The effect of trace addition of 0.2 wt.% Zn on the microstructures and mechanical properties of the age-hardening Mg–4.2Y–2.5Nd–1Gd–0.6Zr (wt.%) (WE43) alloy has been investigated. As compared with ...the WE43 alloy after solid solution treatment at 525 °C, the block-like Zn–Zr phase was still observed in the WE43-0.2Zn alloy. However, the time for WE43-0.2Zn alloy to get peak hardness at 250 °C was two hours, a half earlier than that in WE43 alloy, meaning a accelerated age precipitation kinetics has been achieved due to the addition of 0.2 wt.% Zn. Microalloyed with 0.2 wt.% Zn enhanced the ultimate tensile strength (UTS) slightly and ductility significantly both in the solutionized and peak aged condition. The enhancement in strength and ductility is possible associated with the larger volume fraction of precipitation phases due to a reduction of the solubility of rare earth elements (RE) in the α-Mg matrix, the larger aspect ratio (length to width) of precipitates and a decrease in stacking fault energy by addition of Zn.
In this study, newly developed quaternary micro-alloyed Cu wires (MACs) with added trace amount of noble metals (Pt, Au, and Pd) added were compared with 4N Cu and Au/Pd-coated copper wire (CPA). ...Furthermore, tensile and power cycling tests were designed to investigate the wire properties and the electrothermal failure mechanism. Studies have indicated that alloying elements were distributed in the Cu grains in a “micro-hypoeutectoid” manner, with no precipitation phase produced in the matrix. This only caused slight lattice distortion and improved the tensile properties of the Cu micro-alloy wire compared to pure Cu wire with a slight increase in electrical resistance, significantly improving the power cycling lifetime.
The addition of Pt can help to shorten the length of the heat-affected zone and reduce the free-air ball (FAB) diameter, which can increase bonding density. For wire bonding, replacing traditional Al pads with Cu pads can avoid the Al splash effect and the formation of Cu–Al intermetallic compounds (IMCs), resulting in lower interfacial resistance. Compared with commercial 4N Cu and CPA wires, the quaternary Cu micro-alloyed wires were more reliable and innovative, and the Cu pads also improved the negative effects of Al pads. Therefore, the MAC-Cu pad bonding system has excellent application potential.
Dynamic recrystallization (DRX) grain size of a Nb-Ti microalloyed steel is investigated at various strain rates and temperatures. Electron microscopy reveals that Nb preferably precipitates on TiN ...particles at temperature range of T < 1100 °C. As a result, considerable data scatterings are observed for the power law relationship between the normalized DRXed grain size (DDRX/b) and the Zener-Hollomon parameter (Z), the peak strain (εp) and the normalized steady state stress (σss/E). Much better fittings are achieved, however, when distinct analyzes are carried out within the two temperature ranges of T < 1100 °C and T ≥ 1100 °C. It is found that the well-known universal relationship suggested earlier for DDRX/b does not agree with the present results when they are analyzed separately at the two ranges of temperatures. Through this separation, an approach is developed for quantitative analysis of DRX retardation by Nb solute atoms. Moreover, the results show that separate analyses at the two temperature ranges result in almost similar dependencies of DDRX/b, εp and σss/E as a power function of Z with indexes in the range of 0.11–0.15.
High strength and high toughness steels can be developed by warm caliber rolling in ferrite region. However, high deformation resistance limits its application. In the present study, warm rolling was ...applied to plate rolling which is more suitable for industrial production to develop high strength and high toughness steels. To reduce deformation resistance, warm rolling was carried out in dual phase region. We elucidate here the evolution of microstructure and crystallographic texture and their influence on mechanical properties of microalloyed steel subjected to warm rolling. The study suggests that high strength and high toughness can also be obtained by warm rolling in the dual phase region. Elongated ultrafine microstructure and intense α-fiber texture component and γ-fiber texture component can be obtained through warm rolling. The main mechanism of microstructure evolution during warm rolling was dynamic recovery. Reducing warm rolling temperature can refine grain size, enhance α-fiber texture component and weaken γ-fiber texture component. Warm rolling can greatly enhance strength by ~64–158MPa compared to the conventional controlled rolling (CR) process, and the warm-rolled plates had high elongation in spite of high strength. The toughness was improved because of grain refinement and delamination. Delamination can induce ductile fracture at low temperature, and delay the occurrence of brittle fracture such that high toughness is obtained in steel plates. The effect of warm rolling temperature and impact test temperature on delamination and impact property was elucidated.
The state-of-the-art technology in the production and application of ferroalloys containing rare earth and alkaline earth metals is considered. The possibility of developing wasteless production of ...such ferroalloys using ore-coal briquettes is demonstrated. It is shown that for out-of-furnace processing of steel, multicomponent alloys with a microcrystalline structure are most efficient.
