钛合金激光清洗及其对激光焊接气孔的影响

采用砂纸打磨、酸洗、激光清洗等方式对Ti6Al4V钛合金进行焊前清洗。通过扫描电镜、白光干涉仪、能谱仪分析了各种清洗方式下的表面形貌、粗糙度和化学成分，研究了不同清洗方式及参数对清洗效果的影响。在均匀熔透和表面质量良好的同一激光焊接条件下，比较了不同清洗条件对气孔率的影响。合适的激光清洗可有效清除焊接试件表面氧化层，并改善表面粗糙度，得到较低的气孔率，其焊缝可达到中国航天工业行业标准I级焊缝要求。     

基于降噪时序深度学习网络的风电功率短期预测方法

利用风电场历史功率数据预测未来一段时间内的风功率,对保障电网安全稳定运行具有重要的意义。本文提出一种基于奇异谱分析SSA(singular spectrum analysis)和长短时记忆LSTM(long-short term memory net⁃work)网络的时序特征预测框架用于短期风功率的预测。首先通过SSA对历史风功率原始数据进行降噪处理,然后经过数据转换之后,以LSTM网络为基础进行预测模型的训练,最后通过某风电场提供的两个风机的历史功率数据进行验证。实验结果表明,奇异谱分析对风电场的历史数据具有良好的降噪性,SSA+LSTM模型在测试数据上取得了较好的预测性能,能够有效进行短期风功率的预测。     

冷轧退火对FeMnCoCrAl高熵合金组织和力学性能的影响

使用真空电弧炉熔炼出(Fe₅₀Mn₃₀Co₁₀Cr₁₀)₉₄Al₆合金,利用冷轧及在不同温度对合金进行退火,以期望得到由多尺度再结晶晶粒构成的层状结构;并对不同退火温度的样品进行拉伸性能测试。利用扫描电镜和EBSD对合金组织形貌进行表征,采用X射线衍射方法研究其相组成。结果表明:合金在铸态和冷轧后相组成未发生变化,700 ℃退火得到较好的多尺度再结晶晶粒的层状结构,其屈服强度为487 MPa,抗拉强度为708 MPa,断后伸长率为39%,表现出良好的综合力学性能。     

Corrosion behaviour and mechanism of 6082 aluminium alloy in NaCl and Na2SO4 etchants

The corrosion behaviour of 6082 aluminium alloy was studied by measuring the electrochemical impedance spectra and electrode polarization curves. After the electrochemical tests, a microstructural analysis of the samples was conducted by using optical microscopy and electron scanning microscopy techniques to determine the corrosion mechanism. The results show that the Nyquist plot of the electrochemical impedance data in the NaCl solution consists of high- and low-frequency capacitive impedance loops. When ions are added to the NaCl etchant, the Nyquist plots of the electrochemical impedance data are composed of two different curves: a high-frequency capacitive impedance loop and a low-frequency inductive impedance loop. The corrosion current density increases with increasing concentration, and as a result, the corrosion resistance of the aluminium alloy decreases. The microstructures of 6082 aluminium alloy consist of Mg₂Si secondary particles in a large α-Al matrix. Pitting corrosion initially occurs at the boundary between the matrix and secondary particles because the electrode potentials of the matrix and secondary particles are different. Then, corrosion paths develop along the network-like grain boundaries, and finally, massive network-like corrosion occurs throughout the entire alloy.     

Microstructure and corrosion behaviors of FeCrNiBSiMox stainless steel fabricated by laser melting deposition

In this paper, FeCrNiBSiMo_x (x = 1.0, 1.5, 2.0, 2.5) stainless steels were successfully prepared using a laser melting deposition technology, with the aim to investigate the effect of Mo content on microstructure and corrosion behaviors. The results showed that the as-deposited specimens were composed mostly of α-Fe and a small amount of (Cr, Mo)₇C₃, and (Cr, Mo)₇C₃ existed in the inter-dendritic (ID) region. As the Mo content increased, grain refinement could be clearly observed, and the area of the ID region increased from 27% to 54%. The low-angle boundaries accounted for 60–70% of the grain boundaries of the as-deposited specimens. Increasing the content of Mo improved the microhardness of the as-deposited specimens from 652 HV to 813 HV. The corrosion current density of the as-deposited specimens with the Mo mass fractions of 1.0%, 1.5%, 2.0%, and 2.5% were 1.37 × 10⁻⁶, 1.02 × 10⁻⁷, 6.19 × 10⁻⁷, and 3.06 × 10⁻⁷ A/cm², respectively. The as-deposited specimen with Mo content of 1.5% had lower cumulative erosion loss and erosion loss rate than other as-deposited specimens. The FeCrNiBSiMo_x (x = 1.5) specimen exhibited excellent resistance to electrochemical corrosion and cavitation erosion.     

