Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract: The microstructure of Mg-10Gd-2.5Nd-0.5Zr (mass fraction, %) alloy after solid solution and aging treatment were characterized by means of OM, XRD, TEM and SEM. The average corrosion rate in 3.5% (mass fraction) NaCl solution was measured for 0~96 h. The results show that the microstructure of the as-cast alloy is composed of α-Mg matrix and coarse dentritic crystal β phase. After heat treatment, the β phase has experienced a course of dissolution and then precipitation, while the discontinued net-like β-phase transformed into cuboid-shaped particles due to the solution and aging treatment. The heat treatments are beneficial to the corrosion resistant of the alloy in 3.5% NaCl solution, while its corrosion rate was 0.74 mg·cm-2·d-1 for the as-cast, 0.41 mg·cm-2·d-1 for the solid solution treated and 0.35 mg·cm-2·d-1 for the aging treated ones respectively. The corrosion products of the alloy is mainly composed of Mg(OH)2.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: To improve the over sedimentation of fillers, the poor adhesive strength and wear resistance of ceramic/epoxy (EP) composite coating, SiO2 powder with particle size of 5~50 μm was sprayed on the surface of liquid epoxy coating to let the particles settling naturally in the coating. The graded SiO2/EP composite coating was prepared by controlling the curing temperature and time and thereby the sedimentation depth of the SiO2 particles of different sizes. It follows that the adhesive strength and wear resistance of the SiO2/EP composite coating prepared by the new process is higher than that prepared by the traditional blending method.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《材料研究学报》
Abstract: Nd2Fe14B/α-Fe composite magnets were fabricated by mechanically ball milling. The influence of Dy2O3 doping on the coercivity of the nanocomposite magnets was studied in detail. It was found that the coercivity of the composite magnets can be significantly improved by Dy2O3 doping, and the annealing temperature corresponding to the maximum coercivity decreases with the increase of Dy2O3 content. X-ray diffraction analysis shows that the lattice parameters of Nd2Fe14B decreased due to Dy2O3 doping, indicating that (Nd, Dy)2Fe14B hard magnetic phase formed after Dy partial replacement for Nd. Therefore, the enhancement of coercivity of the magnets can be mainly attributed to the increase of the magnetic crystalline anisotropy of the hard magnetic phase. However, with the increase of the magnetic crystalline anisotropy, the effective exchange coupling length was shortened, thereby, the coercivity dropped due to over doping of Dy2O3.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《材料研究学报》
Abstract: Fusion weld of TA1/X80 composite plate was carried out by taking foils of TiNi, and NiCrMo as the double transition layer weld material. Then the microstructure, morphology, chemical and phase composition and mechanical properties of the weld metal were characterized by means of metallography, SEM, EDS, XRD. Results revealed that the weld seam with TA1/TiNi weld metal exhibited a microstructure with equiaxed grains, and the Ti content drastically descended along a line from TA1 side to TiNi side while Ni content gradual increases. The weld seam with TiNi/NiCrMo exhibited a dendritic microstructure and there existed a 40 μm wide transitional zone, and the Ti content rapidly reduced along a line from TiNi side to NiCrMo side, while Ni content decreased first and then restored, but Cr and Mo increased gradually. The weld seam of NiCrMo/X80 showed a mixed grain- and acicular- like microstructure, and the Fe content increased sharply at the interface. while the Ni content and Cr content reduced dramatically along a line from the NiCrMo side to the X80 side. The strength and toughness of welded joint are lower than that of the base metal area due to that there existed a certain number of brittle phases in the weld seams with TiNi and NiCrMo.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract: Magnetron sputtering ion plating (MAIP) is limited by the low density and low ionization of target atoms, which results in that the films deposited by MAIP have poor compactness, low adhesion and the quick decreasing in thickness along the target-to-substrate distance, so this disadvantages of the film quality and property can not satisfy the harsh need of modern society. Based on the physical gas discharging plasma theory, the gas discharge could be introduced into the glow-arc discharge section between the glow discharge and the arc discharge by increasing the target current density. By means of the collision kinetic energy of Ar+ and the Joule heating effect of electrons, the electrons and atoms could be spontaneously induced to emit by overcoming the surface work function. Thus the deposited particles with a high density, a high energy and a high ionization can be obtained. Two groups of the Ti films were deposited in glow discharge and glow- arc discharge sections respectively. The film thickness at different target- to- substrate distances was measured by the CLSM. The microstructure of films was characterized by XRD, SEM, AFM and TEM. The adhesion between the film and substrate was determined by the microscratch tester. The results showed that the Ti film deposited in the glow-arc section of gas discharge had nanocrystal size, dense structure, uniform thickness, high deposition rate and excellent adhesion.