Effects of Sb and heat treatment on the microstructure of Al-15.5wt%Mg_2Si alloy

The modification effects of alloying element Sb and heat treatment on Al-15.5wt%Mg2Si alloy were investigated by Olympus microscopy （OM）, scanning electron microscopy and energy disperse spectroscopy （SEM-EDS）, and X-ray diffraction （XRD）. It is found that Sb plays a significant role in shaping primary Mg2Si phase and eutectic Mg2Si phase in Al-15.5wt%MgzSi alloy. The Sb addition of about 1.0wt% makes the resultant alloy show the finest primary Mg2Si phase and the eutectic Mg2Si phase with well distribution. But further increasing the Sb content decreases the amount of primary Mg2Si phase, and some segregated phases appear at regions between the grains. In addition, heat treatment can modify the microstructural feature of Sb-modified Al-15.5wt%Mg2Si alloy in terms of obviously shortening the nodulizing time of primary Mg2Si phase and eutectic Mg2Si phase.

Influence of Water and Humidity on Wood Modification with Lactic Acid

Impregnation of dry wood with pure lactic acid oligomers(OLAs)followed by heat treatment confers promising properties to wood because of OLA’s good diffusion,in-situ polymerization and persistence in cell walls.Treatment provides drastic reduction of the equilibrium moisture content,high dimensional stability and good durability.The presence of water during treatment has been evaluated.Curing of OLA impregnated dry wood in humid atmosphere leads to a strong and global degradation of the material.OLA treatment of wet wood only impacts the water leaching rate negatively.Treatment of dry wood with OLA diluted in water additionally decreases the biological resistance and is not efficient for decreasing hygroscopicity.Treatment of dry wood with lactic acid solution leads to a lower polymerization level but confers good properties.

Effects of solution heat treatment on microstructure and mechanical properties of AZ61-0.7Si magnesium alloy

The effects of solution heat treatment on the microstructure and mechanical properties of AZ61-0.7Si magnesium alloy were investigated.The results indicate that the solution heat treatment can modify the Chinese script shaped Mg2Si phases in the AZ61-0.7Si magnesium alloy.After being solutionized at 420℃ for 16-48 h,the morphology of the Mg2Si phases in the AZ61-0.7Si alloy changes from the Chinese script shape to the short pole and block shapes.Accordingly,the tensile and creep properties of the AZ61-0.7Si alloy are improved.After being solutionized at 420℃ for 24 h and followed by aging treatment at 200℃ for 12 h,the heat-treated alloy exhibits relatively high tensile and creep properties than those of the as-cast alloy.

Effect of holding time on microstructure of Mg-9Al-1Si alloy during semisolid isothermal heat treatment

The effects of isothermal holding time on the semisolid microstructure of Mg-9Al-1Si(mass fraction,%)alloy were investigated.The research results indicate that the Mg-9Al-1Si alloy with non-dendritic microstructure can be produced by the semi-solid isothermal heat treatment.With holding time varying from 5 to 30 min,the volume fraction of liquid is gradually enlarged from 29.3%to 38.6%,the morphology ofα-Mg grains changes from initial dendritic shape to spherical types and their average sizes increases from 41.1 to 56.1μm.In addition,during the isothermal heat treatment,the eutectic Mg2Si phase changes from the initial Chinese script shape to granule and/or polygon shape in Mg-9Al-1Si alloy.The modification of Mg2Si phase is possibly attributed to a shift of the eutectic composition of the liquid in semi-solid slurries,towards lower silicon contents with increasing Al content due to a redistribution of Al during isothermal heat treatment.

