研究目的
To understand the thermokinetics associated with the laser powder bed fusion (LPBF) additive manufacturing (AM) process and its correlation with the microstructure evolved in additively manufactured Ti6Al4V alloy.
研究成果
The computational model developed in the current study helped to understand the thermal evolution during single laser tracks associated with the LPBF fabrication of Ti6Al4V alloy. The cooling rate predicted at martensite start temperature supported formation of martensite as confirmed through XRD and SEM micrographs. The computationally predicted thermal evolution during processing a single layer yielded thermal history with varying cooling rates and directional thermal gradients. These computational results assisted in understanding the experimental observations such as formation of martensite phase, columnar prior β grains, and morphological orientation of martensite.
研究不足
The study focuses on the thermokinetics and microstructural evolution in LPBF manufactured Ti6Al4V alloy, but does not extensively cover the evolution of stress during the LPBF process.
1:Experimental Design and Method Selection
A three-dimensional thermokinetic model based on the finite element method was developed to simulate the thermokinetics of the LPBF process. The study involves a computationally efficient approach of adaptive re-meshing and individual study steps corresponding to building of each layer.
2:Sample Selection and Data Sources
The LPBF parts were produced in the AconityMIDI system equipped with continuous wave (CW) Nd:YAG laser of 85 μm beam diameter. The powder bed was prepared with a commercial grade-23 Ti6Al4V alloy of extra-low interstitial elements.
3:List of Experimental Equipment and Materials
AconityMIDI system, CW Nd:YAG laser, Ti6Al4V alloy powder, Ti6Al4V circular seed plate.
4:Experimental Procedures and Operational Workflow
The samples were produced using laser power of 150 W and a scanning speed of 800 mm/s. Each fused powder layer was fabricated by running multiple subsequent parallel linear laser scans. The distance between the centers of two consecutive laser scans was maintained at 120 μm.
5:Data Analysis Methods
The microstructural examination was performed on the nano scanning electron microscope (SEM) by FEI. In addition, the semiquantitative elemental analysis was performed using energy dispersive spectroscopy (EDS). The samples were also examined in the XY plane, orthogonal to the build direction, to detect the presence of any phases by Rigaku Ultima high-resolution X-ray diffractometer (XRD).
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