Key Engineering Materials Vol. 923

Abstract: Iron is the main component of the earth's core, the most abundant element on the earth (about 35%), and it is relatively high in the sun and other stars. Also, it is a common and cheap metal in the manufacturing industry. Recently, with the rapid development of electric vehicles, more and more automotive companies are willing to develop new lightweight material for electric motors used in electrical vehicles. The iron–containing aluminum alloys can be considered as a good candidate, due to its great strength and electricity performance. This review describes various properties of aluminum-iron alloys including mechanical properties and electrical conductivities, as well their relation to the Fe contents. Also, metallurgical aspects of aluminum-iron alloys, including phase diagrams, equilibrium and non-equilibriun solidification, microstructure development, and castability. The further research and development work are outlined in terms of developing aluminum-iron alloys for some potential and value-added automotive applications.

Abstract: Ti-6Al-4V is one of the popular choices for biomedical implants due to multiple advantages, such as corrosion resistance, high strength-to-weight ratio, biocompatibility, lightweight, durability, and osseointegration properties. However, Young’s modulus (E) of Ti-6Al-4V is much higher than the E of natural human bone, which may lead to stress shielding. Therefore, it is critical that we need to fabricate the implant with specific mechanical properties that can match the patient’s existing bone. With the advent of 3D printing, we now can design porous structures with the most suitable E through adjusting porosity to suit individual needs. Porous structures with various porosities were manufactured by selective laser melting (SLM). Mechanical testing was performed to show that the E of the printed samples was related to the porosities only. Based on the simulated and actual results, there are still many areas that can be improved to enhance the quality of the printed structures. Indirect cytotoxicity tests were performed to verify the biocompatibility of the porous structures.

Abstract: In this study, the effects of Nb and O contents on the negative thermal expansion behaviors including the coefficient of negative thermal expansion and matensite (α) stability of cold rolled (CR) Ti-34Nb alloys was investigated by optical microscopy, X-ray diffraction and Thermomechanical analysis. Results show that texture strength of CR-Ti-xNb-xO alloys is related to β stability, the addition of Nb and O (β stabilizers) enhances the texture strength. XRD results indicate that Nb and O inhibit the formation of α. The coefficient of negative thermal expansion of CR-Ti-xNb-xO alloys decrease with the increase of Nb and O contents. Moreover, cyclic thermal expansion results reveal that Nb and O promote the decomposition of α.

Abstract: Currently, there is no function in commercial CAM systems to generate optimal quality machining for curved surfaces. In computer-aided manufacturing (CAM) systems, the toolpath (cutter location data) is derived as an approximately straight-line segment based on a plane approximation surface instead of a free-form surface from the designed shape. Due to this approximation, machining accuracy and quality are decreased, especially in the region with characteristic lines like in an outer automobile covering part. This paper presents an algorithm procedure for toolpath generation to process complex parts with characteristic curves with high-quality and high-accuracy machining by dividing the surface into different regions, the region where machining accuracy is not required as a plane approximation surface and the remaining region where accuracy is required as free-form surfaces. The proposed method was confirmed by machining experiments that actual machining realized high machining quality and accuracy compared to the conventional CAM system.

Abstract: For the purpose of determining the optimal value for the technological parameters from the experimental results when evaluating the forming ability through the processing time during the processing of SUS 304 sheet material by SPIF technology. The article has conducted experiments to collect parameters and experimental planning to establish a mathematical model; at the same time, determine the optimal value for the parameters of the machining process such as tool diameter, tool feed and tool running speed which directly affect the machining time. The optimal technological parameters have practical applicability to improve the efficiency and productivity of the processing process for SUS 304 sheet metal in particular and other sheet metal materials in general.

Abstract: Nowadays, Fuse Deposition Modeling (FDM) technology is being broadly applied in many fields. However, one of the major limitations of the current FDM technology is the surface roughness, an important criterion in evaluating the surface quality of mechanical products. Therefore, it is necessary to improve the surface quality of 3D printed products using FDM technology. In the paper, we study the effect of forming parameters on product surfaces roughness of parts manufactured by FDM technology on plastic materials Polylactic Acid (PLA). The experimental planning method and design of experiment (DOE) are applied to access and evaluate to find out the optimal forming parameters for plastic products by FDM technology.

Abstract: Fused Deposition Modeling, a great potential technology, has been increasingly applied in various industries as rapid prototyping for testing, casting prototyping and final products manufacturing. This widely usage comes with high products accuracy requirements. Currently, industrial 3D printers are very high in price that open-source low cost printers are the most suitable for hobbyist and researchers in the world. Therefore, research to improve product quality for low-cost 3D printers to serve industrial demand is greatly necessary. Realizing that in FDM technology, the feeding method is one of the important issues that determine the accuracy of printed products. The problem to be studied here is to design and manufacture a filament feeding system for a low-cost 3D printer and find out an optimal set of parameters for the fabricated feeder. This paper analyzes the feeding systems for 3D printers that have been used on the market, thereby offering a design and manufacturing feeder for the low-cost 3D printer. Then, experiments with Polylactic Acid (PLA) filament will be taken to check the accuracy of printed products and figure out the optimal set of technological parameters for the 3D printing process. Thereby improving product quality and shortening printing time. Continue to research and perfect the design can help commercialize low-cost 3D printers and stimulate research as well as 3D printing in industries.

Abstract: Ultrasonic Vibration-Assisted Machining (UVA) is a machining process that adds a micro-scale high frequency vibration to the motion of a cutting tooltip to interrupt the continuous interaction of tool - workpiece surface. A good point of machining with UVA is more effective than conventional processes such as lower machining forces, higher machining stability, less tool wear and better surface finishes. In molds fabrication with some narrow cavities having a conversion space diameter of less than 3mm will face many difficulties while low surface roughness is required. Low stiffness of technological system in these cases of finishing machining is the reason of a weak machining in high-speed cutting. The ability to achieve cutting speeds for surface finishing of this type in tight spaces is also an interesting application for UVA tools. This paper discusses the finishing machining tool design with UVA for milling machine in such as analyze of the main parameters, adding diagonal split and simulation of the generated vibration effects to evaluate the achieved results before fabrication by using the help of ANSYS.

Abstract: Damage and fracture processes in high temperature creep of an investment cast B1914 Ni-based superalloy with the increased amount of boron to 0.08wt.% for high temperature applications were analysed. Constant load creep tests in tension were conducted at temperatures from 800 to under applied stress ranging from 150 to 700 MPa. The microstructure of fractured specimens was investigated by scanning electron microscope Tescan equipped with an electron-back scatter diffraction. Microstructure investigation showed that the microstructure of the B1941 superalloy consists of a gamma (γ) phase with a dendritic structure and gamma prime (γ ́) phase with a cuboidal shape. Precipitates of γ ́and a lamellar eutectic, composed of γ/(Mo,Cr,Ni)₃B_2, were identified in the interdendritic region. Creep damage and fracture are closely connected with decohesion of the interface between M₃B₂ boride and matrix.