不同晶化温度对硅锰渣铸石的内部温差、析晶和物理性能的影响规律

以硅锰渣为主要原料,采用熔渣冷却析晶一步法(铸石浇铸法),在800、900、1000和1050℃四个不同晶化温度,分别制备了规格为ϕ100 mm×20 mm的铸石样品CT-800、CT-900、CT-1000和CT-1050,通过构建实验装置,测试了熔渣在成型和热处理全过程中心与边缘温度变化规律,并结合X射线衍射(XRD)、差示扫描量热分析(DSC)、扫描电子显微镜和能谱(SEM–EDS)等手段,分析了不同晶化温度对铸石中心和边缘的温差、析晶与物理性能的影响规律.研究表明:以硅锰渣为主要原料在900~1050℃保温析晶可以制备出满足天然花岗岩建筑板材标准(GB/T18601—2009)的铸石,晶相为辉石、黄长石以及硫化锰.CT-1000和CT-1050铸石析出更多和更大尺寸的晶相,存在微观孔隙和宏观缩孔,降低了其力学性能.CT-900具有最佳性能,而CT-800以玻璃相为主,热处理后发生断裂.在本实验条件下,最大温差(32℃)发生在把熔渣倒入模具的凝固成型阶段,且晶化温度越低,温差越大.CT-1000和CT-1050析晶阶段存在的大量析晶放热导致温差二次增大,延长了中心和边缘温度一致的时间.硫化锰是高温熔融态下析出晶相,易于氧化分解,快速冷却的边缘存在更多硫化锰相.黄长石较辉石在更高的温度下析出,较高的晶化温度处理样品和相同晶化温度下样品的中心部分均存在相对更多的黄长石相.

Enhanced high-temperature mechanical properties of laser-arc hybrid additive manufacturing of Al-Zn-Mg-Cu alloy via microstructure control

Recently,rapid and cost-effective additive manufacturing solutions for lightweight aluminum alloys with excellent high-temperature mechanical properties have been increasingly in demand.In this study,we combined laser-arc hybrid additive manufacturing with solution and artificial aging treatments to achieve Al-Zn-Mg-Cu alloy with favorable high-temperature strength via microstructure control.Hydrogen pores became the major defect in the as-deposited and heat-treated specimens.The continuous distribution of eutectics with hard-brittle characteristics at the grain boundaries was destructed following heat treat-ment.High-densityηprecipitates were uniformly dispersed in the heat-treated Al-Zn-Mg-Cu alloy,whereas appeared coarsened and dissolved at 473 K,owing to the rapid diffusion of Zn and Mg.The average 0.2%yield strength(318±16 MPa)and ultimate tensile strength(362±20 MPa)at 473 K af-ter heat treatment were enhanced by approximately 58%and 51%,respectively,compared to those of the as-deposited specimen.In addition,theηprecipitates contributed to lattice distortions and strain fields,which prevented dislocation motion and increased slip deformation resistance at high temper-atures.The as-deposited specimen exhibited intergranular fracture at 473 K,with cracks preferring to propagate along the aggregated eutectics.However,crack propagation proceeded in the sections with more pores in the heat-treated specimen.Our approach may provide a valid option for achieving alu-minum alloys with excellent high-temperature mechanical properties.

一种基于蛭石的多维度改性研究

基于蛭石特有的层状结构及高温膨胀特性,研究不同浓度、不同种类的无机盐添加剂对不同粒径蛭石的改性影响,从多维度提高改性蛭石高温下的膨胀倍数,并进行微观形貌和物相组成分析。研究结果表明:在相同温度条件下,添加NaHCO_(3)和KCl无机盐的改性蛭石体积膨胀率高于未改性蛭石。当添加相同浓度的NaHCO_(3)和KCl时,随着蛭石粒径从0.2 mm增加到0.8 mm,在100—900℃温度范围内,改性蛭石的体积膨胀倍数随温度升高而增加,随粒径增加而增加,且添加KCl的改性效果优于添加NaHCO_(3)。随着这2种无机盐添加剂浓度的逐渐增加,改性蛭石的膨胀倍数均呈现先增加后降低的趋势。