退火温度对新型锆合金薄板带材析出相和织构的影响

采用扫描电镜和超高分辨透射电镜,对具有良好冲制性能的新型锆合金薄板成品带材进行含晶粒、第二相粒子等在内的显微组织研究,并探索真空退火处理条件下温度对带材显微组织的影响。结果显示:新型锆合金薄板成品带材晶粒平均尺寸2.17 μm,存在{0001}<1010>和{0001}<1120>两种织构,大部分晶粒<1120>平行带材RD方向,较少晶粒<1010>平行带材RD方向;第二相粒子分布在晶粒内部及晶界,平均尺寸114 nm,尺寸较大的为不规则椭圆形的Zr-Nb-Fe相,尺寸较小的为圆形的β-Nb相;热处理退火温度降低,带材晶粒尺寸减小,第二相粒子细小弥散分布;新型锆合金薄板成品带材良好冲制性能主要源于轧制积累应变诱发再结晶过程进行充分,导致晶粒细小及孪晶发生破碎;相对轧制变形,退火对带材冲制性能影响不显著。     

等温退火对8030铝合金导线组织性能的影响

研究了不同等温退火工艺对8030铝合金导线组织及性能的影响。结果表明:等温退火前后合金均由α-Al基体和Al₆Fe相组成。在同一等温温度下,随着等温时间的延长组织逐渐趋于均匀化;同一等温时间下,随着等温温度的升高,组织趋于均匀化的时间缩短。经过等温退火处理后铝合金导线的导电率均有所提高,在470 ℃均匀化退火24 h后再经240 ℃等温4 h,合金导电率达到最高值57.21%IACS,比未经热处理试样的导电率提高了2.4%IACS。经过等温退火处理后铝合金导线的硬度及抗拉强度均有所降低,塑性大幅度提高。在470 ℃均匀化退火24 h后再经260 ℃等温8 h,合金的伸长率最高可达23.64%。热处理前后合金均为塑性断裂。     

镁合金网格壁板压弯成形数值模拟及实验研究

为探索镁合金整体壁板压弯成形的可行性,以及镁合金壁板压弯成形过程中金属的流动规律,对AZ31镁合金网格壁板压弯成形进行了数值模拟和实验研究。建立了有限元数值模拟的几何模型,采用有限元计算软件对AZ31镁合金网格壁板压弯成形过程进行了数值模拟研究,分析了镁合金网格壁板压弯成形中的温度场、应变场、应力场、破坏系数等的分布规律。确定了合适的AZ31镁合金壁板压弯成形工艺参数,并对镁合金网格壁板压弯成形进行了实验研究,获得了合格的镁合金网格壁板弯曲件,并分析了镁合金网格壁板成形件尺寸精度,模拟结果与实验结果相吻合,最大相对误差为16.7%。     

HF刻蚀工艺对AZ91D镁合金疏水膜性能的影响

为了改善AZ91D镁合金表面疏水膜的疏水性,对以HF和N^MoOq为主要成分的刻蚀液进行了研究。通过改变刻蚀温度、刻蚀时间、HF的浓度及Na2MoO4的质量浓度,确定了最佳的刻蚀工艺条件为:HF 0.10 mol/L,Na2MoO41.00 g/L,1525°C,90 so实验结果表明:使用HF刻蚀液可以在镁合金表面形成理想的微纳结构。通过刻蚀构建的微纳结构可以明显提高疏水膜的疏水性。     

Damping and mode shape modification for additively manufactured walls with captured powder

This paper describes the fabrication, modeling, and dynamic testing of laser powder bed fusion stainless steel walls with captured powder cores. The purpose of the study is to determine the increased structural damping, or energy dissipation, and mode shape modification caused by the inclusion of the unmelted powder core within the solid walls. It is shown experimentally that the damping increases with larger powder core width and that the damping addition is mode dependent. Damping increases over the solid wall values by factors of 2.9–225 are reported depending on the mode number and core width. It is also seen that the mode shapes are distorted relative to the solid wall results as the core width is increased and wall thickness is decreased. Comparisons with finite element models confirm this trend.