To investigate the effect of dual-phase content on the corrosion resistance of aluminum matrix composites, the 1 wt%, 3 wt% and 5 wt% (TiC+Al3Ti)/6061 composites were prepared by in-situ reaction of Al-K2TiF6-C system. The accelerated corrosion, electrochemical corrosion and immersion corrosion were tested. The experiments demonstrate a progressive improvement in the corrosion resistance of the composites as the (TiC+Al3Ti) content increased. As the reinforcement content reached 5 wt%, the composites exhibited 93% reduction in average corrosion depth, 98.6% reduction in corrosion current density, and 98.5% decrease in corrosion rate compared to the 6061Al matrix. The improvement of corrosion resistance is primarily attributed to the grain refinement effect of (TiC+Al3Ti) and the inhibitory effect of TiC at grain boundaries against intergranular corrosion.

This study presents the differences in microstructure and corrosion behavior among AlCrFeCoNi (high-entropy alloy), CrFeCoNi (medium-entropy alloy), and CrCoNi (medium-entropy alloy). CrFeCoNi and CrCoNi exhibit a single-phase face-centered cubic (FCC) structure, whereas AlCrFeCoNi consists of an island-like FCC structure and a dendritic structure. The latter comprises radiating dendritic body-centered cubic (BCC) phases and interdendritic FCC phases. In AlCrFeCoNi, the (111) crystallographic orientation displays the highest texture intensity at 19.5 %. In 3.5 wt% NaCl solution, CrCoNi shows a lower corrosion current density Icorr of 0.056 mu A & sdot;cm- 2 and a higher polarization resistance Rp of 146.1 Omega & sdot;cm2. Additionally, its film resistance Rf reaches the highest value of 1.246 x 106 Omega & sdot;cm2, indicating that CrCoNi possesses the strongest corrosion resistance and the best passivation behavior. In U-bending immersion corrosion tests at various temperatures, AlCrFeCoNi exhibits a lower mixing enthalpy Delta Hmix of -12.32 kJ/mol and a valence electron concentration VEC of 7.2, which together contribute to a gradual reduction in corrosion rate during thermal exposure. Additionally, its dual-phase microstructure leads to galvanic corrosion, resulting in progressive pitting. CrCoNi maintains the highest apparent activation energy across the temperature range, confirming its superior corrosion resistance.

In-situ synthesized 1 wt.%, 3 wt.% and 5 wt.%TiC/6061 nanocomposites were prepared by the reaction using Al-K2TiF6-C as starting materials. Microstructure, mechanical properties and strengthening mechanism of the nanocomposites were investigated. SEM observation illustrates the in-situ synthesized ceramic TiC particles show shape of a polygon and its average size is 60 nm. TEM results show that the interface between the Al matrix and TiC reinforcement is clear and no reaction products can be found. Grain refining can be observed in the composites, as the TiC content increased from 0 wt.% to 3 wt.%. However, grain coarsening appears in the 5 wt.%TiC/6061 composites. As increasing the TiC content from 0 wt.% to 5 wt.%, the mechanical properties of the composites increase firstly and then decreases. The Vickers hardness, yield strength, tensile strength and elongation of the as-cast 3 wt.%TiC/6061 composites achieve the maximum value of 80.7 HV, 135 MPa, 202 MPa and 15.3%, respectively. Strengthening mechanisms of the TiC/6061 nanocomposites is the micromechanical strengthening mechanisms. As the TiC content increasing, CTE strengthening plays an important role.

In situ synthesized 3 wt.%TiB2/6061 composites with different La contents were fabricated by an Al-K2TiF6-KBF4 system at 850 °C with ball milling and stirring casting. The effects of La content (0 wt.%, 0.1 wt.%, 0.3 wt.%, 0.5 wt.%) on the microstructures and mechanical properties of the composites at room temperature were investigated. The results showed that the addition of La could refine α-Al grains and modify the morphology of TiB2 particles significantly. In 0.3 wt.%La-3 wt.%TiB2/6061 composites, there are chamfering planes on the surface of TiB2 particles, which are caused by the adsorption of La on the {112¯0}, {12¯12} and {101¯1} crystal planes. The values of YS, UTS and EL of the composites with 0.3 wt.% La were 216.8 MPa, 273.0 MPa and 11.2%, which were 69.2%, 34.8% and 5.7% higher than those of the 3 wt.%TiB2/6061 composites. The improvement of mechanical properties was mainly attributed to the grain refinement, distributed particles and transformation of particle morphology. In friction behavior, 0.3 wt.%La-3 wt.%TiB2/6061 composites have the best wear resistance properties with the smallest and shallowest grooves on the surface after wearing. The main mechanisms of the composites are adhesive wear and abrasive wear. In summary, the best content of La addition in 3 wt.%TiB2/6061 composites is 0.3 wt.%.

