Effect of Processing Condition on Texture and Drawability of a Ferritic Rolled and Annealed Interstitial-Free Steel

The processing conditions of the texture formation and deep drawability of a Ti-IF steel strip hot-rolled in ferritic region and subsequently annealed were investigated. The r-value increases with the decrease of reheating temperature, and finish rolling temperature and the increase of reductions in ferritic region. For lubricated ferritic rolling and annealing, the r-value is raised up to 1.75, and elongation rate is over 50% at the finish rolling temperature of 650 ℃, which is suitable for DDQ grade products. However, the r-value is below 1.0 in the case of unlubricated rolling. The X-ray diffraction was used to analyze the textural characteristic of samples. For samples subjected to lubricated rolling and annealing, the strong { 111 }//ND recrystallization texture is distributed homogeneously along the thickness direction, and the intensity of { 110} recrystallization texture is very low even in surface. However, for unlubricated samples, the {111} texture is distributed inhomogeneously and is weak along the thickness direction, and （110}//ND recrystallization texture is strong, which deteriorates the formability.     

Effect of Processing Condition on Texture and Drawability of a Ferritic Rolled and Annealed InterstitialFree Steel

The processing conditions of the texture formation and deep drawability of a TiIF steel strip hotrolled in ferritic region and subsequently annealed were investigated. The rvalue increases with the decrease of reheating temperature, and finish rolling temperature and the increase of reductions in ferritic region. For lubricated ferritic rolling and annealing, the rvalue is raised up to 175, and elongation rate is over 50% at the finish rolling temperature of 650 ℃, which is suitable for DDQ grade products. However, the rvalue is below 10 in the case of unlubricated rolling. The Xray diffraction was used to analyze the textural characteristic of samples. For samples subjected to lubricated rolling and annealing, the strong {111}∥ND recrystallization texture is distributed homogeneously along the thickness direction, and the intensity of {110} recrystallization texture is very low even in surface. However, for unlubricated samples, the {111} texture is distributed inhomogeneously and is weak along the thickness direction, and {110}∥ND recrystallization texture is strong, which deteriorates the formability.     

Wetting Behavior and Evolution of Microstructure of Sn–3.5Ag Solder Alloy on Electroplated 304 Stainless Steel Substrates

In the present study, wetting characteristics and evolution of microstructure of Sn?C3.5Ag solder on Ag/Ni and Ni electroplated 304 stainless steel (304SS) substrates have been investigated. Solder alloy spread on Ag/Ni plated 304SS substrates exhibited better wetting as compared to Ni/304SS substrate. The formations of irregular shaped and coarser IMCs were found at the interface of solder/Ni/304SS substrate region whereas, solder/Ag/Ni/substrate interface showed continuous scallop and needle shaped IMCs. The precipitation of Ag₃Sn, Ni?CSn, FeSn₂ and lesser percentage of Fe?CCr?CSn IMCs were found at the interface of solder/Ag/Ni/substrate region whereas, solder/Ni/304 SS substrate exhibited predominantly FeSn₂ and Fe?CCr?CSn IMCs. Presence of higher amount of Fe?CCr?CSn IMCs at the solder/Ni/304SS substrate interface inhibited the further wetting of solder alloy.     

Structure Evolution and Solidification Behavior of Austenitic Stainless Steel in Pulsed Magnetic Field

 To understand the solidification behavior of austenitic stainless steel in pulsed magnetic field, the solidification process is investigated by means of the self made high voltage pulse power source and the solidification tester. The results show that the solidification structure of austenitic stainless steel can be remarkably refined in pulsed magnetic field, yet the grains become coarse again when the magnetic intensity is exceedingly large, indicating that an optimal intensity range existed for structure refinement. The solidification temperature can be enhanced with an increase in the magnetic intensity. The solidification time is shortened obviously, but the shortening degree is reduced with the increase of the magnetic intensity.     

Multilayer Mg–Stainless Steel Sheets,Twinning and Texture Evolution

In the present study, different combinations of multilayer sheets were prepared from 1 and 2 mm Mg AZ31 along with 0.25, 0.5, and 1 mm 304 L stainless steel. The texture and microstructure of the elongated samples (20 and 30 pct strain) were studied. It was found that the transversal stress plays an important role in both texture evolution and twinning in these composites. The obtained pole figures revealed an axial texture tilt with increasing steel layer volume fraction (V _f). It was found that this is a direct effect of transverse stress, which becomes more significant upon reducing Mg V _f. This extra stress component tilts the basal planes away from the original normal direction in monolithic samples. Moreover, our results indicate that with decreasing Mg V _f, twinning activity was increased in the 20 pct deformed samples but reduced in the samples with 30 pct elongation. It is known that at high strains where sufficient transverse stress is generated, the activity of prismatic slip is significantly enhanced, which promotes the motion of dislocations and reduces the necessity of twinning. With decreasing Mg V _f, stronger transversal stress is generated and Mg reaches the critical threshold of prismatic activity at lower strains.

