Influence of Mn on microstructural evolution in Ti-killed C–Mn steel

The influence of manganese on the microstructure in C–Mn steels containing a small amount of titanium oxide particles as inoculants for acicular ferrite during the austenite–ferrite transformation has been studied. An acicular ferrite dominant microstructure could be produced when the Mn concentration is larger than about 2 wt.%.     

Effect of 475 °C embrittlement on fractal behavior and tensile properties of a duplex stainless steel

The fractal dimension variations of several tension fracture surfaces of a duplex stainless steel broken at room temperature has been studied after several aging treatments performed at 475 °C for 1, 2, 6.5, 12, 24, 40, and 120 h. A dimple type of fracture mode was observed for small aging times and transgranular as well as dimple rupture for 24, 40, and 120 h of aging. The higher the time of aging is, the smaller the fractal dimension and the true fracture strain. An expected reduction of the strength with the time of aging was observed.     

Effect of annealing parameter on microstrucmre and magnetic properties of cold rolled non-oriented electrical steel

The microstructure and magnetic properties of cold rolled non-oriented electrical steel, annealed at 200-1 000℃ for 0-240 min with different heating rates, were investigated by optical microscopy, scanning electron microscopy, Epstein frame, and transmission electron microscopy. The results show that the magnetic properties of cold rolled non-oriented electrical steel can be improved by controlling the annealing process to obtain uniform coarse grains with critical sizes after the recovery, recrystallization and growth of grains. Additionally, the annealing temperature influences the magnetic properties more significantly than annealing time, and with the increase of heating-up rate during the annealing process, the magnetic properties of the cold rolled non-oriented electrical steel increase.     

Microstructure and high temperature tensile properties of Al–Si–Cu–Mn–Fe alloys prepared by semi-solid thixoforming

The differences in the microstructure and elevated temperature tensile properties of gravity die cast, squeeze cast, and semi-solid thixoformed Al–Si–Cu–Mn–Fe alloys after thermal exposure at 300 °C were discussed. The results demonstrate that the elevated temperature tensile properties of semi-solid thixoformed alloys were significantly higher than those of gravity die cast and squeeze cast alloys, especially after thermal exposure for 100 h. The ultimate tensile strength (UTS) of semi-solid thixoformed alloys after thermal exposure at 300 °C for 0.5, 10 and 100 h were 181, 122 and 110 MPa, respectively. The UTS values of semi-solid thixoformed alloys were higher than those of heat resistant aluminum alloys used in commercial applications. The enhanced elevated temperature tensile properties of semi-solid thixoformed experimental alloys after thermal exposure can be attributed to the combined reinforcement of precipitation strengthening and grain boundary strengthening due to thermally stable intermetallic phases as well as suitable grain size.     

Effect of microstructural heterogeneities on scatter of toughness in multi-pass weld metal of C–Mn steels

Often, scatter in mechanical properties of multi-pass steel weldments is qualitatively attributed to the underlying heterogeneous microstructure brought about by spatial variations of multiple thermal cycles. In this research, a method for quantitative heterogeneity calculation based on measured variations of microstructure and hardness throughout the multi-pass weld metals including various reheated regions was explored. Published data from multi-pass welds with controlled titanium additions (7–32 wt ppm) were correlated to comprehensive microstructure characterization. The scatter in 7 wt ppm Ti steel welds was larger than that of 32 wt ppm Ti steel welds. This change in scatter is correlated to spatial distributions of microstructural heterogeneity parameter, rather than the average value of heterogeneity parameter for the whole weldment.     

