Structure and specific features of strain hardening upon extension of a hot-rolled nitrogen-bearing austenitic–martensitic 27Kh15AN3MD2 steel

The microstructure and the static tensile stress–strain curve of a hot-rolled nitrogen-bearing austenitic–martensitic corrosion-resistant 27Kh15AN3MD2 steel have been studied. It is found that the curve has three straight line portions with different slopes at strains of 2–4.3% (portion I), 4.3–13.8% (portion II), and 13.8–19.5% (portion III). The intersection of the straight lines in portions I and II corresponds to the onset of the γ → α transformation at a strain of 4.3%. It is shown that strain-hardening coefficient dσ/dε of the steel in portion II is significantly larger than that in portions I and III. Insignificant twinning and fragmentation of martensite crystals are observed after extension by 2%. A 25% strain leads to significant twinning intensity, refinement, and an increase in the martensite content to 90%.     

Effect of tempering on change of structure and properties of high-strength strip steel of strength category Kh90–Kh100 after thermomechanical treatment

Metallurgist - The correlation of structure, formed during heat treatment in steel of strength category Kh90–Kh100, with mechanical properties of sheet steel and the effect of subsequent...     

Effect of two step cold rolling — continuous annealing on micro-structures,textures and mechanical properties in IF and IF-HS steel sheets

In the present work, the objectives were to investigate the type of microstructure and texture that developed after two step cold rolling — continuous annealing. Further, an attempt has been made to correlate the microstructure and texture with mechanical properties. Interstitial free (IF) and interstitial free — high strength (IF-HS) steel sheets which contain almost γ-fiber textures, were subjected to two step cold rolling for different percentage of reduction and further continuously annealed. It was observed that cold rolling strengthened the region of (223)[1$ bar 1 $ bar 1 0] and 335[1$ bar 1 $ bar 1 0] orientations of α-fiber as well as γ-fiber. After continuous annealing, cold rolled γ-fiber as well as (223)[1$ bar 1 $ bar 1 0] and 335[1$ bar 1 $ bar 1 0] orientations transformed to extremely strong new γ-fiber. It was found that at two steps 80% cold rolling -continuous annealing, drawability of IF steel sheet was exceptionally high i.e. around 3.15, whereas for IF-HS steel sheets, it was around 2.7. Although, two steps cold rolling -continuous annealing enhanced percentage elongation and stretchability exceptionally, but it reduced the yield strength substantially. However, ultimate tensile strength was hardly affected. In addition, it is also observed that two steps cold rolling — continuous annealing developed uniform grain size in both the grades of steel sheets.     

Effect of the solidification and aging conditions on the mechanical properties of Pb–Ca–Sn battery alloys

The influence of the mold temperature on the mechanical properties and the structure of Pb–Ca–Sn battery alloys during their solidification and subsequent aging is studied.     

Effect of annealing treatment on microstructure and mechanical properties of hot isostatic pressing compacts fabricated using Ti–6Al–4V powder

The effects of annealing temperature and annealing time on microstructure evolution and mechanical properties of Ti–6Al–4V titanium alloy prepared using powder hot isostatic pressing were investigated. The results showed that when annealing temperature was <?1173?K, the globularisation of primary α was observed, and the morphology of secondary α changed from acicular shapes to acicular and continuous lathy grains. Scanning electron microscopy fracture surface showed that the fracture mechanism changed from transcrystalline dimple type to a mixture of transcrystalline and intercrystalline dimple types with increasing annealing temperature. The tensile strength and elongation varied with the temperature in an opposite trend. However, they varied similarly with increasing annealing time. Microhardness was sensitive to the annealing time, resulting into a maximum microhardness of 396.95?HV at 1173?K for 3?h.     

Influence of the solidification temperature–time parameters on the structure and mechanical properties of nickel aluminide–based alloys

The influence of the technological parameters of directional solidification, namely, the solidification rate and the temperature gradient, on the microstructure, the structure–phase parameters, and the mechanical properties of nickel aluminide–based intermetallic alloys is considered.     

Effect of deformation and heat treatment on the structure,the mechanical properties,and the fracture characteristics of an ultrafine-grained Zr–1Nb alloy

The effect of cold working and annealing for various times on the structure, the mechanical properties, and the fracture characteristics of an ultrafine-grained Zr–1 wt % Nb alloy after three-dimensional pressing is studied. Possible causes for increasing the thermal stability of the strength properties of the ultrafine-grained Zr–1 wt % Nb alloy during prerecrystallization annealing after additional cold working by rolling are discussed.     

Influence of quenching methods on martensitic transformation and mechanical properties of P/M processed Cu–Al–Ni–Ti shape memory alloys

The effect of quenching conditions on phase transformation characteristics and microstructural features of Cu–Al–Ni–Ti shape memory alloys (SMAs) have been studied. The alloys were synthesised via conventional powder metallurgy process using elemental metal powders. Four different quenching techniques, such as (a) two-step quenching, first to 100°C and then to 0°C; (b) two-step quenching, initially to 40°C and later to 0°C; (c) direct quenching to 40°C and (d) direct quenching to 0°C, were used. The microstructural features and phase transformations that the alloys had undergone were studied using FE-SEM and XRD techniques. The martensitic phase transformation analyses were carried out by differential scanning calorimeter while the mechanical properties were studied by microhardness and flexural bending tests. The results obtained clearly indicate that the quenching routes followed have a remarkable influence on the properties of Cu-based SMAs.     

