Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract： Coupons of the grounding material Q235 steel were buried in an artificial soil of diatomite with different pH values for 20 d, and then the corrosion behavior of the steel was examined. The results indicated that the pH value of the artificial soil had a great effect on the corrosion behavior of Q235 steel. With the increasing of pH value, the corrosion rate of the steel in the artificial soil decreased, which accorded fairly well with that in the actual soil, correspondingly the corrosion type of the coupons turned from rather serious uniform corrosion to slight local corrosion. The corrosion products formed in acidic artificial soil are consistent with those in an alkaline artificial soil, they all composed mainly of α-FeOOH, Fe3O4, γ-FeOOH and Fe2O3, however the products in the late case contained higher Fe3O4 and less α-FeOOH.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract： Corrosion behavior of weathering steels with different nickel content was studied by wet/dry cyclic test. The mass loss method was used to evaluate the weatherability of weathering steel, while the rust layers formed on weathering steel were characterized by using SEM, XRD and electrochemical measurements. The result indicates that the higher Ni content，the better corrosion resistance the steel is. The corrosion resistance of the steels with Ni content above 3%(mass fraction) are about twice of the counterpart steel without Ni. The addition of Ni enhances the free corrosion potential of the steel and promotes the formation of α-FeOOH, so as to improve the protectiveness of the formed rust. The EIS results indicate that with the increasing Ni content of the steels, the impedance of the rust layer becomes bigger.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《材料研究学报》
Abstract： The high-temperature single-pass compression test was carried out by utilizing Gleeble- 1500D thermal simulation compression testing machine for Si-Mn-Cr-B alloy steel, while its thermal deformation behavior was studied by different strain rate (0.01-5 s-1) in temperature range 950-1200℃ for the same deformation degree i.e. 50%. The influence of strain rate and temperature on the stress - strain curve and microstructure evolution was explored, and the thermal deformation constitutive equation of Si- Mn-Cr-B alloy steel was established on the basis of Arrhenius hyperbolic sine function. The results show that: the peak stress of the high temperature deformation of the Si-Mn-Cr-B alloy steel increases with the increase of strain rate and the decrease of deformation temperature, but high temperature deformation is controlled by thermal activation energy and its thermal activation energy is Q=372.6 kJ/mol; dynamic recrystallization occurs during deformation, and the average size of the dynamically recrystallized grains all shows a trend of increase with the increase of temperature and the decrease of strain rate.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《材料研究学报》
Abstract： The effect of V and Si on the microstructure and mechanical properties of medium-carbon pearlitic steels for wheel was studied by means of OM、SEM and TEM, as well as tensile and impact tests. The results showed that the austenite grain size, the pearlite colony size and interlamellar spacing were significantly refined by increasing V content, which also led to an increase in the volume fraction of proeutectoid ferrite of the steels. With the increasing of V content, the yield strength at room temperature and the impact toughness at - 20℃ were enhanced due to precipitation strengthening and grain refinement effects of VC. However, the tensile strength at room temperature was decreased due to the increasing of the soft phase, i.e., proeutectoid ferrite. The increase of Si content resulted in the great decrease of proeutectoid ferrite and the significant refinement of pearlite interlamellar spacing but the slight refine-ment of austenite grain size. Si addition also promoted the VC precipitation but had only a little influence. The yield- and tensile-strength were enhanced mainly by the effect of solid solution strengthening and the refinement of pearlite interlamellar spacing due to Si addition. The balance of strength and toughness in medium-carbon pearlite steels could be effectively optimized by microalloying with the combination of medium 0.07%-0.08%V(mass fraction) and relatively high 0.8%-0.9%Si (mass fraction).