豌豆蛋白物理改性技术研究进展

豌豆作为一种低致敏性、高营养价值植物蛋白的重要来源,近年来受到了人们的广泛关注。然而,受自身结构和工业化制备过程影响,豌豆蛋白的溶解性、乳化性、起泡性等功能特性较差,无法满足食品市场的需求。为此,多种改性技术被开发,以改善其功能特性。本文系统性综述豌豆蛋白物理改性技术的研究进展,并展望豌豆蛋白物理改性技术的发展,为豌豆蛋白在食品工业中的应用提供依据。

Low-Carbon,Mn-Si Cast Steel Structure Modification by Fluidized Bed Heat Treatment

The effect of fluidized bed heat treatment (FBHT) on low-carbon Mn-Si cast steel strength properties improvement,strictly ductility is shown in this paper.Fluidized bed heat treatment variants are chosen in order to eliminate the structure defaults after a crystallization process.FBHT parameters are set considering an initial state material chemical composition,structure morphology and application criterion after heat treatment.The results are verified according with the standard BS 3100:1991 recommendations.Fluidized bed heat treatment variants are chosen mainly in order to the Widmanst tten ferrite structures elimination,carbides morphology modification and matrix optimum performance properties achievement.The ZG35SiMn (EN:L30GS) FBHT processes results are verified by the metallographic researches,hardness/microhardness measurements and tensile strength examination.

Effect of vanadium on modification of inclusions in Mn-and Si-deoxidized steel during heat treatment at 1 473 K

The effect of vanadium （V） on the modification of oxide inclusions in steels with different concentra- tions of Mn, Si, and V was determined before and after heat treatment at 1473 K. Changes in the morphology, size, and composition of these inclusions were analyzed. Equilibrium relations between the inclusions and steels at 1873 K and 1473 K were calculated using available thermodynamic data to roughly approximate the stable oxide inclusions in the steels, The results revealed that the concentra- tions of V and Si in the steel are critical for controlling the modification of the inclusions during heat treatment at 1473 K. MnO-SiO2-type oxide inclusions gradually transformed into MnO-V2O3-type or Mn-SiO2- and MnO-V2 O3-type inclusions in low Si high-V steels heat-treated for 60 min, In addi- tion, the morphology of the inclusions changed from spherical to irregular. A Si-accumulated zone and a V-depleted zone formed close to the interface in the steel matrix. The experimental and calcula- tion results indicated that, during the heat treatment, an interface chemical reaction occurred be- tween the Fe-Mn-Si-V steel and the MnO-SiO2 type oxide inclusion.

热处理对小麦粉品质特性影响的研究进展

热处理常用于小麦及小麦粉的杀菌、钝酶、脱毒、干燥以及改性,是小麦储藏与加工过程中常用的物理方法。研究发现,适当的热处理可显著改善小麦粉的营养品质、理化特性及储藏稳定性,而不当的热处理则对小麦粉的加工品质有不利影响。本文总结了热处理在小麦中的应用研究概况,分析了不同热处理方式在处理过程中对小麦粉结构及品质特性的影响,结果认为,热处理主要通过影响淀粉的表面结构、结晶区域、淀粉链结构,蛋白质的分子结构以及基质间的相互作用来影响小麦粉的粉质、糊化特性等加工品质。

干热处理改性谷物淀粉的研究进展

谷物是人类主食的加工原料,淀粉是谷物最基本的组成成分。干热处理作为一种简便、绿色的物理改性方法,不仅可以有效改善谷物淀粉的特性,而且能够提升谷物食品的品质,是近年来淀粉改性研究的热点之一。该文综述了当前谷物淀粉干热改性的相关研究,总结了淀粉干热改性的原理与方法,论述了干热改性对谷物淀粉组成结构及理化性质的影响,阐述了共存成分(离子胶、氨基酸、小分子糖等)辅助干热改性谷物淀粉的有益效果,简述了谷物淀粉干热改性在食品工业中的应用情况,分析了谷物淀粉干热改性研究中存在的主要问题,并对未来的研究进行了展望。