Structure and properties of strip for large-diameter pipe made from steel in strength categories Kh80–Kh100

We studied structure formation in high-strength strip for trunk pipelines made from steel in strength classes Kh80–Kh100. The structural morphology was shown to have an effect on the mechanical properties of the thick rolled sheet. Weldability studies and low-temperature brittle-fracture-resistance studies were performed on the steels developed as part of this study.     

Effect of separate and combined milling of Cu and TiB2 powders on the electrical and mechanical properties of Cu–TiB2 composites

The present work compares the properties of the Cu–TiB₂ composites prepared by varying the mechanical milling conditions. The Cu–TiB₂ composites were processed using Cu–TiB₂ powders combined milling, a powder mixture consisting of separately milled Cu & TiB₂ and a powder mixture prepared by the combination of separate and combined milling. The hardness and flexural strength of the combined milled powders were found to be maximum, despite of their lower sintered density. The separately milled powders achieved excellent electrical properties combined with moderate hardness and flexural strength. The properties of composites processed using the combination of separate and combined milling laid in between the two conditions of combined and separate milling.     

Effect of oxygen addition on mechanical properties of TiAl at 293–1273 K

Mechanical properties of Ti−50, −53, and −56 at.% Al alloys doped with 0, 0.1, 0.2 and 0.3 mass% oxygen have been studied in compression tests at temperatures from 293 K to 1273 K in a vacuum. The yield stress in Ti−50 at.% Al alloy increased by about 1.5 times owing to the addition of 0.3 mass% oxygen at all testing temperatures. In Ti−53 and −56 at.% Al alloys the increases of yield stress due to the addition of oxygen were not as pronounced as those in Ti−50 at.% Al alloys. The work hardening coefficients increased at 293–873 K but they decreased at 1073–1273 K with increasing oxygen and aluminum content. Insoluble particles extracted isolated by a mixed acid from TiAl alloys were α-Al₂O₃ phase and the amount of α-Al₂O₃ phase increased with increasing aluminum and oxygen content. The increase of yield stress at all testing temperatures occurred owing to the solid solution hardening of oxygen in Ti−50 at.% Al alloy and the dispersion strengthening of α-Al₂O₃ in Ti−53 and Ti−56 at.% Al alloys.     

Wear resistance and structure–phase states in the surface of the welding-deposited coating on steel

The elemental and phase composition, the state of a defect substructure, and the tribological characteristics of the layer deposited on the surface of a low-carbon low-alloy steel by a welding method are studied. The deposited layer on the steel surface causes the formation of a multilayer structure, and the wear resistance of the deposited layer is found to increase.     

Influence of ingot homogenization on the impact properties of 4X5MΦC steel strip

The homogenization of 4X5MΦC (1.2343/H11) steel ingots and cooling of the rolled bar are corrected so as to obtain a transverse work of impact of ?200 J in the vacuum-treated product with constant forging. Longer holding in homogenization reduces the liquation in the metal, while intermediate air cooling of the metal prior to slow pit cooling prevents the formation of a carbide network in the microstructure. Over the whole cross section of the final metal bar (diameter 165–190 mm), the work of impact meets Bohler specifications and exceeds 200 J.     

Effect of heat treatment on the behavior ofδ-ferrite in B410D martensitic stainless steel

The morphology and the evolution ofδ-ferrite existing in B410D slabs,hot-rolled plates,annealed plates and quenched plates were studied through metallographic observation.Results show thatδ-ferrite forms during the solidification process and that it easily grows and increases in quantity during high temperature annealing.Band-shapedδ-ferrite in hotrolled plates is difficult to be eliminated by conventional heat treatment and hard to recrystallize.     

Influence of heat treatment conditions on the mechanical properties of Ti–6Al–4V alloy

In the current work, several heat treatments were carried out below and above the beta-transition temperature of the Ti–6Al–4V alloy followed by aging at 550 °C for 6 hours. The resultant microstructures and their effects on the mechanical properties of Ti–6Al–4V alloy were investigated. The results showed that solution treatment of Ti–6Al–4V samples followed by water quenching from β and α/β fields raised the alloy hardness from 380 to 575 and 656?HV, respectively, while no remarkable changes were observed after aging. The hot tensile strength of the as-forged sample increased from 671 to 756?MPa after water quenching from the ß- or α/ß- field, while the air cooling from β-phase field decreased the tensile strength to 644 MPa. The fracture mode of the tensile samples was more ductile in case of the solution-treated samples compared to the as-forged samples. A subsurface layer was formed due to the diffusion of oxygen into the surface at high temperatures. This layer which is known as ‘oxygen diffusion layer’ masked the differences of wear behaviour of the specimens.