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In this study, specimens of AlSi10Mg fabricated by laser-powder bed fusion were exposed to 200, 220, 240, 260, 275, and 300 °C for various times to characterize the changes in mechanical properties over time. The duration of each isothermal treatment was varied from 15 min to 1000 h; one group of specimens was left in the "as-printed" condition as a control. The resulting microstructure and mechanical properties were characterized. Percent elongation, 0.2% offset yield strength, ultimate tensile strength, and hardness were measured and compared. The morphology of the silicon-rich phase was observed at several time and temperature conditions using optical and scanning electron microscopy. The strength and hardness decreased while the elongation increased 1) with increasing time at a given temperature and 2) with increasing temperature for any given time of exposure. The properties never reached a stable value for the durations of the exposures in this study, as indicated by the change in measurements after 300 °C and 1000-h exposure. The effects of time and temperature on mechanical properties are modeled well with the Larson–Miller parameter. The microstructure changes from having a fine network of silicon-rich precipitates to a coarse, equiaxed silicon particles with increased temperature of exposure. [ABSTRACT FROM AUTHOR]

Hydrogen was intentionally introduced into ultra-high strength steel by cadmium plating. The purpose was to examine the effect of cadmium plate thickness and hence hydrogen on the impact energy of the steel. The AISI 4340 steel was austenitized at 1000 °C for 1 h, water quenched, and tempered at temperatures between 257 and 593 °C in order to achieve a range of targeted strength levels. The specimens were cadmium plated with 0.00508 mm (0.2 mils), 0.00762 mm (0.3 mils), and 0.0127 mm (0.5 mils). Results demonstrated that the uncharged specimens exhibited higher impact energy values when compared to the plated specimens at all tempering temperatures. The cadmium-plated specimens had very low Charpy impact values irrespective of their ultimate tensile strength values. The model of hydrogen transport by mobile dislocations to the fracture site appears to provide the most suitable explanation of the results. [ABSTRACT FROM AUTHOR]

Titanium alloy Ti-3Al-2.5V is cheaper to produce and has the potential of improved ductility and formability compared to the Ti-6Al-4V alloy. Various heat treatments were performed on cylindrical tensile test bars in order to optimize the mechanical properties of Ti-3Al-2.5V. The tensile properties of heat-treated Ti-3Al-2.5V were determined at four annealing temperatures with different quenching methods and five different solution treatments and five different aging treatments for varying hours. The samples were tensile tested. The results indicated that optimum properties of high strength and ductility were reached at 926 °C of solution treatment and 480 °C of aging. [ABSTRACT FROM AUTHOR]

Tempered AISI 4340 steel was hydrogen charged and tested for impact energy. It was found that samples tempered above 468 °C (875 °F) and subjected to hydrogen charging exhibited lower impact energy values when compared to uncharged samples. No significant difference between charged and uncharged samples tempered below 468 °C (875 °F) was observed. Neither exposure nor bake time had any significant effect on impact energy within the tested ranges. [ABSTRACT FROM AUTHOR]

Welding stainless steel generates hazardous air pollutants (HAPs). Two technologies were developed to reduce these HAPs. The first, tetramethylsilane is added to the welding shielding gas, and welding proceeds as normal. Reactive oxygen species are consumed, and the resulting metal fume particles are encapsulated. In the second technique, new chromium-free welding consumables are introduced nearly eliminating Cr(VI) in the welding fume. [ABSTRACT FROM AUTHOR]

Aluminum and copper cylindrical shells were plastically buckled under quasi-static and dynamic loading conditions with an Absorption Compression-Torsion Plasticity (ACTP: Patent No. WO 2005090822) combined mechanical testing device. Optical microscopy and transmission electron microscopy (TEM) analysis were used to study the microscopic evolutions in the mechanically buckled aluminum and copper alloy samples. Optical microscopy showed evidence of the presence of second-phase particles in both the aluminum and copper alloys samples. Under dynamic loading aluminum samples showed more energy absorption as compared to copper samples. Material flow lines were more pronounced in the copper samples when observed by optical microscopy. The evidence that supports the increased energy absorption in the aluminum cylindrical shells can be supported by the TEM analysis more than the optical microscopy analysis. The TEM results showed highly oriented textured morphology with the presence of few dislocation cells structures and sub-structures. [ABSTRACT FROM AUTHOR]

