4:00pm - 4:30pmInvited
Functional Additive Manufacturing with Smart Materials
Singapore University of Technology and Design, Singapore
Smart materials such as shape memory polymers, hydrogels and others have recently gained great attention due to their abilities of switching configurations in response to various environmental stimuli. Unique properties and advantages of these materials, however, have not been fully exploited because manufacturing and material processing for this new class of materials still rely on conventional methods. The rapid advanced 3D printing technique provides unprecedented freedom of design and manufacturing and allows us to fabricate complex 3D structures and devices with smart materials. The technique of printing 3D structures with smart materials that change configurations over time sometimes also refers to as “4D printing”.
In this talk, I will introduce a paradigm of printed active composites that is realized by using a commercial 3D printer to print composites with complex and controllable anisotropic thermomechanical behavior via prescribing the architecture, shape, size, orientation and even spatial variation of the fibers with shape memory effects. I will also introduce a new high resolution multifunctional 3D printing technique developed for printable active materials - projection micro-stereolithography (PμSL). PμSL is a 3D micro-stereolithography technology capable of rapidly building highly complex microstructures by converting photocurable resin into solid layer-upon-layer. PμSL allows us to freely tune the thermomechanical properties for smart materials with inexpensive commercial available materials. Using PμSL, we are able to print freely tunable smart materials with multi-functinoal behaviors and fabricate highly deformable complex 3D shape memorable devices with refined features.
4:30pm - 4:45pmOral
3D Stereolithography of Polymer Composites Reinforced with Orientated Nanoclay
1Singapore Institute of Manufacturing Technology, Agency for Science, Technology and Research (A*STAR), Singapore; 2Singapore Centre for 3D Printing, Nanyang Technological University, Singapore
Polymer parts fabricated by 3D stereolithography tend to have poorer mechanical properties as compared to their counterparts fabricated via conventional methods. Furthermore, due to cross linkage among polymer chains in the thermoset polymers, the 3D printed parts tend to have low elongation and undergo brittle fracture during failure. Various types of fillers have been added into photopolymer to improve the mechanical properties. In this study, montmorillonite nanoclays (plate-shaped) are first homogenously dispersed in the photopolymer, and during the printing process, the lowering of build platform into the tank provides a downward force to orientate the plate-shaped nanoclays for each print layer. The nanoclays will be immobilized during photopolymerization, thus maintaining their orientation. This drastically improves the elongation by more than 100% and enhances the tensile stress and Young’s Modulus in the aligned direction. The dispersion, alignment, size and loadings of the montorillonite nanoclays were discussed. This new approach will open up possibilities for printing high performance parts using stereolithography.
4:45pm - 5:00pmOral
Additive Manufacturing of Nickel and Titanium alloys: A Review on Microstructural Evolution and Mechanical Properties
Advanced Remanufacturing and Technology Center (ARTC), Agency for Science, Technology and Research (A*STAR), Singapore
Additive manufacturing (AM) provides a sophisticated rapid manufacturing tool that allows layer-by-layer fabrication of complex and multifunctional components for use in critical engineering applications such as jet engines, power plants and reactor vessels. Since AM technologies involves a complex interplay between the energy transfer and microstructural evolution, it is critical to clearly understand the relationship between various AM processes, the key process variables, and resulting microstructural and mechanical properties. This article reviews various research efforts deployed so far on the development of nickel and titanium alloys using different powder bed fusion and directed energy deposition additive processes. Published key microstructural characteristics such as grain growth, precipitates and crystallographic texture are discussed in terms of powder raw materials, key process variables and post-processing conditions. The mechanical properties reported under tension, indentation and compression loads as obtained from open literature are summarized. The effects of build direction and test orientation, post-processing, heat treatment, when available, are also provided. Special attention is also given to collate available information regarding the structural properties of powder raw materials.
5:00pm - 5:15pmOral
Additive Manufacturing of Porous Titanium by 3D Inkjet Printing of TiH2
Singapore Institute of Manufacturing Technology, Agency for Science, Technology and Research (A*STAR), Singapore
Porous Ti component provides manipulatable specific surface, permeability, density and mechanical properties, and pure Ti has outstanding properties such as excellent corrosion resistance, biocompatibility and high specific strength. These attributes make porous Ti one of the most competitive materials for some special applications, like corrosion-resistant filter, dental and orthopaedic implant. This study first reports additive manufacturing of porous Ti by the efficient 3D inkjet printing of low cost TiH2 powder mixed with Poly[vinyl alcohol] (PVA) and sintering in hydrogen environment. The final porosity was controlled by adjusting both the PVA content in the precursor material and sintering protocol. The influence of PVA on the behaviour of TiH2 decomposition and sintering was investigated by differential scanning calorimetry (DSC), thermogravimetry (TG) and thermal dilatometry analysis. The microstructure and pore morphology were characterized using optical microscopy (OM) and scanning electron microscopy (SEM). The microhardness and compressive properties were also determined. The effects of contamination by oxygen and carbon were briefly discussed.
5:15pm - 5:30pmOral
Characteristics of Metallic Powders for 3D Additive Manufacturing
1Singapore Institute of Manufacturing Technology, Agency for Science, Technology and Research (A*STAR), Singapore; 2School of Mechanical & Aerospace Engineering College of Engineering, Nanyang Technological University, Singapore
Metallic powders play an important role in the quality of additive manufactured parts. Powders are produced by various methods and have different characteristics. Thus, not all types of powders are suitable for the additive manufacturing process. Understanding the powders’ characteristics would enhance the overall quality of built parts and reduce the need for post-processing. This present study gives insights into the metallic powders’ production methods as well as the characteristics for additive manufacturing applications. Different types of metallic powders, such as stainless steel, Inconel, titanium and aluminum alloy powders, show different flow and packing behaviors. In addition, the relationships of powders’ characteristics, the quality of built parts and the roles of oxygen and moisture are discussed.
