ZL104铝合金连杆半固态挤压铸造工艺实验研究

研究了传统液态挤压铸造与半固态挤压铸造成形ZL104铝合金连杆的充填状态、微观组织及力学性能。结果表明:传统液态挤压铸造成形连杆充填饱满,但其抗拉强度及伸长率低于半固态挤压铸造成形连杆。对于半固态挤压铸造成形,浇注温度高于565℃时,铸件充填性能良好;平均晶粒尺寸及形状因子随浇注温度的升高而逐渐增大;连杆抗拉强度及伸长率先增加后减小。挤压压力高于25MPa时,铸件均充填饱满;挤压压力升高,平均晶粒尺寸不断减小且形状因子不断增大,连杆机械性能不断提高。模具预热温度升高,平均晶粒尺寸和形状因子不断增大,连杆机械性能逐渐提高。但当模具预热温度超过300℃时,平均晶粒尺寸进一步增大而其形状因子减小,导致连杆的机械性能下降。     

Experimental and numerical assessment of energy absorption capacity of thin-walled Al 5083 tube produced by PTCAP process

The energy absorption capacity of the Al5083 thin-walled tube produced by parallel tubular angular pressing (PTCAP) process was evaluated. Also, microstructure, mechanical properties, and anisotropy coefficients were studied in the peripheral and axial directions. Results showed that values of energy absorption decreased with processing pass increasing and the values for the unprocessed, first and second passes were obtained to be 167, 161.4 and 160.7 J, respectively. The differences between the simulation results for the energy absorption values and their experimental values for the unprocessed, the first and the second PTCAP passes samples are about 5%, 10%, and 13%, respectively. The energy absorption capacity was related to the anisotropy coefficient and microstructure. The results demonstrated that grain refinement occurred and ultimate tensile strength (UTS) and microhardness after the first and second PTCAP passes were enhanced, while the increase rate in the first pass was much severer. Also, by applying PTCAP, the deformation modes were altered, such that the deformation mode of the annealed tube was quite symmetrical and circular while for the first and second passes there have been triple and double lobes diamond. The results of the numerical simulation for the deformation mode of the annealed and PTCAPed tubes were consistent with the experimental results. The deformation mode of tubes is dependent on their mechanical properties and variation of the mechanical properties during PTCAP process.     

A review of particulate-reinforced aluminum matrix composites fabricated by selective laser melting

Selective laser melting (SLM) is an emerging layer-wise additive manufacturing technique that can generate complex components with high performance. Particulate-reinforced aluminum matrix composites (PAMCs) are important materials for various applications due to the combined properties of Al matrix and reinforcements. Considering the advantages of SLM technology and PAMCs, the novel SLM PAMCs have been developed and researched in recent years. Therefore, the current research progress about the SLM PAMCs is reviewed. Firstly, special attention is paid to the solidification behavior of SLM PAMCs. Secondly, the important issues about the design and fabrication of high-performance SLM PAMCs, including the selection of reinforcement, the influence of parameters on the processing and microstructure, the defect evolution and phase control, are highlighted and discussed comprehensively. Thirdly, the performance and strengthening mechanism of SLM PAMCs are systematically figured out. Finally, future directions are pointed out on the advancement of high-performance SLM PAMCs.     

Synthesis of blue-emitting AlN:Eu2+ spherical phosphors by carbothermal reduction nitridation method

In this study, blue-emitting AlN:Eu²⁺ spherical phosphors were successfully synthesized for the first time by the carbothermal reduction nitridation (CRN) method, assisted with high nitrogen pressure, appropriate synthesis temperature, and the addition of CaF₂. The influence of typical experimental parameters, such as N₂ pressure, heating temperature, CaF₂ content and Eu²⁺ concentration on the morphologies and luminescence properties of AlN phosphors were comprehensively investigated. The formation mechanism of spherical morphology were significantly proffered, indicating that sufficient liquid Ca-aluminates during the AlN growth stage were essential for the spheroidization process under the action of surface tension. The synthesized AlN:Eu²⁺ spherical phosphors presented an intense blue emission band centered in the range of 427- 476 nm relative to the reaction temperature. The lifetime of AlN:Eu²⁺ phosphor was calculated to be around 1.89 μs. The temperature-dependent PL spectra suggested that the emission band did not shift until 225°C. In addition, the spectral analysis strongly suggested that the luminescence property of AlN:Eu²⁺ phosphors was significantly enhanced by the large particle size, spherical morphology, reduced impurity content, and appropriate Eu²⁺ concentration.     