In order to explore the influence of reinforcement distribution on microstructure and mechanical properties of the in-situ TiC/Al composites, the network/point cluster structured TiC/6061 aluminum composites were prepared. The network TiC/6061 composites can be prepared by in-situ reaction of K2TiF6-C, tensile strength and maximum compress load of the composites get the peak value of 273.13 MPa and 457.13 MPa for 5 wt% nominal TiC content. The point cluster TiC/6061 can be prepared by in-situ reaction of Al-K2TiF6-C, tensile strength and maximum compress load of the composites achieve the highest value of 246.92 MPa and 407.57 MPa, as the TiC nominal content is 3 wt%. The network TiC/6061 composites can obtain better mechanical properties than the point cluster TiC/6061 composites.

The microstructure and corrosion behaviors of the in-situ synthesized nano TiB2/6061 composites with La doping were investigated by scanning electron microscope, potentiodynamic polarization and electrochemical impedance spectroscopy in 3.5 wt% NaCl solution. The results indicated that La can make a significant improvement of corrosion resistance for TiB2/6061 composites. The corrosion potential of La-TiB2/6061 composites has increased by 11.31% compared with the composites without La. With La doping, the dispersive distribution of TiB2 particles suppressed the extending of corroded pits, the refined grains promoted the formation of oxide film in passive environment.

The corrosion interface characteristics and corrosion behavior of Cu-C alloys in liquid Ga at 100-180 degrees C were studied in this paper. The corrosion mechanism of Cu-C alloys was microscopically studied via the first-principles calculation based on the density functional theory (DFT). The results, the diffusion of Ga atoms leads to the phase transition of Cu in the Cu-C alloy and the generation of the corrosion product CuGa2. The corrosion rate of the Cu-C alloy is related to the dissolution rate, and growth rate and exfoliation rate of corrosion product layer. C led to much better corrosion resistance of Cu-C alloys.

The interface characteristics and corrosion behavior of Cu/C composites subjected to static corrosion in liquid gallium (Ga) were investigated. The results revealed that the wettability of Cu/C composites and liquid Ga was weakened by C phase, and the progress of corrosion was effectively hindered by C phase. At 720 h following corrosion, the corrosion thickness loss of Cu/C composites was only 33.37% of that of Cu. The corrosion products of Cu/C composites and Cu in liquid Ga were CuGa2. The CuGa2 and the residual C phase generated by the corroded Cu/C composites formed a mixed corrosion product layer, effectively preventing the composites from being corroded by liquid Ga. The diffusion of atoms can be blocked by C phase during the corrosion process, and thus the corrosion of the Cu/C composites and the growth of CuGa2 are inhibited.

文章以连接成形及增材制造设备及工艺课程为例,探索工科专业课程思政的教学目标、思政元素引入形式、情境设计和实施方式等,挖掘其蕴含思政元素的资源以及探索其与受教育者相契合的教育教学模式.经实施发现,开展"工程应用—实际问题—解决问题的人—职业素养的培养—价值观的树立"五步递进的项目引导式课程思政,能够使学生有效融入教学情境,学生的思想品质和专业素养也得到了明显提高.

In-situ 3 wt.%TiB2/6061 composites were fabricated by the reaction of Al-K2TiF6-KBF4. The effects of 0.3 wt.% Mn addition on the microstructure evolution and properties improvement of the composites were investigated. The in-situ synthesized TiB2 particles were distributed more evenly in the composites and the grains of the composites were refined obviously by trace Mn addition. Compared with the composites without Mn in as cast and T6 state, the UTS and YS of the composites with 0.3 wt.% Mn were increased by 10.6%, 13.6% and 26.7%, 23.4%, respectively, which due to the distribution improvement, size decrease and morphology changing of TiB2 particles. The T6 state in-situ 0.3 wt.%Mn-3 wt.%TiB2/6061 presents excellent corrosion resistance properties.

以真空熔炼制备的Al-7.02Zn-2.6Mg-0.35Mn合金为研究对象,进行均匀化、固溶处理和双级时效处理.测试合金硬度,观察合金组织,研究合金腐蚀性能.结果表明,在终时效160℃×8 h下,Al-7.02Zn-2.6Mg-0.35Mn合金时效硬化曲线呈现出两个硬度峰值,在预时效4 h观察到第一个硬度峰值(峰值Ⅰ)为176.80 HB,而在8 h出现第二个硬度峰值(峰值Ⅱ)为173.90 HB.Al-7.02Zn-2.6Mg-0.35Mn合金组织为α(Al)相和MgZn2相.在双级时效为105℃×8 h+160℃×8 h时,基体上分布着均匀且细小的过渡相(MgZn2')以及晶界处粗大不连续的MgZn2相.随着预时效时间从4 h变为8 h,极化曲线向左大幅度移动.自腐蚀电位从-872.81 V下降到-865.43 V,腐蚀电流密度从50.12μA/cm2下降到39.35μA/cm2,峰值Ⅱ合金容抗弧比峰值Ⅰ合金大一倍.峰值Ⅱ合金比峰值Ⅰ的耐腐蚀性更高.从电化学阻抗和腐蚀形貌分析可以得出,Al-7.02Zn-2.6Mg-0.35Mn合金在3.5％NaCl溶液中发生的电化学腐蚀是合金的点蚀诱导期.

