用DSC测量葡萄糖溶液部分玻璃化转变温度的新方法

用差示扫描量热仪,采用经过退火处理的连续扫描法,以不同浓度(20％、45％)的葡萄糖溶液为研究对象,研究了退火温度对Tgf(部分结晶的玻璃化转变温度)的影响,给出了确定Tg'(部分玻璃化转变温度)的新方法．研究发现,不同退火温度下的Tgf不同．在-50℃以上退火,Tgf随着退火温度的增大而减小;在-50℃以下退火,Tgf随着退火温度的增大而增大,都有很好的线性关系．不同浓度的溶液具有相似的规律．提出从Tgf确定Tg'的方法: Tgf在-50℃上下随退火温度变化线的交点所对应的部分结晶玻璃化转变温度即为Tg'．使用该方法测得葡萄糖的Tg'为-55℃．

草莓玻璃化转变温度的DSC测量

在测量溶液的部分玻璃化转变温度时,往往无法直接测得溶液在最大冻结浓缩状态下的部分玻璃化转变温度(Tg’),而是测得部分结晶玻璃化转变温度(Tgf)。本文用差示扫描量热仪,采用不经过退火处理的连续扫描法、分步扫描法对草莓打浆液、榨汁草莓经抽滤的草莓汁液和浓缩掉三分之一水分的浓缩草莓汁进行了玻璃化转变温度的测量。研究发现,用同一种方法测得的三者的玻璃化转变温度相差不大。在-48℃以下退火,玻璃化转变温度随着退火温度的增大而增大,在-48℃以上退火,玻璃化转变温度随着退火温度的增大而减小,并有很好的线性关系,从Tgf确定Tg’的新方法是两侧Tgf的交点对应的温度为Tg’。得到草莓的Tg’为-52.8℃。

CSP微合金钢混晶问题分析

讨论了CSP生产铌微合金钢Q345C的化学成分和轧制工艺,并就其产生的混晶现象从理论和实践上加以分析,最后提出CSP生产铌微合金化钢板的有关建议。

Microstructure evolution and mechanical properties of ZK60 magnesium alloy produced by SSTT and RAP route in semi-solid state

The microstructure evolution and mechanical properties of a ZK60 magnesium alloy produced by the semi-solid thermal transformation （SSTT） route and the recrystallization and partial melting （RAP） route were studied, respectively. The microstructure evolution during partial remelting was studied at different temperatures for different time. The tensile mechanical properties of thixoformed components by the two routes at room temperature were examined. The results show that coalescence is dominant in the SSTT alloy and Ostwald ripening is dominant in the RAP alloy. Compared with the SSTT route, the RAP route can produce finer semi-solid microstructure under the similar isothermal holding condition. The microstructure of the RAP alloy is much more spheroidized compared with the SSTT alloy. Thixoforming for the ZK60 magnesium alloy produced by the SSTT and RAP route results in successful filling of the die, and the thixoforming process improves the mechanical properties of ZK60 magnesium alloy. The RAP alloy shows significantly advantageous mechanical properties over that of the SSTT alloy.

膏状蜂蜜的生产技术

膏状蜜又称精细结晶蜜。由于蜂蜜系过饱和溶液,结晶很难避免,通常蜂蜜由于晶核较少,在室温下结晶缓慢,形成的结晶颗粒都比较大,有时甚至凝为一个大结晶团,食用时不易倾倒,而且由于部分结晶的存在,结晶部分水含量很低,而未结晶部分水含量较高,因此在未结晶部分容易形成一个细菌繁殖的环境,常常引起发酵,使蜂蜜口味变坏。

加工方式对POE/EPDM二元共混体系相容性、结构及力学性能的影响

采用不同的共混方式(双螺杆挤出机共混和转矩流变仪共混)制备了乙烯-辛烯无规共聚物/部分结晶的三元乙丙橡胶(POE/EPDM)二元共混体系,采用差示扫描量热仪(DSC)、小角X射线散射(SAXS)、万能拉伸试验机对所制备的复合材料进行微观结晶结构及力学性能进行分析。结果表明,当POE与EPDM的共混比为50∶50时,采用转矩流变仪制备的复合材料具有两个熔融峰和两个结晶峰,产生两相分离结构。采用双螺杆挤出机制备的POE/EPDM共混体系只有一个结晶峰和熔融峰,两相的相容性更好;POE与EPDM的共混比为70∶30时,采用双螺杆制备的材料拉伸强度、断裂伸长率更大,而共混比为50∶50时,双螺杆和转矩流变仪制备的材料的拉伸强度、断裂伸长率差别不大。因此,采用转矩流变仪共混更有利于降低复合材料的永久形变。

