稀土钇强化Al-Zn-Mg-Cu铝合金的组织特征

在熔炼过程中以铝钇中间合金形式加入Y元素,研究0～0.30%范围内不同Y加入量对铝合金铸态和均匀化处理后凝固组织的影响.金相显微和扫描电镜检测结果显示:当Y的加入量在0.25%时,铸态组织中晶粒细化效果明显,晶粒度由基体的60～70μm下降到40～50μm,二次枝晶间距减小,晶界处的主要平衡相是T(AlZnMgCu)相和含Y相.经过450℃,12h的均匀化处理后,晶界不再粗大、连续,析出物呈点链状或长条状.对于0.25%Y-7055合金,晶界中析出相不再明显,晶界、晶内可见2～3μm的含Y相Al3Y和Al2Y,加Y后的合金组织材料性能得到改善.     

喷射成形高锌Al-Zn-Mg-Cu合金的时效行为

系统研究了喷射成形高锌Al-Zn-Mg-Cu合金在不同时效处理条件下的显微组织与力学性能.结果表明:自然时效合金在晶界处已析出强化相;单级时效合金随时效时间的延长,晶内和晶界析出相逐渐粗化;双级时效合金的析出相进一步粗化,并且晶界析出相为断续特征;回归再时效合金具有较细的晶内组织及类似于双级时效的晶界组织.同时发现,双级时效合金的抗拉强度比峰时效合金的强度下降了13%左右,而回归再时效合金的强度优于峰时效合金的强度.     

Cu基亚稳难混溶合金液-液相变

通过气体雾化技术研究了Cu100-XFeX (X=15, 20, 30和40)合金的凝固行为. 考虑少量相液滴形核、扩散长大、空间迁移、凝固界面与液滴间的相互作用以及体积分数等共同影响因素,建立了能描述该类合金凝固组织演变动力学模型. 将数学模型与雾化液滴飞行过程中运动、传热和传质的控制方程相耦合,给出了数值求解方法,模拟计算了Cu基亚稳难混溶合金液-液相分离过程. 结果表明:富Fe粒子的平均尺寸随着Fe含量的增加而增大;少量相液滴形核发生在基体熔体过饱和度峰值附近;随着冷却速度的增大,雾化液滴中少量相液滴的形核率增大,但平均半径减小;少量相液滴在Marangoni迁移和与固/液界面相互排斥共同作用下,向雾化液滴中心迁移,使雾化粉末最终形成壳型组织结构.     

液氮球磨制备Al-Zn-Mg-Cu纳米晶粉末及组织分析

利用液氮球磨技术制备了Al-Zn-Mg-Cu纳米合金粉末. 采用X射线衍射对材料在球磨过程中的固态相变、晶粒尺寸和微观应变进行了研究,利用金相显微镜和透射电镜观察了微观组织. 研究表明,随着球磨的进行,雾化粉末中的MgZn2第二相逐步减少,并最终完全超饱和固溶于α-Al之中. 低速(200 r·min-1)球磨10 h后仍有少部分粗晶存在于粉末心部;高速(400 r·min-1)球磨能够使粉末纳米晶粒更加均匀. 材料经过低速液氮球磨6 h以后平均晶粒大小稳定在45 nm,并保持到10 h不再变化;增加主轴转速到400 r·min-1继续球磨5 h后,粉末平均晶粒大小降到34 nm. 微观应变随着球磨进行呈现先增大后降低的趋势.     

