Materials Science Forum Vols. 534-536

Abstract: Aluminium Alloys with a 22 wt.-% Mg2Si content were spray formed. This alloy features a low density and is therefore a superior material for lightweight applications. The main problem in the spray forming of this type of alloy was the occurrence of high porosities. First process optimizations have been performed to decrease porosity under a certain level, so that it can be closed by an extrusion process.

Abstract: Metal/diamond binary composite coatings on Al substrate without grit blasting were deposited by cold spray process with in-situ powder preheating. Microstructural characterization of the as-sprayed coatings with different diamond size, strength and with/without Ti coating on diamond was carried out by OM and SEM. The assessment of basic properties such as tensile bond strength and hardness of the coatings, and the deposition efficiency was also carried out. Particular attention on the composite coatings was on the diamond fracture phenomenon during the cold spray deposition and the interface bonding between the diamond and the Fe-based metal matrix.

Abstract: NiTiZrSiSn bulk metallic glass powder was produced using inert gas atomization and then was sprayed onto a SS 41 mild steel substrate using the kinetic spraying process. Considering the principle of kinetic spraying and the temperature dependent deformation behavior of the bulk metallic glass, an attempt to change the in-flight particle temperature was tried by modifying the kinetic spraying apparatus. Through this study, the effects of thermal energy of in-flight particle and crystallization degree by powder preheating temperature were evaluated. The deformation behavior of bulk metallic glass is very interesting and it is largely dependent on the temperature and the strain rate. The crystalline phase formation at impact interface was dependent on the in-flight particle temperature. In addition, variations in the impact behavior need to be considered at high strain rate and in-flight particle temperature.

Abstract: Ti45Zr38Ni17 powders were thermally sprayed onto mild steel substrates in air and under a reduced pressure of argon. Two kinds of powder samples were used in this study. For one type the elemental powders were gently (manually) mixed in a vial, and for the other type they were mechanically alloyed by a planetary ball mill. Several kinds of oxides were formed after thermally-spraying the mechanically-alloyed powders in air. After spraying in a reduced pressure of argon, on the other hand, the coating layers obtained from the gently mixed powders consisted of the three elemental metals (Ti, Zr, Ni), but an amorphous phase primarily appeared in the thermallysprayed mechanically-alloyed powders. This amorphous phase transformed into the icosahedral quasicrystal phase and a minor Ti2Ni-type crystal phase after annealing in vacuum at 828 K. The Vickers hardness and the contact angle with pure water for the quasicrystal layers were about 7 GPa and 92˚ respectively.

Abstract: The fabrication of complex-shaped parts out of Co-Cr-Mo alloy and 316L stainless steel by three-dimensional printing (3DP) is studied using two grades of each alloy with average particle size of 20 and 75 )m, respectively. To produce sound specimens, the proper 3DP processing parameters were determined. The sintering behavior of the powders is characterized by dilatometric analysis and by batch sintering in argon atmosphere at 1280°C for 2h. The 3DP process has successfully produced complex-shaped biomedical parts with total porosity of 12-25% and homogenous pore structure, which is suitable for tissue growth into the pores.

Abstract: Laser additive direct deposition of metals is a new rapid manufacturing technology, which combines with computer aided design, laser cladding and rapid prototyping. The advanced technology can build fully-dense metal components directly from CAD files without a mould or tool. With this technology, a promising rapid manufacturing system called “Laser Metal Deposition Shaping (LMDS)” is being constructed and developed. Through the LMDS technology, fully-dense and near-net shaped metallic parts can be directly obtained through melting coaxially fed powder with a laser. In addition, the microstructure and mechanical properties of the as-formed samples were tested and analyzed synthetically. The results showed significant processing flexibility with the LMDS system over conventional processing capabilities was recognized, with potentially lower production cost, higher quality components, and shorter lead time.

Abstract: Direct Metal Laser Sintering (DMLS) has been utilized for prototype manufacturing of functional metal components for years now. During this period the surface quality, mechanical properties, detail resolution and easiness of the process have been improved to the level suitable for direct production of complex metallic components for various applications. The paper will present the latest DMLS technology utilizing EOSINT M270 laser sintering machine and EOSTYLE support generation software for direct and rapid production of complex shaped metallic components for various purposes. The focus of the presentation will be in rapid manufacturing of customized biomedical implants and surgical devices of the latest stainless steel, titanium and cobalt-chromium-molybdenum alloys. In addition to biomedical applications, other application areas where complex metallic parts with stringent requirements are being needed will be presented.

Abstract: This paper investigates the characteristic of single-layered and multi-layered compacts made by selective laser sintering using titanium powder. The surface texture and tensile strength were investigated by using single-layered compacts. There were few defects in surface of specimen laser sintered in vacuum, and the roughness was smoother than that of the specimen laser sintered in argon. Maximum tensile strength of single-layered compact laser sintered in vacuum was about 200MPa. The shrinkage and mechanical strength were investigated by using multi-layered compacts. There was a unique tendency in the shrinkage of multi-layered compacts, which the density was around 75% and the adhesive bonding was not observed between layers, resulted in 70MPa of maximum bending strength and 50MPa of maximum tensile strength.

Abstract: Powder library of pseudo four components Li-Ni-Co-Ti compounds were prepared for exploring the composition region with the single phase of the layer-type structure by using combinatorial high-throuput preparation system “M-ist Combi” based on electrostatic spray deposition method. The new layer-type compounds were found wider composition region than the previous report. This process is promising way to find functional multi-component materials.

Abstract: New powder compaction process, in which a Bingham semi-solid/fluid mold is utilized, is developed to fabricate micro parts. In the present process, a powder material is filled as slurry in a solid wax mold, dried and compressed by either of conventional pressing methods, such as isostatic pressing or die compaction. It is important to use slurry for filling because dry powder is hard to fill in the micro cavity. It is also essential to control process temperature to treat micro parts. The wax mold is heated during compaction and becomes semi-solid state, which can acts as a pressurized medium for isostatic compaction. Since the compacted micro parts are very fragile, the mold's temperature is controlled to higher than its melting point during unloading, to avoid breakage of the compacts. To demonstrate effectiveness of this process, some micro compacts of alumina are shown as examples.