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<p>The Prediction of residual stresses in direct laser deposition (DLD) additive manufacturing is critical for preventing workpiece cracking and enhancing mechanical performance. Traditional experimental approaches for evaluating residual stresses under varying process parameters are time-consuming and costly. In this study, a coupled thermo-mechanical finite element model incorporating temperature-dependent material properties and element activation/deactivation techniques was used to simulate the multi-layer DLD process of γ-TiAl alloys (nominal composition: Ti–48Al–2Cr2Nb). Validation using thermocouple measurements and X-ray diffraction residual stress data confirmed the accuracy of the model. The simulations revealed that the maximum tensile residual stresses (≈&#xa0;600&#xa0;MPa, model-predicted) were concentrated at the wall-substrate interface along the laser scanning direction (<i>x</i>-axis), primarily driven by the steep thermal gradient between the preheated powder and room-temperature substrate during the initial layer deposition. Parametric studies demonstrated that increasing the laser power from 600 to 780 W reduces predicted interfacial stresses by 25 pct through enhanced substrate melting and stress homogenization, whereas lowering the scanning speed from 5 to 4&#xa0;mm/s decreases the predicted internal stress fluctuations by 50 pct. Furthermore, preheating the substrate to 773&#xa0;K resulted in an additional 25 pct predicted interfacial stress reduction by mitigating the thermal mismatch.</p>

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Numerical Simulation of Residual Stress Evolution and Interfacial Cracking in Directed Laser Deposition of γ-TiAl Alloys

  • 期刊论文

  • 发表日期：

    2025年10月14日

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  • Zheng Zhou,
  • Jianfeng Gu,
  • Daming Tong

摘要

The Prediction of residual stresses in direct laser deposition (DLD) additive manufacturing is critical for preventing workpiece cracking and enhancing mechanical performance. Traditional experimental approaches for evaluating residual stresses under varying process parameters are time-consuming and costly. In this study, a coupled thermo-mechanical finite element model incorporating temperature-dependent material properties and element activation/deactivation techniques was used to simulate the multi-layer DLD process of γ-TiAl alloys (nominal composition: Ti–48Al–2Cr2Nb). Validation using thermocouple measurements and X-ray diffraction residual stress data confirmed the accuracy of the model. The simulations revealed that the maximum tensile residual stresses (≈ 600 MPa, model-predicted) were concentrated at the wall-substrate interface along the laser scanning direction (x-axis), primarily driven by the steep thermal gradient between the preheated powder and room-temperature substrate during the initial layer deposition. Parametric studies demonstrated that increasing the laser power from 600 to 780 W reduces predicted interfacial stresses by 25 pct through enhanced substrate melting and stress homogenization, whereas lowering the scanning speed from 5 to 4 mm/s decreases the predicted internal stress fluctuations by 50 pct. Furthermore, preheating the substrate to 773 K resulted in an additional 25 pct predicted interfacial stress reduction by mitigating the thermal mismatch.