The effect of Si on the corrosion of an Fe-B-Si alloy in liquid zinc was investigated. Corrosion tests of Fe-B-Si were conducted in a pure zinc bath (99.99 wt pct Zn). The results indicated that Si in α-Fe phase had a significant effect on the structure and evolution of corrosion interfaces in a directional Fe-B-Si alloy immersed in liquid zinc. Moreover, Si enrichment of the corroded interface induced changes in the mode of element diffusion, thereby affecting the Fe-Zn reaction and the quantity and volume of Fe-Zn compound. The Fe-Zn compound was occluded with the residual Fe2B closest to the corrosion interface, this structure could prevent direct contact between the liquid zinc and the alloy, and firm rooting of the compound at the interface. Therefore, Si in α-Fe phase had a significant effect on the corrosion resistance of Fe-B-Si alloy in liquid zinc. At a Si content of 0.318 wt pct, the densest composite corrosion product layer and highest corrosion resistance were obtained.

采用真空辅助搅拌铸造法制备了TiCp/7075复合材料,利用XRD和SEM对复合材料进行物相分析和微观组织观察,研究了复合材料的力学性能和耐磨性能.结果表明,TiC增强体颗粒均匀分布在7075铝合金基体中,并且显著细化了基体合金的晶粒尺寸.TiC颗粒使基体合金的晶粒由200μm的树枝晶转变为约100μm的等轴晶.TiCp/7075复合材料的布氏硬度和抗拉强度分别为163HBW和362 MPa,较基体合金分别提高了20.7％和20.3％,这是细晶强化和颗粒承载机制共同作用的结果.TiC颗粒的加入有效改善了7075基体的耐磨性,在10 N载荷下,复合材料的磨损量为2.9 mg,较基体减少54.7％.复合材料在磨损过程中裸露的TiC硬质颗粒优先与对磨材料接触,减小了复合材料与对磨材料的有效接触面积,提高了复合材料的耐磨性.

In-situ synthesized TiB 2 /6061 composites were prepared from Al-K 2 TiF 6 -KBF 4 by high energy ball milling and stir casting. Phase analysis and microstructure observation of the samples were characterized by XRD, SEM and EDS, respectively. The effect of TiB 2 particle content on the microstructure, tensile properties and wear resistance of the composites was studied. The results show that the average size of TiB 2 particles is 1 μm, which is polygonal shape. The average grain size of the composites can be refined significantly as the TiB 2 particle mass content increased from 1 to 3%; however, the grain coarsening occurs in the 5 wt.% TiB 2 /6061composites. The 3 wt.% TiB 2 /6061 composites have best tensile strength, yield strength and Young’s modulus among the composites in ranges of the TiB 2 mass fraction from 1 to 5%. Strengthening mechanisms of the TiB 2 /6061 composites were fine grain strengthening, Orwan strengthening and CTE strengthening, in which the CTE strengthening plays an important role as increasing the TiB 2 content. The pin-on-disk wear test results indicated that the average friction coefficient and wear rate of the TiB 2 /6061 composites increased firstly and then decreased with increasing the TiB 2 content from 1 to 5 wt.%. The wear mechanism of the TiB 2 /6061 composites was discussed.

以Al-KBF4为反应体系,采用熔盐反应法制备了原位自生3％AlB2/6061复合材料(质量分数),对比6061基体材料,研究了AlB2颗粒对复合材料组织、 硬度和耐磨性能的影响.结果表明,在6061基体材料中原位自生了六边形AlB2颗粒,颗粒尺寸为0.5～2.0μm.经T6热处理后,3％AlB2/6061复合材料的硬度为HB 119.1,较6061基体提高了26.57％.复合材料比磨损率为1.83×10-8 kg·N-1·m-1,较6061基体下降了17.94％.AlB2颗粒与基体材料之间的润湿性好,界面结合强度高,且其本身硬度高,在磨损时能够起到承载作用,有效地减少了复合材料与对磨材料间的接触面积,提高了复合材料的耐磨性.复合材料的磨损机制主要为磨粒磨损和粘着磨损,其平均摩擦系数为0.235,相较于6061基体材料降低了17.54％.

