Recent findings on corrosion of ferritic stainless steel weldments: A review

This study covers the review of the degradation of ferritic stainless-steel weldments between 2015 and 2022. The industrial and automotive sectors make extensive use of ferritic stainless steel (FSS) due to its superior oxidation and corrosion resistance, low price, high thermal conductivity, and low thermal expansion. However, it has been reported that ferritic stainless steel is harder to weld than austenitic stainless steel and that doing so would probably result in a weaker welded joint owing to the coarsening of grains high welding temperatures. According to past research, the amount of heat applied during the welding procedure affected how soon the FSS (409 M) weldment degraded after being exposed to NaCl (3.5%) medium. The coarsening of the grains was considered to be the cause of this. When the shielding gas' CO2 content increased, the intergranular corrosion of the FSS weld metal was found to increase. Welds made with the ER430LNb filler metal had significantly lower intergranular corrosion of FSS (AISI 441) than those made with the ER430Ti filler metal. It was discovered that boiling Cu-CuSO4 - 50% H2SO4 solution increased the corrosion rate for the FSS (AISI 430) weldment more than boiling 40% HNO3 Solution. Weldments made of FSS (AISI 430) were found to be negatively affected by the CuCuSO4 - 50% H2SO4 environment in terms of intergranular corrosion attack

Martensite aging phenomena in Cu-based alloys: Effects on structural transformation, mechanical and shape memory properties: A critical review

Cu-based shape memory alloys have been hyped as the ‘heir’ and pragmatic substitute to NiTi alloys for shape memory applications. Considerations from relatively low materials cost, processing ease, and modest shape memory properties, have been advanced as reasons justifying this projection. However, structural transformation induced phase stabilization - referred to as martensite ageing, has been reported to be a huge scourge constraining the thermo-responsiveness of these alloys, and limiting their service reliability. Studies on the mechanisms and effects of martensite ageing in Cu-based shape memory alloys (SMAs) have been reported in bits and patches, or encapsulated in broad ranged topical issues on the system. A comprehensive and exclusive review of martensite ageing in Cu-based SMAs has been lacking – thus the need for the present work. This review covers the general mechanisms of martensite ageing and its effects on the transformation behaviour, mechanical properties, shape memory functionality, and considers the implications on commercial utilization of the Cu-based SMAs. Specifically, Cu-Al-Mn, Cu-Al-Be, Cu-Al-Ni, Cu-Zn-Al, and Cu-Zn-Sn alloys were studied. The observations indicated that factors such as alloy composition, phase and microstructural parameters, and processing conditions, significantly dictate the mechanism and propensity to martensite stabilization, and also the extent to which the mechanical and shape memory characteristics are altered

Wear and corrosion behavior of selected up-quenched and step-quenched CuZnSn shape memory alloys

The effect of thermal treatment on the wear and corrosion behavior of three categories of Cu-Zn-Sn-Fe SMAs designated A, B, and C is studied. Wear properties were investigated using a tribometer whilst corrosion in 0.3 M H2SO4 and 3.5%NaCl media was studied using the potentiodynamic polarization method. The microstructure of the alloys mainly consists of FCC Cu-rich phase and Cu5Zn8 phase. The up-quenched A alloys show the highest hardness and lowest wear rate values of 72.1 HRB and 0.143 mm3/N/m respectively. Average COF was higher for the samples subjected to direct-quenching (0.35–0.12) than the up-quenched (0.16–0.12) and step-quenched (0.2–0.08) samples. Wear occurred by mixed mode mechanisms of abrasion and adhesion evident by grooves and wear particles on the surface. In 0.3 M H2SO4 medium, step-quenched alloys had corrosion rates in the range of 0.1022 to 1.1705 mm/yr, which is lower than the range of 0.1466 to 0.2855 mm/yr, and 0.1730 to 0.6027 mm/yr obtained for direct quenched and up-quenched samples respectively. In 3.5% NaCl solution, step-quenched alloys had the lowest corrosion rates 0.0251 mm/yr relative to samples subjected to up-quenching and direct quenching treatment. Generally, step-quenching treatment effectively improved the corrosion resistance of alloys in both media

Effect of Electrode Coating on Austenitic Stainless Steel Weld Metal Properties

The effect of electrode coating on austenitic stainless steel weld metal properties was studied. Manual metal arc welding method was used to produce the joints with the tungsten inert gas welding serving as the control. Metallographic and chemical analyses of the fusion zones of the joints were conducted. Results indicate that the weldment produced from E 308-16/12 lime-titania electrode has a higher ductility and strength of about 36% in terms of percentage elongation and 517 N/mm2respectively, compared to 26% and 18% and 475 N/mm2and 425 N/mm2respectively, obtained from weldments produced from E 308-16/10 rutile and E 308-16/12 rutile electrodes respectively. The presence of lime which is a slag former in E 308-16/12 lime-titania electrode was relevant in slowing down the cooling rate of both the weld pool and the just solidified weld metal resulting in the overall improvement of the resultant weld metal properties. It was found that the values of the strain hardening exponent were 0.379 for E 308-16 gauge 10, rutile electrode, 0.406 for E 308-16 gauge 12 rutile electrode, 0.382 for TIG welding, 0.353 for E 308–16 gauge 12, lime-titania electrode, 0.435 for E 310-16 gauge 10, rutile electrode. E 310 – 16 gauge 10, rutile electrode had the greatest strength and strain hardening coefficients of 1180 N/mm2and 0.435 respectively, and will be more amenable to cold working. Keywords: Austenitic stainless steel, microstructure, electrode coating, welding, joints.</jats:p

