Annealing Temperature Dependence of the Tensile Behavior of 10 pct Mn Multi-phase TWIP-TRIP Steel

In the present study, the relationship between the microstructure and the mechanical properties of Fe-10 pct Mn-3 pct Al-2 pct Si-0.3 pct C multi-phase steel was investigated. The 10 pct Mn multi-phase steel exhibits a combination of high tensile strength and enhanced ductility resulting from deformation-twinning and strain-induced transformation occurring in succession. A pronounced intercritical annealing temperature dependence of the tensile behavior was observed. The annealing temperature dependence of the retained austenite volume fraction, composition, and the grain size was analyzed experimentally, and the effect of the microstructural parameters on the kinetics of mechanical twinning and strain-induced martensite formation was quantified. A dislocation density-based constitutive model was developed to predict the mechanical properties of 10 pct Mn multi-phase steel. The model also allows for the determination of the critical strain for dynamic strain aging effect.     

Tensile Behavior of Intercritically Annealed 10 pct Mn Multi-phase Steel

The exceptional elongation obtained during tensile testing of intercritically annealed 10 pct Mn steel, with a two phase ferrite–austenite microstructure at room temperature, was investigated. The austenite phase exhibited deformation-twinning and strain-induced transformation to martensite. These two plasticity-enhancing mechanisms occurred in succession, resulting in a high rate of work hardening and a total elongation of 65 pct for a tensile strength of 1443 MPa. A constitutive model for the tensile behavior of the 10 pct Mn steel was developed using the Kocks–Mecking hardening model.     

Warm Formability of 0.2 Pct C-1.5 Pct Si-5 Pct Mn Transformation-Induced Plasticity-Aided Steel

The warm stretch formability and flangeability of 0.2 pct C-1.5 pct Si-5 pct Mn transformation-induced plasticity-aided sheet steel with annealed martensite matrix were investigated for automotive applications. Both formabilities were enhanced by warm forming at peak temperatures of 423 K to 573 K and 423 K to 523 K (150 °C to 300 °C and 150 °C to 250 °C), respectively. The superior warm formabilities were mainly due to the stabilization of a large amount of retained austenite by warm forming and the consequent considerably suppressed void growth at the interface between the matrix and transformed martensite, despite there being large hole punching damage for the stretch flangeability. High peak temperatures for stretch formability and flangeability were associated with apparently increased M _S of the retained austenite resulting from the increased mean normal stress on stretch forming and hole expansion.     

Effect of Coiling Temperature on the Microstructure and Mechanical Properties of Hot-Rolled Ti–Nb Microalloyed Ultra High Strength Steel

A novel low carbon Ti–Nb microalloyed hot rolled steel with minimum yield strength of 700 MPa and good balance of stretch-flangeability and impact toughness has been developed by controlled thermo-mechanical processing following thin slab direct rolling route. In the present work, the effects of two coiling temperatures on the resulting microstructure, micro-texture and mechanical properties on this Ti–Nb microalloyed steel have been studied. It is observed that increase in coiling temperature from 520 to 580 °C significantly affects the mechanical properties. Higher dislocation density and increased precipitation along with slightly smaller grain size is observed for 580 °C coiling temperature resulting in about 50 MPa increase in yield and tensile strengths as compared to 520 °C coiling temperature.     

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 Bonding Temperature on Microstructure and Mechanical Properties of WC–Co/Steel Diffusion Brazed Joint

In this work, the diffusion brazing of AISI 4145 steel to WC–Co cemented carbide using RBCuZn-D interlayer with bonding temperature values of 930, 960, 990 and 1020 °C was studied. The microstructure of the joint zone was evaluated by scanning electron microscope (SEM) and X-ray diffraction (XRD). Vickers microhardness and shear strength tests were performed to investigate mechanical behaviors of the brazed joints. The XRD and SEM results indicated that with increase of bonding temperature, the elements readily diffused along the interface and formed various compounds such as γ, α and β and Co₃W₃C. The results also showed that with the increase of bonding temperature from 930 to 960 °C, a sound metallurgical bond was produced, however in higher bonding temperatures (990 and 1020 °C) a decrease in mechanical properties of the joints was observed which could be due to the excessive zinc evaporation, interface heterogeneity and voids formation. The maximum shear strength of 425 MPa was obtained for the bond made at 960 °C.     

