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In this study, the results pertaining to the influence of various metallurgical parameters on the tensile properties of Al–Si–Cu–Mg 354-type casting alloys are presented. This is discussed with an emphasis on acquiring an insight regarding the mechanical limits of Al–Si–Cu–Mg 354-type alloys in the context of these parameters, and to obtain an understanding of the effects of the addition of nickel and/or zirconium on alloy 354 with respect to the mechanical properties obtained at high temperature (155 °C and 300 °C for holding times at temperature ranging from 10 to 100 h). Based on an analysis of the results obtained, the following conclusions may be drawn. The results show that additions of Zr and Zr + Ni increase the high-temperature tensile properties, in particular for the alloy containing 0.2 wt% Zr + 0.2 wt% Ni, which exhibits an increase of more than 30% in the tensile properties at 300 °C compared with the base 354 alloy. In other words, the addition of 0.4 wt% Ni + 0.4 wt% Zr to the 354 alloy is not sufficient to resist softening at 300 °C/100 h (cf. UTS: 52 MPa, YS: 45 MPa, %El: 23% with UTS: 361 MPa, YS: 343 MPa, %El 1.23%, observed after T6 treatment). The addition of 0.4 wt% Ni to alloy 354 leads to a decrease in the tensile properties, compared to the base alloy. This decrease may be attributed to a Ni–Cu reaction which could interfere with the formation of the Al2Cu strengthening precipitates, thereby affecting the age hardening process. As a consequence, percentage elongation increases with the testing temperature, from as-cast to T6-treated samples tested at high temperature (155 °C and 300 °C, respectively). In summary, the best high-temperature tensile properties are displayed by the alloy containing 0.2 wt% Zr + 0.2 wt% Ni.

The present study was carried out to investigate the effects of Ni and Zr additions, individually or in combination, on the room-temperature tensile properties of 354 casting alloy (Al–9wt%Si–1.8wt%Cu–0.5wt%Mg) which was isothermally treated at temperatures in the range of 155–350 °C and aging times up to 1000 h. Tensile tests were carried out in the as-cast, solution heat-treated, and aged conditions using different aging times up to 1000 h. Quality charts were used as an evaluation tool for selecting the optimum conditions to achieve superior tensile properties and optimum quality in 354-type alloys. Zirconium reacts only with Ti, Si, and Al to form (Al,Si)2(Zr,Ti), (Al,Si)3(Zr,Ti), and Al3Zr phases. The beneficial effects of Zr and Ti additions appear in the refining of the α-Al grain size which reduces the size of the Al2Cu and α-Fe particles. Tensile test results at ambient temperature show a slight increase in alloys with Zr and Zr/Ni additions, particularly at aging temperatures above 240 oC. It is suggested that the maximum obtainable quality index values by means of heat treatment are the difference between the quality index values for the as-cast and solution heat treatment conditions.

The principal aim of the present research work was to investigate the effects of minor additions of nickel and zirconium on the strength of cast aluminum alloy 354 at room temperature (25°C). A decrease in tensile properties of ∼10% with the addition of 0.4 wt.% nickel is attributed to a nickel-copper reaction which interferes with the formation of Al2Cu precipitates. The platelet-like phases (Al,Si)3(Zr,Ni,Fe) and (Al,Si)3(Zr,Ti) are the main features observed in the microstructures of the tensile samples of alloys with Zr additions. The reduction in mechanical properties is due to the increase in the percentage of intermetallic phases formed during solidification; such particles would act as stress concentrators, decreasing the alloy ductility. The main effect of Zr addition lies in a significant reduction in the alloy grain size ∼40%, rather than an increase in the mechanical properties. Quality index charts could be used in assessing the effects of the Ni and Zr additions to the base alloy, as well as evaluating the heat treatment relationships to the alloy tensile properties, in particular when the system shows multiple precipitation reactions. Due to the high liquidus temperature of the Al-Zr binary phase diagram, addition of Zr beyond 0.2% is not recommended to avoid undissolved Zr.