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： With the development of Ti microalloying technology, the application and theory research of Ti in microalloyed steels are becoming more deeply and widely. However, the effect of tempering time on the microstructure and mechanical properties of high Ti microalloyed quenched martensitic steel has been rarely touched upon, meanwhile, it has long been inconclusive whether precipitated phases coarsening or the recovery and softening of martensitic matrix is the dominant role resulting in the decrease of hardness along with long time tempering of microalloyed steel. In this work, the effect of tempering time on the microstructure and mechanical properties of high Ti microalloyed quenched steel was systemactically investigated by TEM, XRD and Vickers-hardness test, and the interaction between precipitation hardening and microstructural softening of the high Ti microalloyed steel was also studied. The results indicate that the hardness increases for Ti microalloyed steel with tempering time 10~300 s, which is attributed to the fact that the precipitation hardening by nano-sized TiC particles is greater than the recovery and softening of matrix. With the tempering time from 300 s to 10 h, nano-sized TiC particles precipitate more and more and the mass fraction of TiC with the size less than 5 nm increases, owning to the precipitation hardening produced by tiny TiC which offsets the hardness decrease due to the gradual softening with recovery of matrix, and therefore, the hardness can keep a long platform; in addition, with the tempering time 10~20 h, the hardness decreases significantly and the deacreasing rate of hardening for steel with Ti microalloying is higher than that for steel without Ti microalloying. The average particle size of TiC increases from 2.76 nm at 10 h to 3.15 nm at 20 h. Calculation results show that the decrease of hardness caused by coarsening of TiC is 11.94 HV, while caused by recovery of matrix is 24.56 HV. It is shown that the recovery of matrix is the dominating factor for reduction in hardness, but coarsening of tiny TiC speeds the decrease of hardness and is also an important factor resulting in the decrease of hardness.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract： The semi-solid ZCuSn10 alloy billets were prepared with strain induced melt activated (SIMA) method involved with hot rolling and reheating process. The microstructure evolution process and spheroidizing mechanism of α(Cu) phase were studied by means of optical microscope, scanning electron microscope and image analysis software. The results show that when a hot rolled ZCuSn10 copper alloy billet with a deformation rate 16%was reheated at 930℃, of which the semi-solid primary phase spheroidized gradually with the increasing holding time; while the average grain size of the copper alloy decreases firstly with time from 68.24 μm for 8 min to 62.31 μm for 10 min and then increases to 71.09 μm for 25 min; the liquid fraction increases from 18.14% for 8 min to 25.32% for 25 min; the shape factor decreases firstly with time from 2.91 for 8 min to 1.67 for 15 min and then increases to 2.43 for 25 min. The alloy exhibits the best semi-solid microstructure for 15 min holding with an average grain size 65.64 μm, a liquid fraction 23.66% and a shape factor 1.67. The microstructure evolution mechanism involves with merge of grains and growth as well as atom diffusion leading to grain growth and spheroidization.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract： Anodic oxidation films of TiO2 were prepared on titanium alloys Ti-6Al-4V(TC4) in an electrolyte system of oxalate, silicate and phosphate hybrid by means of anodic oxidation with TC4 as anode and stainless steel as cathode. Then the crystallographic structure, three-dimensional topography, microstructure and bioactivity of the prepared TiO2 films were characterized by means of X-ray diffractometer, X-ray photoelectron spectroscopy, AFM and scanning electron microscope etc. The results show that the applied voltage has almost no effect on the crystal structure of TiO2 films which are amorphous. There exist certain amount of pores and convex particles with ca.1.3 μm in diameter on the surface of rough TiO2 film prepared by an applied voltage of 30 V. With the increasing applied voltage, the convex particles on TiO2 films are slowly dismissed due to the field assisted dissolution. There are many nanopores of ca. 240 nm in diameter on the films without convex particles when the applied voltage is 100 V. There are many hydroxyls and micro/nano structures on the surface of anodic oxidation films on TC4 titanium alloy, which is useful for the enhancement of bioactivities and bone growth characteristics of the formed TiO2 oxide films.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract： Effect of heat treatment processes on the microstructure and mechanical properties of a medium carbon low alloy steel was studied by means of color metallography, XRD and mechanical tests. The adopted heat treatment processes included air quenching and then austempering in salt bath, watercooling and then austempering in salt bath, as well as directly austempering in salt bath. The results show that after treatments according to the above three processes the steel may exhibited microstructure composed of different amount of bainite and martensite, and better mechanical properties in comparison with the cast ones, i.e. its impact toughness and hardness were increased by 92%-183% and 31%-55% respectively. For the case of air cooling and then austempering in salt bath, the amount of bainite decreased gradually with the increase of air cooling time while the amount of martensite progressively increased, correspondingly its hardness and impact toughness showed a tendency of increase and decrease respectively. The mechanical performance of the medium carbon low alloy steel is closely related to the ratio of bainite to martinsite in the microstructure. It is noted that the steel with a duplex microstructure of 50%-60% bainite and 30%-40% martensite exhibited an optimal comprehensive mechanical performance.