The Effect of Microstructure and Strain Rates on the Mechanical Properties of Additively Manufactured Metallics

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Materials Science and Engineering".

Deadline for manuscript submissions: 20 June 2024 | Viewed by 1823

Special Issue Editors


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Guest Editor
Department of Mechanical and Mechatronics Engineering, Central University of Technology, Bloemfontein 9301, Free State, South Africa
Interests: additive manufacturing of metallic; polymers and their reinforced composites; natural and synthetic fiber; particulate composites

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Guest Editor
Department of Mechanical and Mechatronics Engineering, Central University of Technology, Bloemfontein 9301, Free State, South Africa
Interests: additive manufacturing of titanium; platinum group metals and related composites; design for additive manufacturing; qualification of additively manufactured components

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Guest Editor
South African Council for Scientific and Industrial Research (CSIR), Pretoria 0001, South Africa
Interests: additive manufacturing; laser surface coating; laser welding

Special Issue Information

Dear Colleagues,

The microstructure of additively manufactured metallics varies as a function of process parameters, types of metallics, cooling rates and post-processing. This in turn impacts their mechanical properties. The mechanical response of additively manufactured metallics is dependent on the imposed strain rates, which affect their dislocation density and microstructure and therefore mechanisms of failure.

Metallics’ response to AM is a function of the optical, thermal and physical properties of the powder and the melt produced. Whilst most alloys used in AM are prealloyed, there is a growing interest in in situ alloying. The work conducted on in situ alloying highlights some degree of loss of the alloying metals, and partial prealloying is recommended in such cases.

The addition of ceramic and nanoparticle-reinforcing phases, while enhancing the thermal, physical and mechanical properties of the produced parts, comes with challenges in optimizing the process parameters. The optimal process parameters in such cases are not singular as when single alloys and metals are used but rather vary with the volume fraction of the reinforcing phases.

This Special Issue will focus on the evolution of different microstructures and resulting mechanical properties of built parts as a function of the AM build process, composition of in situ alloying powders, type and volume fraction of reinforcing phases, post-treatment and imposed strain rates.

Prof. Dr. Maina Maringa
Prof. Dr. Willie Du Preez
Prof. Dr. Sisa Lesley Pityana
Guest Editors

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Keywords

  • additive manufacturing
  • microstructure
  • process parameters
  • in situ and pre-alloying
  • AM composites
  • strain rates
  • thermal
  • physical and mechanical properties

Published Papers (1 paper)

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Research

11 pages, 3503 KiB  
Article
Numerical Simulation of the Taylor Impact Test for Laser Powder Bed Fusion Parts Based on Microstructural Internal State Variables
by Amos Muiruri, Maina Maringa and Willie du Preez
Appl. Sci. 2023, 13(9), 5372; https://doi.org/10.3390/app13095372 - 25 Apr 2023
Viewed by 1178
Abstract
The response of any engineering design components to stresses should be predictable, While the response of a material to complex loading, such as high strain rates experienced during service, is difficult to represent with simple tests, the Taylor impact test is one of [...] Read more.
The response of any engineering design components to stresses should be predictable, While the response of a material to complex loading, such as high strain rates experienced during service, is difficult to represent with simple tests, the Taylor impact test is one of a number of tests devised for high strain rate complex loading. To expedite the acceptance of LPBF Ti6Al4V (ELI) for use in demanding structural applications, there is a need to develop numerical models based on the internal microstructural state variables to predict the performance of the alloy over a wide range of high strain rates using such complex tests. This paper documents the numerical simulation of Taylor impact tests for direct metal laser-sintered and post-processed Ti6Al4V (ELI—Extra Low Interstitial) alloy. A microstructural variable-based constitutive model was used to predict the mechanical properties (stresses and evolution of plastic strains) of the material. The corresponding material parameters of the model were based on the specific microstructure obtained upon post-process heat treatment. The model was first implemented as a user material subroutine in the explicit finite element program ABAQUS using the VUHARD subroutine. Subsequently, the symmetrical Taylor impact tests of Laser Powder Bed Fusion (LPBF) Ti6Al4V (ELI) parts were numerically simulated using the VUHARD subroutine at different impact velocities. The equivalent von Mises stress and plastic strain obtained from numerical simulations were compared with the analytical solutions based on the strain rates obtained. It was shown that the instantaneous and average absolute errors between the numerical and analytical values of the model were generally less than 5%. The mushroom end, commonly observed in a Taylor test specimen, was also seen in the numerical model. Full article
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