POE-g-MAH含量对POE/EPDM复合材料相容性、结构及力学性能的影响

采用熔融共混的方式制备了乙烯-辛烯无规共聚物(POE)/三元乙丙橡胶(EPDM)复合材料,研究了相容剂马来酸酐接枝聚烯烃弹性体(POE-g-MAH)对复合材料的流动性,相容性,结晶结构以及力学性能的影响。结果表明,当添加少量的POE-g-MAH时复合材料的流动性略微增大,随着POE-g-MAH含量的增加,复合材料体系黏度增大,流动性变差;并且复合材料结晶峰半峰宽呈减小的趋势,晶体结构分布变窄。同时小角X射线散射(SAXS)结果说明,POE-g-MAH的加入对复合材料的层状堆积结构影响较小;动态热机械分析(DMA)测试表明,复合材料的储能模量和损耗模量随着POE-g-MAH增加而降低,然而,随着POE-g-MAH含量的增大,EPDM(包含POE)的转变峰略微向低温方向移动,且峰强有所增大,POE的α转变峰的强度呈下降趋势,说明复合材料的相容性得到改善;当加入7份的POE-g-MAH时,复合材料具有最佳的力学性能,在拉伸强度没有降低的条件下,断裂伸长率提高了。

Microstructure and tensile properties of AM50A magnesium alloy prepared by recrystallisation and partial melting process

Prior to thixoextrusion, the microstructural evolution of semi-solid AM50A magnesium alloy prepared by the recrystallisation and partial remelting (RAP) route was investigated.The effect of compressive ratio on microstructure of semi-solid AM50A magnesium alloy was studied.Furthermore, tensile properties of thixoextruded components were determined.The results showed that the occurrence of recrystallised grains was closely associated with the location of the first liquid formed above the solidus.With prolonging holding time, deformed microstructure was penetrated, causing fragmentation, which resulted in the decrease of average grain size.Moreover, prolonging holding time was favorable for the improvement of the degree of spheroidization due to the increase in the amount of liquid.With the increase in compressive ratio, the size of solid grain decreased, the degree of spheroidization was improved during partial remelting, and the tensile properties of thixoextruded AM50A components were improved.The tensile properties for AM50A magnesium alloy thixoextruded from starting material produced by the RAP route were better than those of the same alloy produced by die-casting and thixomolding.

Origin of the Volcanic Rocks Erupted in the Eastern Manus Basin：Basaltic Andesite-Andesite-Dacite Associations

There has been much recent interest in the origin of intermediate lava and several hypotheses are: 1) direct melting of the mantle under water-saturated conditions, 2) partial melting of altered crust, 3) fractional crystallization of parent magma, and 4) magma mixing of mafic magmas with dacitic/rhyolitic magmas. Volcanic rocks series ranging from basaltic andesite to dacite(SiO_2 ranges from 53.8 to 63.0 wt.%) from the eastern Manus Basin were detected for major and trace element compositions to understand their origin. Low H_2O contents, positive correlations of La-SiO_2 and Yb-SiO_2, oxygen isotope data and the indistinct change of trace element concentrations in oscillatory zoning of plagioclase phenocrysts rule out the models in which silicic lava results from direct melting of hydrous mantle, partial melting of altered oceanic crust or gabbros, and magma mixing, respectively. Besides, the geochemical data of whole rock and melt inclusions indicate that fractional crystallization plays a dominant role in generating the intermediate lava with subduction features.

The Law of Element Abundance Relationships in Igneous Rocks Petrogenetically Associated with Fractional Crystallization

Reported in this paper are:1)the law of element abundance relationships:element abun-dances are of power function with each other in an igneous rock petrogenetically associated with fractional crystallization,2)deduction of the law and relevant parameters:abundance relationship constant(a°) and phase constant? from Henry's law and the law of mass conservation,3)the data basis and evidence of the law of element abundance relationships,4)establishment of the equa-bions for element abundance relationships in igneous rocks formed from the same parental magma during the same fractional crystallization stage ,and all measurable parameters involved in the equations.

Effect of partial recrystallization on microstructure and tensile properties of NiFeCoCrMn high-entropy alloy

To obtain a balance between strength and ductility in NiFeCoCrMn high-entropy alloy, the degree of dislocation strengthening was tuned via partial recrystallization during traditional thermomechanical processing(cold rolling and recrystallization). The tensile properties in each state were then examined. Significant improvements in uniform elongation and work hardening rate, with decrease in yield strength and ultimate tensile strength, are associated with increase in the recrystallized fraction, i.e., reductions in the degree of strain hardening. In particular, recrystallized fractions of 37% and 74% are obtained by annealing at 650 ℃ for 10 min and 15 min, respectively, which results in yield strengths of 1003 MPa and 742 MPa and uniform elongations of 4% and 24%, respectively. The strengthening is due to the unrecrystallized grains with a high density of dislocations, whereas the ductility benefits from the presence of recrystallized strain-free grains.

