Effect of cold single-roll drive rolling on the microstructural evolution and mechanical properties of ferritic stainless steel

In this study, the microstructural evolution and mechanical behavior of AISI 430 ferritic stainless steel produced by cold single-roll drive rolling were investigated. By increasing the rolling deformation, the width of the grains decreased, and after 60% rolling, highly elongated ferrite grains and shear bands occurred in the microstructure. With the increase in the strain, first, the shear texture and then the deformation texture were strengthened in the samples. Dislocation density increased with increasing strain, which led to increasing the macro and microhardness. Also, the up and down surfaces of the sample had different hardness values due to being exposed to two rolls with different speeds. The 60% rolled sample had the highest yield strength (823 MPa), the highest ultimate tensile strength (833 MPa), and the lowest ductility (10.7%), which was due to increasing dislocation density and shear bands. After 60% rolling, the number, size, and depth of dimples decreased compared to the initial steel. However, the fracture mode of all deformed samples was ductile

Effect of compression bonding temperature on the strength-ductility balance of AA7075 alloy

In this study, the effect of compression bonding temperature on the microstructure and strength-ductility balance of AA7075 alloy was investigated. The results showed that dynamic recovery (DRV) was the dominant restoration mechanism in the compressed samples at 25, 100, 200, and 300 °C decreasing the dislocation density of elongated grains, while dynamic recrystallization (DRX) was predominant in the compressed sample at 400 °C forming fine equiaxed grains. By increasing the compression temperature, the bonding quality is improved. Several MgZn2 peaks could be observed in the diffraction pattern of the processed sample at 400 °C, confirming the occurrence of overaging. By increasing the compression temperature from 25 °C to 300 °C, the texture parameter of {200} (as recrystallization texture) was continuously reduced from 2.13 to 1.11, while the texture parameter of {220} (as deformation texture) was continuously enhanced from 2.09 to 4.91 due to the higher height reduction in the larger compression temperature. By further increasing the compression temperature to 400 °C, the texture parameter of {200} is significantly increased from 1.11 to 3.21, while the texture parameter of {220} is remarkably decreased from 4.91 to 0.83 owing to the occurrence of DRX. By increasing the temperature from 25 °C to 400 °C, the hardness of both AA7075 and pure aluminum layers was decreased due to the intensifying recovery and recrystallization. After the compression bonding, no evidence of the Portevin Le Chatelier was found and the stress-strain curves exhibited normal behavior. With increasing the temperature from 25 °C to 400 °C, yield and ultimate tensile strength were decreased from 672.7 MPa and 689.8 MPa to 187.4 MPa and 374.9 MPa, respectively, while the total elongation and energy absorption were increased from 6.2% to 40.6 J/cm3 to 33.7% and 108.1 J/cm3, respectively. At the early stage of plastic deformation, the strain hardening rate of the compressed sample at 400 °C was significantly lower than that of other compressed samples. However, when the ε reaches 0.09, the strain hardening rate of the sample became larger than that of other processed samples due to the recovery of the strain hardening rate (RSHR) phenomenon at stage III in the compressed sample at 400 °C. The fracture features of all samples were characterized by dimples and cleavage facets, indicating the occurrence of a mixed ductile/brittle mode of fracture. However, by increasing the compression temperature, the dimpled portion of the fracture surface was increased. The dimples were coarsened when the compression temperature increased owing to the softening of samples as well as coarsening of MgZn2 precipitates at higher temperatures

Evading the strength-ductility trade-off dilemma in AA2024 alloy by short-term natural re-aging after T351 temper

