Additive Manufacturing of Emerging Materials

While laser additive manufacturing is becoming more and more important in the context of advanced manufacturing for the future, most of the current efforts are focusing on optimizing the required parameters for processing well-matured alloys from powder feedstock to achieve reproducible properties, comparable to, or better than, their conventionally processed counterparts. However, laser additive manufacturing also opens up a new avenue in terms of processing novel alloys and composites that are difficult to process using traditional processing routes. Metal matrix composites (MMCs) are the new class of advanced materials in which rigid ceramics reinforcements exhibiting excellent strength as well as elastic modulus are embedded in a ductile metal or alloy matrix to overcome the inadequacy of metals and alloys in providing both strength and stiffness to the structure. Metal matrix composites possess excellent physical as well as mechanical properties, which makes them suitable for structural, automotive and aerospace applications. MMCs are mainly classified into two categories, ex-situ, and in-situ based on the formation of ceramic reinforcement during their processing. In situ reactions during laser additive processing takes place either between elemental blend powder or between elemental blend powder and reactive gases (e.g. nitrogen, oxygen, etc.). This chapter mainly discuss on laser additive manufacturing of in situ metal matrix composites. Laser additive processing of nickel, aluminum, and titanium matrix composites are the focus of this chapter.

The electrical discharge machining (EDM) is a non-conventional machining process widely used in recent days in the field of aerospace, biomedical, automobile, tool and die industries. Other conventional and non-conventional machining process does the production of EDM electrode, therefore, the cost of production of EDM electrodes account for more than 50% of the cost of the final product. Therefore, additive manufacturing (AM) technology provide the direct fabrication of the EDM electrode. Selective laser sintering (SLS) is the most suitable AM process used for the preparation of EDM tool electrode, that reduce the tool production time and total production cost of the final product. The main difficulty of the production of EDM electrode by the SLS process is the selection of the appropriate material for tool. So that, it can be easily prepared by the SLS process as well as contain the properties of EDM tool electrode. In this work, a newly developed non-conventional metal matrix composite of Al, Si and Mg is prepare directly by SLS process and used as the EDM electrode. To study the EDM performance of the newly prepared AlSiMg electrode, Titanium-alloy (Ti6Al4V) is use as work piece material and commercial grade EDM 30 oil as dielectric fluid. The performance of the newly prepared AlSiMg SLS electrode is compare with conventional copper and graphite electrodes. The EDM is performed by varying different process parameters like open circuit voltage (V), discharge current (Ip), duty cycle (τ) and pulse-on-time (Ton). Three responses like material removal rate (MRR), tool wear rate (TWR) and average surface roughness (Ra) are used to analyze study the EDM process. To reduce the number of experiments, design of experiment (DOE) approach like Taguchi’s L₂₇ orthogonal array is used. The three output responses of the EDM specimens are optimized by GRA method combined with Firefly algorithm and the best parametric setting is reported for the EDM process.

Lightweight metal matrix composites (MMCs) have attracted a great attention in modern industries because of their outstanding properties including low density, high strength, low coefficient of thermal expansion, and excellent wear resistance. Additive manufacturing (AM) has recently provided new technological opportunities for fabricating MMCs parts with unique microstructures and mechanical properties. This chapter focuses on AM of lightweight MMCs including aluminium- and titanium-matrix composites which are commonly used in aerospace, automotive, and biomedical applications. The effects of process parameters, characteristics of mixed powder system as well as forces and flows in the melt pool are widely explored on the features of reinforcements incorporated into the matrix. The main objective is to discuss an in-depth relationship between the melt pool thermodynamics, reinforcement features, and the quality of additively manufactured lightweight MMCs.

Additive manufacturing (AM) refers to a group of technologies providing rapid production of three-dimensional parts with complex shapes in a layer-by-layer manner. AM technologies are currently applied in various industries including tooling, automotive, aerospace, and biomedical industries. Besides the most commonly used metallic materials such as steel, titanium, aluminum, nickel-based and cobalt-chromium alloys, AM technology has recently opened the door for developing more complex materials such as composites and functionally graded materials. A relatively new focus in AM is the development of high quality metal matrix composites (MMCs) that meet the requirements of automotive and aerospace industries. However, processing of these materials still needs noticeable research and development. Although preliminary works on AM of MMCs are underway, many objectives such as process optimization and defect-free production need to be yet explored. The main objective of this chapter is to establish a detailed relationship between the material properties, processing parameters, microstructural evolutions and mechanical properties of the additively manufactured MMCs.

