高温高压水排放过程中高强度噪声的治理

介绍了高温高压水通过二次节流气液扩容分离和小孔变频扩散等多种方法,使排放时高达１５０ｄＢ的噪声降到５０ｄＢ以下。     

Effects of Temperature and Strain Rate on the Plastic Deformation of Fully Dense Polycrystalline Y1Ba2Cu3O7−x Superconductor

The knowledge of the steady-state stress for plastic deformation as a function of temperature and strain rate is essential for hot-forming superconducting material into commercially useful shapes. In this paper, results are presented on the experimental determination of the rheology of fully dense polycrystalline Y₁Ba₂Cu₃O_7−x superconducting material at temperatures ranging from 750° to 950°C and strain rates of 10⁻⁴, 10⁻⁵, and 10⁻⁶ s⁻¹. The data are best fitted by a power law: ε(s⁻¹)=8.9 × 10⁻¹⁷. (s⁻¹) σ^2.5 (Pa) exp [−2.01 × 10⁵(J·mol⁻¹)|RT]. X-ray analysis shows that the superconducting material retains its phase composition after nearly 70% total strain of the sample. A strong anisotropy in the resistivity of the deformed samples is observed because of the development of a preferred orientation of the a or b axis of Y₁Ba₂Cu₃O_7−x orthorhombic perovskite single crystals perpendicular to the principal maximum compressive stress.     

Calculation of Phase Diagrams for the YO1.5—BaO—CuOx System

The thermodynamic data for the YO_1.5–BaO, BaO-CuO_x, and YO_1.5–CuO_x quasi-binary systems were optimized from experimental phase diagrams. They were used to calculate tentative phase diagrams for the YO_1.5–BaO—CuO_x quasi-ternary system. The equilibrim liquidus surface and the isothermal sections of the ternary system at 900°, 925°, 950°, 975°, and 1000°C were calculated. The isopleths containing YBa₂Cu₃O_7-δ were also calculated.     

The Relationship Between Oxidation and Thermal Fatigue of Martensitic Hot-Work Die Steels

Thermal fatigue behaviors of two forged hot-work die steels subjected to cyclic heating(650 °C)–water quenching were investigated. A martensitic hot-work die steel containing 10% Cr(HHD), showing superior oxidation resistance and thermal fatigue resistance to the commercial martensitic hot-work die steel(Uddeholm DIEVARò), was developed. The maximal crack length in HHD was 35% shorter than that in DIEVAR after 2000 thermal cycles, and the hot yield strength at 650 °C of HHD was 14% lower than that of DIEVAR prior to thermal fatigue testing, which is 30% higher after 1500 cycles. It is found that cracks initiated and propagated along the oxide layers in the grain boundaries, suggesting that the oxidation-induced thermal fatigue cracks can significantly reduce the mechanical performance and service life for the hotwork die steel. High-temperature oxidation behavior is crucial for thermal fatigue crack formation, while high-temperature yield strength and ductility play a less important role.     

Improvement of High-Temperature Mechanical Properties of Low-Carbon RAFM Steel by MX Precipitates

To investigate the influence of tantalum content on high-temperature mechanical properties of low-carbon reduced activation ferritic/martensitic(RAFM) steels, RAFM steels containing different tantalum contents(0 and 0.073%) were fabricated, and the tensile tests at room temperature and high temperature were performed, as well as the creep tests were conducted at 550 °C with the applied stress of 180 and 220 MPa. It was found that 0.073% tantalum addition results in the increase in amount of stable carbonitrides(MX), and the creep rupture time of the steel under 180 MPa is obviously increased. In addition, the increase in MX caused by tantalum addition also leads to the improvement of high-temperature tensile strength. The improvement of high-temperature mechanical properties of RAFM steels is primarily related to the evolution of precipitates.     

Enhancing High-Temperature Strength and Thermal Stability of Al_2O_3/Al Composites by High-Temperature Pre-treatment of Ultrafine Al Powders

Amorphous Al_2 O_3-reinforced Al composite(am-Al_2 O_3/Al) compacted from ultrafine Al powders for high-temperature usages confronts with drawbacks because crystallization of am-Al_2 O_3 at high temperatures will result in serious strength loss.Aiming at this unsolved problem,in this study,high-temperature Al materials with enhanced thermal stability were developed through introducing more thermally stable nano-sized particles via high-temperature pre-treatment of ultrafine A1 powders.It was found that the pre-treatment at ≤550℃ could introduce a few Al_2 O_3 in the Al matrix and increase the strength of the composites,but the strength was still below that of am-Al_2 O_3/Al because without being pinned firmly,grain boundaries(GBs) were softened at high temperature and intergranular fracture happened.When the pre-treatment was carried out at 600℃,nitridation and oxidation processes happened simultaneously,producing large numbers of intergranular(AlN+γ-Al_2 O_3) particles.GB sliding and intergranular fracture were suppressed;therefore,higher strength than that of am-Al_2 O_3/Al was realized.Furthermore,the(AIN+γ-Al_2 O_3)/Al exhibited more superior thermal stability compared to amAl_2 O_3/Al for annealing treatment at 580℃ for 8 h.Therefore,an effective way to fabricate high-temperature Al composite with enhanced thermal stability was developed in this study.     

