INFLUENCE OF COMPOSITION AND DISPERSOID ON FATIGUE FRACTURE BEHAVIOUR OF Al-Mg-Si ALLOYS

A study was made of the fatigue fracture behaviour under different aging conditions of two Al-Mg-Si alloys with different chemical compositions and dispersoid contents.The dispersoid phase can alter the mode of the deformation uniformity of alloys.The dispersoid it- self may decohere from the dispersoid/matrix interface under cyclic stress to form small dimples.

Effects of dispersoid preforming via multistep sintering of oxide dispersion-strengthened CoCrFeMnNi high-entropy alloy

Dispersoid formation and microstructural evolution in an oxide dispersion-strengthened CoCrFeMnNi high-entropy alloy(HEA)using a newly designed multistep sintering process are investigated.The proposed multistep sintering consists of a dispersoid preforming heat treatment of as-milled 0.1 wt%Y_(2)O_(3)-CoCrFeMnNi high-entropy alloy powders at 800℃,followed by sintering at 800–1000℃ under uniaxial pressure.In the conventional single-step sintered bulk,the coarsened BCC Y_(2)O_(3)dispersoids mainly form with an incoherent interface with the HEA matrix.In contrast,finer FCC Y_(2)O_(3)dispersoids,an atypical form of Y_(2)O_(3),are formed in the matrix region after multistep sintering.Nucleation of FCC Y_(2)O_(3)disper-soids is initiated on the favorable facet,the{111}plane of the austenitic matrix,with the formation of a semi-coherent interface with the matrix during the dispersoid preforming heat treatment and it maintains its refined size even after sintering.It is found that dispersoid preforming prior to sintering appears promising to control the finer dispersoid formation and refined grain structure.

Dispersoid Formation and Recrystallization Behavior in an Al-Mg-Si-Mn Alloy

The nucleation and precipitation of Mn-containing dispersoids in an Al-Mg-Si-Mn alloy （6082） have been studied by optical microscopy,EPMA （electron probe microanalysis） and TEM （transmission electron microscopy）.The influence of Mn-containing dispersoids on the recrystallization behavior was also investigated.The size and distribution of dispersoids were strongly affected by both the homogenization process and the alloying element distribution formed in the direct chill cast procedure.The Mn-containing dispersoids were observed to nucleate preferentially on the β-Mg 2 Si phase and to be aligned along the 〈100〉 direction of the matrix.After cold deformation,the morphology of dispersoids greatly influences the recrystallization and grain growth behavior in the annealing process.

Improvement of elevated-temperature strength and recrystallization resistance via Mn-containing dispersoid strengthening in Al-Mg-Si 6082 alloys

The precipitation behavior of Mn-containing dispersoids in Al-Mg-Si 6082 alloys with different Mn contents(0,0.5 and 1.0 wt%)during various heat treatments(300–500℃)was investigated.The effects of dispersoids on elevated-temperature strength and recrystallization resistance during hot-rolling and post-rolling annealing were evaluated.The results showed that the dispersoids in the Mn-containing alloys(0.5 and 1.0%)began to precipitate at 350℃and reached the optimum conditions after 2–4 h at 400℃.However,the dispersoids coarsened with increasing holding time at temperatures above450℃.After the peak precipitation treatment at 400℃for 2 h,the yield strength at 300℃increased from 28 MPa(base alloy free of Mn)to 55 MPa(alloy with 0.5%Mn)and 70 MPa(alloy with 1%Mn),respectively,demonstrating a significant dispersoid strengthening effect at elevated temperature.In addition,the dispersoids were thermally stable at 300℃for up to 1000 h holding owing to its relative high precipitation temperature(350–400℃),leading to the superior constant mechanical performance at elevated temperature during the long service life.During hot rolling and post-rolling annealing,the presence of a large amount of dispersoids results in the higher Zener drag PZcompared with base alloy and then significantly improved the recrystallization resistance.The alloy containing 0.5%Mn exhibited the highest recrystallization resistance among three experimental alloys studied during the post-rolling process,likely resulted from the lower coarsening rate of dispersoids and the lower dispersoids free zone.