Polymer adhesives are finding increased use in panel joining applications in aircraft and aerospace structures where the applied stresses permit their use and where a uniform stress distribution is needed. One such adhesive, Hysol EA-9394™, was compared to three other formulations in this study. The new formulations were Hysol EA-9396, Hysol EA-9396 filled with nickel nanofibers and mixed by machine (Jamesbury Blender), and Hysol EA-9396 filled with nickel nanofibers and hand mixed in the laboratory. The comparison consisted of measuring shear lap strengths of aluminum test pieces bonded together with the candidate adhesives. The mechanical tests were supplemented by a Weibull analysis of the strength data and by a visual inspection of the failure mode (adhesive/cohesive). The lap shear strengths (fracture stress values) of all three Hysol EA-9396 adhesives were greater than that of the baseline Hysol EA-9394 polymer. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the acceptability of nonpenetrating, key-locked inserts in 2099 aluminum-lithium. The tests conducted to make this assessment were: (1) microscopic examination for thread damage and delaminations after key installation, (2) pull-out load at 21 °C (70 °F) and)179 °C (-290 °F), and (3) mechanical cycling tests at room temperature and -179 °C (-290 °F). The test results indicated that for the three sizes evaluated, key-locked inserts in 2099-T6 and 2099-T8 were acceptable and although delaminations did occur on some T6 temper specimens, it was only as a failure mode at ultimate load and such behavior was judged to be acceptable. [ABSTRACT FROM AUTHOR]

AISI 52 100, 440C, REX20, and Crucible CRU80 steel samples were exposed to 16 different heat treatments to vary the levels of retained austenite. Rockwell C hardness measurements, optical microscopy, and compression testing were used to compare the properties of the different steels. [ABSTRACT FROM AUTHOR]

Aluminum alloys 6061, 2024, and 7075 were heat treated to various tempers and then subjected to a range of plastic strain (stretching) in order to determine their strain limits. Tensile properties, conductivity, hardness, and grain size measurements were evaluated. The effects of the plastic strain on these properties are discussed and strain limits are suggested. [ABSTRACT FROM AUTHOR]

Extruded I sections of 7075-T6 aluminum were machined into four different sections shapes: L, short depth L, T, and short depth T. The furnace was preheated to 416 °C (780 °F) and the samples were placed inside. The temperature was raised to 471 °C (880 °F) and then the samples were quenched in either a 30% polyalkylene Glycol solution or water, both at 15 °C (59 °F). Points on the distorted samples were recorded before and after the solution treatment; the difference between the measurements indicated the extent of warpage. [ABSTRACT FROM AUTHOR]

The purpose of this case study is to determine the cause of failure of a conveyor trunnion shaft from a solid bowl centrifuge. The trunnion shaft fractured at the weld joint, which joins a flange to the end of the shaft. Fracture occurred through the walls of the shaft. It was determined that the failure was caused by defects related to the welding procedures. These defects included cracks in the weld joint, unfused welds, slags, and porosity. The causes of these defects were due to poor welding techniques prior to and during the welding procedure. The weld joint was an area of high stress concentration, in addition the flange was inaccurately machined, which may have caused high bending stresses during operation and contributed to the failure. It is recommended that certain welding techniques be used prior to and during welding to reduce incomplete fusion and to prevent the formation of slags and porosity. It is also recommended that the trunnion shaft be redesigned to reduce stress concentration at the weld joint between the shaft and the flange and to properly machine the flange to reduce high bending stresses. [Copyright &y& Elsevier]