In the present work, the hot deformation behavior of four TWIP steels is studied by conducting compression tests at the strain rates in the range 0.01–5/s and temperatures in the range 950–1100 °C ...using a Gleeble thermomechanical simulator. The four steels differed with respect to their chemical compositions. They were non-microalloyed, Nb-microalloyed, V-microalloyed and high-Al V-microalloyed. The microstructural evolutions are studied by a scanning electron microscope (SEM) equipped with electron backscattered diffraction (EBSD) detector. Also, the hot deformation behavior of the steels are modeled using the dislocation density based Bergstrom and the diffusional transformation based Kolmogorov-Johnson-Mehl-Avrami models. The peak stresses of the high-Al V-microalloyed variant occurred at higher strains than in the V-microalloyed variant. The microstructure of the Nb-microalloyed variant showed that dynamic recovery was more active than dynamic recrystallization (DRX) when the steel was deformed at lower temperatures, i.e. lower than 1000 °C. Bergstrom modeling showed that as the Zener–Hollomon parameter (Z) increases, the hardening parameter for the V-microalloyed steel increases at a clearly higher rate than the others. Finally, it was seen that increased strain rate leads to decreased Avrami exponents (nA) for the Nb-microalloyed and the high-Al V-microalloyed variants suggesting the occurrence of dynamic recrystallization (DRX) with nucleation on grain and twin boundaries.
Structure of binary Fe-19Ga and ternary Fe-19Ga-Tb alloys at room temperature are investigated by TEM and high-resolution neutron diffraction (ND). In contrast with as cast or water quenched samples ...with A2 structure, the D03 ordering was detected in slowly cooled or annealed samples by ND. According to TEM, the D03 ordering takes place in the form of ordered clusters with the size of about 5 nm embedded into an A2 matrix. Disordering of the D03 clusters at heating and ordering at cooling were investigated by three in situ techniques: ND, vibrating sample magnetometry (VSM), and internal friction (IF). Temperatures of ordering-disordering were estimated by VSM and IF to be close to 500 °C. The effect of Fe-Ga alloys doping with Tb is also analyzed.
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•Fe-19Ga alloys structure is examined at room temperature and up to 800 °C.•Different cooling regimes lead to formation of A2 or D03 structure.•D03 structure stability is examined at heating and cooling by several in situ methods.
Corrosion resistance is a critical consideration in the selection of materials for various applications. In this study, we employed a data-driven approach using machine learning techniques and a ...large dataset of corrosion data to design and test four different low-alloy steels with varying amounts of tin (Sn) microalloying (0.1 wt%, 0.2 wt%, 0.3 wt% and Sn-free) for improved corrosion resistance in Beijing outdoor atmosphere. Using experimental methods such as corrosion morphology and rust layer analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and potentiodynamic polarization measurements, we verified that the 0.2 wt% Sn microalloying steel exhibited the best corrosion resistance. Our findings demonstrate the potential of data-driven approaches and machine learning techniques, such as the use of corrosion big data, in the identification and optimization of optimal alloy compositions of corrosion-resistant materials for outdoor environments.
Microalloying is an effective approach to improve the performance of CuCr alloys. This paper presents a new idea for the preparation of CuCrFe alloys by self-propagation reduction in-situ ...microalloying. It is found that the addition of Fe alloying components reduces the Gm and ΔGm of the CuCr melt, which inhibits the occurrence of the liquid phase decomposition process. When the Fe content of CuCrFe alloy is 1.5%, compared with the Cr-rich phase of CuCr alloy, the second phase undergoes significant refinement, the average particle size refined from 21.7 μm to 19.3 μm and the standard deviation reduced from 10.59 to 8.73, and the addition of Fe is beneficial to the spheroidization and refinement of the Cr-rich phase. Fe is mainly combined with Cr, and CuCrFe alloy still exists in the form of two phases. After solution + aging treatment, the average particle size of the second phase in CuCr alloy decreases from 21.8 μm to 17.9 μm, and that in CuCrFe alloy decreases from 19.6 μm to 18.6 μm. The conductivity of CuCrFe alloy increases from 10.5 MS m−1 to 15.9 MS m−1, and the hardness increases from 95.0 HB to 117.0 HB. After heat treatment, the nano-spherical are present in the Cr-rich phase of the CuCrFe alloy, while Fe is completely solid-soluble in the Cr-rich phase; the Cu-rich matrix shows a diffuse distribution of fine second phases, which play a role in strengthening the second phase in the matrix.
The present paper describes an attempt to reveal the effects of microalloying element niobium (Nb), normalizing and tempering temperatures on microstructure, strength and especially toughness of low ...carbon microalloyed cast steels. Four kinds of microalloyed cast steels with different contents of niobium have been examined by optical microscopy (OM), transmission electron microscopy (TEM), and electron back scatter diffraction (EBSD), tensile testing and room temperature Charpy V-notch impact toughness testing. As compared to Nb-free steel, the grains in the Nb-microalloyed cast steels are refined and the average grain sizes are about 20.8~34.6% lower. Moreover, fine spherical NbC precipitates with a diameter of about 1–15nm are formed in the Nb-microalloyed cast steels. When normalized at 900°C and tempered at 550°C, the yield strength (YS) and ultimate tensile strength (UTS) of the microalloyed cast steel with 0.044wt.% of Nb are increased to 350MPa and 520MPa from 290MPa and 485MP, respectively, as compared to Nb-free cast steel. Meanwhile, the impact energy is improved by 25.6% with ductility remained almost the same.
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•The yield and ultimate tensile strength of Nb-microalloyed cast steel can be improved by 60MPa and 35MPa, respectively.•The impact toughness of Nb-microalloyed cast steel can be improved by 25.6 % with ductility remained almost the same.•It will be most effective in grain refining by adding 0.044 wt % Nb and the grains can be refined by 34.6 %.•The grains will be coarsened when normalizing and tempering temperatures are higher than 900°C and 550°C, respectively.
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