As the forging counterpart of fusion-based additive processes, additive friction stir deposition offers a solid-state deformation processing route to metal additive manufacturing, in which every vo...

https://www.tandfonline.com/doi/pdf/10.1080/21663831.2020.1847211

Additive friction stir deposition: a deformation processing route to metal additive manufacturing

Welding is a major manufacturing process that joins two or more pieces of materials together through heating/mixing them followed by cooling/solidification. The goal of welding manufacturing is to join materials together to meet service requirements at lowest costs. Advanced welding manufacturing is to use scientific methods to realize this goal. This paper views advanced welding manufacturing as a three step approach: (1) pre-design that selects process and joint design based on available processes (properties, capabilities, and costs); (2) design that uses models to predict the result from a given set of welding parameters and minimizes a cost function for optimizing the welding parameters; and (3) real-time sensing and control that overcome the deviations of welding conditions from their nominal ones used in optimizing the welding parameters by adjusting the welding parameters based on such real-time sensing and feedback control. The paper analyzes how these three steps depend on process properties/capabilities, process innovations, predictive models, numerical models for fluid dynamics, numerical models for structures, real-time sensing, and dynamic control. The paper also identifies the challenges in obtaining ideal solutions and reviews/analyzes the existing efforts toward better solutions. Special attention and analysis have been given to (1) gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) as benchmark processes for penetration and materials filling; (2) keyhole plasma arc welding (PAW), keyhole-tungsten inert gas (K-TIG), and keyhole laser welding as improved/capable penetrative processes; (3) friction stir welding (FSW) as a special penetrative low heat input process; (4) alternating current (AC) GMAW and double-electrode GMAW as improved materials filling processes; (5) efforts in numerical modeling for fluid dynamics; (6) efforts in numerical modeling for structures; (7) challenges and efforts in seam tracking and weld pool monitoring; (8) challenges and efforts in monitoring of keyhole laser welding and FSW; and (9) efforts in advanced sensing, data fusion/sensor fusion, and process control using machine learning/deep learning, model predictive control (MPC), and adaptive control.

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Advanced Welding Manufacturing: A Brief Analysis and Review of Challenges and Solutions

Directed energy deposition (DED) has matured into an essential additive manufacturing (AM) branch. DED has been broadly implemented in the design and fabrication of novel materials. These include metals, ceramics, and composites. Successful DED operation requires a good understanding of many critical phenomena, including laser-material interactions, fundamentals of casting and solidification of alloys, welding metallurgy and joining interfaces, along with microstructure-mechanical properties relations. Also critical are powder flowability, heat transfer, and various machine-related parameters. Several review articles have been published in recent years on metal AM via powder bed fusion (PBF) and DED, focusing on either a specific material system, mapping the recent technologies for AM, or issues related to the deposition process or material properties. Yet, no recent review is dedicated to a comprehensive presentation of material systems, design, fabrication, challenges, and the relationship between microstructures and mechanical properties of various DED'ed material families. Since the DED-based approach is becoming popular to manufacture bimetallic and multi-material structures, repair high-value structures, and alloy design, this comprehensive review focuses on materials design via DED, including a survey of a variety of monolithic and multi-material compositions. Finally, the critical challenges and opportunities in this area are highlighted. 

http://manuscript.elsevier.com/S0921509322003744/pdf/S0921509322003744.pdf

Laser-based directed energy deposition (DED-LB) of advanced materials

Friction stir alloying is primarily employed for the fabrication of surface composite to improve surface properties like hardness, wear resistance, and corrosion resistance without significantly af...

https://journals.sagepub.com/doi/pdf/10.1177/0021998319859427

Fabrication of bulk aluminum-graphene nanocomposite through friction stir alloying:

Laser Additive Manufacturing is relatively new in the manufacturing industry. This paper focuses on the effect of hybrid coatings of Al-Cu-Fe on a grade five titanium alloy (Ti6Al4V) using laser metal deposition (LMD) process at different laser power and scanning speeds. Icosahedral Al-Cu-Fe as quasicrystals are a relatively new class of materials which exhibit unusual atomic structure and useful physical and chemical properties. Ti6Al4V/Al-Cu-Fe composite were analysed using Optical microscopy, Scanning electron microscopy (SEM) with energy dispersive microscopy (EDS), indentation testing, X-Ray Diffraction (XRD), corrosion and wear testing. deposit width and height, heat affected zone (HAZ) height), dilution rate, aspect ratio and powder efficiency of each sample remarkably increased with increasing laser power due to the laser-material interaction. It was observed that there are higher number of aluminium and titanium presented in the formation of the composite. The indentation testing reveals that for both scanning speed of 0.8m/min and 1m/min, the mean hardness value decreases with increasing laser power. It was found that due to dilution effect, a part of Ti entered into molten pool from the substrate. The results indicate that Ti, Al 3 Ti, Ti 3 Al, CuTi 2 can be produced through the in situ metallurgical reactions during the LMD process.