Effect of neutron irradiation and postradiation annealing on the microstructure and properties of an Al–Mg–Si alloy

The effect of long-term neutron irradiation and postradiation thermal-induced aging on the microstructure and mechanical properties of an aluminum-based reactor Al–Mg–Si alloy grade SAV-1 has been studied. The material under study is the shell of an automatic fine-control rod used to control the reactivity of the core of a VVR-K research reactor. Successive 1-h annealings of specimens of the SAV-1 alloy irradiated to doses of 0.001 and 5 dpa in the temperature range of 100–550°C have been carried out. The evolution of the fine structure of the material and changes in its mechanical characteristics have been studied. The phenomenon of the acceleration of the aging of the SAV-1 alloy under the effect of a high neutron fluence at an irradiation temperature of 80°C has been observed, which involves the formation of numerous lineage (stitch) Guinier–Preston zones in the alloy. It has been shown that the strength characteristics of the SAV-1 alloy depend significantly on the degree of its radiation- and thermal-induced aging.     

The effect of annealing on microstructure and tensile properties of Ti–22Al–25Nb electron beam weld joint

This study investigated the microstructure evolution and tensile properties of Ti–22Al–25Nb EBW joints. The fusion zone of the as-welded joint exhibited a fully B₂ microstructure. Widmanstätten O particles precipitated out of B₂ matrix after annealing and their size increased within a temperature range from 750 °C to 900 °C. In the heat affected zone, there was a transition of microstructure moving away from the fusion zone towards the base material. Strength and elongation of the as-welded sample were significantly improved after annealing, which was attributed to the strengthening effect of O precipitates and the slip transmission between O and B₂ phases. Samples tensile tested at 650 °C all failed within the fusion zone and exhibited intergranular failure instead of transgranular failure at room temperature. The room temperature strength and hardness of the joints decreased with annealing temperature due to the coarsening of O precipitates. At 650 °C, failure occurred by intergranular fracture in the fusion zone and the joint strength of all annealed samples was similar due to similar B₂ grain boundary strength.     

Effect of cold-rolling and annealing on interfacial structures and properties of A500/steel bimetal strip

The effect of cold-rolling, by both a series of small passes and single-pass with different deformations as well as the subsequent annealing, on the interfacial structures and properties of A500 （AlSn8 Pb2 Si2.5 Cu0.8 Cr0. 2 ） / steel bimetal strip produced by liquid-solid roll cladding was investigated. Experimental results of the cold-rolling by a series of small passes show that the interracial bonding strength increases slightly when the total deformation is less than 7.32 % and then decreases gradually with the increase in deformation. Subsequent annealing has no effect on the interfacial structures and properties. The effect of cold-rolling by single-pass less than 33.2 % deformation on the interracial structures and properties is the same as that of multi-pass cold-rolling, whereas cold-rolling by singlepass more than 33.2% deformation followed by annealing at 350 ℃ for 2.5 h can make the interracial bonding strength increase to a great extent. Metallographic examination of the interface shows that there exist only transverse cracks within the interfacial layer and the clad strip does not split along the interface during cold-rolling if the thickness of interfacial layer is less than 4 - 5μm. The thick interfacial layer（〉5 - 6μm）, however, crumbles during cold-rolling, thus resulting in the splitting of the clad strip.     

Effect of swaging on microstructure and tensile properties of W–Ni–Fe alloys

The objective of this study was to investigate the effect of swaging on the microstructure and tensile properties of high density two phase alloys 90W–7Ni–3Fe and 93W–4.9Ni–2.1Fe. Samples were liquid phase sintered under hydrogen and argon at 1480 °C for 30 min and then 15% cold rotary swaged. Measurement of microstructural parameters in the sintered and swaged samples showed that swaging slightly increased tungsten grain size in the longitudinal direction and slightly decreased tungsten grain size in the transverse direction. Swaging increased the contiguity values in both longitudinal and transverse directions. Swaging led to more severe deformations at the edges than at the center of the specimens. Solidus and liquidus temperatures of the nickel-based binder phase in the sintered and swaged samples were determined by differential scanning calorimetry measurements. An increase in tensile strength with a reduction in ductility was observed due to strain hardening by swaging.     