Size effect in the Al3Sc dispersoid-mediated precipitation and mechanical/electrical properties of Al-Mg-Si-Sc alloys

A significant size effect is found in the Al3 Sc dispersoid-mediated precipitation in an Al-Mg-Si-Sc alloy.When the Al3 Sc dispersoid size smaller than about 40 nm,β " precipitates nucleate directly on the coherent dispersoids and grow by sacrificing the latter.While the dispersoid size greater than^40 nm,Q' and U2 phases are additionally produced that nucleate on the dislocations induced by the semi-/incoherent dispersoids.Mechanical and electrical properties are highly sensitive to the Al3 Sc dispersoid-tuned precipitation.The co-precipitation of β",Q' and U2 phases leads to an obvious improvement in hardness and simultaneously in electrical conductivity.

The effects of Y pre-alloying on the in-situ dispersoids of ODS Co Cr Fe Mn Ni high-entropy alloy

Oxide dispersion strengthened CoCrFeMnNi high-entropy alloys(ODS-HEAs)were prepared using two different powder preparation methods classified by yttrium addition strategy to investigate the effects of in-situ and ex-situ oxide dispersoid formation on the microstructure and mechanical properties.Systematic micro structural analysis was carried out by X-ray diffraction(XRD),electron backscattered diffraction(EBSD),high-resolution transmission electron microscopy(HRTEM),atom probe tomography(APT),and small-angle neutron scattering(SANS).Cryo-milled powder analysis,grain structure evolution after spark plasma sintering,dispersoid characteristics,and matrix/dispersoid interface structure analysis of the insitu and ex-situ dispersoids within the high-entropy alloy(HEA)matrix were performed.The in-situ dispersoid formation was dominantly observed in the Y-alloyed ODS-HEA through the construction of a coherent interface relationship with complex chemical composition,leading to an increase in the Zener pinning forces on the grain boundary movement.ODS-HEA with in-situ oxide dispersoids enhanced the formation of ultrafine-grained structures with an average diameter of 330 nm at a sintering temperature of 1173 K.This study shows that the Y pre-alloying method is efficient in achieving fine coherent dispersoids with an ultra fine-grained structure,resulting in an enhancement of the tensile strength of the CoCrFeMnNi HEA.

均匀化退火工艺对Al-Zn-Mg-Cu-Zr高强合金第二相的影响

研究了不同工艺均匀化退火过程中Al-Zn-Mg-Cu-Zr合金中组织、低熔点结晶相和弥散相的演变规律。结果表明:铸态Al-Zn-Mg-Cu高强铝合金中主要结晶相为AlMgZnCu四元相,均匀化退火后该相部分消除。均匀化退火过程中,随着温度的提高及时间的延长,合金中的非平衡结晶相逐渐溶解,未溶结晶相的体积分数降低。弥散相Al3Zr的尺寸及分布取决于均匀化退火过程中的升温速度,在缓慢升温条件下,弥散相Al3Zr的尺寸细小,分布比较弥散,密度高,合金的电导率最低;随着升温速度提高,Al3Zr相的析出数量减少,尺寸增加,析出相的密度降低,合金的电导率升高。二段均匀化退火后,弥散相Al3Zr的尺寸更加细小,密度更高,平均直径为15 nm,密度为1.27×10^(15)/cm^(3)。

预处理对喷射沉积Al-Cu-Li合金中Al_(3)Zr粒子析出及再结晶行为的影响

本文为探究如何调控喷射沉积Al-Cu-Li合金中Al_(3)Zr粒子的析出以及其析出机制,通过扫描电镜、透射电镜和电子背散射衍射研究了预处理对喷射沉积Al-Cu-Li合金中Al_(3)Zr粒子的析出行为及其对再结晶的影响。研究结果表明,喷射沉积Al-Cu-Li合金中Al_(3)Zr粒子存在分布不均匀,其粒子数量密度在Zr原子过饱和度高的晶内更高,在过饱和度低的晶界附近更低;晶界附近和晶内均存在局部无沉淀析出带,且晶界附近存在少量粒子线性团簇。在均匀化过程中Zr原子与位错攀移之间发生交互作用使得Al3Zr粒子析出。在均匀化前热变形预处理增加了基体中位错数量进而促进了Al_(3)Zr粒子析出,改善了粒子分布,抑制了局部无沉淀析出带。相比于(573 K/12 h)退火预处理和673 K下压缩10%预处理,673 K下压缩30%预处理试样中Al3Zr粒子密度更高,分布更均匀,尺寸更小。经过热压缩和固溶处理后,3种热压缩试样大角度晶界占比分别为30.3%、21.6%和17.3%。本研究将为喷射沉积Al-Cu-Li合金的研发提供依据。

