Utjecaj lantana na mikrostrukturu i svojstva čelika ASTM A216

In order to satisfy the rudder horn casting standards of the International Association of Classification Societies, the properties of ASTM A216 steel should be improved. Therefore, in this article the rudder horn casting and accompanying specimens were cast moulded by arc furnace smelting, external refining, and modification treatment of the molten steel by lanthanum. The samples were first underwent normalizing treatment at 900 °C for 10 hours, then air cooled, followed by tempering treatment at 600 °C for 7 hours and samples were air cooled again. The mechanical properties and microstructures of the samples were measured. The crystallography relationships between lanthanum compounds formed in the molten steel and primary δ-Fe were analysed. The nucleation effect of lanthanum compounds as a heterogeneous nucleation core of primary δ-Fe were calculated and discussed based on two-dimensional mismatch theory. The results indicated that the strip MnS inclusions in ASTM A216 steel became granular rare earth compound inclusions due to La. The refined microstructures were obtained by a synergistic effect of the enhanced condensate depression and the nucleation rate of melt and La compounds as the heterogeneous nucleation caused by La.Da bi se zadovoljili standardi Međunarodnog udruženja klasifikacijskih zavoda (IACS) za lijevanje krmenog roga, potrebno je poboljšati svojstva čelika ASTM A216. Odljevci krmenog roda i prateći uzorci, nakon taljenja čelika u elektrolučnoj peći, rafiniranja i dodatka lantana, izrađeni su lijevanjem čelika u kalupe. Uzorci su prvo normalizirani zagrijavanjem 10 sati na 900 °C, ohlađeni na zraku, potom podvrgnuti popuštanju 7 sati na 600 °C i ponovno ohlađeni na zraku. Određena su mehanička svojstva uzoraka i proučena mikrostruktura. Analizirana je sličnost kristalne građe spojeva lantana nastalih u rastaljenom čeliku i δ-željeza. Izračunata je učinkovitost lantanovih spojeva kao podloge za heterogenu nukleaciju δ-željeza na temelju dvodimenzijskog nepodudaranja struktura. Dodatkom lantana vrpčasti uklopci MnS postaju zrnasti uklopci spoja rijetke zemlje. Finija mikrostruktura dobivena je sinergijskim djelovanjem povećane depresije kondenzata i brže nukleacije uz lantan

Microstructure evolution and strengthening mechanism of A356 composites reinforced with micron and nano SiCp

The single scale SiC _p reinforcement has a limited effect on the comprehensive performance of the composite, which restricts the optimization and improvement of its comprehensive performance. In order to improve the material’s strong plasticity, wear resistance, thermal expansion and other properties of the comprehensive requirements. The (micron and nano) dual-scale SiC _p /A356 composites with different volume fractions were prepared using the combination of powder metallurgy and hot extrusion. The effects of different volume fractions of dual-scale SiC _p (15, 20, 25, 30 vol.%) on the microstructure and mechanical properties of A356 composites were studied, and the strengthening mechanism of dual-scale SiC _p /A356 composites was analyzed. The results show that with the increasing of dual-scale SiC _p content, the distribution uniformity and mechanical properties of SiC _p first increase and then decrease. When the content of dual-scale SiC _p is 25%, the mechanical properties reach their maximum values, with the hardness, yield strength and tensile strength of 112.3 HBW, 228 MPa and 310 MPa, respectively. They are improved by 86.9%, 81.0%, 74.2% as compared with those of A356 alloy, respectively. The fracture modes of dual-scale SiC _p /A356 composites are mainly Al matrix tearing and SiC _p fracture. The main strengthening mechanism is Orowan strengthening, along with thermal mismatch strengthening, load transfer strengthening and fine grain strengthening

Interfacial Characterization and Bonding Properties of Copper/Aluminum Clad Sheets Processed by Horizontal Twin-Roll Casting, Multi-Pass Rolling, and Annealing

