基于CA算法的轧制工艺动态再结晶过程模拟

为研究低碳钢轧制变形过程的组织演化,建立了一套奥氏体动态再结晶模型。利用CA算法,基于Deform研究了热轧过程中的再结晶比率和晶粒尺寸的变化。结合变形条件对模型系数的影响,将模型计算所得的组织演变、再结晶体积分数、晶粒尺寸与实验进行了比较,证明了模型的有效性。     

Production of β-SiC by pyrolysis of rice husk in gas furnaces

Short fibers and fine particles of β-SiC were obtained by pyrolysis of Colombian rice husk (RH). The synthesis of SiC was carried out in a gas furnace: a mathematical model was developed in order to design and build this equipment and the process was optimized using an experimental design that included variables such as temperature, pyrolysis time, type of catalyst, and process atmosphere. The obtained material was characterized by using FTIR, DRX and SEM for microstructural characterization and EDS technique for chemical analysis.     

多模终端待机低功耗设计

如今的移动通信网络是由多种制式及多个频段融合而成的多模网络,对于商用终端而言,多种难题交织在一起,其中待机时长是必须要解决的一个关键问题.为此,不同于传统增大电池容量的方法,采用降低待机功耗的策略:时域的时隙控制、频域的电流控制、睡眠和唤醒的电源门控制、低频时钟高频化,其中高频时钟校准低频时钟是降低睡眠态功耗的关键措施.这一系列方案的实施,使得终端在多模实际网络环境下的待机电流小于5 mA,终端的待机低功耗达到了有竞争力的商用水平.     

热加工工艺对C-Mn钢组织结构的影响

研究了热加工工艺制度对0.23％C-0.60％Si-1.50％Mn-0.44Ceq中低碳钢亚晶组织结构的影响规律.验证了晶内先共析铁素体的析出条件,测定了不同变形温度下试样的应力-应变曲线及动态CCT曲线.分析了变形温度对试样软化率、动态再结晶率、相变温度点、珠光体片间距、铁素体晶粒度,位错密度的影响.     

Mesoscale simulation of discontinuous dynamic recrystallization using the cellular automaton method

A dynamic recrystallization (DRX) cellular automaton (CA) model that can mark the microstructure with DRX circle was developed. The effects of initial grain size on the stress-strain curve, mean grain size and DRX fraction were mainly investigated, and the simulated results were compared with those obtained from previous researches. The results show that the shape of the stress-strain curve is sensitive, while the stress and mean grain size at the steady state are insensitive to the initial grain size. The transition from a multiple-peak stress-strain curve to a single-peak one can be explained by variations in DRX circle fraction, and the initial grain size to make this transition is between 70 and 80 μm.     

Structural and morphological characterizations of ZnO nanopowder synthesized by hydrothermal route using inorganic reactants

Zinc oxide nanoscale powder has been synthesized by a hydrothermal route using zinc sulfate and sodium hydroxide. The as-prepared powder was annealed at 600 °C for 2 h and then characterized by X-ray diffraction(XRD), scanning electron microscopy and infra-red Fourier transformed spectroscopy. XRD measurements have shown a Zn O hexagonal wurtzite polycrystalline structure with good crystallinity and the formation of a new sodium pyrosulfate phase in the as-prepared powder. The annealing improves the crystalline quality of the powder and transforms the sodium pyrosulfate phase to a sodium sulfate one. The thermal treatment does not affect the lattice parameters and the Zn–O bond length but improves the random orientation of the Zn O crystallites growth.Zn O crystallites have an interconnected-nano-needles morphology forming irregular shaped aggregates. The size of the crystallites is about 20 nm. EDX analysis has shown the presence of C and S in addition to Zn and O. FTIR spectra confirm the formation of Zn O and sodium sulfate. The synthesized Zn O powder has a very high crystalline quality and the used method is a very advantageous one for the fabrication of nanosized metal oxides from inorganic reactants for photo-catalysis applications.     

喷射成形GH738合金热变形特性及微观组织演变

在温度950~1200℃、应变速率0.13~6.5 s~(-1)及工程应变50%的条件下,利用Gleeble-3500~(TM)热模拟试验机对喷射成形GH738合金进行热压缩试验,研究了合金的热流变行为并建立了流变本构关系,结合显微组织分析及统计技术研究了合金的组织演变情况。结果表明,流变应力随温度的升高和应变速率的减小而降低。合金热变形激活能为580.81kJ·mol~(-1)。随着形变温度的升高,高位错密度处晶界弓出形核使晶界"锯齿"化并形成项链组织,在1100℃获得完全动态再结晶组织,随温度继续升高及应变速率的降低组织明显长大。     

CHARACTERIZATION OF ULTRAFINE ZIRCONIA PARTICLES PRODUCED BY A GAS-SOLID REACTION

The microstructure of a zirconia powder prepared from a gas-solid reaction was determined by SEM, EDXS, DRX and TEM analysis. At low temperatures (773 K) and up to 0.5 of reaction degree two types of particles were formed: a melaslable tetragonal ZrO₂ phase fixed on the Fe₂O₃ grain surfaces and isolated grains of monoclinic ZrO₂ phase.     

Effect of powder preparation technology on the hot deformation behavior of HIPed P/M nickel-base superalloy FGH96

In this paper, the hot deformation characteristics of P/M nickel-base superalloy FGH96 prepared by different powder preparation technologies were studied in the deformation temperature range from 1000 °C to 1100 °C and the strain rate range from 0.001 s⁻¹ to 1 s⁻¹ using hot compression tests. The peak stress vs. deformation temperature curves and the peak stress vs. strain rate curves were established, respectively. The results show that the specimens prepared by plasma rotation electric pole (PREP) powder were more sensitive to deformation temperature and strain rate. On the basis of the dynamic material model, the processing maps for hot working were developed. The activation energies and Zener-Hollomon parameters were obtained by linear statistical regression method. For the specimens prepared by PREP powder, the peaks of power dissipation mainly located in lower temperature domain (1000-1030 °C), and the efficiencies of power dissipation (EPD) obtained in the strain range from 0.1 to 0.7 were essentially similar. This indicated that strain had a slight influence on processing maps. For the specimens prepared by argon atomization (AA) powder, the effects of strain on EPD and instability domains were significant. The lower activation energies and Z values indicated that the workability of the specimens prepared by AA powder is better than that prepared by PREP powder. Moreover, it was found that effects of the heat treatment time on activation energy and Zener-Hollomon parameter were significant. With the increase of heat treatment time, the dislocation density and the volume fraction of precipitation phase gradually decreased. Microstructural observation demonstrated that the phenomenon of recrystallized grains coarsening existed in the specimens prepared by longer heat treatment time. The heat treatment time of the specimens prepared by AA powder should be appropriately shortened in order to prevent recrystallized grains coarsening.     

不连续接收与电压岛结合的省电方法

LTE系统支持高速的数据传输。高的数据传输速率需要更复杂的基带调制解调器芯片,这就加快了终端电池的能量的消耗。因此,LTE引入了不连续接收机制(DRX)来延长终端的电池试用时间。结合DRX,本文提出了一个动态的电源管理方案—分层多级电压岛(HMVIP),并建立省电类。结果表明,在单一的LTE终端芯片上,DRX结合HMVIP可以达到更好的省电性能。