多羟基糖类物质对冷冻虾仁中水的重结晶的改善作用

探讨不同糖类对冻藏温度波动下冷冻虾仁的抗冻保水作用。以南美白对虾为对象,以焦磷酸钠和蒸馏水分别为阳性和阴性对照,在-55℃与-24℃冻藏温度波动条件下,分析低聚木糖、卡拉胶寡糖、海藻糖和海藻胶寡糖对虾仁肌肉品质特性的影响。结果表明,在温度波动条件下冻藏144 d过程中,相比于蒸馏水处理组,低聚木糖、卡拉胶寡糖、海藻糖和海藻胶寡糖显著降低了冷冻虾仁的解冻损失率,其中最低的为卡拉胶寡糖组(8.58%)。且糖处理组有效维持了虾仁肌肉组织的质构特性,弹性和咀嚼性最佳分别为1.42 mm和6.80 mJ。同时,几种糖类物质减缓了重结晶虾仁的肌原纤维蛋白含量(106.10 mg/g～111.67 mg/g)、Ca~(2+)-ATPase活性(0.124 U/mg～0.136 U/mg)和总巯基含量(7.6 mmol/L～8.1 mmol/L)的下降速率。微观结构观察发现,相比于蒸馏水组,糖类处理后的虾仁肌肉结缔组织结构较为完整,肌束间空隙较小,且并未发生大面积扭曲、断裂现象,其对冻藏虾仁组织结构具有较好的维持作用。由上,低聚木糖、卡拉胶寡糖、海藻糖和海藻胶寡糖可作为冷冻虾仁的抗冻保水剂加以开发与利用。     

Precipitation location of secondary phase and microstructural evolution during static recrystallization of as-cast Ti-25V-15Cr-0.3Si titanium alloy

The microstructural evolution and precipitation location of the secondary phase of an as-cast Ti-25V-15Cr-0.3Si titanium alloy were investigated via isothermal compression experiments and heat treatment. The average aspect (length-to-width) ratio, average area and size of the grains at different heat treatment temperatures and holding time were analyzed and the effects of deformation and annealing time on the grain area and size were considered. It was found that the grain size was strongly influenced by the height reduction and holding time. Grain growth was significant when annealing time increased from 10 min to 2 h at 950 °C and height reduction of 30%; however, grain growth was minimal at annealing time between 2 and 4 h. Many dispersion particles were observed to form in continuous chains; the precipitation location was confirmed to be along initial grain boundaries, and the dispersion particles were identified to be Ti₅Si₃ phase by TEM.     

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。     

Fe基非晶合金增强1060铝基多层复合材料的组织与性能

采用累积叠轧焊+中间退火法复合轧制1060Al/Fe基非晶多层铝合金复合板材。利用光学显微镜、扫描电镜、X-衍射分析仪以及拉伸试验机分析Al基复合材料的微观组织结构变化、断口形貌、物相组成以及力学性能。结果表明:Fe基非晶复合材料的增强体在300 ℃中间退火过程中发生部分晶化,在累积变形轧制过程中发生破碎,并随着变形道次的增加,破碎程度随之增大;复合板前6道次的累积轧制变形出现了明显的加工软化现象,并且随着变形道次的增加,其加工软化的效果愈明显;随着累积轧制变形道次增加,Al基复合材料的力学性能发生了明显的变化,第2道次轧制变形后屈服强度与抗拉强度达到了最大值为140 MPa和156 MPa,伸长率为5.53%,达到最佳综合性能。     

Temperature Effects on the Microstructures of Mg-Gd-Y Alloy Processed by Multi-direction Impact Forging

A high strain rate multi-directional impact forging(MDIF) was applied to a solutionized Mg-Gd-Y-Zr alloy in the temperature range of 350-500℃.Results demonstrate that the dominant deformation mode is twinning at a temperature below 400℃,whereas at a medium temperature of 450℃ considerable continuous dynamic recrystallization was promoted by{10-12} extension twins.At a higher temperature of 500℃,twinning activation was suppressed.New DRX grains were observed but their sizes were much bigger than those resulting from the MDIFed 50 passes at 450℃,which are ascribed to the larger grain boundary mobility and atomic diffusion at 500℃.Moreover,a non-basal weak texture was gained afterward MDIF at each temperature,which is credited to the MDIF process and the minor strain applied in each pass.     