Effect of tensile deformation on micromagnetic parameters in 0.2% carbon steel and 2.25Cr–1Mo steel

The influence of prior tensile deformation on the magnetic Barkhausen emission (MBE) and the hysteresis (B–H) curve has been studied in 0.2% carbon steel and 2.25Cr–1Mo steel under different tempered conditions. This study shows that the micromagnetic parameters can be used to identify the four stages of deformation, namely (i) perfectly elastic, (ii) microplastic yielding, (iii) macroyielding and (iv) progressive plastic deformation. However, it is observed that the MBE profile shows more distinct changes at different stages of tensile deformation than the hysteresis curve. It has been established that the beginning of microplastic yielding and macroyielding can be identified from the MBE profile which is not possible from the stress–strain plot. The onset of microplastic yielding can be identified from the decrease in the MBE peak height. The macroyielding can be identified from the merging of the initially present two-peak MBE profile into a single central peak with relatively higher peak height and narrow profile width. The difference between the variation of MBE and hysteresis curve parameters with strain beyond macroyielding indicates the difference in the deformation state of the surface and bulk of the sample.     

The effects of temperature,strain rate and minor boron on tensile properties of wrought Ti–47Al–2Mn–2Nb alloy

The effects of temperature from 77 to 1375 K, strain rate from 10⁻⁵ to 10⁻¹s⁻¹ and 1.0 at% boron were systematically investigated on tensile properties and fracture mode of a wrought Ti–47Al–2Mn–2Nb alloy. For both alloys with and without boron, σ_0.2 and _b show non-monotonous strain rate sensitivity at intermediate temperatures, positive strain rate sensitivity at low and high temperatures, δ fluctuates with the change of the strain rate at low and intermediate temperatures, but decrease monotonically at high temperatures. Brittle-to-ductile transition (BDT) was found in the alloys. BDT temperature, T_BD rises with the increase of strain rate. The fractography analysis and theoretical calculation using the Nabarro model added up to the speculation that the BDT of the alloys is controlled by dislocation climbing. The addition of 1.0% B increased σ_0.2 and _b substantially, as well as , although to a less degree, at low and intermediate temperature. It was found that the boron addition can lower the T_BD more than 100°C under different strain rate from 10⁻⁵ to 10⁻¹s⁻¹.     

Effect of niobium and grain boundary density on the fire resistance of Fe–C–Mn steel

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The effect of annealing on the microstructure and tensile properties of a β/γ′ Ni–Al–Fe alloy

The evolution of the microstructure of a (β/γ ′) Ni–32 at.% Al–5 at.% Fe alloy during annealing has been studied by electron microscopy and X-ray diffraction. Annealing at 800°C and 1100°C causes a reverse martensitic transformation, L1₀→B2 (β), and a B2→L1₂ (γ ′) phase transformation. The lower annealing temperature leads to a higher volume fraction of the γ ′-phase but a smaller size of the γ ′-particles. The kinetic laws of the coarsening and of the increase in the volume fraction of the γ ′-phase are discussed. The orientation relationships between the β and γ ′ phases appeared to be mainly of Nishiyama–Wassermann and Bain types after 800°C annealing, while Kurdjumov–Sachs and Bain orientation relationships were predominant in the alloys annealed at 1100°C. A strong correlation between the volume fraction of the γ ′-phase and the tensile characteristics of the alloy has been established.     

Effect of substrate temperature on microstructural and optical properties of ZnO films grown by pulsed laser deposition

ZnO thin films were deposited on n-Si （111） at various substrate temperatures by pulsed laser deposition （PLD）. X-ray diffraction （XRD）, photoluminescence （PL）, Fourier transform infrared spectrophotometer （FTIR）, and scanning electron microscopy （SEM） were used to analyze the structure, morphology, and optical property of the ZnO thin films. An optimal crystallized ZnO thin film was obtained at the substrate temperature of 600℃. A blue shift was found in PL spectra due to size confinement effect as the grain sizes decreased. The surfaces of the ZnO thin films were more planar and compact as the substrate temperature increased.     

