Abstract: The research on the explosive compaction of reactive powders is a hot issue. In this work, unreacted Ti-Si block with high compactness has been successfully fabricated under explosive-driven compaction process. The precursors of Ti-Si powder with different stoichiometric ratios undergo pre-compaction shaping by hydraulic press and then shock loading treatment by using low-detonation-velocity explosives of varying loading conditions. The results show that the chemical reaction between Ti and Si powders are partly initiated even under low detonation pressures, indicating extremely low reaction threshold in the Ti-Si system. Meanwhile, optimal experimental conditions are displayed as the initial pressing compactness degree of 61%, and shock pressure of 11GPa. A compactness of 97% is achieved in the synthesized Ti-Si block with the lowest reactivity.
Abstract: In this study, dissimilar grade aluminium plates were explosively cladded by placing a wire mesh/ceramic particle between them. The stainless steel 316 mesh with 90o orientation and SiCp (1.5 volume %) are employed to enhance the mechanical properties of the aluminium composites. Microhardness and microstructure of the explosively cladded composite materials were evaluated. Significant improvement in the microhardness of the wire mesh/ceramic particle reinforced aluminium composite is established.
Abstract: Explosive cladding employs a controlled chemical explosive detonation to craft a metallurgical bond between similar and dissimilar metals. Aluminum 5052-copper and aluminum 5052-aluminum 1100 plates are explosively cladded with a stainless steel wire-mesh, having 900 orientation between them, at varied loading ratios (mass of explosive/mass of flyer plate). Microstructural, corrosion and mechanical properties of the clad were evaluated as per relevant standards and the results are presented. The dissimilar wire-mesh interlayered explosive clad reveal wavy topography, with the interfacial wave amplitude and wavelength proportional to loading ratio, R. The mechanical behavior of wire-mesh reinforced clad is better than weaker aluminum parent plate.
Abstract: This paper describes the comparison between simple seam welding and adjacent parallel seam welding by a magnetic pulse welding method for Al-Al sheets. In the case of the parallel seam welding, the sheets collided at high speed in two parallel along a narrow central part of a one-turn flat coil. The central part had two parallel upper parts. The width of the central part was same as that of the simple seam welding. The increase of the parallel seam-weld zones was more than double in total in comparison with the simple seam-weld zones. Two inside parallel seam-weld zones were connected each other with a small cavity.
Abstract: Impact joining device was developed to achieve the joining at plate edge. The sheared faces obtained by high-speed shear are availed in the joining method. The temperature remarkably elevates and the material softens in the thin severely deformed layer. The cut faces are contacted each other with sliding motion immediately after shearing process. Slight overlap for the opposed cut faces is set. In the similar material combination of mild steel (SPC), the effect of overlap length on the average joining efficiency was not clear. The data spread became smaller for the shorter overlap length. Microscopic observation discovered that there is a narrow band where the grain flow was not visible due to the remarkable temperature rise. In the dissimilar material combination of titanium (TP340C) and SPC, generation of a certain metallic compound was implied by energy dispersive X-ray analysis.
Abstract: An easy and fast vacuum detonation method was designed to prepare TiO2/Na2Ti6O13 powders. The mixed explosives, prepared by usage of Ti-Na-contained precursor, ammonium nitrate, hexogen and a certain mass of polystyrene foam ball (EPS) in beaker, were detonated in a vacuum detonation reactor to synthesize powders. The prepared light-grey powders were characterized by powder X-ray diffractometer and transmission electron microscopy to ascertain the phase composition and morphology. It was found that the powders were consisted of TiO2 and Na2Ti6O13, and the TiO2 almost was rutile phase. The intensity of Na2Ti6O13 peak was enlarged with increase of EPS mass. The TiO2/Na2Ti6O13 particles were irregular sphere or long rhombus, and some particles were 10 nm. In general, the dispersity of the powers was decreased with the mass of EPS increasing.
Abstract: This study focuses on effect of post weld heat treatment (PWHT) on interfacial and mechanical properties of Al 5052-SS 316 explosive clad with copper interlayer at varied loading ratios and inclination angles. The use of interlayer is proposed for the control of additional kinetic energy dissipation and to alleviate the formation of intermetallic compounds at the interface. The Al-Steel clads are subjected to PWHT at varied temperatures (300°C-450°C) for 30 minutes and the results are presented. The microstructural characterization of as-clad and PWHT samples is observed by an optical microscope and Scanning Electron Microscope (SEM). Maximum hardness is obtained at the interface of the as-clad and PWHT samples. Increase in PWHT temperature enhances the tensile strength of the composite, whereas, the tensile strength decreases at 300°C due to the diffusion of Al and Cu elements and the formation of detrimental intermetallic compounds.
Abstract: In this study, aluminum based composites with stainless steel wire-mesh as reinforcement is fabricated by explosive compaction technique. Stacks containing four layers of alternatively positioned aluminum sheets and stainless steel wire-meshes are explosively compacted at varied explosive masses and the results are reported. Microstructure of explosive compacted aluminum composite reveal a smooth interface at lower explosive mass, while formation of reacted products are observed at higher energetic conditions. Though the hardness of the post clad composite is higher than pre-clad materials, the maximum hardness is observed at the first interface.
Abstract: AlN nanopowders are successfully synthesized via electrical Al wire explosion in liquid nitrogen. After pickling in 15 % HCl-ethanel, the purified AlN nanopowders are characterized by various techniques. It is observed that the synthesized AlN nanoparticles are hexagonal AlN (h-AlN) exhibiting various shapes, including sphere, spheroidicity, polygon and hexagon. The results show that the charging voltage affects on the AlN content and the morphology of samples, significantly. Further more, it is observed that synthesized AlN particles in the size of 100-300 nm are coated by an amorphous layer mostly resulted from the high cooling rate in liquid nitrogen.