The research shows the characterization of mechanical properties in dissimilar steel welded unions: a structural steel ASTM A537 (I) overlap welded with an austenitic stainless steel ASTM A240 (304L) through semiautomatic electrical arc welding process protected by inert gas (GMAW); Argon is used as a protecting gas and austenitic stainless steel ASTM A240 (308L) as a supplier material. Samples were tested in not welded conditions so as to characterize the materials involved in the research, and they were also tested in welded conditions, not being submitted to pre and post welding Thermal Treatment (TT). Welded-based material samples were characterized through Optical Microscopy (OM) and Scanning Electron Microscopy (SEM), an inspection of Not Destructive Test (NDT) with penetrating liquids and ultrasound was also conducted. The following mechanical tests were completed, not only on the Base Metals (BM), on the Welding Join (WJ) as well: Vickers micro hardness profile, tension, and face bending test. Results showed a proper mechanical steel behavior, welded by GMAW procedure, under monotonic, in spite of the relatively high values of microhardness in the Heat Affected Zone (HAZ), specifically near the fusion line between weld and stainless steel.
Copper-based alloys and composites are widely used in engineering applications. The properties of alloys are exceptionally are improved when processed and structured at the nano-scale [1]. The present work focuses on the processing synthesis and microstructural characterization by transmission electron microscopy (TEM) of an 89wt%Cu-10wt%Ni/1%wt Al2O3 composite material. The synthesis procedure is reported elsewhere [2]. The metallic powder obtained was cold press into pellets under uniaxial pressure at 15 MPa and sintered at 600°C under pure H2 for 30 minutes and cooling under the same atmosphere down to room temperature. The pellets were transformed into the ribbons by 80% coldrolling followed to annealing at 600ºC for 30 minutes.Microstructural characterization was conducted by transmission electron microscopy (TEM) using LaB6 Jeol 2010 instrument under 200 kV accelerating potential operating in diffraction contrast mode. TEM specimens were prepared by typical mechanical thinning down to about 100µm. The thickness of the thinned sample was decreased to 5 µm using a dimpling machine (South Bay Technology model 515) and, finally, submitted to ion milling at low incident angle (Gatan PIPS 691).
Nanocomposites ribbons of 89wt%Cu-10wt%Ni-1%wtAl 2 O 3 were produced by chemical route synthesis of nanoparticles and thermomechanical processing. The nanoparticles synthesis procedure is reported elsewhere [1]. While the metallic constituent of CuNi is a solid solution, the ceramic Al 2 O 3 are dispersed nanoparticles. The present study reports the microstructural evolution of different steps of the processing: from nanoparticles to cold pressed pellets and, finally, ribbons. The final products of CuNi-Al 2 O 3 composites were obtained after cold rolling the pellets down to ribbons reaching 40%, 60% and 80% reductions in thickness.
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