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Dislocations in solids

Selective laser melting (SLM) has emerged as one of the primary metal additive manufacturing technologies used for many applications in various industries such as medical and aerospace sectors. However, defects such as part distortion and delamination resulted from process-induced residual stresses are still one of the key challenges that hinder widespread adoptions of SLM. For process parameters, the laser beam scanning path will affect the thermomechanical behaviors of the build part, and thus, altering the scanning pattern may be a possible strategy to reduce residual stresses and deformations through influencing the heat intensity input distributions. In this study, a 3D sequentially coupled finite element (FE) model was developed to investigate the thermomechanical responses in the SLM process. The model was applied to test different scanning strategies and evaluate their effects on part temperature, stress and deformation. The major results are summarized as follows. (1) Among all cases tested, the out-in scanning pattern has the maximum stresses along the X and Y directions; while the 45° inclined line scanning may reduce residual stresses in both directions. (2) Large directional stress differences can be generated by the horizontal line scanning strategy. (3) X and Y directional stress concentrations are shown around the edge of the deposited layers and the interface between the deposited layers and the substrate for all cases. (4) The 45° inclined line scanning case also has a smaller build direction deformation than other cases.

Stress and Deformation Evaluations of Scanning Strategy Effect in Selective Laser Melting

Microstructural evolution of a Ni-based superalloy (617B) at 700 °C studied by electron microscopy and atom probe tomography

Full length articleStress and deformation evaluations of scanning strategy effect in selective laser melting

Build direction dependence of microstructure and high-temperature tensile property of Co-Cr-Mo alloy fabricated by electron beam melting

The effect of boron additions ranging from 5 to 210 ppm on the microstructure and transverse properties of a directionally solidified (DS) superalloy was studied. Lamellar borides were observed in the as-cast specimens when B addition was increased to 210 ppm. The borides gradually decomposed during solution heat treatment. γ′ envelope formed around carbides in B containing alloys after solution heat treatment. No secondary carbides were found during the formation of the γ′ envelope. The transverse creep lifetime and the tensile properties at both room temperature and 870 °C were significantly improved when boron was added. However, further increasing in B content showed different effect on creep strength and tensile properties at different experimental conditions.

Langhong Lou

Papers

Effect of boron additions on the microstructure and transverse properties of a directionally solidified superalloy

Effect of Long-term Thermal Exposure on Microstructure and Stress Rupture Properties of GH3535 Superalloy

Effect of Withdrawal Rates on Microstructure and Creep Strength of a Single Crystal Superalloy Processed by LMC

Effect of Solidification Condition and Carbon Content on the Morphology of MC Carbide in Directionally Solidified Nickel-base Superalloys

Role of tantalum in the hot corrosion of a Ni-base single crystal superalloy