The principal aim of the present research work was to compare the role of dispersoids Al2O3 (∼15 μm average particle size) and SiC (∼15 μm average particle size) with that offered by Zr- and Ni-based intermetallics (∼35–70 μm average particle size) on the hardening of cast aluminum 354 alloy (9.1% Si, 0.12% Fe, 1.8% Cu, 0.008% Mn, 0.6% Mg, and 87.6% Al) at ambient temperature. There is no observable poisoning effect on the refinement of grain size after the addition of Zr to the alloys investigated in this study. The tensile test results were examined in light of the microstructural features of the corresponding alloy samples. The contribution of the added dispersoids or Ni and Zr alloying elements on the tensile properties of the 354 alloys was determined employing ∆P plots (where P = Property, UTS, YS, or %El), using the base alloy (in the as-cast condition) as a reference point. The tensile results were supported by investigating the precipitation-hardening phases using scanning and transmission electron microscopy as well as examining the fracture surfaces of selected conditions applying field emission scanning electron microscopy. The results show that, in all cases, Al2Cu phase is the main hardening agent. The contribution of about 1.5 vol% of SiC or Al2O3 to the strength of the base alloy is higher than that offered by Zr- and Ni-based intermetallics, under the same aging treatment.

A failure analysis was performed on bolts (Monel K-500) that serve to support and join critical components of an electrical submergible pump (ESP) located in a saline solution environment. Based on the experimental results, it can be concluded that pitting corrosion was the primary cause of failure. All fracture surfaces displayed an initial zone of intergranular fracture promoted by pitting corrosion and a propagation zone with transgranular fracture due to mechanical load. High concentrations of sulfur (S) and chlorine (Cl) were found on two corrosion product layers covering the bolt surface, revealing that an aggressive electrochemical reaction occurred in the stagnant environment. Under these layers, small pits of 10–30 μm in depth were observed that initiated the cracking paths that eventually became complete fractures.

The wear performance of the Co–Cr alloys used for total joint replacement is a critical variable for the success of the implant. In order to add information in this field, the effect of superlattice coatings on wear response was investigated. In this work, TiN/CrN superlattices produced alternating TiN and CrN layers of nanometer-scale, were deposited by the means of reactive magnetron sputtering technique using two types of disc substrates: cast Co–Cr (ASTM F75) and cast Co–Cr+1 wt% B alloys. As the first attempt, a simple ball-on-disc tribological configuration was performed using Ringer׳s solution and Al 2 O 3 balls. In addition, scratch testing, optical and scanning electron microscopy were used to elucidate on the wear mechanisms involved. Adhesive and abrasive wear mechanisms were found on the wear track. Co–Cr+1 wt% B showed massive secondary phases precipitation which increases the adherence resistance in the interface between the system coating and the substrate improving slightly the wear response.

The principal aim of the present work was to investigate the effects of minor additions of nickel and zirconium on the strength of cast aluminum alloy 354 at ambient and high temperatures. Tensile properties of the as-cast and heat-treated alloys were determined at room temperature and at high temperatures (190. °C, 250. °C, 350. °C). The results show that Zr reacts only with Ti, Si and Al. From the quality index charts constructed for these alloys, the quality index attains minimum and maximum values of 259. MPa and 459. MPa, in the as-cast and solution-treated conditions; also, maximum and minimum values of yield strength are observed at 345. MPa and 80. MPa, respectively, within the series of aging treatments applied. A decrease in tensile properties of ~10% with the addition of 0.4. wt.% nickel is attributed to a nickel-copper reaction. The reduction in mechanical properties due to addition of different elements is attributed principally to the increase in the percentage of intermetallic phase particles formed during solidification; such particles act as stress concentrators, decreasing the alloy ductility. Tensile test results at ambient temperatures show a slight increase (~10%) in alloys with Zr and Zr/Ni additions, particularly at aging temperatures above 240. °C. Additions of Zr and Zr. +. Ni increase the high temperature tensile properties, in particular for the alloy containing 0.2. wt.% Zr. +. 0.2. wt.% Ni, which exhibits an increase of more than 30% in the tensile properties at 300. °C compared with the base 354 alloy.