Titanium alloys have been extensively used in medical field, especially for load-bearing implants due to their excellent properties such as high strength and great corrosion resistance. In addition to the well-known CP-Ti and Ti-6Al-4V alloy, many beta type titanium alloys comprising of non-toxic and non-allergic elements have being developed for the next generation of bone implant materials. However, the hard machinery and high cost of materials removal arising from the conventional manufacturing processes are the two main obstacles of various potential applications of titanium alloys. As emerging advanced manufacturing technologies, additive manufacturing techniques are providing the ideal platform for the creation of these customized devices, where three dimensional complex parts could be realized by sequential production of two dimensional layers. Thus, additive manufacturing facilitates the manufacturing of parts with almost no geometric constraints and is economically feasible down to a batch size of one. This chapter mainly review the recent progress of the additive manufacturing (via selective laser melting and electron beam melting) of titanium alloys and their products, including the processing optimization, microstructure, mechanical properties and fatigue properties for different types of titanium alloys (CP-Ti, Ti-6Al-4V and Ti-24Nb-4Zr-8Sn) and their porous structures.

Owing to the layer-wise characteristic of additive manufacturing (AM) technologies, the microstructure of AM-produced titanium alloys inevitably differs from the alloys produced by conventional methods. Such a resultant microstructure would affect their mechanical properties and corrosion resistance. Selective laser melting (SLM) and electron beam melting (EBM) are the two main forces in the manufacture of the titanium alloys. However, most of the researches on AM-produced titanium alloys have only focused on the mechanical properties of the AM-produced titanium alloys, and just an insufficient part of them are used for the research of corrosion properties. This chapter reviews the very recent progress of the corrosion behavior of SLM- and EBM-produced Ti-6Al-4V alloys, SLM-produced CP-Ti and Ti-TiB composites in different testing solutions as well as various manufacturing planes. The work sheds light the corrosion resistance properties and its mechanisms for AM-produced titanium alloys.

In spite of numerous applications, the functionality of FDM patterns is severely influenced by poor surface finish which must be maintained as it would be further inherited by castings. The impact of process parameters of an advanced finishing technique i.e. Vapour Smoothing (VS) has been investigated on surface roughness, hardness and dimensional accuracy of hip implant replicas. The Taguchi L₁₈ Orthogonal Array and ANOVA statistical tools were used to scrutinize the significant parameters. The exposure of hot chemical vapours tends to melt the upper surface of ABS parts which are immediately cooled. This led to improvement in surface finish and surface hardness as layers settle down as smooth surface. The shrinkage in FDM parts has been noticed due to layer re-settlement. Based on significant parameters, the mathematical models for each response were formulated using Buckingham Pi theorem. The multi-response optimization study was performed to endorse a single set of process parameters to attain best surface characteristics. The Differential Scanning Calorimetry tests were performed which reveal that VS process enhanced thermal stability of material due to increase in bonding strength.

This chapter highlights the in house development of low cost alternative FDM feedstock filament with tailor made properties. The experimental study was performed to fabricate (Nylon6-Al-Al₂O₃ based) alternative fused deposition modeling (FDM) feedstock filament in place of commercial acrylonitrile butadiene styrene (ABS) filament (having specific rheological and mechanical properties) for rapid manufacturing (RM) and rapid tooling (RT) applications. The detailed steps for fabrication of alternative FDM feedstock filament (as per field application) with relatively low manufacturing cost and tailor made properties have been highlighted. The rheological and mechanical suitability of Nylon6-Al-Al₂O₃ feedstock filament has been verified experimentally. The approach is to predict and incorporate essential properties such as flow rate, flexibility, stiffness, and mechanical strength at processing conditions and compared with commercial ABS material. The proportions of various constituents have been varied in order to modify and improve rheological behavior and mechanical properties of alternative FDM feedstock filament. The developed feed stock filament was loaded in commercial FDM setup without any change in hardware and software. The results of study suggest that the newly developed composite material filament has relatively poor mechanical properties but have high thermal stability and wear resistant as compared to ABS filament and hence can be used for tailor made applications.