Effect of δ Phase on Mechanical Properties of GH4169 Alloy at Room Temperature

Tensile tests of GH4169 alloy were performed at room temperature. Different fractions, distributions and shapes of δ phase was prepared by aging treated at 880 °C, 930 °C and 980 °C for 5 h or 10 h. The effect of δ phase on the mechanical properties of GH4169 alloy was investigated. The results show that 0.2% yield strength and ultimate tensile strength of GH4169 alloy increase by 61 MPa and 78 MPa respectively when the fraction of δ phase increases from 2.20% to 5.21%. Then, the ultimate tensile strength remains at 1 012 MPa even when the fraction of δ phase reaches 7.56%. The fraction effect of δ phase on the strength improvement of GH4169 alloy is more significant than morphology, and the critical fraction value is 5.21%. In addition, the elongation decreases by 14.1% when the fraction of δ phase increases from 2.20% to 7.56%. Excessive needle or short rod shaped δ phase is responsible for the reduction of elongation.     

The Effect of Annealing Temperature and Temper-Rolling on Microstructure,Mechanical Properties,and Lüders Strain of Fe–0.25C–5.9Mn–1.0Al–1.57Si Medium Mn Steel

This study investigates the effect of austenite reverted transformation (ART) annealing temperature and temper-rolling on the microstructure, mechanical properties, and deformation behaviors of cold-rolled Fe–0.25C–5.9Mn–1.0Al–1.57Si transformation-induced plasticity (TRIP) steel. The cold-rolled steel annealed at 700 °C demonstrates excellent mechanical properties. The ultimate tensile strength, total elongation, and product of strength and elongation are observed as 1212 MPa, 31.8%, and 38.6 GPa%, respectively. The excellent combination of strength and ductility is related to the discontinuous TRIP effect; still, an inhomogeneous deformation is observed during tensile deformation, known as the Lüders strain. Temper-rolling is used for the ART-annealed specimens at 700 and 720 °C, and yield point elongation decreases when temper-rolling reduction increases. When the temper-rolling reduction increases by 8%, the yield point elongation of the specimen annealed at 700 °C is noted at 1%, while the specimen annealed at 720 °C exhibits continuous yielding. The strain-induced martensite transformation and increased dislocation density in the ferritic matrix improve the early-stage strain hardening rate, thus suppressing the Lüders band's formation.     

Effect of Annealing Temperature and Time on Martensitic Transformation Temperatures and Mechanical Properties of the Ti–50.7 at % Ni Shape Memory Alloy

Russian Journal of Non-Ferrous Metals - The influence of temperature and time of recrystallization annealing on the characteristic temperatures of martensitic transformation and mechanical...     

Intercritical Rolling Induced Ultrafine Lamellar Structure and Enhanced Mechanical Properties ofMedium-Mn Steel

The medium-Mn steel with ferrite and austenite structure was rolled in the intercritical region down to dif- ferent rolling reduction. The microstructure and mechanical properties of the rolled steels were investigated by scan- ning electron microscopy, transmission electron microscopy, X-ray diffraction and tensile tests. It was found that the ferrite and austenite structure gradually evolved into an ultrafine structure from the random directional lath structure to lamellar structure with lath longitudinal direction parallel to the rolling direction with increasing rolling strain. It was found that the thickness of the laths was gradually refined with increasing rolling strain. The lath thickness is about 0. 15 9m stored with high density dislocations and the austenite volume fraction of the steel is about 24% after 80% rolling reduction. Furthermore, it was interesting to find that yield strength, tensile strength and total elongation of the 80% rolled medium-Mn steel are about 1000 MPa, 1250 MPa and 24%, respectively, demonstrating an excellent combination of the strength and ductility. Based on the microstructure examination, it was proposed that the grain refinement of the medium-Mn steels could be attributed to the duplex structure and the low rolling temperature. Analysis of the relationship between the microstructure and the mechanical properties indicated that the high yield strength mainly resulted from the ultrafine grain size and the high density dislocation, but the improved ductili- ty may be attributed to the large fractions of austenite retained after intercritical rolling.     

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.     

Effect of the Rare Earths on the High Temperature Properties of Deformed Leaded-Brasses

The effect of the rare earths on the high temperature properties of deformed leaded-brasses has been stu-died with the high temperature tensile test.The results show that the rare earth additives can increase elongationof alloys at high temperature,but they had little effect on the maximum flow stress.With the help of SEM.X-ray diffraction instrument,quantitative metallography analysis instrument,etc.,the effect of the rare earthelements on the mierostrueture of alloys has also been examined.     

