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Oxide dispersion strengthened (ODS) alloys, due to their high irradiation resistance and good mechanical properties at high temperatures, are promising for applications in Generation IV reactors, especially GFR, and fusion installations. However, the biggest challenge in applying ODS materials is related to fabrication techniques. This paper aims to evaluate powder metallurgy processing and the effect of small additions of oxide- and carbide-forming elements on the microstructure and mechanical properties of Fe–Cr–Al-based ODS alloys. The series of ODS alloys with Y2O3 and different additions of Ti and V was prepared by mechanical alloying (MA) and consolidated by spark plasma sintering (SPS), which is less often employed to fabricate ODS alloys than hot extrusion or hot isostatic pressing. The investigations were performed on MAed powders, bulk-sintered samples, and samples after homogenization annealing. The MAed powders reveal two body-centered cubic (bcc) alloyed phases with close lattice parameters. The sintered samples show a single bcc phase (a = 2.88–2.89 Å) matrix and a high-volume fraction of homogenously distributed nanometric oxide precipitates. The addition of vanadium and titanium leads to the formation of vanadium- and titanium-rich nanometric oxides and carbides. The bulk samples show fine grain and stable microstructure with an average grain size slightly below 1 µm. Moreover, after homogenization annealing and air cooling, the relative density slightly increases. Hardness after heat treatment is relatively stable, which was confirmed by nanoindentation and Vickers microhardness results. These experimental findings promise to develop Fe–Cr–Al-based ODS materials tailored for operation under harsh conditions in nuclear reactors. [ABSTRACT FROM AUTHOR]

This paper utilizes the plasma arc as the heat source to successfully fabricate well-formed thin-walled parts using combined cable wire duplex stainless steel 2209. Microstructure of parts exhibited the favorable two-phase ratio and the absence of σ-phase. It was found that appropriate heat input (1.68 kJ/cm) and cooling rate (5 °C/s) can effectively avoid the precipitation of σ-phase. Furthermore, the properties of the as-deposited samples were comparable to those of the samples heat-treated at 1300 °C, proving that no subsequent heat treatment was required for 2209 stainless steel fabricated by plasma arc additive manufacture. The samples showed excellent properties, in which the ultimate tensile strength and yield strength were improved by about 7% and 24% compared with GB/T4237-2015. The impact toughness meets the requirements of EN10028-7-2016, which is about 35% higher than that of the cold metal transfer samples, and the corrosion resistance is comparable to that of hot rolled 2205. [ABSTRACT FROM AUTHOR]

In this work, the influence of Mo in the CoNiFeMn system during heat treatment after prior hot and cold rolling was investigated. At present, relatively few studies on static recrystallization and grain growth kinetics in high entropy alloys are available. This paper focuses on static recrystallization and grain growth kinetics as well as the influence of molybdenum on these phenomena. This work compares two alloys, CoNiFeMn and (CoNiFeMn)95Mo5, in relation to the formations of the brittle µ phase at room- and high-temperature plastic deformation regimes due to its negative affect on material ductility. Microstructures were characterized by energy dispersive X-ray spectroscopy analysis and by scanning electron microscopy, whereas the mechanical properties were assessed by tensile testing. The effect of recrystallization and grain growth behaviours on the microstructural evolution and the final mechanical properties was assessed. It was found that Mo addition into the CoNiFeMn system has a strong effect on both the static recrystallization and grain growth kinetics as well as the final mechanical properties. [ABSTRACT FROM AUTHOR]

The effects of 0.1 wt.% Ca addition, heat treatment, and SPD processing using the MaxStrain module of the Gleeble thermomechanical simulator on the microstructure, mechanical properties, and electrical conductivity of Cu–0.7Mg (wt.%) alloy were investigated in this work. The binary alloy exhibited a single-phase microstructure, whereas the ternary alloy featured uniform dispersion of Cu5Ca intermetallic particles inside the grains as well as on grain boundaries. These particles resulted in an average hardness that was 33% higher than that of the binary alloy, as well as 13% higher yield strength and 13% higher ultimate tensile strength. The heat treatment process not only enhanced the yield strength and ultimate tensile strength of the samples, but also resulted in the partial spheroidization of Cu5Ca particles within the microstructure of the ternary alloy, resulting in its improved ductility. Following MaxStrain processing, ternary samples exhibited a smaller grain size and a higher fraction of high-angle grain boundaries than binary samples, which was attributed to the vital role of Cu5Ca intermetallic particles in hindering the dislocation motion during deformation. MaxStrain-processed samples exhibited marginally lower electrical conductivities than their initial counterparts; yet, all MaxStrain-processed samples satisfied the electrical conductivity threshold for classification as HSHC Cu alloys. [ABSTRACT FROM AUTHOR]

In this work, multicomponent PEEK coatings with PTFE particles and TiN nanoparticles were developed on Ti-6Al-4V alloy substrates using electrophoretic deposition (EPD) and post-EPD heat treatment. Three different polyelectrolytes involving chitosan, PAZO and sodium alginate were used to enable the co-deposition of all particles on one electrode. All polyelectrolytes were effective and enabled coating deposition through electrosteric stabilization of suspension. The EPD mechanism consisted of the adsorption of the dispersant on the surface of the particles and the imparting of a positive (chitosan) or negative (PAZO, sodium alginate) charge. Heat treatment densified the coatings but also caused microcrack formation in the coating with chitosan, shrinkage of the polymers in the coating with PAZO, and open porosity in the coating with sodium alginate. Coatings obtained from suspension with chitosan showed excellent adhesion strength and scratch resistance, higher that those deposited from suspensions containing PAZO or alginate. The introduction of TiN and PTFE particles into the PEEK matrix resulted in a simultaneous reduction of the friction coefficient and wear rate of the titanium alloy in the case of coatings with chitosan and alginate. These coatings are promising for improving the wear and friction properties of titanium alloys. [ABSTRACT FROM AUTHOR]

In the current research, strong strain-hardening capability in 1045 carbon steel was achieved by cold rolling and heat treatment of the lamellar structure. After 60% cold rolling, the proeutectoid ferrite and pearlite were severely elongated along the rolling direction. Cementite layers with brittle nature were fragmented under the action of stress and also by shear band formation during rolling. The lamellar heterogeneous microstructure of the heat-treated samples was formed by the proeutectoid ferrite as the soft domain and the pearlite as the hard domain. Increasing the heat treatment duration promoted the spheroidization transformation of cementite, and the spheroidization degree of cementite increased. With the increase in the time of heat treatment, the number of recrystallized grains is increased. Heat treatment led to weakening the deformation texture (⟨100⟩‖ND or θ fiber) and strengthening the recrystallization texture (⟨110⟩‖ND or ζ fiber). The heat-treated steels revealed an average microhardness value much higher than its macrohardness due to changes in the texture of ferrite grains. Heat treatment decreased the strength and hardness, and increased the ductility and toughness of steel compared to the cold-rolled sample owing to the annihilation of dislocations and the strengthening transition from strain hardening to grain refinement. The heat-treated samples exhibited a wider range of uniform plastic deformation and a larger strain hardening rate than the cold-rolled sample owing to the occurrence of the recovery of strain hardening rate phenomenon. The appropriate collocation of the fine spherical cementite and the soft/hard domains (with a large difference in mechanical properties) was beneficial to obtaining excellent strength-ductility balance in plain medium carbon steel. After heat treatment, the extent of ductile fracture considerably increased. With increasing the time of heat treatment from 1 to 3 h, the number of lamellar dimples decreased owing to the creation of more fine spherical cementite. [ABSTRACT FROM AUTHOR]