Influence of the alloy grain size on the oxidation behaviour of PM2000 alloy

The influence of the alloy grain size on the oxidation behaviour in air between 900 and 1400 °C of oxide dispersion strengthened PM2000 alloy was studied. The grain size of the alloy affects the morphology, the composition of the alumina scale as well as the size, composition and volume fraction of nodules formed on the alumina scale, but has only a small influence in the kinetics. In the fine-grained PM2000, grain boundaries act as rapid pathways for aluminium diffusion, leading to the establishment of a purer alumina scale than that formed on coarse-grained material. On the coarse-grained alloy, there is enough time for the nucleation of oxides other than alumina. These oxides, impeding alumina grain growth, can lead to the formation of a fine-grained alumina layer. The outward cation and inward oxygen diffusion in this fine-grained alumina layer may contribute to both the slight increase in mass-gain and the increased tendency to form nodules at the outer surface.     

钛合金表面激光熔覆AlCoCrFeMoVTi高熵合金涂层的摩擦磨损和高温抗氧化性能

为提高钛合金的摩擦磨损和高温抗氧化性能,采用激光熔覆技术在Ti6Al4V(TC4)钛合金表面制备了近等原子比的AlCoCrFeMoVTi高熵合金(HEA)涂层。借助X射线衍射(XRD)、扫描电镜(SEM)、能谱仪(EDS)等分析了涂层的物相组成和显微组织;利用HDX-1000维氏硬度仪测试了熔覆层显微硬度;通过UMT-3摩擦磨损试验机和GSL-1400X型管式电阻炉分别测试了HEA涂层的摩擦磨损性能和高温抗氧化性能。结果表明,HEA涂层主要由面心立方(fcc)、体心立方(bcc)二元共晶相组成;HEA涂层最高显微硬度HV0.2为10 990 MPa,是基体TC4的3.29倍;涂层摩擦系数为0.31,磨损体积为1.79×10~(-4)mm~3,分别为基体的59.62%和12.01%;在800℃恒温下氧化50h后,HEA涂层的氧化增重为1.49 mg,仅为基体的16.37%。激光熔覆高熵合金AlCoCrFeMoVTi涂层能显著改善Ti6Al4V钛合金的摩擦磨损和高温抗氧化性能。     

锆表面磁过滤阴极真空弧离子镀Cr涂层高温蒸汽氧化行为研究

采用磁过滤阴极真空弧离子镀(FCVAD)技术在纯锆表面制备了厚度约为4 μm的Cr金属层,对比研究了它们在不同温度水蒸汽环境中的氧化行为,并利用XRD、XPS、SEM及EDS分析了 Cr涂层及氧化膜的物相组成、微观结构及成分分布.结果表明,在900、1000和1100℃水蒸汽环境中,镀Cr涂层大幅度降低了锆的氧化速率,...     

High-Temperature Plasticity Enhanced by Multiple Secondary Phases in a High-Si Austenitic Stainless Steel

An austenitic stainless steel with 6 wt% Si and multiple secondary phases was produced with the aim to achieve enhanced plasticity during hot deformation. The microstructure of the steel after fracture was characterized via electron back-scattered diffraction, transmission Kikuchi diffraction and scanning transmission electron microscopy. From the tail of the gage to the necking region, the microstructure of the material evolved from low-angle grain boundaries (LAGBs) to mixtures of LAGBs and high-angle grain boundaries (HAGBs), and fine equiaxed recrystallized grains. The elongation to failure in the tensile test exceeds 167%. During the hot deformation, continuous dynamic recrystallization of the austenitic matrix was promoted by the multiple secondary phases. The dislocations introduced by the secondary phases were rearranged and continuously transformed into HAGBs. The initially coarse grains (30.5 μm) were refined into ultra-fine equiaxed grains (1 μm), which contributed significantly the enhanced plasticity during hot deformation of the steel. In the necking area of the sample, twins were nucleated in the stress concentration regions and accommodated the local strain by discontinuous dynamic recrystallization, which was also beneficial to improving the plasticity.