δ-Ferrite Formation and Its Effect on the Mechanical Properties of Heavy-Section AISI 316 Stainless Steel Casting

Metallurgical and Materials Transactions A - δ-Ferrite formation across the thickness of a heavy-section AISI 316 casting slab and the effect of its decomposition on the bending properties...     

Temperature Dependence of the Dynamics of Portevin-Le Chatelier Effect in Al-2.5 Pct Mg Alloy

Tensile tests were carried out by deforming polycrystalline samples of Al-2.5 pct Mg alloy at four different temperatures in an intermediate strain rate regime of 2 × 10⁻⁴ s⁻¹ to 2 × 10⁻³ s⁻¹. The Portevin-Le Chatelier (PLC) effect was observed throughout the strain rate and temperature region. The mean cumulative stress drop magnitude and the mean reloading time exhibit an increasing trend with temperature, which is attributed to the enhanced solute diffusion at higher temperature. The observed stress–time series data were analyzed using the nonlinear dynamical methods. From the analyses, we established the presence of deterministic chaos in the PLC effect throughout the temperature regime. The dynamics goes to higher dimension at a sufficiently high temperature of 425 K (152 °C), but the complexity of the dynamics is not affected by the temperature.     

Effect of Grain Size on Mechanical Properties of NickelFree High Nitrogen Austenitic Stainless Steel

The fine grained structures of nickelfree high nitrogen austenitic stainless steels had been obtained by means of cold rolling and subsequent annealing. The relationship between microstructure and mechanical properties and gain size of nickelfree high nitrogen austenitic stainless steels was examined. High strength and good ductility of the steel were found. In the grain size range, the HallPetch dependency for yield stress, tensile strength, and hardness was valid for grain size ranges for the nickelfree high nitrogen austenitic stainless steel. In the present study, the ductility of cold rolled nickelfree high nitrogen austenitic stainless steel decreased with annealing time when the grain size was refined. The fracture surfaces of the tensile specimens in the grain size range were covered with dimples as usually seen in a ductile fracture mode.     

Effect of Rare Earths on Properties of BNbRE Rail Steel

The development and properties of BNbRE rail steel and the effect of RE on rail steel were studied. The results show that the properties of rail steel (δb ≥980 MPa, δ5≥ 8 % ) can be improved by adding RE and niobium and adjusting the content of C, Si and Mn in steel. At the same time, the abrasion resistance, contact fatigue and fatigue property of BNbRE rail steel are excellent. It also shows that RE in rail steel has the functions of purifying steel, modifying inclusion and micro-alloy action effect. The improved steel-making process enhances the quality of molten steel. Although the content of RE is low, excellent properties of BNbRE rail steel are achieved.     

Mechanical and Functional Properties of Laser-Welded Ti-55.8 Wt Pct Ni Nitinol Wires

As interest increases in incorporating Nitinol alloys in different microapplications and devices, the development of effective procedures for laser microwelding (LMW) these alloys becomes necessary. Laser welding processes applied to Nitinol have been shown to lower strength, induce inclusions of intermetallic compounds (IMCs), and alter the pseudoelastic and shape memory effects. Inconsistency in reported weld properties has also suggested that further studies are required. The current study details the mechanical, microstructural, and phase transformation properties of Nd:YAG LMW crossed Ti-55.8 wt pct Ni Nitinol wires. The effects of surface oxide on joint performance were also investigated. Fracture strength, weld microstructure, and phase transformation temperatures at varying peak power inputs were studied and compared to the unaffected base metal. Results showed good retention of strength and pseudoelastic properties, while the fusion zone exhibited higher phase transformation temperatures, which altered the active functional properties at room temperature.     

On the Stacking Fault Energy of Fe-18 Pct Mn-0.6 Pct C-1.5 Pct Al Twinning-Induced Plasticity Steel

The stacking fault energy (SFE) of Fe-18 pct Mn-0.6 pct C-1.5 pct Al twinning-induced plasticity (TWIP) steel was measured using weak-beam dark-field imaging of dissociated dislocations observed in transmission electron microscopy. The SFE was found to be 30 mJ/m². A relatively wide scatter was observed in the experimentally measured partial dislocation separation of screw dislocations. It is argued that the anomalously wide partial dislocation separation is due to the interaction of point-defect pairs involving interstitial C atoms with the strain field of the partial dislocations. Internal friction (IF) experiments were carried out to detect the presence of point-defect pairs that might affect the dislocation separation, and a clear Finkelshtein–Rosin (FR) peak related to point-defect pairs involving interstitial C atoms was observed in the IF spectrum.