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Here, statistics descriptive and inferential were employed to understand the acquired data from the process output variables such as porosity percentage, thickness, and deposition efficiency of the obtained coatings as a function of process input variables such as nozzle type, standoff distance, and the particle in-flight velocity before impact on the substrate. Coatings were produced by the LPCS process with copper powder deposited onto aluminum 6061 substrates, using two different nozzle shapes (rectangular and round) and two standoff distances (SOD) of 12.5 and 22.5 mm. It was found that nozzle type is the process input parameter with the most substantial contribution to the final coating properties. Particle in-flight velocity decreased by 38% at the standoff distance of 22.5 mm with the rectangular nozzle shape. In contrast, at the same standoff distance for the round nozzle shape, the in-flight particle velocity only diminished by 15%. The rectangular nozzle exhibits the uppermost change of in-flight particle velocity, impacting the particles at a very high speed. This could cause a high percentage of rebounded particles, diminishing the thickness and increasing the porosity percent. It was concluded that the round nozzle type is recommended to achieve coatings with low porosity levels without deep dependence on the standoff distance. This conclusion applies to the experimental conditions of this study with the given geometrical nozzle features. [ABSTRACT FROM AUTHOR]

In this work, the effect of ageing and retrogression on the polarization resistance of the Al 6061 was assessed, in order to improve the corrosion resistance of the alloy with a negligible effect on the tensile strength. The corrosion resistance behavior was studied by exposing an Al 6061 alloy to a simulated marine environment, and then, the corrosion current density (icorr) was measured. The obtained corrosion results were correlated with tensile strength (TS) reported elsewhere and both measured, the icorr and TS and both were modeled by multiple linear regression. The results showed that the polarization resistance is inversely proportional to the temperature increment of the ageing and retrogression processes. In addition, the samples subjected to 200 °C of ageing and 250 °C of retrogression temperatures exhibited an enhancement on both corrosion resistance and tensile strength, when compared to the T6 condition and to lower ageing and retrogression temperatures. Furthermore, an empirical equation was proposed to correlate the icorr as a function of heat treatment parameters such as: ageing temperature and retrogression time–temperature for the aluminium alloy. [ABSTRACT FROM AUTHOR]

In this work, a novel combination of designed heat treatments and cold work performed on Al-6063 alloy was proposed. The consumption of aluminium and its alloys in the automotive and aeronautic industries has increased over the past few years, in the same way, as the consumption of material for manufacturing moulds for casting of plastic parts and dies for plastics and metals. Then, it is important to find a low-cost alternative to maximise the mechanical properties of aluminium, with a negligible effect on the ductility of the alloy, which is important due to thermal and mechanical fatigue on mould and dies. It is well known that precipitation hardening increases the mechanical and yield strength of aluminium alloys with a major ductility loss. However, the developed methodology consists of a solution heat treatment, followed by cold working (strain hardening), and lastly a heat treatment (precipitation hardening and stress reliever) to produce Al 6063 aluminium alloys with enhanced mechanical strength and with a negligible ductility loss. The proposed methodology increases around 23.45% of the tensile and yield strength, with a ductility reduction of less than 1.5% in the elastic materials region. The experimental tensile testing results are correlated with nanoindentation experimental results in order to confirm that the level of cold working is directly proportional to mechanical strength levels by two different characterisation techniques at a macro- and nanoscales, respectively. [ABSTRACT FROM AUTHOR]

In this work, an alternative statistical multiple linear robust regression methodology was used to analyze the experimental data obtained from tensile tests performed on heat treated samples of an aluminium 6063 alloy. The proposed methodology allows the identification of empirical relations between the ageing temperature and process time with the mechanical strength (UTS) and yield point (YS) of the alloy. Through these empirical relationships: a) UTS=0.0932TatA−0.1356tA2−0.0002434Ta2tA+0.00063tA3 and b) YS=5.10Ta−20.32tA−0.05281Ta2+0.2297TatA+0.0001459Ta3−0.0006192Ta2tA, obtained by using the multiple linear robust regression methodology, it was possible to find that an ageing temperature of 192 °C for 120 min would produce the maximum strength levels for the Al-6063 alloy. For such alloy, empirical relationships were successfully determined for ageing heat treatment design. [ABSTRACT FROM AUTHOR]

In this study, a novel flexural fatigue testing apparatus was designed to evaluate the fatigue behavior of 3D-printed materials. The machine was validated using polylactic acid (PLA) 3D-printed samples and fiber-reinforced thermoformed polypropylene (PP). The investigation focused on the effects of varying infill percentages of PLA and fiber reinforcement in PP under constant deflection, in accordance with Newton’s third law. The results provided significant insights into the fatigue life of these materials, including stiffness degradation and damage accumulation, thereby confirming the machine’s efficacy. This research contributes to a deeper understanding of 3D-printed material behavior under cyclic loading and enhances the machine’s capability to assess both conventional and specialized plastics. Furthermore, we compared the indirect measurement of elastic modulus obtained from fatigue testing with direct measurements for various percentages of reinforced PP, demonstrating the feasibility of deriving elastic modulus from fatigue testing. [ABSTRACT FROM AUTHOR]