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract: Composites 45 steel/T2 copper and 304 Stainless steel/T2 copper were prepared by hightemperature vacuum casting. The interface bonding strength, microstructure, microhardness and composition change of the phase boundary zone of the composites were investigated by SEM observation, EDS analysis, XRD and mechanical property test. The results show that interdiffusion occurred of alloy elements Fe, Cr and Cu of the two substrates resulting in formation of phases such as a new iron carbon compounds (CFe15.1) and solid solution Cu0.81 Ni0.19, and Cr- Ni- Fe- C, there existed a dentate interdiffusion layer of about 60 to 70 microns without obvious intermetallics in the transition zone and its microhardness is about 183 and 119HV for 45-T2 and 304-T2 respectively; tensile/shear strength of the composite are 278/263MPa and 217/201 MPa respectively for 45/T2 and 304/T2; break occurs in the copper side with typical ductile fracture characteristics. Cu element plays an important role in improvement of the stability and strength of the substrates 304 stainless steel and 45steel.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract: Luminescent phosphors GdVO4: Eu3 + was prepared in solutions with different pH values by hydrothermal synthesis route using Gd2O3, NH4VO3 and Eu2O3 as precursors, and cetyl trimethyl ammonium bromide (CTAB) as surfactant. The synthesized products were characterized in terms of morphology, structure and luminescent performance by means of XRD, SEM, TEM, and PL. The results show that in an acid solution with pH=1, the size of synthesized GdVO4: Eu3 + crystal grains is of micron scale; in a solution with pH=4 , their size shrinks to nano-scale; it turned out well-dispersed nano-flakes of about 50 nm in solution with pH=7; besides, in solution with pH=10, a certain amount of impurity Gd(OH)3 was detected by XRD for the synthesized GdVO4: Eu3+ crystal grains. On the other hand, the surfactant affected obviously the final morphology of the synthesized GdVO4: Eu3 + crystal grains in terms of changes in the crystal growth direction and the aggregation shape, correspondingly, the luminescent properties were affected by grain size and crystallinity. It turned out that square GdVO4: Eu3+ nano-crystals with well crystallinity represented the optimal emission performance. But it is noted that the aggregation effect may weaken the luminescent property of the products.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract: The influence of addition of alloying elements of medium carbon Fe-Mn and Ni in the welding flux on the microstructure and toughness of the weld seam of FV520(B) steel was investigated by means of impact test, metallographic microscope, SEM and X-ray diffractometer. The results show that the microstructure of the weld seam of FV520(B) steel mainly composed of tempered sorbite and lath martensite with some residual austenite and secondary phases. With the increasing amount of alloying elements Mn and Ni, the microstructure of weld seam became finer, and the lamellae of martensite became thinner and distributed more uniformly. The addition of allying elements into a basic flux rather than an acidic ones showed much higher effectiveness in improvement of the toughness of the weld seam. The induced Mn and Ni can enhance the austenitic amount in the weld seam, which in turn plays an important role in enhancing its toughness. Moreover, the induced Ni rather than Mn was more effective in enhancing the toughness of the weld seam.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract: The low carbon bainite steel was welded by double-sided submerged arc welding and the microstructure and low temperature toughness of the joints was studied by optical microscope and PSW750 instrumented impact testing machine. The results show that the microstructure of the weld seam consisted of acicular ferrite and granular bainite, however the HAZ shows a microstructure consisted of bainite ferrite and granular bainite. The hardness at HAZ near the weld bond is the highest and then decreases gradually approaching to the hardness of base metal. In comparison to the matrix the weld seam and HAZ show a lower toughness with a ductile brittle transition temperature at -20℃and -60℃ respectively, which may be ascribed to the occurrence of solidification segregation, highly concentrated dislocations and formation of carbon nitrides of alloying elements such as Ti and Mo at grain boundaries etc.in the weld joints during rapid cooling after welding.
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-15 Cooperative journals: 《金属学报》
Abstract:采用超音速微粒轰击(SFPB)和表面机械滚压处理(SMRT)相结合的混合表面纳米化方法,在2A14铝合金上制备出梯度纳米结构(GNs)表层,对比研究了原始样品和常温空气和低温液氮环境下混合表面纳米化样品在3.5%NaCl水溶液中的电化学腐蚀行为。结果表明:经混合表面纳米化处理后,2A14铝合金晶粒尺寸由最表层约30nm逐渐增大到基体的原始尺寸,塑性变形层厚度约130 ,表面粗糙度Ra约为0.6 ,表面微小裂纹消失。与原始样品相比,经过SFPB处理的样品耐点蚀能力没有得到提高,混合表面纳米化样品的耐点蚀能力得到提高,其中常温空气环境下样品的自腐蚀电位和点蚀击破电位分别由-1.01228和-0.29666V升高到-0.67445和0.026760V,耐点蚀能力最强。分析表明,表层晶粒尺寸纳米化、纳米晶界显著增多、残余压应力以及表面粗糙度的改善有利于提高样品的耐点蚀性能。