     

In Situ Observation of Phase Transformation and Structure Evolution of a 12?pct Cr Ferritic Stainless Steel

This work focuses on an in situ observation of phase transformation of a 12?pct Cr ferritic stainless steel using high-temperature laser scanning confocal microscopy. ?????????? phase transformation temperatures are determined to be approximately 1073?K and 1423?K (800?°C and 1150?°C), respectively. The onset of phase transformation is found to occur at grain boundaries. When the temperature is beyond 1518?K (1245?°C), the grain growth rate suddenly becomes very high, and the grain growth is related to the self-organizing of adjacent grains. ?????? phase transformation has been mostly restrained when cooling rates are in the range of 22.4?K/s to 13.3?K/s (22.4?°C/s to 13.3?°C/s) except for at grain boundaries. Martensitic phase transformation, rather than ?????? phase transformation, occurs when the cooling rates are in the range of 8.5?K/s to 2.2?K/s (8.5?°C/s to 2.2?°C/s). The starting temperature of martensitic phase transformation is approximately 697?K to 728?K (424?°C to 455?°C) for specimens heated to 1373?K (1100?°C) (i.e., ?? phase field), which is 50?K to 100?K (50?°C to 100?°C) higher than that of specimens heated to 1723?K (1450?°C) (i.e., ?? phase field). Many bulges remain on the surfaces of the specimen heated to 1723?K (1450?°C), and their formation mechanism is analyzed.     

Effect of Grade on Thermal–Mechanical Behavior of Steel During Initial Solidification

Thermal–mechanical analysis of solidification is important to understand crack formation, shape problems, and other aspects of casting processes. This work investigates the effect of grade on thermal–mechanical behavior during initial solidification of steels during continuous casting of a wide strand. The employed finite element model includes non-linear temperature-, phase-, and carbon content-dependent elastic–viscoplastic constitutive equations. The model is verified using an analytical solution, and a mesh convergence study is performed. Four steel grades are simulated for 30 seconds of casting without friction: ultra-low-carbon, low-carbon, peritectic, and high-carbon steel. All grades show the same general behavior. Initially, rapid cooling causes tensile stress and inelastic strain near the surface of the shell, with slight complementary compression beneath the surface, especially with lower carbon content. As the cooling rate decreases with time, the surface quickly reverses into compression, with a tensile region developing toward the solidification front. Higher stress and inelastic strain are generated in the high-carbon steel, because it contains more high-strength austenite. Stress in the δ-ferrite phase near the solidification front is always very small, owing to the low strength of this phase. This modeling methodology is a step toward designing better mold taper profiles for continuous casting of different steels.     

Amorphous Intergranular Film Effect on the Texture and Structural Evolution During Cold-Rolling of Nanocrystalline Ni–Zr Alloys

Metallurgical and Materials Transactions A - The presence of amorphous intergranular films (AIFs) in nanocrystalline (NC) metals improves the mechanical properties and thermal stability. However,...     

The Effect of Bridge Geometry on Microstructure and Texture Evolution During Porthole Die Extrusion of an Al–Mg–Si–Mn–Cr Alloy

Porthole die extrusion is used to produce complex hollow aluminum cross-sections for automotive applications. In a porthole die, the material is first divided into multiple streams which are separated by a bridge, before rejoining in the weld chamber and finally passing through the die orifice. The rejoining of the material in the weld chamber produces lines known as weld lines in the final extruded product. The microstructure along the weld line and its associated quality are strongly influenced by the thermal-mechanical history the material experiences as it passes through the portholes, the weld chamber, and the die orifice, which can be altered by die design and, in particular, the bridge geometry. To study the influence of bridge geometry on weld line microstructure and final quality, a series of porthole die extrusion experiments was conducted using an Al–Mg–Si–Mn–Cr alloy and two different types of bridge geometry (streamlined and flat). The experimental results showed that bridge geometry had a significant effect on the local microstructure and crystallographic texture at the weld line. Specifically, EBSD analysis indicated that the weld line texture associated with a streamlined bridge geometry consisted of a deformation texture (mainly the copper component), while the local texture produced by a flat bridge was a recrystallization texture consisting of Cube, Goss, and Cube_RD texture components. Simulation of the extrusion process, using DEFORM 3D, indicated that the weld line produced using a flat bridge experienced a slightly higher temperature, but much higher equivalent strains than the streamlined case. Material away from the weld line was very similar for both cases, indicating that the effect of the die bridge geometry is localized to the region close to the weld line.

