Thermo-Mechanical Analysis and Characterization of Wire Arc Additive Manufactured Components

Mechanical components are typically isotropic when manufactured by traditional methods such as casting, forging, etc. However, complex geometries would be difficult with these methods. In order to fabricate the complex components, various methods have been suggested. One of such methodsis weld based additive manufacturing wherein welding is used to join the material selectively at the different locations. Mechanical tests are usually employed in investigational work in order to obtain information for use in design and manufacturing to ascertain whether the material meets the specifications for its intended use, to produce desired mechanical properties like hardness and tensile tests The intention of performing a simulation or numerical model is to predict the physical performance of an existing process. On the other hand, it may be essential to compromise the results in terms of accuracy, computational time of the model. The aim of the current work is to survey and develop a modeling method to simulate the deposition of a single straight bead and implementing the same towards constructing thin wall components using the finite element analysis. The simulating phenomenon is carried out numerically and followed by DFLUX subroutine. The model must be efficient and reliable enough to be functional in the designing and path planning of the fabricating features. In addition, a transient thermal distribution of deposited weld metal is modeled analytically in aspects of various heat sources. Importantly the heat distribution of the Goldak’s heat source is explored to improve the results of the experimental analysis. An attempt has been made to correlate the microstructural analysis with the modeling results. Hence the phase proportion, deformed shape, residual stresses, the microstructural analysis could be evaluated

Microstructure evolution along build direction for thin-wall components fabricated with wire-direct energy deposition

Purpose: The use of a gas metal arc welding-based weld-deposition, referred to as wire-direct energy deposition or wire-arc additive manufacturing, is one of the notable additive manufacturing methods for producing metallic components at high deposition rates. In this method, the near-net shape is manufactured through layer-by-layer weld-deposition on a substrate. However, as a result of this sequential weld-deposition, different layers are subjected to different types of thermal cycles and partial re-melting. The resulting microstructural evolution of the material may not be uniform. Hence, the purpose of this study is to assess microstructure variation along with the lamination direction (or build direction). Design/methodology/approach: The study was carried out for two different boundary conditions, namely, isolated condition and cooled condition. The microstructural evolution across the layers is hypothesized based on experimental assessment; this included microhardness, scanning electron microscopy imaging and electron backscatter diffraction analysis. These conditions subsequently collaborated with the help of thermal modeling of the process. Findings: During a new layer deposition, the previous layer also is subject to re-melt. While the newly added layer undergoes rapid cooling through a combination of convection, conduction and radiation losses, the penultimate layer, sees a slower cooling curve due to its smaller exposure area. This behavior of rapid-solidification and subsequent re-melting and re-solidification is a progressing phenomenon across the layers and the bulk of the layers have uniform grains due to this remelt-re-solidification phenomenon. Research limitations/implications: This paper studies the microstructure variation along with the build direction for thin-walled components fabricated through weld-deposition. This study would be helpful in addressing the issue of anisotropy resulting from the distinctive thermal history of each layer in the overall theme of metal additive manufacturing. Originality/value: The unique aspect of this paper is the postulation of a generic hypothesis, based on experimental findings and supported by thermal modeling of the process, for remelt-re-solidification phenomenon followed by temperature raising/lowering repetitively in every layer deposition across the layers. This is implemented for different types of base plate conditions, revealing the role of boundary conditions on the microstructure evolution. © 2021, Emerald Publishing Limited