Experimental investigation of laser metal deposited icosahedral Al-Cu-Fe coatings on grade five titanium alloy

Laser metal deposition process is an additive manufacturing technology that is capable of producing three dimensional components as well as repair of an existing worn out components. Processing parameters play an important role on the resulting properties of the processed materials using the laser metal deposition process. This study investigates the influence of gas flow rate and scanning speed on the microstructural and microhardness properties of laser metal deposited Ti6Al4V, an important titanium alloy used in the aerospace industries. Nd-YAG laser was used in this work with the maximum laser power of 4.0 kW. The laser power used was 3.0 kW and the powder flow rate of 2.88 g/min was maintained throughout the experiments. The scanning speed was set between 0.01 and 0.04 m/s while the gas flow rate was varied between 1 and 4 l/min. The microstructures of the samples were studied using optical microscope while the microhardness profiling was conducted using microhardness indenter. The results showed that, as the scanning speed was increased, the microstructure changed from fine basketweave structure to coarse martensitic structure. The microhardness was found to increase with increasing scanning speed. By increasing the gas flow rate results in decrease in microhardness values while the microstructure was observed to change from martensitic structure to basketweave structure. The result from this study is especially useful in repair application in order to achieve the desired properties. Introduction Ti6Al4V is an important aerospace alloy and the most widely used titanium alloy, because of the excellent properties it possess which include high strength to weight ratio and excellent corrosion resistance properties [1, 2]. Though Ti6Al4V has excellent properties but it is classified as difficult to machine material [3]. The use of traditional manufacturing method to process Ti6Al4V challenging and time consuming. Laser metal deposition process that belongs to the directed energy deposition class of additive manufacturing technology is a candidate alternative manufacturing process that can be used to process difficult to machine materials such as Ti6Al4V because it is a contactless manufacturing process and it does not come in contact with the work material. Laser metal deposition process can also be used to repair existing worn out part as well as in the fabrication of functionally graded materials [46]. Laser metal deposition (LMD) process is a fairly new additive manufacturing process that has gain a lot of interest in the research community because of its importance and the promises it offers. Aside from the ability of the LMD process in the fabrication of near net shape part that is made directly from the three dimensional (3D) computer aided design (CAD) image of the part through the materials addition layer by layer, LMD is also capable of repairing high valued parts that were not repairable in the past [79]. It also promised to reduce buy-to-fly ratio in the aerospace industry, ability to produce composite and functionally graded materials and its mass customization capability [10-13]. Advances in Engineering Research (AER), volume 102 102 Second International Conference on Mechanics, Materials and Structural Engineering (ICMMSE 2017) This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). Copyright © 2017, the Authors. Published by Atlantis Press. Experimental Method The materials used in this study are the Ti6Al4V powder and Ti6Al4V substrate. The Ti6Al4V powder used is 99.6% pure and it is of particle size range between 150 and 250 μm. The Ti6Al4V substrate used is also a 99.6% pure square sheet of 5 mm. Nd-YAG laser with maximum capacity of 4 kW was used for the LMD process. The laser was attached to the end effector of a Kuka robot with the coaxial powder nozzle. The experimental set-up used in this study is available at the CSIR, National Laser Center Pretoria, South Africa. An improvised glove box was provided to prevent the deposited samples from environmental such as atmospheric oxygen and Nitrogen. The laser metal deposition process was achieved by the laser beam that is used to create a melt-pool on the surface of the substrate while the powder material is then delivered into the melt-pool. A solid track of the deposited sample is seen on the path of the laser beam when the melt-pool solidifies. The experimental set-up and the schematic diagram of the LMD process are shown in Fig. 1a and Fig. 1b respectively. The laser power and the powder flow rate used in this study were fixed at 3.0 kW and 2.88 g/min respectively. The scanning speed was varied between 0.01 and 0.04 m/s while the gas flow rate was varied between 1 and 4 l/min. The processing parameters used are presented in Table 1. The laser beam spot size was maintained at 2 mm through the constant focal length of 195 mm above the substrate. The substrate was sandblasted and washed with acetone to prepare the surface to aid the laser energy absorption prior to the deposition process. A total of eight (8) samples were produced according to the processing parameters in Table 1. After the experiments were completed, the samples were cut in transverse direction to reveal the cross section of the samples. The cut samples were mounted in resin, ground and polished following the standard metallurgical preparation of titanium and its alloys [14]. The polished samples were then etched using the Kroll’s reagent. The microstructures of the samples were observed under the optical microscopy (OP) by Olympus BX51M. (a) (b) Fig. 1 (a) Pictorial diagram of the experimental set-up (b) Schematic diagram of the LMD process (adapted from Mahamood et al. [15]). The microhardness of the polished samples were measured using the Metkon microhardness tester with a load of 500g and a dwelling time of 15s. The distance between indentation were kept at 15μm. The microhardness was measured according to the ASTM standard [16]. Advances in Engineering Research (AER), volume 102

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Gas Flow Rate and Scanning Speed influence on microstructure and Microhardness Property of Laser Metal Deposited Titanium-alloy

