Effect of plastic strain on the solidification cracking of Hastelloy-X in the selective laser melting process

Kitano, Hiroshi; Tsujii, Masakazu; Kusano, Masahiro; Yumoto, Atsushi; Watanabe, Makoto

doi:10.1016/j.addma.2020.101742

Cited by 13 publications

(13 citation statements)

References 18 publications

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“…As described in the Introduction section, the absorptivity is significantly dependent on the laser power and scanning speed [ 20 ]. The authors also studied the shape of a single bead of HX, which can be deep or shallow depending on the laser power and speed of the SLM process [ 7 ]. Thus, parameters calibrated for the specific laser scan conditions may not be useful for other conditions.…”

Section: Discussionmentioning

confidence: 99%

Novel Calibration Strategy for Validation of Finite Element Thermal Analysis of Selective Laser Melting Process Using Bayesian Optimization

2021

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Selective laser melting (SLM) produces a near-net-shaped product by scanning a concentrated high-power laser beam over a thin layer of metal powder to melt and solidify it. During the SLM process, the material temperature cyclically and sharply rises and falls. Thermal analyses using the finite element method help to understand such a complex thermal history to affect the microstructure, material properties, and performance. This paper proposes a novel calibration strategy for the heat source model to validate the thermal analysis. First, in-situ temperature measurement by high-speed thermography was conducted for the absorptivity calibration. Then, the accurate simulation error was defined by processing the cross-sectional bead shape images by the experimental observations and simulations. In order to minimize the error, the optimal shape parameters of the heat source model were efficiently found by using Bayesian optimization. Bayesian optimization allowed us to find the optimal parameters with an error of less than 4% within 50 iterations of the thermal simulations. It demonstrated that our novel calibration strategy with Bayesian optimization can be effective to improve the accuracy of predicting the temperature field during the SLM process and to save the computational costs for the heat source model optimization.

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Section: Discussionmentioning

confidence: 99%

Novel Calibration Strategy for Validation of Finite Element Thermal Analysis of Selective Laser Melting Process Using Bayesian Optimization

2021

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“…In a previous study, the authors investigated the correlation between the strain behavior in the high-temperature region, which can be obtained via a thermal elastoplastic analysis, and the occurrence of solidification cracking in the actual parts of single-track melt components within the process parameter range assuming the SLM process [16]. As a result, it was clarified that solidification cracking occurs when the maximum value of the incremental plastic strain in the solid-liquid coexistence temperature range during the cooling process ∆ε max p , obtained through the thermal elastoplastic analysis, exceeds a threshold value.…”

Section: Methods For Determining Solidification Crack-free Process Parameters 221 Prediction Methods For Solidification Cracking By Thermmentioning

confidence: 99%

“…∆ε max p is the maximum value of incremental plastic strain in the region, where the maximum temperature larger than the liquidus temperature. The material properties used in the thermal elastoplastic analysis were the same as those used in the previous study [16]. The maximum incremental plastic strain threshold value for the occurrence of solidification cracking was set to 0.0041, as determined in the previous study [16].…”

Section: Methods For Determining Solidification Crack-free Process Parameters 221 Prediction Methods For Solidification Cracking By Thermmentioning

confidence: 99%

“…Recently, the authors proposed a method for predicting solidification cracking, which is the dominant type of cracking in the SLM of solution-strengthened Ni-based superalloys, using the plastic strain behavior in the high-temperature region obtained from a thermal elastoplastic analysis [16]. Solidification cracking occurs when the residual liquid film at the columnar interface cannot fully resist shrinkage strain during the solidification process of the material and the cracks are not healed by residual liquid in the surrounding area.…”

Section: Introductionmentioning

confidence: 99%

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Process Parameter Optimization Framework for the Selective Laser Melting of Hastelloy X Alloy Considering Defects and Solidification Crack Occurrence

et al. 2021

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Recent years have witnessed increasing demand for selective laser melting (SLM) in practical applications; however, determining the appropriate process parameter range remains challenging. In this study, a framework was developed to determine the appropriate process parameter range considering the occurrence of defects and cracks by conducting a single-track test and thermal elastoplastic analysis. Keyholing, balling, and the residual unmelted regions were considered defects. The occurrence of solidification cracking, which is predominant in the SLM of solution-strengthened Ni-based alloys, was considered. Using the proposed framework, we could fabricate a part with largely no defects or cracks, except for the edges, under the determined optimal process parameters.

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“…The brittle temperature range (BTR) is an important factor to evolute the susceptibility to cracking. BTR is defined by the temperature difference between the liquidus and solidus temperatures and is usually evaluated by Scheil model calculation [21]. The Scheil model is based on the local equilibrium assumption with regard to the interface between solid and liquid phases.…”

Section: Introductionmentioning

confidence: 99%

Non- and Quasi-Equilibrium Multi-Phase Field Methods Coupled with CALPHAD Database for Rapid-Solidification Microstructural Evolution in Laser Powder Bed Additive Manufacturing Condition

Nomoto

Segawa

Watanabe

2021

Metals

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A solidification microstructure is formed under high cooling rates and temperature gradients in powder-based additive manufacturing. In this study, a non-equilibrium multi-phase field method (MPFM), based on a finite interface dissipation model, coupled with the Calculation of Phase Diagram (CALPHAD) database, was developed for a multicomponent Ni alloy. A quasi-equilibrium MPFM was also developed for comparison. Two-dimensional equiaxed microstructural evolution for the Ni (Bal.)-Al-Co-Cr-Mo-Ta-Ti-W-C alloy was performed at various cooling rates. The temperature-γ fraction profiles obtained under 105 K/s using non- and quasi-equilibrium MPFMs were in good agreement with each other. Over 106 K/s, the differences between the non- and quasi-equilibrium methods grew as the cooling rate increased. The non-equilibrium solidification was strengthened over a cooling rate of 106 K/s. Columnar-solidification microstructural evolution was performed at cooling rates of 5 × 105 K/s to 1 × 107 K/s at various temperature gradient values under a constant interface velocity (0.1 m/s). The results show that, as the cooling rate increased, the cell space decreased in both methods, and the non-equilibrium MPFM was verified by comparing with the quasi-equilibrium MPFM. Our results show that the non-equilibrium MPFM showed the ability to simulate the solidification microstructure in powder bed fusion additive manufacturing.

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Effect of plastic strain on the solidification cracking of Hastelloy-X in the selective laser melting process

Cited by 13 publications

References 18 publications

Novel Calibration Strategy for Validation of Finite Element Thermal Analysis of Selective Laser Melting Process Using Bayesian Optimization

Novel Calibration Strategy for Validation of Finite Element Thermal Analysis of Selective Laser Melting Process Using Bayesian Optimization

Process Parameter Optimization Framework for the Selective Laser Melting of Hastelloy X Alloy Considering Defects and Solidification Crack Occurrence

Non- and Quasi-Equilibrium Multi-Phase Field Methods Coupled with CALPHAD Database for Rapid-Solidification Microstructural Evolution in Laser Powder Bed Additive Manufacturing Condition

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