In this research, the influence of short-term natural re-aging after T351 temper on the microstructural evolution and mechanical behavior of AA2024 aluminum alloy was investigated. Grain growth occurred in the microstructures of the natural re-aged sample and a large number of Al7Cu2Fe particles were located inside the alpha grains. At the re-aging time of 1440 min, the peaks of XRD were shifted strongly to the right due to the formation of θ′′, S″, θ′, and S′. The results revealed that the precipitation rate was high in the AA2024 alloy during natural aging. With increasing the re-aging time, texture parameters remained almost unchanged. The hardness increased slowly within the first 60 min, then enhanced rapidly between 60 and 2880 min, and finally became stable at around 139 HV between 2880 and 11520 min. When the natural re-aging time increased from 240 to 2880 min, the strengthening trended speed up, viz, the yield strength increased from 226.6 to 357.3 MPa, and the ultimate tensile strength enhanced from 452.2 to 535.5 MPa. Compared to the as-received sample (T351 temper), the ultimate tensile strength of the re-aged sheet improved from 455.5 to 535.5 MPa, the ductility remained unchanged, and the hardness increased from 128.8 to 138.2 HV, which was owing to the acceleration of the precipitation caused by the presence of high-content Al7Cu2Fe particles in the interior of the alpha-aluminum grains in the natural re-aged sample. It was found that the Portevin-Le Chatelier instability of AA2024 alloy was effectively postponed after natural re-aging. With increasing the natural re-aging time, the strain hardening rate of the AA2024 sheet increased. The strengthening of the natural re-aged sample for 1440 and 2880 min was a result of a synergistic effect of precipitation hardening due to the formation of θ′′, S″, θ′, and S′ phases, elimination of Portevin Le-Chatelier instability, and highly efficient load transfer from alpha-aluminum to Al7Cu2Fe. Finally, to use the A2024 alloy produced by natural re-aging for 1440 or 2880 min, two methods were proposed

Electrochemical aspects and in vitro biocompatibility of Ti-SS304 layered composite

In the current research, in order to eliminate the release of toxic ions from the stainless steel 304 layer, a bi-layered Ti-SS304 biocomposite was made using the friction stir welding process, and the corrosion-cellular behavior of this biocomposite in simulated body fluid (SBF) was studied. The results show that the increasing temperature induced by increasing welding heat input during friction stir welding increases the thickness of the oxide layer formed on the titanium layer. By increasing the thickness of the oxide layer, the corrosion current density increases to 3.45 μA cm−2, the corrosion potential decreases to −0.24 V, and the corrosion rate increases to 0.029 mm/year. In addition, compared to samples fabricated with different traverse speeds of 5, 10, and 20 mm/min, the composite samples fabricated with different rotational speeds of 600, 800, and 1000 rpm did not show significant differences in corrosion current density due to competition effect of the titanium oxide layer and residual stress formed during friction stir welding by different rotational speeds. The two-layered Ti-SS304 composite fabricated at a rotation speed of 1000 rpm and a traverse speed of 20 mm/min shows the lowest corrosion current density and corrosion rate and the highest cell viability of 4.9 × 10 −7 A/cm−2, 4.26 × 10 −3 mm/year, and 92%, respectively

A low-cost strategy to enhance strength-ductility balance in AISI1045 steel

In the current research, the impact of cold single-roll drive rolling as a low-cost technique on the microstructural evolution and mechanical properties of the AISI1045 sheet was studied. The microstructure of the as-received sample was a lamellar structure consisting of soft domains (proeutectoid ferrite) and hard domains (pearlite). The average grain size of proeutectoid α decreased from 24.5 μm (for the initial steel) to 7.1 μm (for the 60 % rolled steel) due to the occurrence of continuous dynamic recrystallization (CDRX). With an increase in the rolling deformation, the homogeneity of the ferrite and pearlite distribution in the microstructure was improved. Fragmentation and bending of the θ lamellae and several shear bands were seen in the 60 % deformed steel. By increasing the strain, the rotation of ferrite grains towards the θ fiber (as shear texture) increased due to the introduction of severe shear plastic deformation caused by the single-roll drive rolling. By increasing the intensity of ⟨100⟩‖ND (caused by the rolling deformation increasing), the amount of hardness enhanced less in the RD-TD section compared to the RD-ND section. As the rolling reduction increased to 60 %, the yield and tensile strength significantly enhanced and reached a maximum of 993.1 MPa and 1017.8 MPa, respectively. This was due to work hardening, grain refinement strengthening of α, and fragmentation of θ. The decreasing trend of the work hardening of the 60 % rolled steel was not similar to the strain hardening behavior of homogeneous materials, indicating that the number of geometrically necessary dislocations accumulated at the hard domain/soft domain interfaces was large, which was beneficial to the increment of work hardening in the second stage. After the rolling reduction increased, the proportion of dimples reduced, the depth and number of dimples decreased, and the plasticity reduced, which had a large effect on the secondary cracks

