Fundamental studies on the evolution of stress and other defects during additive manufacturing.
Abstract
In this research proposal, we put forward the hypothesis that there are still important unresolved specific technical challenges and scientific issues related to the evolution of stress and porosity during additive manufacturing (AM) processing that require systematic, fundamental research. This argument is made on the basis of our prior experience with AM, as well as on our review of current scientific literature. To that effect most current research focuses on minimizing surface roughness and geometrical inaccuracies, predicting microstructural evolution through unique thermal cycles, avoiding incorporation of un-molten particles and porosity, and ameliorating the effects of residual stress. These issues are influenced by a number of process parameters and variables, such as the laser power and powder feed rate, as well as the scan sequence and timing of laser passes, which can alter thermal transfer behavior. There are also some interesting and critical but more challenging problems related to the melt pool that require in-depth studies of a fundamental nature, including powder interactions with the laser beam and melt pool, convective and turbulent melt flow behavior, keyhole formation in the melt pool, rapid melting, potential vaporization, non-equilibrium solidification involving phase transformations, and possible chemical reactions between reactive elements. The scientific objectives of the proposed research are to provide fundamental insight into mechanisms that govern evolution of stress and porosity during laser directed energy deposition (DED). To accomplish these objectives, we describe a research proposal that involves carefully designed experiments, advanced diagnostics (microstructure and mechanical behavior) and modeling analysis in combination with binary materials systems with well-established thermodynamic and physical properties. The materials systems proposed herein were selected in order to facilitate interpretation and analysis of the results that will be generated. More specifically, the proposed research is oriented to establish the framework that is required to deploy fundamental studies on particleÐpool interactions and their effects on porosity and residual stresses in materials fabricated via DED. We propose to use laser engineered net shaping (LENS¨), one of the DED technologies designed to fabricate 3D structures via a powder injection mechanism. The proposed program will generate the information insightful into unresolved technical challenges and scientific issues related to AM processing, and furthermore leverage the optimization of material performance and component functionality during AM. The proposed program will have significant impact on education in materials science and engineering, as well as on the training of post-doctoral researchers.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 14, 2019
- Source ID
- W911NF1810279
Entities
People
- Enrique J. Lavernia
Organizations
- Army Contracting Command
- United States Army
- University of California, Irvine