High temperature deformation behavior and microstructure evolution of wrought nickel-based superalloy GH4037 in solid and semi-solid states

Cylindrical samples of Ni-based GH4037 alloy were compressed at solid temperatures (1200, 1250 and 1300 °C) and semi-solid temperatures (1340, 1350, 1360, 1370 and 1380 °C) with different strain rates of 0.01, 0.1 and 1 s⁻¹. High temperature deformation behavior and microstructure evolution of GH4037 alloy were investigated. The results indicated that flow stress decreased rapidly at semi-solid temperatures compared to that at solid temperatures. Besides, the flow stress continued to increase after reaching the initial peak stress at semi-solid temperatures when the strain rate was 1 s⁻¹. With increasing the deformation temperature, the size of initial solid grains and recrystallized grains increased. At semi-solid temperatures, the grains were equiaxed, and liquid phase existed at the grain boundaries and inside the grains. Discontinuous dynamic recrystallization (DDRX) characterized by grain boundary bulging was the main nucleation mechanism for GH4037 alloy.     

Microstructure and tensile properties of rapid-cooling friction-stir-welded AZ31B Mg alloy along thickness direction

Rapid-cooling friction-stir-welding (FSW) was used to join AZ31B magnesium alloy plates of 6 mm in thickness. The microstructure and mechanical properties in thickness direction were carefully investigated with electron backscattered diffractometer, and transmission electron microscope. The obtained results showed that ultrafine grains with high dislocation density were obtained in the top region of the weld due to liquid CO₂ cooling. A large number of twins and second-phase particles were also induced in these refined grains. The basal texture intensity was significantly reduced due to the appearance of twins. The top region showed the higher strength and elongation compared with the bottom region, and the welding efficiency reached 93%. This work provided a simple and efficient strategy for manufacturing a gradient structure in the FSW Mg alloy joint.     

Ice Crystal Growth in Sucrose Solutions Containing Kappa- and Iota-Carrageenans

Measurements of ice recrystallization inhibition (IRI) and thermal hysteresis (TH) activities of kappa (κ)- and iota (ι)-carrageenans were carried out to examine whether they can be novel cryoprotectants or not. IRI measurements indicate that both carrageenans reduce recrystallization in sucrose solution, but that the IRI activity of κ-carregeenan is higher than that of ι-carrageenan. TH measurements indicate that κ- and ι-carrageenans do not exhibit TH activity. TH activity measurements of antifreeze glycoprotein (AFGP) in the presence of κ-carregeenan demonstrate that this carregeenan neither influences the TH activity of AFGP nor the shape of the ice crystals. The round ice crystal shape transformed into an angular and elongated shape in the presence of both carregeenans.     

热变形工艺对含硫非调质钢流变应力及组织的影响

在变形温度950~1150 ℃和应变速率0.01~5 s^-1下,通过Gleeble-3500热模拟试验机进行单道次压缩试验,研究了热变形工艺对含硫非调质钢F45MnVS流变应力及组织的影响。结果表明:随着应变速率的增大,热压缩过程中的峰值应力增加,随着温度的升高,峰值应力降低;动态再结晶平均晶粒尺寸随着应变速率、变形量的增加而减小,随着温度的提高而增大。     

IF钢退火过程中再结晶行为的EBSD表征

借助EBSD等技术研究了从冷轧到退火过程中IF钢中铁素体再结晶晶粒的取向演变。研究结果表明,从冷轧到退火过程中,铁素体晶粒取向向着平行于法向的[111]晶粒演变,而平行于法向的[100]晶粒逐渐消失;在冷轧变形过程中,铁素体晶粒的晶体取向决定着发生滑移变形的难易程度,与[100]晶粒相比,[111]晶粒更易于发生滑移变形,并在晶粒内部积累大量的位错,储存了大量的应变能,在随后的退火过程中,应变能较高的[111]晶粒优先形核并长大,优先发生再结晶,而应变能较低的[100]晶粒的再结晶受到阻碍。随着退火温度的升高,γ织构([111]//ND)明显增强,其织构组分(111)[112]尤为明显。