TiAl-Nb合金相平衡转变及显微组织结构研究

采用定性定量衍射检测和金相检测法分析了Ti-Al和Ti-Al-Nb合金中的物相组成和显微组织结构特征,研究Nb元素的添加对Ti-Al-Nb合金物相组成、晶粒尺寸和分布等特征的作用和影响。结果表明,Nb元素能够促进合金结构中β相和α₂相的稳定性,抑制α相的生成和γ相的析出,扩展了α₂+γ两相区并使得γ相区右移。另外,Nb元素的添加在特定的成分范围内细化了合金的晶粒。     

Preparation of high-strength Al-Mg-Si-Cu-Fe alloy via heat treatment and rolling

An Al-Mg-Si-Cu-Fe alloy was solid-solution treated at 560°C for 3 h and then cooled by water quenching or furnace cooling. The alloy samples which underwent cooling by these two methods were rolled at different temperatures. The microstructure and mechanical properties of the rolled alloys were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and tensile testing. For the water-quenched alloys, the peak tensile strength and elongation occurred at a rolling temperature of 180°C. For the furnace-cooled alloys, the tensile strength decreased initially, until the rolling temperature of 420°C, and then increased; the elongation increased consistently with increasing rolling temperature. The effects of grain boundary hardening and dislocation hardening on the mechanical properties of these rolled alloys decreased with increases in rolling temperature. The mechanical properties of the 180°C rolling water-quenched alloy were also improved by the presence of β″ phase. Above 420°C, the effect of solid-solution hardening on the mechanical properties of the rolled alloys increased with increases in rolling temperature.     

升温固溶对Al-Zn-Mg-Cu合金组织与力学性能的影响

研究了7075合金升温固溶处理过程．结果表明升温处理可使极限固溶温度高于多相共晶温度,同时能避免过烧组织的形成,有效强化了残余结晶相的固溶,显著提高了7075合金的力学性能．通过强化固溶,7075合金的断裂和屈服强度可达660MPa和606MPa．     

放电等离子烧结制备Al-Zn-Mg-Cu纳米晶合金的组织

利用低温液氮球磨和放电等离子烧结工艺制备了块体纳米晶Al-Zn-Mg-Cu合金.采用X射线衍射(XRD)技术分析了材料的晶粒尺寸和微观应变,利用透射电镜(TEM)研究了合金微观组织的演变.结果表明:采用放电等离子烧结法制备的7000系纳米铝合金具有两种不同的纳米晶结构,以晶粒尺寸50～100nm的等轴晶为主,少量200～400nm的大晶粒为辅;烧结过程中发生再结晶及第二相析出,析出的第二相以η(MgZn2)为主,θ(Al2Cu)以及S(Al2CuMg))为辐.     

Al-Zn-Mg-Cu系高强铝合金显微组织的定量分析

借助于光学显微镜、SEM、EDS和MTS拉伸试验机等测试手段,研究Al Zn Mg Cu系新型高强铝合金不同制备工艺下断口形貌、显微组织及力学性能,利用定量金相技术对该合金中残留第二相尺寸、数量及圆滑度等特征参数进行较系统的定量分析.实验结果表明:制备工艺不同,合金中残留第二相的特征参数有较大差异,对合金的断裂韧性影响显著;通过制定合理的工艺参数,可达到控制显微组织和改善性能的目的.     

喷射沉积AlFeVSi合金热暴露过程中相转变与沉积态组织特点

采用喷射沉积工艺制备快速凝固AlFeVSi合金薄片和沉积管坯,通过示差热分析、X射线衍射分析、金相显微组织观察、透射电镜组织观察、硬度测试等检测手段,研究了喷射沉积AlFeVSi合金快凝薄片在高温热暴露过程中的相变和组织演变规律,并分析了喷射沉积AlFeVSi合金坯组织特点。结果表明,喷射沉积AlFeVSi快凝薄片基本上为呈微胞状的过饱和α-Al固溶体。加热温度低于500℃时,在高温热暴露过程中微胞状结构发生分解,α-Al过饱和固溶体脱溶,形成α-Al Al12(Fe,V)3Si(bcc,a≈1.260 nm)弥散颗粒的分解产物,当温度高于500℃时,Al12(Fe,V)3Si颗粒粗化聚集,并以独立形核长大的方式生成θ-Al13Fe4块状相。随着热暴露温度升高,喷射沉积AlFeVSi合金薄片的硬度呈下降趋势。喷射沉积AlFeVSi坯主要由α-Al固溶体和Al12(Fe,V)3Si颗粒组成,但也存在少量含粗大片状或块状相的非快速凝固组织。     

