized microstructures. These digitalized microstructures are subjected to virtual mechanical testing in finite-element simulations applying a nonlocal crystal plasticity model. Thirdly, the influence of pores on the mechanical properties of AM metal is investigated, which is another observed characteristic of AM microstructure. In the last part of this work, pore volume fraction and size are varied to observe their influence on strain hardening behavior.

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