Additive manufacturing of metallic components – Process, structure and properties

The production of metal parts via laser powder bed fusion additive manufacturing is growing exponentially. However, the transition of this technology from production of prototypes to production of critical parts is hindered by a lack of confidence in the quality of the part. Confidence can be established via a fundamental understanding of the physics of the process. It is generally accepted that this understanding will be increasingly achieved through modeling and simulation. However, there are significant physics, computational, and materials challenges stemming from the broad range of length and time scales and temperature ranges associated with the process. In this paper, we review the current state of the art and describe the challenges that need to be met to achieve the desired fundamental understanding of the physics of the process.

Laser powder bed fusion additive manufacturing of metals; physics, computational, and materials challenges

A review of the wire arc additive manufacturing of metals: properties, defects and quality improvement

Materials for additive manufacturing

Effect of Selective Laser Melting (SLM) process parameters on microstructure and mechanical properties of 316L austenitic stainless steel

Effect of inter-layer dwell time on distortion and residual stress in additive manufacturing of titanium and nickel alloys

Thermomechanical Modeling of Additive Manufacturing Large Parts

Residual stress mapping in Inconel 625 fabricated through additive manufacturing: Method for neutron diffraction measurements to validate thermomechanical model predictions

In this work, a finite element model is developed for predicting the thermo-mechanical response of Ti-6Al-4V during electron beam deposition. A three-dimensional thermo-elasto-plastic analysis is performed to model distortion and residual stress in the workpiece and experimental in situ temperature, and distortion measurements are performed during the deposition of a single-bead-wide, 16-layer-high wall built for model validation. Post-process blind hole–drilling residual stress measurements are also performed. Both the in situ distortion and post-process residual stress measurements suggest that stress relaxation occurs during the deposition of Ti-6Al-4V. A method of accounting for such stress relaxation in thermo-elasto-plastic simulations is proposed where both stress and plastic strain are reset to 0, when the temperature exceeds a prescribed stress relaxation temperature. Inverse simulation is used to determine the values of the absorption efficiency and the emissivity of electron beam–deposited, wir...

Residual Stress and Distortion Modeling of Electron Beam Direct Manufacturing Ti-6Al-4V

A three-dimensional finite element model is developed to allow for the prediction of temperature, residual stress, and distortion in multi-layer Laser Powder-Bed Fusion builds. Undesirable residual stress and distortion caused by thermal gradients are a common source of failure in AM builds. A non-linear thermoelastoplastic model is combined with an element coarsening strategy in order to simulate the thermal and mechanical response of a significant volume of deposited material (38 layers and 91 mm3). It is found that newly deposited layers experience the greatest amount of tensile stress, while layers beneath are forced into compressive stress. The residual stress evolution drives the mechanical response of the workpiece. The model is validated by comparing the predicted in situ and post process distortion to experimental measurements taken on the same geometry. The model accurately predicts the distortion of the workpiece (5% error).

Erik R. Denlinger

Papers

Effect of inter-layer dwell time on distortion and residual stress in additive manufacturing of titanium and nickel alloys

Thermomechanical Modeling of Additive Manufacturing Large Parts

Residual stress mapping in Inconel 625 fabricated through additive manufacturing: Method for neutron diffraction measurements to validate thermomechanical model predictions

Residual Stress and Distortion Modeling of Electron Beam Direct Manufacturing Ti-6Al-4V

Thermomechanical model development and in situ experimental validation of the Laser Powder-Bed Fusion process