Kinetics for static recrystallization after hot working of 0.38C-0.99Cr-0.16Mo steel

The restoration mechanisms for static recrystallization of work-hardened austenite were investigated by using double-pass compression tests performed on medium-carbon steel containing chromium and molybdenum. The softening fraction was defined by 2% offset method. The results show that Avrami exponent of about 0.21 is insensitive to deformation temperature, indicating that the action of steel grade should be considered. The time of 50% recrystallization (t0.5) decreases noteworthily with the increase of deformation temperature. Apparent activation energy for static recrystallization of 195 kJ/mol, which is close to that of vanadium microalloyed steel, is obtained by calculating. The increasing trend of the driving force for recrystallization is opposite to that of the deformation temperature, which is attributed to the number of operative slip system increasing as temperature increasing.

Nanowear of a Zr Based Bulk Metallic Glass/Nanocrystalline Alloy

The hardness, elastic modulus, nano-scratch resistance and wear depth for a bulk metallic glass of and its partial crystallization alloys have been measured by using nanoindentation method. The results showed that partial crystallization did not influence the reduced elastic modulus but increased the hardness, and then increased the scratch coefficient. The scratch coefficient increased linearly with increasing the hardness H but decreases when W>6.2GPa. Partial crystallization decreased evidently the wear depth, and when the load was large the wear depth decreased with increasing the hardness.

预退火温度对Ni-5%W合金立方再结晶织构的影响

作为制备高温超导涂层导体的金属镍基带,需要具有良好的立方织构,而轧制变形量和退火温度对金属镍基体立方织构的形成有很大的影响。采用电子背散射衍射(EBSD)技术研究了不同预退火温度对冷轧形变量为89%的Ni-5%W(原子分数)合金立方再结晶织构的影响。样品先在300和670℃预退火1 h,然后经10%小变形量冷轧,最后在900℃退火1 h。结果表明:预处理温度对于立方再结晶织构的形成有重要的影响,经300℃预回复和670℃部分再结晶退火之后的样品在最终退火后都形成了较高含量的立方织构,且预退火温度对立方晶粒的形核、数量和尺寸有重要作用,经部分再结晶退火之后的样品在最终退火后形成的立方织构含量明显高于经预回复的样品。分析认为,预回复和部分再结晶样品经小变形轧制后,使立方取向晶粒回复加快,增加了立方取向晶粒形核的优势,从而促进立方再结晶织构含量的增加。与此同时,由于部分再结晶预退火比预回复退火形成的立方晶核多,再经小变形量轧制后,通过尺寸优势和应变诱导晶界移动机制(SIBM),部分再结晶预退火得到更多的立方晶粒。

钢材混晶组织缺陷的形成机理及控制策略

混晶是钢材极易产生的一种内部组织缺陷,对于钢材的微观组织和综合力学性能有很大损害。消除混晶缺陷,实现组织均匀化控制是提升钢材综合性能的必然要求。首先明确了混晶的概念及其定量分析评价方法;其次结合已有的研究基础从钢材变形和加热过程出发揭示了混晶组织缺陷的形成机理,依据成因将其分为4类混晶组织以阐述混晶的特征,包括热变形时部分再结晶引起的混晶、低于临界变形量形变引起的混晶、组织均匀的钢材二次加热后出现的混晶和加热时异常不均匀长大引起的混晶;最后针对性地提出了有效控制策略,对于钢材生产过程提供理论性指导。

不同退火工艺下TWIP钢微观组织及力学性能演变

以在650℃温轧的Fe-24Mn-2Al-1Si-0.05C TWIP钢为研究对象,通过金相显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)、室温拉伸等实验手段,研究温轧TWIP钢在回复退火、部分再结晶退火、高温短时退火以及高温退火等不同退火工艺下其微观组织及力学性能的演变。结果表明,随着退火工艺的改变,实验钢的微观组织由回复退火时包含高密度位错、形变孪晶等的变形晶粒逐渐向高温退火时的无畸变再结晶晶粒转变;而部分再结晶退火时,实验钢的微观组织由未再结晶区的变形晶粒和细小的再结晶晶粒混合组成。随退火工艺的改变,实验钢拉伸前、后的硬度变化趋势为先下降然后基本不变最后上升;实验钢的变形机制逐渐由位错滑移为主向孪生滑移为主转变。

高强钢冲击功分析和改善

500 MPa级高强钢-20℃冲击功均值为18 J,针对冲击功不合格的高强钢,利用金相显微镜检测钢板组织,发现铁素体尺寸大小差异大、表面和芯部组织差异大,且芯部有少量珠光体。分析认为铁素体尺寸不均产生的原因是精轧第三机架轧制后发生了部分再结晶,造成奥氏体尺寸不均,并遗传至铁素体。芯部少量珠光体是由于卷取温度较高、冷速慢造成奥氏体发生了珠光体转变。通过提高精轧速度和降低卷取温度解决了500 MPa级高强钢冲击功不合格的问题。