连续冷却和搅拌条件下树枝晶向粒状晶转变时间的估算

介绍了连续冷却和搅拌条件下树枝晶向粒状晶转变的填充间隙(FAS)和颈缩熔断(NMAR)两种机制, 并通过理论推导得到了可以用来计算其转变时间的数学公式. 两种机制下的转变时间计算结果与实验结果吻合较好.     

半固态连铸技术研究现状与展望

分析了半固态连铸技术研究现状和存在的主要问题 ,提出了该领域今后的主要研究课题 ,并对半固态连铸的应用前景进行了探讨     

钢铁材料半固态坯料制备与成形的研究现状与展望

半固态成形技术是冶金材料领域重要研究课题。本文总结了半固态钢铁等高熔点材料制备与成形技术中的组织演变、坯料制备和成形工艺等方面理论与应用研究成果，对其发展现状与趋势进行了分析与讨论，并指出钢铁等高熔点材料半固态成形技术广阔的应用前景。     

SCR工艺参数对A2017半固态合金组织的影响

采用自行设计的SCR实验机制备A2017半固态合金，研究了SCR工艺参数对A2017半固态合金组织的影响。实验结果表明，合金液浇注温度和轧辊冷却水流量共同影响辊靴间隙中半固态合金的固相率，降低浇注温度或者增大冷却水流量，辊靴间隙高固相率合金区间增长，晶粒尺寸变小；减小辊靴间隙或者提高轧辊转速提高合金层流剪切强度，利于枝晶破碎；增大出口半固态浆料冷却速率能有效抑制晶粒继续生长，保留其完整的非枝晶半固态组织。合金液浇注温度为760～780℃，辊靴间隙为4～6mm，轧辊冷却水流量200～300ml／s条件下，SCR技术可获得浆料状A2017半固态合金，凝固后坯料为均匀、细小的非枝晶等轴晶组织，晶粒大小在40～50μm之间，SCR技术是一种制备半固态加工坯料的理想方法。     

两相区铸造AZ91D半固态坯料的部分重熔工艺与组织演变

对在两相区铸造进行半固态制浆所得AZ91D镁合金坯料的部分重熔工艺条件及组织演变进行了研究. 结果表明 AZ91D镁合金在两相区温度(585 ℃)静置30 min且在水冷铁模中浇注的两相区铸造半固态坯料, 在575 ℃下保温30～45 min进行部分重熔时, 其组织具有固相颗粒球化程度高、颗粒细小且粒度均匀、有效液相体积分数高等特点; 坯料组织演变初始化阶段、球化阶段和集聚合并长大等3阶段部分相互重叠. 对特定原始半固态坯料, 改变部分重熔温度, 可缩短重叠区, 扩大球化区, 实现坯料重熔进程及组织形态的优化, 从而增加工艺可控性和提高坯料的触变性.     

MECHANISMS UNDERLYING THE ROLE OF FRICTION IN ORAL TEXTURE

The role of friction in food texture sensations are reviewed with the focus on results from our own laboratory, concentrating on texture sensations that are affected by the lubricative properties (e.g., roughness and creaminess), by the viscosity (e.g., melting and thickness) and by the used thickeners (e.g., airiness and heterogeneity). A food's lubricative properties are affected by its fat content, fat droplet size, particle size and shape and thickener. Foods with lower fat contents, larger fat droplets, larger particles and specific thickeners exhibited higher friction while their creaminess and fattiness sensations, associated with good lubrication, are reduced. Roughness and dryness sensations, associated with poor lubrication, are increased. Taste and flavor compounds also affected these texture sensations, albeit via a different mechanism. Specific compounds can affect the lubricative properties of saliva resulting in friction‐related sensations, such as astringency. Astringent compounds interact with proline‐rich proteins in saliva, causing precipitation that may be sensed as discrete particles and/or increased roughness. Alternatively, the compounds may precipitate dead cells and other debris present in saliva. Astringent compounds may also directly affect the surface properties of the oral mucosa.     