The copper/aluminum (Cu/Al) clad sheets were produced on a horizontal twin-roll caster and then were multi-pass rolled and annealed. The thickness of the as-cast clad sheet was 8 mm. Rolling was performed with total reductions of 12.5%, 25%, 37.5%, 50%, and 62.5%, separately. The effects of the rolling and annealing processes on the interface and peel strength of the Cu/Al clad sheets were investigated. The evolution of the interface and crack propagation were studied. The interface thickness of the as-cast clad sheet reached 9 μm to 10 μm. The average peel strength (APS) was only 9 N/mm. After multi-pass rolling, the peel strength first slightly increased and then gradually decreased with the increase of the rolling pass number. After annealing, the peel strength remarkably improved. The APS reached 25 N/mm when the rolled thickness was 7 mm. The improvement in the peel strength was due to the following three factors: (1) mechanical locking formed in the Cu/Al direct contact region after rolling, (2) the region of the Al matrix fracture, and (3) mechanical biting from the Cu/Al direct contact region

Effects of Heating Mode and Temperature on the Microstructures, Electrical and Optical Properties of Molybdenum Thin Films

In this paper, molybdenum (Mo) thin films are deposited on soda-lime glass (SLG) substrates by direct current magnetron sputtering and heated in three different modes at different temperatures, including substrate heating, annealing treatment, and both substrate heating and annealing treatment. The effects of heating temperature and heating mode on the structures, morphology, optical and electrical properties of Mo thin films were systematically investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), atomic force microscope (AFM) and UV-visible spectrophotometer (UV-vis spectra). It is shown that as the substrate and annealing temperature increase, the crystallinity of Mo thin films is improved, and the grain sizes become bigger. Especially in the mode of both substrate heating and annealing treatment at higher temperature, the obtained Mo thin films show higher crystallinity and conductivity. Moreover, with the increase of substrate and annealing temperature in different heating modes, both the surface compactness of Mo films and the optical reflectance increase correspondingly. Furthermore, the Mo film, prepared at the substrate heating temperature of 400 °C and annealed at 400 °C, showed excellent comprehensive performance, and the resistivity is as low as 1.36 × 10−5 Ω·cm. Using this optimized Mo thin film as an electrode, copper indium gallium selenium (CIGS) solar cells have a maximum photo-conversion efficiency of 12.8%

Effect of deep cryogenic treatment on the microstructure and mechanical properties of Al–Cu–Mg–Ag alloy

Effect of deep cryogenic treatment (DCT) on the aging behavior and tensile properties of Al–Cu–Mg–Ag alloy was investigated. Results show that DCT of Al–Cu–Mg–Ag alloy produces plastic deformation of about 0.2% and high-density dislocations in the α-Al matrix. These dislocations cut second-phase particles in under-aged Al–Cu–Mg–Ag alloy, resulting in a decrease in the size of Ω precipitates and an increase in the number density, thereby weakening the adverse effects of DCT on the tensile properties of the alloy

Effects of Thickness Ratios and Sputtering Mode on the Structural, Electrical and Optical Properties of Bilayer Molybdenum Thin Films

In this paper, the bilayer Mo films with a constant thickness were deposited by direct current and direct current (DC/DC), radio frequency and direct current mixed (RF/DC) magnetron sputtering, respectively. Changing thickness ratios of bottom layer to total thickness of bilayer film in the range from 10% to 50%, ten types of bilayer Mo thin films were deposited. The purpose is to improve the photo-conversion efficiency of Cu(In, Ga)Se2(CIGS) solar cells by changing the sputtering modes and thickness ratio. The microstructures, electrical and optical properties of the bilayer Mo thin films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscope (AFM), Hall Effect measurement system, ultraviolet-visible spectrophotometer (UV-vis) and four-point probe resistance system. It was found that with the increase of thickness ratios in two sputtering modes, both the crystallinity and grain size decreased, while the reflectance increased. Especially, when the thickness ratio was 40%, the resistivity of Mo film prepared in RF/DC mode was as low as 3.365 ×10-5 Ω·cm and the highest reflectance was above 60%. Using this optimized Mo thin film as electrode, the highest photo-conversion efficiency for the CIGS thin film solar cells was as high as 11.5%