     

Effect of Cr–Mo Addition on the Microstructure and Mechanical Properties of Medium-Carbon Steel

Herein, the effects of Chromium–Molybdenum (Cr–Mo) addition on the microstructural evolution and mechanical properties of medium-carbon steel after spheroidization annealing are systematically studied through scanning electron microscopy, electron backscatter diffraction, and tensile testing. Cr–Mo addition hinders the proeutectoid ferrite + pearlite transformation, thereby promoting the bainite transformation. Moreover, it refines the pearlite lamellar spacing as well as decreases the average carbide diameter, increases the number of carbides per unit area, and hinders ferrite recrystallization. Compared with those in the B1 steel annealed for 8 h, the size of carbides and their number per unit area in the CM1 steel are 30% lower and 2.2-fold higher, respectively. Due to finer ferrite grains, smaller carbides, and a higher amount of carbides, the strength of steel improves, and the plasticity slightly reduces after Cr–Mo addition. After 2 h of annealing, the yield strengths of Cr–Mo steels are 77.5–109.5 MPa higher than those of base steels; the elongations are above 20%. The contributions of the strengthening mechanism of steel to the yield strength are as follows (from high to low): grain boundary, precipitation, solid solution, and dislocation strengthening.     

Effect of Phase-Selective Nanoscale Precipitates on the Bauschinger Effect in Austenitic–Ferritic Duplex Stainless Steels

Metallurgical and Materials Transactions A - The Bauschinger effect in austenitic–ferritic duplex stainless steel 1.4462 was investigated using tension–compression tests combined with...     

The Effect of Cold Rolling on Microstructure and Mechanical Properties of a New Cr–Mn Austenitic Stainless Steel in Comparison with AISI 316 Stainless Steel

In the present study the effect of room temperature rolling on microstructure and mechanical properties of a new Cr–Mn austenitic stainless steel (containing 12 %Cr, 23 %Mn and 0.13 %C) and AISI 316 steel was investigated. The specimens of these steels were cold rolled at various thickness reductions of 0, 12, 25, 37 and 50 %. Microstructural investigations were carried out using optical microscopy, magnetic field test and X-ray diffraction technique. Hardness and tensile test methods were also done to evaluate the mechanical properties. Results showed that some of austenite phase transformed to martensite during cold rolling in the 316 steel, while there was no strain induced transformation in the Cr–Mn steel. It was also found that the newly developed steel had higher strength and higher specific strength than those of the 316 steel, while its ductility was the same as that of the 316.     

748 K (475 °C) Embrittlement of Duplex Stainless Steel: Effect on Microstructure and Fracture Behavior

22Cr-5Ni duplex stainless steel (DSS) was aged at 748 K (475 °C) and the microstructure development correlated to changes in mechanical properties and fracture behavior. Tensile testing of aged microstructures confirmed the occurrence of 748 K (475 °C) embrittlement, which was accompanied by an increase of strength and hardness and loss of toughness. Aging caused spinodal decomposition of the ferrite phase, consisting of Cr-enriched α″ and Fe-rich α′ and the formation of a large number of R-phase precipitates, with sizes between 50 and 400 nm. Fracture surface analyses revealed a gradual change of the fracture mode from ductile to brittle delamination fracture, associated with slip incompatibility between ferrite and austenite. Ferrite became highly brittle after 255 hours of aging, mainly due to the presence of precipitates, while austenite was ductile and accommodated most plastic strain. The fracture mechanism as a function of 748 K (475 °C) embrittlement is discussed in light of microstructure development.     

