Properties of a reaction-bonded β-SiAlON ceramic doped with an FeMo alloy for application to molten aluminum environments

An FeMo-alloy-doped β-SiAlON (FeMo/β-SiAlON) composite was fabricated via a reaction-bonding method using raw materials of Si, Al₂O₃, AlN, FeMo, and Sm₂O₃. The effects of FeMo on the microstructure and mechanical properties of the composite were investigated. Some properties of the composite, including its bending strength at 700℃ and after oxidization at 700℃ for 24 h in air, thermal shock resistance and corrosion resistance to molten aluminum, were also evaluated. The results show that the density, toughness, bending strength, and thermal shock resistance of the composite are obviously improved with the addition of an FeMo alloy. In addition, other properties of the composite such as its high-temperature strength and oxidized strength are also improved by the addition of FeMo alloy, and its corrosion resistance to molten aluminum is maintained. These findings indicate that the developed FeMo/β-SiAlON composite exhibits strong potential for application to molten aluminum environments.     

Deep-cryogenic-treatment-induced phase transformation in the Al-Zn-Mg-Cu alloy

An aluminum alloy (Al-Zn-Mg-Cu) subjected to deep cryogenic treatment (DCT) was systematically investigated. The results show that a DCT-induced phase transformation varies the microstructures and affects the mechanical properties of the Al alloy. Both Guinier-Preston (GP) zones and a metastable η' phase were observed by high-resolution transmission electron microscopy. The phenomenon of the second precipitation of the GP zones in samples subjected to DCT after being aged was observed. The viability of this phase transformation was also demonstrated by first-principles calculations.     

Microtextural evolution of different TRC AA8006 alloy sections with homogenization

Grain microtexture evolution in twin-roll cast AA8006 alloy sheets subjected to different treatments was investigated using electron backscatter diffraction. The textures of rolling-transverse and normal-transverse sections were characterized in original as-cast twin-roll casting and cold-rolled samples as well as samples homogenized at 500℃ for 8 h and at 580℃ for 4 h. It is found that grains on both the rolling-transverse and normal-transverse sections of cold-rolled samples are made finer by rolling deformation and coarsened after homogenization. Annealing temperature has a stronger effect on the microstructural evolution than annealing time. The grain growth direction is parallel to the normal-transverse section, while grain deformation is more stable on the rolling direction than on the normal direction. The rolling orientations display more obvious anisotropy on the normal-transverse sections than on the rolling-transverse sections. Grain recrystallization and growth occur much easier on the normal-transverse section than on the rolling-transverse section for samples homogenized at 500℃ for 8 h. A special misorientation relationship between cold deformation texture, such as S orientation {123}<634> and cube orientation <110>‖X_axis[cubic], and recrystallization texture after homogenization, such as R orientation {124}<211> and P orientation {011}<122>, is observed.     

Effects of La addition on the microstructure and tensile properties of Al-Si-Cu-Mg casting alloys

The effects of La addition on the microstructure and tensile properties of B-refined and Sr-modified Al-11Si-1.5Cu-0.3Mg casting alloys were investigated. With a trace addition of La (0.05wt%-0.1wt%), the mutual poisoning effect between B and Sr can be neutralized by the formation of LaB₆ rather than SrB₆. By employing a La/B weight ratio of 2:1, uniform microstructures, which are characterized by well refined α-Al grains and adequately modified eutectic Si particles as well as the incorporation of precipitated strengthening intermetallics, are obtained and lead to appreciable tensile properties with an ultimate tensile strength of 270 MPa and elongation of 5.8%.     

热处理工艺对40CrNiMoA合金组织及力学性能的影响

为了提高矿用链轮耐磨性,延长其使用寿命,选取电渣离心铸造40CrNiMoA合金链轮件作为母材,研究热处理工艺对40CrNiMoA合金组织和力学性能的影响。采用正交试验法,研究不同热处理工艺对合金显微硬度、摩擦磨损及拉伸强度等力学性能的影响,并将测试结果进行极差分析和综合加权评分计算,得出最优热处理工艺参数,最后进行试验验证。结果表明,正交试验法得到的最优热处理工艺为880℃淬火0.5 h, 600℃高温回火2 h,样品热处理后的组织主要为回火索氏体,维氏硬度为364 HV,抗拉强度为1 166 MPa,磨损率为0.427×10^-4 mm³/(N·m);验证试验结果与正交试验分析结果相近,且热处理后的样品性能可达到使用要求。研究结果可为矿用链轮件热处理工艺提供理论依据,对有效解决链轮耐磨性和使用寿命问题具有参考价值。     

Ni—Ti合金相变与亚结构的研究

利用高分辨电子显微技术(HREM),在原子尺度上观察研究了Ni-Ti形状记忆合金的固态相变及其亚结构.在此基础上提出了该合金中马氏体相变的模塑.     

P/M钢-氧化铝合金加工硬化特征的探讨

本文以冷加工和退火两种状态的铜-氧化铝合金圆棒,在电子拉伸机上,测绘P-ΔL曲线,探讨该合金的加工硬化特征。讨论了拉伸速度和合金成分对合金机械性能的影响。用第一类加工硬化曲线作图法测量了合金加工硬化指数,并与变形抗力法进行了比较。研究结果表明,该合金的加工硬化程度随应变速率增加而增加,并受合金成分的影响。同时,屈服强度相应提高。     

钼钒型铸铁冷焊焊条的研制

本文通过理论探讨和试验研究,提出一种新型焊条——钼钒型铸铁冷焊焊条,它可代替目前常用的高钒焊条。它具有焊接接头白口区较窄;节省较贵的钒铁;焊接工艺性能较好等优点。     

高温应用形状记忆合金时效初探(英文)

形状记忆合金的应用开发异常活跃。然而,对于环境温度超过100℃的所谓高温应用,却涉及较少。本实验研制了成分为Cu-13Al-2.81Ni(wt%)的铸造合金,其转变温度均大于100℃。淬火后的试样在180℃停放30天,相应进行电阻温度回线测室、X衍射实验及透射电镜观察。实验结果表明:合金于180℃时效,起初随着时效时间的延长,马氏体转变温度提高,而转变量基本不变;25天后,转变量急剧减少,转变温度下降。时效前后,X衍射图谱无明显变化。透射电镜观察到时效30天的样品内部出现大量的块状共格过渡相,该共格过渡相与马氏体结构一致、成分不同,阻碍马氏体的可逆转变。     

钒—氮共掺杂TiO_2光催化剂的合成优化

采用溶胶—凝胶法合成了钒—氮共掺杂TiO2光催化剂,通过在模拟太阳光下降解苯酚测定其光催化活性.考察了钒源用量、水解温度、陈化温度、陈化时间等因素对钒—氮共掺杂TiO2光催化降解苯酚性能的影响.结果显示,最优条件下合成出的钒—氮共掺杂TiO2在模拟太阳光下催化反应4h,对浓度为60mg/L的苯酚的降解率达到91.83%.