Purified high‐sulfur coal as a fuel for direct carbon solid oxide fuel cells

The use of low‐rank coal in a clean and efficient manner is a major challenge facing the current coal technology. A high‐sulfur coal with 4.5 wt% sulfur is chosen to examine the compatibility of the pristine coal and the purified contrast with a solid oxide fuel cell (SOFC) with nickel cermet anodes. Desulfurization of the pristine coal is performed by molten caustic leaching method with a removal ratio of 80%. Analyses of the physicochemical properties of coal samples indicate that the purified coal has a more favorable structure and higher Boudouard reactivity, which is suitable as a fuel for fuel cells. The assessment of electrochemical performance reveals that the purification treatment not only makes the peak power density of SOFCs improve from 115 to 221 mW cm^?2 at 900°C but also extends their durability from 1.7 to 11.2 hours under a current density of 50 mA cm^?2 at 850°C with a fuel availability increasing from 6.25% to 40%. The postmortem analyses show that far less deposited carbon and nickel sulfide are observed on the anode surface. The fuel‐based investigation reveals that the purified coal is a promising fuel for direct carbon fuel cells.     

Experimental research on temperature rise and electric characteristics of aluminum air battery under open‐circuit condition for new energy vehicle

Due to lack of systematic research on open‐circuit voltage (OCV) and electrolyte temperature rise characteristics of aluminum air battery, in order to explore the influential factors on the OCV and electrolyte temperature rise of aluminum air battery, in this paper, for the first time, we studied the effects of different ambient temperature conditions, different concentrations of NaOH and KOH electrolyte, and pure aluminum and aluminum alloy on the OCV and electrolyte temperature rise of aluminum air battery. Results show that the OCV of aluminum air battery is obviously affected by ambient temperature conditions, electrolyte concentration, and different anode materials. The OCV range is 1.5 to 1.8 V at 0°C under different KOH‐electrolyte concentrations when aluminum alloy is used as anode material; with the increase of ambient temperature, the OCV will rise, and the range is 1.8 to 1.95 V. The working process of aluminum air battery is accompanied by the phenomenon of heat release, and the temperature rise range of electrolyte will not exceed 7°C when aluminum alloy is used as the anode material; however, the highest temperature of the electrolyte can reach 100°C when pure aluminum is used as the negative electrode material. The results of this study will provide theoretical guidance for designing aluminum air batteries and identifying their optimal operating conditions.     

Acidification of the electrolyte during the galvanic corrosion of AA7075: A numerical and experimental study

The electrochemical interactions between aluminum alloy 7075 and low-carbon steels under gelled electrolytes were studied. Such electrolytes provided the opportunity to investigate both thick and thin electrolyte systems. The electrolyte was chemically modified to visually track the acidic fronts during the anodic reaction and the subsequent hydrolysis process. Two mathematical models were validated for both thick and ultrathin electrolytes. The acidification of thick electrolytes was extended some millimeters beyond the aluminum alloy surface, whereas the acidic front was localized next to the metallic joint using ultrathin electrolytes. The combination of both numerical and experimental results allows proving (and explaining why) that the acidification process is more aggressive under dilute than under concentrated electrolytes.     

7050铝合金表面喷丸强化层内纳米结构微观组织结构分析

利用喷丸技术在7050铝合金表面制备了纳米结构表面层。采用EBSD、TEM和XRD等方法分析了表面纳米结构层的组织结构。试验结果表明，采用喷丸技术可以在7050铝合金表面制备出纳米结构表面层，表面层是由原始晶粒细化成由表及里梯度分布的不同取向纳米级结构构成，深度～150μm。7050铝合金表面纳米化使材料的表层残余应力变成拉应力，硬度明显降低，与基体相比，表层的硬度降低了～70％。