超声功率对Mg-3Re-3Zn-0.7Y合金组织和力学性能的影响

如果在铸造过程能够细化含有稀土元素的金属间化合物,那么稀土镁合金在耐热应用方面将具有巨大的潜力。本文研究了半固态制浆过程中不同超声功率的超声振动对Mg-3RE-3Zn-0.7Y合金半固态微观组织以及铸态试样力学性能的影响。试验对液相线以上20~40癈镁合金熔体分别施加超声功率为800W至1200W的超声振动,振动时间为90s,结束超声振动温度为液相线以下10℃左右。结果表明,超声振动可以制备出组织中具有细小圆整的初生α-Mg相的优良半固态浆料,并且经过超声功率为1000W的超声处理后浆料组织中初生α-Mg晶粒的平均晶粒直径和平均形状系数SF分别为55μm和0.63。此外,1000W超声处理的铸件试样比未经超声处理的试样抗拉强度提高了25.2%,伸长率提高了93.5%。可见,声空化效应和声流效应使超声振动成为一种制备具有细小圆整初生晶粒的镁合金半固态浆料的有效途径。     

Variation in the effect of carcass decontamination impacts the risk for consumers

To enhance food safety, whole carcass decontamination during slaughter has been considered as a control measure to reduce pathogen concentrations on meat. The effect of such decontamination is usually measured in terms of the mean log reduction in concentration. However, the variation in this reduction may also contribute to the overall impact of the decontamination measure. Therefore, this study focuses on the relative contribution of mean and variation for the effect of decontamination in the slaughter-line expressed in terms of the effect on human health risk.A stochastic risk model is developed to assess the potential effects of pig carcass decontamination at the end of slaughter on the risk of salmonellosis for Danish consumers. Salmonella concentrations are represented by a lognormal distribution fitted to microbiological data, characteristic for Salmonella numbers on carcasses at the end-point of Danish slaughterhouses. Decontamination scenarios are represented by various gamma distributions with different means and standard deviations. The values chosen for these parameters are based on experimental data of the effect of real decontamination procedures applied to pork.Results show that the variation of decontamination has a relevant effect on risk reduction for the consumer: the higher the variation, the lower the overall risk reduction. This effect is particularly evident for procedures with a lower mean reduction (≤2.5 log₁₀), but less so for highly efficient decontamination procedures (>2.5 log₁₀ mean reduction). This difference is affected by the initial level of carcass contamination with Salmonella. With increasing mean and standard deviation of initial bacterial concentrations, it becomes increasingly relevant to account for the variation of the decontamination action, even if the mean decontamination effect is high.We conclude that for decontamination procedures with an overall mean reduction effect of 1–2 log₁₀, it is important to consider the variation in effect: if the variation is large, the final effect of decontamination can be considerably smaller than expected on the basis of the mean only and efforts should be put in place to reduce the variation of the procedure. However, when a treatment of high mean reduction (>2.5 log₁₀) is used, the impact of variation becomes smaller and may be negligible.     

MICROSTRUCTURE AND PROPERTIES OF TiCp/Al COMPOSITE FABRICATED BY CONTACT REACTION METHOD AND SEMISOLID EXTRUSION

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AZ91镁合金的SIMA法半固态组织特征

研究了挤压态AZ91镁合金的SIMA法半固态组织演变.结果表明:挤压合金为以α-Mg再结晶等轴晶为主相,与极少量细粒状成串分布于α-Mg基体上的Mg17Al12颗粒组成的两相组织,基体中存在大量的大角度亚晶及高密度的位错缠结.在二次加热过程中,原子扩散通道多,晶界液化及颗粒球化所需的加热温度低,等温时间短.565℃等温5min,即可获得固相率为57%,颗粒平均直径为58 μm、形状圆整、分布均匀的半固态组织.等温5 min后,半固态颗粒发生长大,其长大机制为Ostwald熟化.