The effects of antimony and hot rolling on the microstructure, texture, and magnetic properties of a non-oriented electrical steel

The present work investigates the effects of antimony and hot rolling on the microstructure, texture, and magnetic properties of a 1.2 wt%Si electrical steel. For this purpose, three samples with 0.002, 0.012, and 0.026 wt% antimony were produced by melting in an induction furnace and casting into ingots, followed by hot rolling with a 75 % reduction. The aim was to better understand the interaction effects of adding antimony and hot rolling on the microstructure, texture, and magnetic properties. Microstructural studies were performed using optical microscopy (OM) and field emission scanning electron microscopy (FESEM). The macrotexture measurement was performed via X-ray diffraction (XRD), while magnetic properties were measured by a vibrating sample magnetometer (VSM). The results showed that increasing the antimony content gradually reduces the grain size, which is due to the effect of antimony on the migration rate of grain boundaries. This behavior was observed in both as-cast and hot-rolled samples. The texture in as-cast samples is random, and θ-fiber is observed after hot rolling. The examination of the texture parameter (TP) showed that the sample with 0.002 wt%Sb has a higher TP compared to other samples. Moreover, the lowest levels of coercivity and remanence are observed in this sample, which is due to the inverse relationship between the grain size and coercivity. The addition of antimony reduces the grain size, thus destroying the magnetic properties under these conditions

Effect of preprocessing heat treatment of the Al-16Si-4Cu alloy on microstructure and tribological behavior of friction-surfaced coating

This study investigated the simultaneous effect of the consumable rod's preprocessing heat treatment conditions (homogenization, solid solution, and artificial aging treatment) and severe plastic deformation on the properties of Al-Si-Cu alloy friction surfaced on a commercially pure aluminum alloy substrate. The friction-surfaced coating's microstructural evolution, mechanical properties, and wear resistance were evaluated. The results showed that coatings fabricated using artificially aging (T6)-treated consumable rods resulted in the highest coating width (17.02±0.83 mm) and maximum efficiency (39.78 ± 1.23 %). Friction surfacing using artificially aged and solid solution-treated consumable rods results in minimum (2.78 ± 0.28 µm) and maximum (6.32±0.34 µm) coating grain sizes, respectively. Friction surfacing using T6-treated consumable rods results in smaller, more uniformly distributed Si particles in the coating microstructure. Compared to the other consumable rods, the coatings fabricated using T6-treated consumable rods result in the highest hardness (110.54±10.29 HV0.1), maximum bond strength (14.15±0.75 kN), and lowest wear rate (0.20±0.03 µg/Nm)

Investigating the relationship between mechanical properties and residual stress in the laser cladding process of Inconel 625 superalloy

In the present study, the tensile strength, fracture surface, hardness, and amount of residual stress in Inconel 625 super alloy cladded with direct metal deposition (DLD) process in the states before and after stress relief was studied. Residual stresses on the cladding layer surface were determined via XRD method. According to results, the yield strength of Am sample increased by 10% compared to thecast sample (reference sample). Although the yield strength experiebced an increase, the ductility followed an opposite trend falling from 42.5% to 26%. According to residual stress test outcomes, tensile residual stress of 361 MPa in the additive-manufactured sample. After stress relaxation heat treatment and almost complete removal of residual stress, the ductility reached 52.5%, the ultimate strength was also improved by 17% from cast sample. Also, after stress relaxation, the hardness of the sample and its fluctuations are reduced