Aluminium matrix composites reinforced with high entropy alloys: A comprehensive review on interfacial reactions, mechanical, corrosion, and tribological characteristics

Aluminium matrix composites (AMCs) reinforced with high entropy alloy particulates (HEAp) represent an innovative category of metal-matrix composites with considerable potential for fulfilling the stringent demands of emerging technological applications. Their appeal lies in the advantageous combination of toughness, strength, ductility, and enhanced workability, addressing acknowledged limitations associated with ceramic-reinforced AMCs. The heightened performance of these composites is attributed to improved wettability between the aluminium matrix and HEAp reinforcement, alongside the intrinsic ductility and hardness of HEAp. This review explores the suitability of high entropy alloys as substitutes for ceramic materials in reinforcing aluminium matrix composites. The mechanical, corrosion, thermal and wear properties of AMCs reinforced with HEAp are thoroughly examined, encompassing fabrication characteristics and interfacial reactions. The incorporation of HEAp is found to notably enhance the strength-ductility ratio of AMCs. Remarkably, HEAp bring about significant improvements in the wear and corrosion resistance of AMCs. The report accentuates the performance benefits and certain challenges associated with the application of HEAp reinforcement in AMCs. Ultimately, this review proposes potential avenues for future research in this domain, outlining directions for further exploration and development

Mycelium based composites: A review of their bio-fabrication procedures, material properties and potential for green building and construction applications

The quest for green products and technologies for applications in the built environment has led to the birth of a new generation of sustainable materials, among which are mycelium-based composites. They are biocomposites derived from the growth of filamentous parts of fungus on an organic substrate. Their low carbon footprint, low energy and processing cost, biodegradability, and attractive range of properties, have made them highly demanded as alternative materials for use in the building and construction sector. Their bio-fabrication procedures, material properties, and prospects in building and construction applications have hardly been considered in a single review. It was noted that these composites have several potential benefits from economic, technical, environmental, and green credentials perspectives which make them desirable for building and construction purposes. However, their low mechanical properties, high water absorption, and lack of standardized development methods limit their applications to semi-structural and non-structural materials such as paneling, furniture, and decking. Future research should aim at reconciling its varying mechanical properties based on substrate, fungus species, growth condition, and processing method. Also, efforts should target improving its weathering and hydrophilic propensities, and scalability, factors that could undermine its long-term commercial success and applicability

Hot deformation behaviour, constitutive model description, and processing map analysis of superalloys: An overview of nascent developments

This review article provides an in-depth discussion on the hot deformability, processing map analysis, and microstructural development in superalloys, as well as the associated constitutive equations employed in flow stress prediction. It describes how hot working can improve the grain structure of superalloys by dynamic recrystallization (DRX), reduce defects, and enhance their mechanical characteristics. The formation of necklace structures, work-hardening analysis to identify the existence and commencement of dynamically recrystallized grains and the influence of processing conditions on DRX grain size are all addressed in this article. The influence of deformation variables, described by the Zener-Hollomon parameter - the occurrence of phases, dynamic precipitation, and alloying elements on the thermomechanical response, and the restoration processes of DRV and DRX are discussed in detail. The utilization of processing maps as a means to determine the most favourable processing conditions and identify the instability regime, encompassing flow instability, defects and cracking, that may arise during the hot-working of superalloys are discussed. Specifically concerning the constitutive modelling of flow stress for characterizing material flow (at various deformation strain rates, temperatures, and strain), the application of threshold stress (as a result of phase transformation during hot deformation), temperature-dependent Young's modulus, and comparing the experimentally observed activation energy and deformation stress exponent to the values predicted by creep theories, are discussed. Also, an analysis of the various modelling techniques and equations for predicting flow curves during hot-working processing is evaluated. Finally, some recommendations are made regarding the potential future research directions

Insights into hot deformation of medium entropy alloys: Softening mechanisms, microstructural evolution, and constitutive modelling—a comprehensive review

The recent discovery of multicomponent principal alloys and the enhanced comprehension of their physical metallurgy have significantly advanced the understanding of microstructure engineering and material selection for high-tech applications. The exceptional combination of characteristics found in MEAs can be attributed to their distinctive phase constitution, which is aided by their multi-principal constituents. These properties are seldom encountered in ordinary alloys. Nevertheless, the use of these materials in their as-cast state is challenging due to issues such as the presence of heterogeneity in their chemical makeup, shrinkage porosity, unrefined dendritic structure, and the presence of a quasi-stable eutectic at grain boundaries. Consequently, the utilization of hot deformation methods for the purpose of achieving uniform and refined microstructures in as-cast MEAs has garnered significant interest as a viable approach to address these limitations. This review provides a comprehensive summary of the hot deformation characteristics of MEAs. Factors such as the alloy composition, the phase constituent, deformation parameters and recrystallization mechanisms were observed to influence the microstructural development and phase transition, flow curve characteristics, and mechanical characteristics of MEAs. Additionally, the use of processing map analysis for the determination of optimal processing zones for the hot deformation of MEAs was appraised. The discussion also encompassed the constitutive model description, molecular dynamics modeling, and machine learning algorithm for the prediction of the governing deformation mechanism and the deformation flow stress. Finally, future research directions are suggested