Effect of Flowing Lead–Bismuth Eutectic on the Mechanical and Structural Properties of Stainless Steel 304L

Stainless steel 304L is being considered as a structural material for a component in a critical facility in an environment of molten lead–bismuth eutectic (LBE) at a temperature between 250 and 350 °C. This paper gives results on the effect, of 10,000 h exposure to non-isothermal liquid LBE at temperatures of 250 and 350 °C, on the mechanical and structural properties of SS 304L. The dissolved oxygen concentration in the molten eutectic was 4 × 10^?10 wt% and flow velocity was 16 cm/s. In order to assess the changes in mechanical properties tensile tests were carried out in air at 25 °C and fractography of fractured surface was observed by scanning electron microscopy. The results showed no change in the mechanical properties of SS 304L after 10,000 h exposure to LBE at 250 and 350 °C. Electron probe microanalysis of the interface of SS 304L with LBE showed that there was no penetration of LBE into the grain boundaries nor preferential dissolution of any of the components of steel in LBE after 10,000 h exposure at either temperature. No oxide layer was observed on the surface of SS 304L.     

Influence of the Initial Microstructure on the Reverse Transformation Kinetics and Microstructural Evolution in Transformation-Induced Plasticity–Assisted Steel

The reverse transformation behavior upon heating to intercritical temperature was studied in Fe-0.21C-2.2Mn-1.5Si (wt pct) alloy with three initial microstructures. One is the cold-rolled (CR) structure and two others are martensite having different fractions of retained austenite. The CR structure exhibits slower reverse transformation kinetics than martensite due to the lesser population of potent nucleation sites and coarse cementite particles. The film type of retained austenite at the martensite lath boundary contributes to the earlier start of the reverse transformation, because it can proceed as the growth of pre-existing retained austenite, which makes the nucleation process less critical. Besides, the growth of interlath austenite plays an essential role in the evolution of fine lath-type reverse-transformed microstructure, which was difficult to obtain from similar initial microstructures of martensite having negligible fraction of interlath austenite.     

Microstructure Evolution During Short Term Creep of 9Cr–0.5Mo–1.8W Steel

P92 steel (9Cr–0.5Mo–1.8W) was subjected to a heat treatment of 1050 °C/30 min/air cooling/780 °C/120 min/air cooling followed by 1080 °C/30 min/air cooling/740 °C/60 min/air cooling to obtain tempered martensite microstructure, for better creep strength. Stress rupture tests carried at 600 °C in the range of 250–350 MPa resulted in rupture times in the range of 200–3000 h. Straight line plot of stress rupture curve indicated no major change in deformation mechanism. Coarsening of precipitates and substructure development were the main reasons for microstructure degradation, consequently leading to reduced hardness of the sample. Gauge and grip portions of the same sample were sectioned to comparatively evaluate the effects of stress and aging. Gauge portion of 3000 h sample showed considerable change in the microstructure in terms of boundary migration, while that of grip portion hardly evolved. The ruptured samples exhibited predominantly ductile fracture with elongated cavities at higher rupture times.     

Effect of Cerium on Structure and Properties of Granular Bainitic Steel

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Effect of RE-Modifier on Microstructure and Mechanical Property of High-Carbon Medium-Manganese Steel

Ｌｉｎｉｎｇｐｌａｔｅｉｓｏｎｅｏｆｔｈｅｍｏｓｔｉｍｐｏｒｔａｎｔｗｅａｒ ｒｅｓｉｓｔａｎｔｃｏｍｐｏｎｅｎｔｓｏｆｂａｌｌｍｉｌｌｓ .Ｉｔｍｕｓｔｍｅｅｔｖａｒ ｉｏｕｓｒｅｑｕｉｒｅｍｅｎｔｓｆｏｒｔｈｅｍａｃｈｉｎｅｓａｃｃｏｒｄｉｎｇｔｏｏｐ ｅｒａｔｉｎｇｃｏｎｄｉｔｉｏｎｓ .Ｒｅｃｅｎｔｌｙ ,ａｓｅｒｉｅｓｏｆｗｅａｒ ｒｅｓｉｓ ｔａｎｔｍａｔｅｒｉａｌｓｈａｓｂｅｅｎｄｅｖｅｌｏｐｅｄｆｏｒｄｉｆｆｅｒｅｎｔｂａｌｌｍｉｌｌｓｉｎＣｈｉｎａ ,ｅ .ｇ .ｈｉｇｈ ｃａｒｂｏｎｍｅｄｉｕ…     

Evolution of Texture,Strain, and Grain Boundary Constitution in Copper–Chromium Coatings and its Effect on Coating Corrosion Behavior

Metallurgical and Materials Transactions A - Microstructural alterations in electrodeposited Cu–Cr coatings (1.5, 3.6, and 6.5 wt pct Cr) and their impact on the coating corrosion behavior...