稀土及热处理对GCr15轴承钢中夹杂物特征的影响

为降低夹杂物对轴承钢疲劳性能的危害,比较研究了稀土Ce及热处理对GCr15轴承钢中夹杂物的改性行为。研究发现:稀土处理使钢中夹杂物球化、平均尺寸降低,有助于降低铝脱氧轴承钢中夹杂物的危害;热处理(1250℃)同样可以球化、细化钢中的夹杂物,夹杂物的平均尺寸、长宽比、面积分数随热处理时间(0~330 min)的增加均呈下降的趋势,继续延长热处理时间(330~510 min),铝脱氧轴承钢中大尺寸夹杂物比例增加,稀土轴承钢中球状Ce-Al-O-S均质夹杂转变为富Al相和富Ce相的非均质夹杂,对轴承钢疲劳性能危害大。在该研究条件下,铝脱氧轴承钢及稀土轴承钢热处理330 min时夹杂物特征最优。

木材压缩变形固定处理技术研究进展

压缩密实化是木材提质增优的处理方法之一。木材作为一种具有形状记忆效应的天然有机高分子材料,当被压缩或弯曲后,在温度和湿度等环境因子的影响下容易发生蠕变回复。木材压缩变形的回复对木材制品的尺寸稳定性和力学性能均有重要的影响,研究木材压缩变形固定处理技术对木材加工改性和高效利用具有重要指导意义。概述了木材压缩变形固定处理技术在国内外的研究进展和现状,重点梳理归纳了水热(蒸汽)预处理、压缩后热处理以及化学处理对木材压缩变形固定的研究进展。在此基础上,分析和提出了木材压缩变形固定处理技术的思路和未来发展方向,以期为压缩材的高效加工利用提供科学指导。

热杀菌期间胰蛋白酶改性对蛋清液耐热性和结构特性的影响

为提高蛋清液的巴氏杀菌温度,开发具有较高耐热性的蛋清液,探究胰蛋白酶改性对蛋清液耐热性和结构特性的影响。本研究设置未改性组和酶改性组,以25℃蛋清液为对照,4种不同热杀菌温度为实验组(56、62、68℃和72℃处理3 min),采用浊度和上清液蛋白含量2个指标衡量蛋清液耐热性的变化,利用表观黏度、粒径、表面疏水性、傅里叶变换红外光谱、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE)和扫描电子显微镜(scanning electron microscope,SEM)等对蛋清蛋白结构进行表征。胰蛋白酶改性能显著降低蛋清液浊度,提高上清液的蛋白含量(P<0.05)。随着热杀菌温度提高,蛋清液的浊度逐渐增加,上清液蛋白含量逐渐减少,粒子大小也逐渐增大。在相同热杀菌温度时,与未改性蛋清液相比,酶改性蛋清液的浊度和表观黏度显著降低,同时表面疏水性显著升高(P<0.05),粒径分布接近正态分布。酶改性可抑制蛋白热聚集,改善耐热性。SEM结果显示酶改性使蛋清蛋白表面孔隙增多,颗粒更加分散,在同一热杀菌温度时,表面保留的颗粒数量明显多于未改性蛋清。SDS-PAGE分析显示酶改性后蛋清中大分子蛋白发生降解。傅里叶变换红外光谱显示,在低于68℃条件时,酶改性蛋清液α-螺旋结构的相对含量显著高于未改性蛋清液(P<0.05),无规卷曲结构相对含量明显低于未改性蛋清液。综合分析,胰蛋白酶可有效改善热杀菌过程中蛋清蛋白热聚集,提高蛋清液的耐热性,对扩大其销售半径有重要意义。