5:30pm - 5:45pmOral
Corrosion; Wear; Hardness; Al-Si-Cu coatings; EISEffects of Composition and Process Parameters on the Tribological and Corrosion Characteristics of Al-Si-Cu Coatings on Ti-6Al-4V Alloy
Tshwane University of Technology, South Africa
The performance of material surface under wear and corrosion environments cannot be fulfilled by the conventional surface modifications and coatings. Therefore, different industrial sectors need an alternative technique for enhanced surface properties. Titanium and its alloys possess poor tribological properties which limit their use in certain industries. The investigation of Al-Si-Cu coatings on titanium alloy (Ti6Al4V) by laser cladding technique is aimed at enhancing the tribological properties. A 3 kW continuous wave ytterbium laser system (YLS) attached to a KUKA robot which controls the movement of the cladding process was utilized for the fabrication of the coatings. The titanium cladded surfaces were investigated for its hardness, corrosion and tribological behaviour at different laser processing conditions. The samples were cut to corrosion coupons, and immersed into 3.65% NaCl solution at 28oC using Electrochemical Impedance Spectroscopy (EIS) and Linear Polarization (LP) techniques. The microstructures of the fabricated coatings were characterized by optical microscope (OM) and field emission scanning electron microscope (SEM/EDS) and thermogravimetric analyzer (TGA). In addendum, the phases present in the coatings were identified by X-ray diffractometer (XRD). The low coefficient of friction, excellent wear resistance and high micro hardness were attributed to the formation of hard intermetallic compounds (TiCu, Ti2Cu, Ti3Al, TiO2). The load bearing capability of the substrate was improved due to the excellent wear resistance of the coatings. The cladded layer showed a uniform crack free surface due to optimized laser process parameters which led to the refinement of eutectic Si particles in the coatings. Moreover, the corrosion resistance of the coating was also enhanced with increasing Cu content. The COMSOL multiphysics model used in this research authenticates reasonably with the experimental results.
5:45pm - 6:00pmOral
Development and Characterization of SiC and Al2O3/AA5083 Composites by Friction Stir Processing
British University in Egypt, Egypt
In this work friction stir processing (FSP) was utilized to incorporate SiC of 20μmsize, Al2O3 of 3μm size and mixture of SiC/Al2O3particles in AA5083. The ceramic powders were packed into grooves of 2 mm width and 6 mm depth cut on 10 mmthickaluminum plates. The top surface of the grooves was closed using pinless tool of 25mm diameter shoulder to prevent the escape of the packed particles during FSP. FSP was performed using conventional tool that was fabricated by H13 tool steel with 25mm diameter shoulder and square probe of 6mm diagonal.FSP tool was plunged into the work piece and traversed along the groove at travelling speed of 60mm/min with different rotational speeds of 400 rpm, 600 rpm and 800 rpm. Two passes were applied at the same FSP parameters. After the preparation of the compositematerials, samples were cut parallel to the processing direction.Tensile samples were prepared parallel to the processing direction and tested using Universal tensile testing machine at strain rate of 10 mm/min. The micro-hardness distribution was measured at the midsection of the processed zone using Vickers micro hardness tester at load of 10 HV. Wear resistance was also examined using pin on ring technique and correlated with the hardness and microstructure. The worn surface were examined by optical scanning electron microscopies. The results showed that the reinforcement particles were distributed homogenously inside the nugget zone. The average hardness increased by 30% with increasing the content of ceramic particles. The addition of ceramic powder (SiC) as a reinforcement into AA5083 improved the wear resistance of the received AA5083 by 40%. Applied load and relative ratio of SiC and Al2O3 particles have a significant influence on the wear resistance. Hybrid composite of 50% SiC and 50% Al2O3 showed a superior wear resistance at a normal load of 20 N.
6:00pm - 6:15pmOral
Infiltration of Pure Magnesium into Inkjet 3D Printed Porous Titanium for Biomedical Applications
Singapore Institute of Manufacturing Technology, Agency for Science, Technology and Research (A*STAR), Singapore
Magnesium (Mg) with low density (~1.74 g/cm3), ability to degrade in vivo and low young's modulus of ~40 to 45 GPa closer to that of cortical bone (~7 to 30 GPa) makes it an attractive biomaterial. When used for orthopedic applications, Mg implants are expected to provide adequate mechanical properties but due to its alarming degradation rate, there are high possibilities for failure of implants before bone healing. To overcome its premature failure, Ti-Mg composite was fabricated by infiltrating pure Mg melt into the porous Ti samples containing interconnected micro-porous structure in this study. Initially, the porous Ti preforms were fabricated by utilizing inkjet 3D printing followed by sintering method. The Ti samples were then characterized for part shrinkage post-sintering, density and porosity using Archimedes principle, internal morphology using microCT scans and surface morphology using optical microscopy, respectively. Spontaneous infiltration of pure Mg was conducted within the resistance furnace. The resulting Ti-Mg composites were then characterized for density and porosity values, microstructural and mechanical properties, and compared with those of commercially pure Ti and Mg.