The influence of the Si content and corrosion temperature on the formation of the compact multiphase corrosionproduct layer when Fe-B-Si alloys were corroded in liquid zinc, was studied. Si was enriched at the corrosion interface and dissolved in the corrosion product layer, thus, affecting the diffusion of Zn and Fe. The multiphase corrosion product layer composed of Fe-Zn compounds with residual Fe2B at the corrosion interface was formed. The Fe-Zn compounds are tightly occluded among the residual Fe2B phase, which can inhibit diffusion. The Fe-Zn compounds tend to dissolve at high temperatures. However, because the complete residual Fe2B skeleton structure was retained and a small number of compounds remained among the residual Fe2B skeletons, the inhibition of the multiphase corrosion product layer did not cease. When the Si content was 0.318 wt%, the corrosion product layer was the densest, and when the Si content was 0.196 wt%, the corrosion product layer had the weakest diffusion-inhibition effect.

真空熔炼制备Zn-5.5Mg-0.4Ba和Zn-5.5Mg-0.4Ba-0.7Gd的锌合金.观察合金显微组织,测试耐磨性,研究其在SBF模拟体液中的腐蚀性能.结果发现,稀土Gd能显著细化Zn-5.5Mg-0.4Ba合金的微观组织.在2和4 N载荷下,Zn-5.5Mg-0.4Ba-0.7Gd合金磨损率分别为1.716及2.071 g/cm2,比Zn-5.5Mg-0.4Ba合金分别降低了16.8％和14.6％.Zn-5.5Mg-0.4Ba-0.7Gd合金在37℃模拟体液浸泡的腐蚀产物为磷酸钙、磷酸锌、磷酸盐、CaP,有良好的生物活性.Zn-5.5Mg-0.4Ba-0.7Gd比Zn-5.5Mg-0.4Ba合金的腐蚀电位正,腐蚀速率降低51.7％.Zn-5.5Mg-0.4Ba-0.7Gd合金的容抗弧比未加Gd的大200％,添加0.7％Gd由于晶粒细化作用及Zn(OH)2的生成促进表面腐蚀膜的生成,对基体形成有效的保护,使合金腐蚀速率降低.

用金相显微镜、XRD、扫描电镜以及电化学工作站,研究不同时效时间对ZA35-1.35Si-0.3Zr合金组织和电化学性能的影响.结果 表明:固溶时效处理可以有效减小ZA35-1.35Si-0.3Zr合金晶粒尺寸,提高其电化学性能;时效时间为6h时,合金晶粒尺寸最小,第二相数量明显增多且颗粒细小、分布均匀;在6h时效时间下合金的电化学性能最好,腐蚀电流密度比铸态ZA35-1.35Si-0.3Zr合金降低71.9％;时效处理ZA35-1.35Si-0.3Zr合金在质量分数为3.5％的NaCl溶液中电化学性能增强的主要原因是合金的容抗弧变大,极化电阻增加,腐蚀速率降低.

以Al-Al2O3-B2O3为反应体系,采用接触反应法制备了原位自生Al18B4O33w/6061复合材料,利用XRD和SEM对复合材料分别进行物相分析及微观形貌观察,对比6061基体材料,研究了Al18B4O33晶须对复合材料硬度和耐磨性能的影响.结果 表明,采用接触反应法,利用Al-Al2O3-B2O3反应体系可直接在6061基体材料中原位自生针状Al18B4O33晶须,Al18B4O33晶须直径为0.1～2 μm,晶须伴生于Mg元素.经T6热处理后,Al18B4O33w/6061复合材料的硬度为HB 132.7,较6061基体提高了27.4％,硬度的提高机制为位错强化和细晶强化.Al18B4O33w/6061复合材料的比磨损率和平均摩擦系数分别为1.96×10-8 kg/(N·m)和0.221,较6061基体下降了12.11％和22.46％.采用原位自生工艺制备的Al18B4O33w/6061复合材料,晶须与基体材料之间的润湿性和界面结合强度良好,且晶须本身强度高,在磨损时能够起到支撑作用,减小了基体的应变和磨损,有效地提高了复合材料的耐磨性.

Al-Zn-Mg合金的应力腐蚀断裂成为其进一步应用的瓶颈问题.对近年来国内外Al-Zn-Mg合金应力腐蚀断裂的研究进展进行了概括,阐述了主要合金元素和微量元素对合金应力腐蚀断裂的影响,重点分析了高温预析出处理、单级时效、双级时效、三级时效等热处理对析出相和合金应力腐蚀敏感性的作用规律.针对Al-Zn-Mg合金应力腐蚀断裂研究目前存在的问题,提出了未来的研究方向.