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract： The volume fraction, morphology and size of reversed austenite in 5.5Ni steel tempered at different temperatures were characterized by X-ray diffraction, scanning electron microscope and transmission electron microscope, and the influence of tempering temperature on mechanical properties of 5.5Ni steel was investigated. The results show that there was no significant change in either the tensile strength or yield strength for the steel tempered in the range from 580℃ to 600℃. There was a slight increment in tensile strength but a great decrement in yield strength, besides, a maximum elongation was obtained for the steel tempered at 620℃. As the tempering temperature increased from 580℃ to 620℃, the volume fraction of reversed austenite in 5.5Ni steel increased gradually but impact energy decreased. Stable, homogeneous, dispersive and fine lamella-like reversed austenite is the main reason of the high impact energy of 148 J when the steel tempered at 580℃. Two types of reversed austenite including lamella ones and block ones were detected in this steel. The former had different length with a width of about 20 nm which could improve the low temperature toughness of the steel. The latter had a size of about 200 nm and tended to gathering together as clusters which were detrimental to the low temperature toughness of the steel.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract： Fe-C-Mo-M steels (where M is Nb, V or Ti, ~0.1%, and Mo ≤0.2% ) were produced by thermal mechanical control processing (TMCP), and then their performance was characterized in terms of failure temperature by means of constant load tensile test while heating from ambient temperature up to 800oC with a heating rate 28 oC/min. The boundary misorientation of the steels after TMCP was examined by electron back scattered diffraction (EBSD), and the precipitates of MC type carbides were characterized by transmission electron microscopy (TEM). The results show that the addition of 0.2% Mo in Fe-C-Nab/V steels increases the failure temperature of steels by 40℃. It is believed that the low-angle grain boundary provided the favorable nucleation site for MC type carbides, which in turn will accelerate the kinetics of precipitation process. The fine and dispersed precipitates of MC type carbides induce significant precipitation strengthening for the steels during the constant load tensile process, thus resulting in higher failure temperature. Among the tested steels, the failure temperature of Ti-Mo steel is the highest due to its highest low-angle grain boundary density which results in the fast precipitation of MC type carbides. The failure temperature of Nb-Mo steel comes the second and that of the V-Mo steels is the lowest because of its lowest low angle grain boundary density leading to the lowest density of precipitated MC type carbides.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract： The edgewise compressive property of sandwich panel of steel plates with isosceles-trapezoid honeycomb core of fiber cloth reinforced epoxy resin is measured by using a material testing machine, while a simulation mode is established to describe the edgewise compressive behavior. The edgewise compressive pressure may induce three types of damages of the sandwich panel, namely, the broken of plates, the buckling instability of the sandwich panel and the detachment of plates with the honeycomb core. Under an applied edgewise compressive pressure, the plates are the main load bearing component of the sandwich panel, while the honeycomb core acts only as a connector and supporter . The parameter related with the structure and the material of the plates has a great influence on the in-panel compressive strength and the bearing stress for the sandwich panel. In the contrast, parameter related with the structure and the material of the honeycomb core has a small influence on the compressive strength of the sandwich panel, but the height of honeycomb core has a great influence on the bearing stress of the sandwich panel.
Subjects: Materials Science >> Materials Science (General) submitted time 2017-03-31 Cooperative journals: 《材料研究学报》
Abstract：为了研究焊接工艺条件对焊缝金属组织性能的影响,采用不同热输入对1200 MPa级低合金高强钢进行熔化极气体保护焊,利用OM、SEM、TEM观察并分析不同焊接热输入对焊缝组织及力学性能的影响规律。结果显示,当热输入为16、20、25 kJ/cm时,焊缝组织主要以针状铁素体为主,并含有少量M-A组元以及粒状贝氏体。随焊接热输入增大,针状铁素体组织有所增多且板条宽度逐渐增大,而粒状贝氏体组织减少。焊缝内非金属夹杂物类型多为促进针状铁素体形核的Ti-Mn-Al-O-S系复合氧化物夹杂。焊缝金属硬度、冲击韧性及焊接接头强度随热输入增大基本呈下降趋势,并且各焊接热输入条件下焊缝金属具有良好的强韧性匹配。随热输入增大,焊缝金属断裂特征由韧性、脆性混合型断裂向脆性断裂转变。热输入为20 kJ/cm时,焊接接头综合性能最佳。
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-15 Cooperative journals: 《金属学报》
Abstract：利用OM, EBSD, XRD及物理化学相分析法，对不同卷取温度下Ti-V-Mo复合微合金化热轧高强钢的强化增量进行了估算和分析，分别讨论了卷取温度对屈服强度和MC相粒子对均匀塑性的影响规律。结果表明，在600 ℃卷取时，实验钢具有最佳的综合力学性能：抗拉强度UTS为1134 MPa，屈服强度YS为1080 MPa, 延伸率A为13.2％, 均匀延伸率Au为6.8％，其析出强化增量σp高达444～480 MPa左右，主要是由质量分数高达72.6 wt％的10 nm以下的(Ti, V, Mo)C粒子提供的。析出强化和细晶强化是实验钢主要的强化方式，σp的改变是导致实验钢不同卷取温度下YS变化的主要因素。随着卷取温度由500 ℃升高至600 ℃，实验钢的UTS和YS不断增加，Au不但没有降低，反而呈线性缓慢增加。其主要原因是σp对屈服强度的贡献量不断提高，在提高强度的同时改善了均匀塑性。
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