微量Mn对Al-Mg-Si合金微观组织与拉伸性能的影响

研究了微量Mn对Al Mg Si合金的微观组织与拉伸性能的影响。结果表明 :微量Mn在Al Mg Si合金中主要以粒状α Al15(FeMn) 3 Si2 弥散相的形式存在 ,尺寸为 12～ 2 10nm ,均匀、弥散分布在基体中 ,有效地钉扎位错和亚晶界 ,抑制合金热挤压变形过程中的再结晶 ;均匀化处理过程中微量Mn可促进长针状 β Al9FeSi相向粒状α Al15(FeMn) 3 Si2 相转变 ,这种含Mn的α相弥散颗粒可作为合金时效强化相 β′(Mg2 Si)的非均匀成核位置 ,促进 β′相的析出 ,从而强化合金 。

均匀化处理温度对6082铝合金组织和性能的影响

采用硬度、电导率测试、金相显微镜、X线衍射、扫描电镜、透射电镜和能谱分析技术,研究均匀化温度对合金组织和性能的影响。研究结果表明:铸态合金由α-Al固溶体和非平衡共晶相组成;490～510℃均匀化,Mg2Si相从过饱和固溶体中析出,在510℃以上均匀化,随着温度的升高,Mg2Si又逐步回溶到基体中,560℃均匀化,Mg2Si相和过剩单质Si完全溶解;随着均匀化温度的升高,非平衡析出物鱼骨状共晶形态逐渐消失,针状β-AlMnFeSi溶解、断裂,转变为具有更高(Mn+Fe)/Si比值颗粒状α-Al(MnFe)Si相,析出相在高温均匀化过程中聚集、球化;560℃均匀化,析出物的连续网状结构转变成链状结构,析出物演化为等轴粒状α-Al(MnFe)Si相。均匀化过程中合金中析出弥散α-Al(MnFe)Si相;在490～560℃保温6h均匀化处理,温度升高,合金的硬度和电导率分别升高和降低。

Al-Zn-Mg-Cu系超强铝合金的研究现状与展望

Al-Zn-Mg-Cu系超强铝合金因为高强度和高韧性,已作为轻质高强结构材料广泛应用于航空航天领域。该文主要介绍国内外高强铝合金的发展历程及最新研究进展,指出Al-Zn-Mg-Cu超强铝合金的研究经历了高强低韧→高强耐蚀→高强高韧耐蚀→超强高韧耐蚀4个发展阶段,认为调控晶界结构及晶界析出相状态已成为目前铝合金研究的重点;简要评述微观组织和晶界结构对超强铝合金性能的影响,并介绍超强铝合金弥散相和形变-热处理工艺的研究现状及其调控晶界结构和晶界析出相状态的原理。最后指出寻找新型弥散相和开发新型的形变-热处理工艺是提高超强铝合金性能的重要发展方向和途径。

均匀化时间对7085铝合金淬火敏感性的影响(英文)

采用末端淬火实验、光学显微镜(OM)、扫描电镜(SEM)和透射电镜(TEM)研究均匀化时间对7085铝合金淬火敏感性的影响。结果表明,均匀化时间从48 h延长至384 h,淬火敏感性有所增加,端淬试样经人工时效后硬度的最大差值从5.2%增加到6.9%。均匀化时间延长对晶粒组织没有影响,但促使T相的溶解,增加Al3Zr弥散粒子的尺寸,减小其密度。慢速淬火时,在晶内的Al3Zr弥散粒子上能观察到一些尺寸较小的淬火析出η相,这降低了时效后的硬度。Al3Zr粒子特征的变化对淬火敏感性影响很小。

分散聚合法制备聚丙烯酰胺水分散体

以丙烯酰胺为单体,采用分散聚合法制备了聚丙烯酰胺(PAM)水分散体。以PAM的相对分子质量和水分散体稳定性为指标,考察了分散介质类型、分散剂种类、引发剂种类及用量、单体含量、聚合温度、聚合时间和搅拌转速等因素对聚合反应的影响。实验结果表明,分散介质类型和分散剂种类是影响PAM水分散体稳定性的主要因素,选择乙醇-水为分散介质、聚乙烯吡咯烷酮为分散剂。采用正交实验确定了最佳合成条件:乙醇-水为分散介质(乙醇的体积分数为70%)、丙烯酰胺的质量分数为30%、引发剂偶氮二异丁腈用量为单体质量的0.3%、分散剂聚乙烯吡咯烷酮用量为单体质量的6%、搅拌转速200r/min、聚合温度80℃、聚合时间8h。在此条件下,可制得相对分子质量较高且稳定性较好的PAM水分散体。