含铜马尾松热处理锯材的防霉特性

以大尺寸马尾松锯材为研究对象,预先用含铜浸渍液处理锯材后,再结合木材热处理技术,基于液相还原反应原理使马尾松锯材内原位生成纳米单质铜,制得含铜马尾松热处理锯材,并采用XRD、XPS、糖分含量分析、pH分析技术手段,研究含铜马尾松热处理锯材内不同位置木材的防霉效果和防霉机制。研究发现,含铜马尾松热处理锯材S1层霉变防治效力大于66.75%,S2层霉变防治效力达到100%,S3层霉变防治效力处于90%~100%之间,而且防霉效果远高于不含铜马尾松热处理锯材,因此含铜浸渍液处理提高了马尾松热处理锯材的防霉效果。经pH、XPS、XRD和糖分含量测试分析结果表明,含铜浸渍液处理后使木材环境由酸性变成碱性,并且木材中的含铜化合物在高温下经还原生成纳米铜,碱性环境和纳米铜粒子的生成都有效抑制了霉菌的生长,提高防霉效果;同时马尾松热处理锯材的糖分含量因受到热处理温度和内含金属盐的影响发生降解而减少,这些变化均会导致防霉变效果的变化。本研究可为大尺寸马尾松锯材实际生产中的防霉技术和热处理技术提供有效数据支撑,对大尺寸锯材的高效和高价值利用具有重要意义。

钢中硫化锰夹杂控制的机理分析与工业实践

钢中MnS夹杂的控制是一个涉及到包括冶炼、凝固、加热和轧制过程等多工序,需要多变量协同控制的系统工程。详细论述了国内外MnS夹杂的研究现状,阐述了不同元素、热处理和轧制工艺对MnS夹杂的影响机理;整理总结了当前MnS夹杂的工艺控制措施,通过采用合适的脱氧工艺提高凝固前沿氧含量、降低精炼渣碱度、采用合适的钙处理工艺、采用低碱度中间包覆盖剂、提高二冷水量加强冷却、降低电磁搅拌强度等方式能够有效地控制MnS夹杂形貌、尺寸和数量。近年来,针对MnS夹杂的变性处理和弥散化分布等控制难点,提出了一些新思路,即向钢液中添加Mg、Ca-Mg、Zr、Ce、Te等元素能够有效控制钢中MnS夹杂形貌、尺寸和数量。

高硼高速钢研究进展

高速钢是一种具有高硬度、高耐磨性、高耐热性和优良红硬性的工具钢,然而由于合金元素价格高,其使用范围受到很大限制。在高速钢生产中以廉价的硼替代钨、钼、钒、铌等贵重金属制得的高硼高速钢既降低了成本,又能保证优异的硬度、耐磨性、强韧性、抗高温氧化性。本文综述了合金化、变质处理和热处理对高硼高速钢组织和性能影响,最后对高硼高速钢未来的发展进行了展望。

杨木脲醛树脂浸渍材及其热处理材胶合性能研究

研究了3种胶黏剂胶合杨木脲醛树脂浸渍材及其蒸汽热处理材的胶合性能。结果表明,胶黏剂的种类、改性木材种类、木材纹理方向及木材组合方式对剪切强度和木破率均有影响。对浸渍材-浸渍材组合时,使用聚氨酯胶黏剂,并采用弦切面-弦切面的胶合方式,剪切强度和木破率最高。

汽车用ZL101铝合金复合稀土变质与热处理工艺研究

采用显微组织观察、拉伸试验研究了ZL101铝合金的Ce-La复合稀土(Ce含量65%,La含量35%)变质与热处理工艺。结果表明:添加0.05%复合稀土对ZL101铝合金进行变质处理,可以有效减小合金中α-Al二次枝晶间距,细化共晶Si组织;与未变质的ZL101铝合金相比,变质处理的ZL101铝合金的抗拉强度、屈服强度和伸长率分别提高了6.5%、4.5%和47.1%。对其进行540℃×4 h固溶+170℃×8 h时效处理后,ZL101铝合金组织中共晶Si相呈颗粒状,均匀分布在晶界处,其抗拉强度、屈服强度和伸长率分别达到306 MPa、231 MPa和6.3%,综合力学性能匹配最好。