Effect of halide anions and temperature on initiation of pitting in Cr–Mn–N and Cr–Ni steels

Abstract

The pitting corrosion of Cr₁₈Mn₁₂N and Cr₁₈Ni₉ steels in halide solutions (F^?, Cl^?, Br^? and I^?) has been investigated. The study involved cyclic potentiodynamic polarisation tests with subsequent examination of the specimens by both optical and scanning electron microscopy. Values of the critical concentrations of halide ions, [X^?]_cr, beyond which pitting occurs, as well as breakdown potentials for pitting in chloride solution, have been established. In addition, the effect of the temperature over the range of 5–80°C on the critical chloride ion concentration [Cl^?]_cr has been investigated and it has been found that temperature has a negligible effect beyond 40°C.     

Effect of annealing and doping with Zr on the structure and properties of in situ Cu–Nb composite wire

Heavily cold-drawn in situ Cu–Nb and Cu–Nb–Zr composites have been studied by transmission electron microscopy and mechanical testing. Ultimate tensile strength and microhardness decrease with introduction of intermediate annealing and increase with Zr doping. Besides, Zr results in formation of dispersed and coarse ZrO₂ particles, and changes the character of fracture from ductile to the brittle one.     

Effect of Y addition on microstructure and mechanical properties of Mg–Zn–Mn alloy

The effects of Y on the microstructure and mechanical properties of Mg–6Zn–1Mn alloy were investigated. The results show that the addition of Y has significant effect on the phase composition, microstructure and mechanical properties of Mg–6Zn–1Mn alloy. Varied phases compositions, including Mg₇Zn₃, I-phase (Mg₃YZn₆), W-phase (Mg₃Y₂Zn₃) and X-phase (Mg₁₂YZn), are obtained by adjusting the Zn to Y mass ratio. Mn element exists as the fine Mn particles, which are well distributed in the alloy. Thermal analysis and microstructure observation reveal that the phase stability follows the trend of X>W>I>Mg₇Zn₃. In addition, Y can improve the mechanical properties of Mg–Zn–Mn alloy significantly, and the alloy with Y content of 6.09% has the best mechanical properties. The high strength is mainly due to the strengthening by the grain size refinement, dispersion strengthening by fine Mn particles, and introduction of the Mg–Zn–Y ternary phases.     

Development and tensile properties of Ti–40Al–10V alloy

A Ti–40Al–10V (at%) intermetallic compound has been developed using vacuum arc remelting and hot-isostatic pressing (HIP), followed by isothermal hot-forging (IHF). The alloy, composed mainly of B2 and γ phases with equiaxial grains of several μm in average diameter and a small amount of α₂ phase with equiaxial grains of smaller size, shows excellent tensile properties; it has an elongation larger than 6% on average and yield strength larger than 700 MPa at low (ambient temperature) to intermediate temperatures, although the strength decreases rapidly at temperatures higher than 600°C.     

Microstructure and tensile properties of orthorhombic Ti–Al–Nb–Ta alloys

Microstructure and tensile properties of orthorhombic Ti–Al–Nb–Ta alloys have been studied. In order to optimize ductility and strength of the orthorhombic alloys with the nominal compositions of Ti–22Al–23Nb–3Ta and Ti–22Al–20Nb–7Ta, various thermomechanical processing steps were implemented as part of the processing route. With a special heat treatment before rolling to obtain a fine and homogeneous rolled microstructure, the rolled microstructure resulted in a good combination of high tensile yield strength and good ductility of the alloys through available solution and age treatments. The duplex microstructure with equiaxed α₂/O particles and fine O phase laths in a B2 matrix, deforming in α₂+B2+O phase field and treating in O+B2 phase field, possesses the highest tensile properties. The R.T. yield strength and ductility of the Ti–22Al–20Nb–7Ta alloy are 1200 MPa, and 9.8% respectively. The yield strength and ductility values of 970 MPa and 14% were also maintained at elevated temperature (650°C).