Finally, the Taguchi experimental log have been designed for investigating the significance of input parameters of screw extruder (such as: mean barrel temperature, die temperature, screw speed, material composition and speed of take up unit) on the diameter deviation of fabricated filaments was analyzed. The tensile strength of alternative feedstock filament has been investigated experimentally according to ASTM-638 standard. The analysis was performed by ANOVA method with the help of MINITAB 17 software. The regression model was developed to realize the influence of input parameters on responses. Tensile strength was significantly affected by the variation of major input parameters during the processing of alternative material on single screw extruder. The ANOVA analysis shows that two process parameters (namely: material composition and die temperature) were significant and remaining two (mean barrel temperature and screw speed) were insignificant. Further a linear regression model has been developed to accurately predict the tensile strength and diameter deviation of alternative feed stock FDM filament. The results highlight that the deviation of <1% was observed in the nine sets of experimental runs, which were compared with predicted values of the regression model. The dynamic mechanical analysis (DMA) result indicates that the filament fabricated with optimum combination of parameters have highest stiffness and more suitable for FDM system. The process capability study suggest that, with optimum combination of single screw extruder parameters, the process lies within the spread of ±4σ having C_p and C_pk value 1.43 and 1.354 respectively. The cost effective solution investigated in this research work may help in enhancing the application of FDM process for various industrial applications.

The thermoplastic materials like acrylonitrile–butadiene–styrene (ABS), Nylon etc. have large applications in three dimensional printing of functional/ non-functional prototypes. Usually these polymer based prototypes lacks in thermal and electrical properties. The graphene (Gr) has attracted impressive enthusiasm in the recent past due to its natural mechanical, thermal and electrical properties. This chapter presents the detailed step by step procedure (as a case study) for development of in-house ABS-Gr blended composite feed stock filament for fused deposition modelling (FDM) applications. The feed stock filament has been prepared by two different methods (mechanical and chemical mixing). For mechanical mixing twin screw extrusion (TSE) process has been used and for chemical mixing the composite of Gr in ABS matrix has been set by chemical dissolution followed by mechanical blending through TSE. Finally electrical, thermal conductivity, shore D hardness and micro structural properties of composite feed stock filament prepared by two different methods have been optimized. The recycling ability of composite prepared was further ensured by differential scanning calorimetry (DSC).

Additive manufacturing (AM) is the process of building 3D objects by layer-upon-layer. AM became a promising technique in various applications as automotive, aerospace and biomedical applications. The AM provides a flexible and versatile technique to produce complex shapes in short time using vast materials in a cost-effective way. So, AM has been successfully utilized to produce complex shaped biomedical implants using a wide range of biomaterials. Metallic Glasses (MG) proved to be an excellent material for biomedical implant applications because of their superior tribological and corrosion properties. However, the microstructure is characterized as a composite of different phases with vastly different mechanical properties such as ductility, strength, resistance to wear, creep and fatigue. A major challenge to utilize AM to fabricate large objects made of MG is the difficulty to preserve the amorphous structure in larger sizes. To get the superior properties benefit of MG in fabricating large objects, the coating of MG on a metallic substrate using laser cladding technique is proposed in this research work. Laser cladding (LC) is considered an outstanding technique to produce MG coating on metallic alloys substrate. This chapter discusses the various effects of LC parameters on the microstructure, phases formation, mechanical and tribo-corrosion properties of the MG coatings. Also, cytotoxicity and biocompatibility of MG are discussed.

In this chapter, detailed procedure for development of biocompatible and biodegradable composite material based feedstock filament, by using twin screw extrusion (TSE) process has been highlighted. The poly lactic acid (PLA) has been selected as a polymer matrix with hydroxyapatite (HAp) and chitosan (CS) as osteo-conductive filler for potential use in medical applications. The feedstock filament of PLA-HAp-CS can be used in fused deposition modelling (FDM) open source 3D printer (without change in any hardware or software of system) for printing of functional/ non functional prototypes. The results are supported by tensile testing; thermal analysis; and scanning electron microscope (SEM) based photomicrographs. Finally the feasibility of fabrication of functional prototypes for medical applications by using in house prepared feedstock filament on the FDM has been ascertained.