Mn对Al-Mg-Si-Cu铝合金车身板组织和性能的影响

通过拉伸和埃里克森实验以及扫描电镜/能谱、透射电镜和金相分析,研究Mn的质量分数对Al Mg Si Cu铝合金汽车板显微组织、力学性能和成形性的影响·研究表明,随Mn质量分数增加,Al Mg Si Cu汽车板铝合金不可溶结晶相及弥散相粒子数量均增加,不可溶结晶相使合金组织纤维化对板材冲压成形性不利,弥散相粒子阻碍再结晶晶粒长大;提高Mn的质量分数,Al Mg Si Cu汽车板铝合金的强度增加,但延伸率和冲压成形性降低·

快速凝固耐热铝合金中的弥散相及其热稳定性

综述了快速凝固耐热铝合金中金属间化合物弥散相的研究现状 ,介绍了常见耐热铝合金中存在的弥散相、快速凝固工艺对弥散相形成的影响和弥散相的热稳定性及其影响因素。简要概述了弥散相的数量、分布。

单级及双级均匀化处理工艺对AA7150合金Al_3Zr弥散相析出的影响(英文)

用半定量电子探针、扫描电镜、透射电镜方法,分析了单、双级均匀化对AA7150合金中Al3Zr分布的影响。结果表明,在铸态条件下Zr在枝晶心部浓度高,枝晶边缘处浓度低。在均匀化温度460°C下处理20h并不足以改变其浓度梯度。当均匀化温度达到460～480°C时,在枝晶心部可获得大量的Al3Zr弥散相,且Al3Zr弥散相的尺寸随着单双级均匀化处理温度的升高而增大。

盐酸洛美沙星分散片及胶囊剂的健康人体药动学

目的研究健康志愿者单剂口服盐酸洛美沙星分散片及胶囊剂后的药物动力学特征。方法采用HPLC法测定血浆中洛美沙星浓度。结果符合一级吸收动力学的二房室开放模型 ,主要药动学参数为tmax为 (0 9± 0 4)h和 (1 1± 0 5 )h ;cmax为 (4 6± 0 9)mg·L-1和 (4 9± 1 1 )mg·L-1;t1/2 为 (7 0± 1 6)h和 (7 4± 1 1 )h ;AUC0 -t为 (2 9 1± 5 2 )mg·h·L-1和 (3 0 4± 5 4)mg·h·L-1;经统计学t检验无显著性差异 (P >0 0 5 )。盐酸洛美沙星分散片对盐酸洛美沙星胶囊剂的相对生物利用度为 96 6%± 1 4 5 %。

7085铝合金的热变形动态再结晶行为（英文）

通过电子背散射衍射(EBSD)、电子探针(EPMA)和透射电子显微镜(TEM)研究7085铝合金在温度573~723 K、变形速率0.01~10 s^(-1)条件热压缩时的动态再结晶行为。结果表明,在高Zener-Hollomon(Z)值时,动态回复是主要的软化机制;随着Z参数值降低,出现动态再结晶。在ln Z=24.01(723 K,0.01 s-1)热压缩时,动态再结晶分数最高,为10.2%。EBSD结果表明,再结晶晶粒出现在初始晶界附近,其取向与变形晶粒接近。应变诱发晶界迁移是最可能的动态再结晶机制。晶界附近的低密度Al_3Zr弥散粒子有利于应变诱发晶界迁移的发生。

制备Y_2O_3弥散铁素体合金粉末方法的研究

为了开发作为快增殖堆及聚变堆结构候选材料的ODS铁素体合金,采用氮气雾化方法制备Fe-Cr-Ti-W-V合金粉末。采用溶胶-凝胶法、沉淀法和化学浸润等方法向合金中添加Y2O3颗粒,对各种添加方法得到合金粉中的Y2O3的形貌、粒度、密度分布进行了分析与对比,结果表明:上述3种方法都可以成功地将Y2O3添加到铁素体基合金粉体中;采用溶胶-凝胶法弥散分布Y2O3,可获得Y2O3颗粒分布均匀、直径在50nm以下的颗粒约占总数的50%、颗粒的平均圆度为1.25的基本圆形的粉体。