The fatigue performance of laser powder bed fusion-fabricated Ti-6Al-4V alloy was investigated using four-point bending testing. Specifically, the effects of keyhole and lack-of-fusion porosities along with various surface roughness parameters, were evaluated in the context of pore circularity and size using 2D optical metallography. Surface roughness of S_a = 15 to 7 microns was examined by SEM, and the corresponding fatigue performance was found to vary by 10² cycles to failure. The S–N curves for the various defects were also correlated with process window examination in laser beam power–velocity (P–V) space. Basquin’s stress-life relation was well fitted to the experimental S–N curves for various process parameters except keyhole porosity, indicating reduced importance for LPBF-fabricated Ti-6Al-4V alloy components.

This research program investigated the effects of layer thickness (50 µm and 100 µm) on the microstructure and mechanical properties of electron beam powder bed fusion (EBPBF) additive manufacturing of Inconel 625 alloy. The as-built 50 µm and 100 µm layer thickness components were also heat treated at temperatures above 1100 °C which produced a recrystallized grain structure containing annealing twins in the 50 µm layer thickness components, and a duplex grain structure consisting of islands of very small equiaxed grains dispersed in a recrystallized, large-grain structure containing annealing twins. The heat-treated components of the microstructures and mechanical properties were compared with the as-built components in both the build direction (vertical) and perpendicular (horizontal) to the build direction. Vickers microindentation hardness (HV) values for the vertical and horizontal geometries averaged 227 and 220 for the as-built 50 µm and 100 µm layer components, respectively, and 185 and 282 for the corresponding heat-treated components. The yield stress values were 387 MPa and 365 MPa for the as-built horizontal and vertical 50 µm layer geometries, and 330 MPa and 340 MPa for the as-built 100 µm layer components. For the heat-treated 50 µm components, the yield stress values were 340 and 321 MPa for the horizontal and vertical geometries, and 581 and 489 MPa for the 100 µm layer components, respectively. The elongation for the 100 µm layer as-built horizontal components was 28% in contrast with 65% for the corresponding 100 µm heat-treated layer components, an increase of 132% for the duplex grain structure.

Power requirements are growing day by day, and more power plants are being constructed all over the world. Now the goal has been to look for more sustainable sources of electricity. Sustainability of power plants is a complicated concept and depends on various criteria and sub-criteria. By evaluating them separately creates a complex problem. For this here Multi-Criteria Decision Analysis (MCDA) methods are used for overall assessment and make a sustainability index for seven mostly used power plants. Consideration is taken to both renewable and non-renewable sources. The goal is divided into three basic criteria (i.e. technology, safety & sustainability, economy) and each criterion is further sub-divided into different sub-criteria. The data is collected from various sources and then analyzed using AHP and PROMETHEE methods. The result indicate renewable sources are typically advantageous over non-renewable sources. In certain cases, nuclear has some benefits over other non-renewable energy sources.

The fatigue performance of laser powder-bed fusion-fabricated Ti-6Al-4V alloy was investigated using 4-point bending testing. Specifically, the effects of keyhole and lack-of-fusion porosities along with surface roughness were evaluated in the context of pore circularity and size and compared with surface roughness parameter, Sa. Surface roughness of Sa = 15 to 7 microns were examined by SEM and the corresponding fatigue performance found to vary by 102 cycles to failure. The S-N curves for the various defects were also correlated with process window examination in laser beam power-velocity (P-V) space.