Titanium alloy-Ti6Al4V is an important aerospace alloy with excellent properties but it is classified as difficult to machine material that requires an alternative manufacturing process. Laser metal deposition process is an ideal alternative manufacturing process that can offset most of the problem encountered while processing the alloy using the traditional manufacturing method. Processing parameter play an important role in the resulting properties of material processed using the laser metal deposition process. The key processing parameters that have significant influence in the properties of the processed material in laser metal deposition process include laser power, scanning speed, powder flow rate and gas flow rate. In this study, the effect of powder flow rate on the evolving microstructure and microhardness of Ti6Al4V using the laser metal deposition process is investigated. The laser power, scanning speed and powder flow rate were kept constant while the powder flow rate was varied between 1.44 g/min and 7.2 g/min. The results showed that the microhardness increased as the powder flow rate was increased. The microstructure was found to change from coarse Widmanstätten alpha to coarse martensitic alpha as the powder flow rate was increased. This study is important to know the required powder flow rate to be employed in order to achieve the desired properties during building of new part as well as repair. Introduction Laser metal deposition (LMD) process is an advanced manufacturing process that is one of the classes of additive manufacturing technologies capable of producing three dimensional object and repair of high valued parts [1, 2]. Laser metal deposition process is a contactless manufacturing process that is used for difficult to process materials such as Ti6Al4V [3]. Aerospace industry is in dear need of technology such as LMD process to reduce buy to fly ratio and for repair of high valued components that were not repairable in the past [4, 5]. The flexibility offered by the LMD process makes it possible to fabricate parts made of composite and functionally graded materials [6-10]. Processing parameters are of great importance in the laser metal deposition process because they affect the resulting microstructure and hence the properties of the deposited materials. A number of studies have been carried out in the literature to understand the influence of processing parameters on the economy and properties of laser metal deposited materials [11-16]. In this study, the influence of powder flow rate on the microstructure and microhardness of laser metal deposited Ti6Al4V. Ti6Al4V is an important aerospace alloy that is widely used because of its excellent properties [17]. Other processing parameters were kept constant and the powder flow rate was varied to understand the effect of this single process parameter on the properties. Advances in Engineering Research (AER), volume 102 109 Second International Conference on Mechanics, Materials and Structural Engineering (ICMMSE 2017) This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). Copyright © 2017, the Authors. Published by Atlantis Press. Materials and Methods The materials used in this study are the Ti6Al4V powder and substrate. The Ti6Al4V powder is of 99.6% pure and of particle size analysis of between 150 μm and 350 μm. The substrate is a sheet of 5mm thick. The laser used is an Nd: YAG laser of maximum capacity of 4.0 kW. The substrate was sandblasted and rinse using acetone before carrying out the deposition process to remove dirt and aid laser absorption process. The laser power, the scanning speed and the gas flow rate were fixed at 3 kW, 0.05 m/s and 2 l/min respectively. The laser focal length was fixed at a distance of 195 mm above the substrate to keep the spot size at a constant value of 2mm. The powder flow rate was varied between 1.44 g/min and 7.2 g/min. The experimental matrix is presented in Table 1. Table 1. Experimental Matrix. Sample Designation Powder Flow Rate (g/min) A 1.44 B 2.88 C 4.32 D 5.76 E 7.2 After the deposition process, the deposited samples are sectioned across the deposition direction to reveal the cross section of the samples. The cut samples are mounted in hot resin. The mounted samples are ground and polished following the standard metallurgical preparation of titanium and its alloys [18]. The microhardness was measured on the polished samples using Metkon Vickers hardness indenter with a load of 500g, dwelling time of 15s and distance between indentations maintained at 15 μm, following the ASTM standard on microhardness measurement [19]. The polished samples are etched using Knoll reagent and then studied under optical microscope for microstructural extermination. Results and Discussions The results of the microhardness are shown in Table 2. The graph of the average microhardness versus powder flow rate is shown in Figure 1. The microhardness is seen to increase as the powder flow rate was increased. The reason for this can be attributed to the fact that at low powder flow rate, the available laser power was able to completely melt the deposited powder and also created a larger melt pool on the surface of the substrate. The larger melt pool created takes longer to solidify which resulted in the formation of Widmanstätten grains structure (see Figure 2a) which in turn resulted in low microhardness because Widmanstätten grains are softer. Table 2. Results. Sample Designation Powder Flow Rate (g/min) Average Microhardness (HV) A 1.44 330.56 B 2.88 367.41 C 4.32 388.02 D 5.76 391.22 E 7.2 392.01 Substrate 300 Advances in Engineering Research (AER), volume 102

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Esther T. Akinlabi

Papers

Gas Flow Rate and Scanning Speed influence on microstructure and Microhardness Property of Laser Metal Deposited Titanium-alloy

Influence of Powder Flow Rate on Properties of Laser Deposited Titanium Alloy -Ti6Al4V

Mono-Fractal Analyses of Roughness of Sputtered Films

Multifractal Characterization of Structure Evolution with Sputtering Parameters of Thin Films

Fractal Prediction of Film Growth and Properties