Fabrication of smart structures through selective laser melting (3D printing) (I)

• Main Author: Lim, Yi Long
• Other Authors: Liu Yong
• Format: Final Year Project
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/67735
• Institution: Nanyang Technological University

Additive manufacturing such as Selective Laser Melting (SLM) has offered new breakthroughs in the fabrication of NiTi SMA from its powdered form. It offers the possible advantage of achieving higher economic viability, production efficiency and improved mechanical and functional properties. As such existing literatures has predominantly focused on studying laser processing parameters and its effect in four main areas: Density, Microstructure, Transformation Temperature and Shape Recovery Property. However most emphasis is placed on the laser processing parameters of power input and scan velocity. Therefore other parameters such as hatch distance is an area of study which possess the potential for greater scientific applications which is now lacking in deeper research. In this study, the effects of hatch distance on density, microstructure and phase transformation temperature are investigated. Laser parameters such as velocity and power input are first varied to find out the optimal laser processing configurations to achieve the highest sample bulk density and closest transformation temperature to the initial powder. Further investigations on hatch distances up to 100μm is carried out to study its effects on the transformation temperature, density and microstructure. In the analysis, it is found that variations in hatch distance up to a 100 μm has an insignificant influence on the transformation temperature. However the choice of hatch distance can have a significant impact on the microstructure and hence densification behaviour. An initial increase in hatch distance led to an increase in sample density until the optimal value of 25-50 μm is reached. However further increase in hatch distance beyond this range led to a decline in bulk density. Highest bulk density is obtained and this is identified at power, scan velocity and hatch distance of 40 W, 100 mm/s and 50 μm. An EDS & XRD study on the highest bulk density parameter is further carried out to identify the possible composition and intermetallic phases present. Finally further recommendations are provided for future studies.