Microstructural characterization of as-cast and homogenized 2D70 aluminum alloy

The microstructure of the as-cast 2D70 aluminum alloy and its evolution during homogenization were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) analysis. The results indicate that the microstructure of the as-cast 2D70 aluminum alloy mainly consists of the dendritic network of aluminum solid solution and intermetallic compounds (Al₂CuMg, Al₂Cu, Al₉FeNi, Cu₂FeAl₇, and Al₇Cu₄Ni). After conventional homogenization, Al/Al₂CuMg eutectic phases are dissolved into the matrix, and a small amount of high melting-point eutectic Al/Al₂Cu phases exist in the matrix, resulting in an increase in the starting melting temperature. Under double homogenization, the high melting point Al/Al₂Cu phases are dissolved, and no obvious change is observed for the size and morphology of Al₉FeNi, Cu₂FeAl₇, and Al₇CuaNi compounds.     

喷射成形含锰高强Al-Zn-Mg-Cu的组织和性能

利用喷射成形和热挤压的方法制备了含锰为2%(质量分数)的高强铝合金Al-8.8Zn-2.9Mg-1.6Cu合金,用X射线衍射(XRD)、光学显微镜(OM)和扫描电镜(SEM)和透射电镜(TEM)等方法研究了铝合金的微观组织,并进行了力学性能测试.研究结果表明:喷射成形制备的含锰铝合金经过热挤压和固溶处理后,基体组织为细小均匀的再结晶晶粒组织,平均尺寸约8μm.MnAl6颗粒在喷射沉积过程中沿晶界析出,经过热挤压后,尺寸大的颗粒破碎,大部分的颗粒则沿挤压方向产生一定的塑性变形.固溶处理对MnAl6颗粒尺寸的影响不明显,但棒状/片状颗粒的边角处发生球化,有利于降低诱发显微裂纹的应力或应变集中.时效后,铝合金达强度为775MPa,延伸率达4.3%,断口以细小的韧窝为主,尺寸小于500nm.     

闪速磁化焙烧及铁矿物的微观相变特征

针对酒泉钢铁(集团)公司粒度小于0.30 mm的富含镜铁矿、褐铁矿和镁(锰)菱铁矿难选铁粉料,介绍采用闪速磁化焙烧动态试验装置开发我国难选低品位细粒级铁矿资源的试验效果;对闪速磁化焙烧前、后相关产品进行光学显微镜观察、XRD和EPMA检测分析,研究焙烧前后铁矿物的相变情况及微观特性.研究结果表明:在弱还原气氛和740～800 ℃条件下,通过60 s之内的闪速磁化焙烧处理,可获得铁品位为55.51%～55.35%的弱磁选铁精矿;弱磁性细粒铁矿物的相变均转变为龟裂较为发育的人造磁铁矿,产物中未见菱铁矿和强磁性的γ-Fe2O3;人造磁铁矿其镜下微观形貌与反光特征仍有差异,且由菱铁矿中的Mg和Mn特征元素含量有差别,可将其区分.     

Near-net shape processing of spherical high Nb-TiAl alloy powder by gelcasting

Spherical Ti-45Al-8.5Nb-(W,B,Y) alloy powder prepared by an argon plasma process was near-net shape by gelcasting. In the non-aqueous system, methaerylate-2-hydroxy ethyl, toluene, benzoyl peroxide, and N,N-dimethylaniline were used as the monomer, solvent, initiator, and catalyst, respectively. To improve sintering and forming behaviors, many additives were included in the suspension. The concentrated suspension with a solid loading of 70vol% was prepared. The high Nb-TiAl powder was analyzed by electron microscopy and X-ray diffraction. It was found that the green bodies had a smooth surface and homogeneous microstructure, exhibiting a bending strength as high as 50 MPa. After sintering at 1480℃ for 2 h in vacuum, uniform complex-shaped high Nb-TiAl parts were successfully produced.     

低温球磨制备纳米晶Al-Zn-Mg-Cu合金

利用低温液氮球磨技术制备了Al-Zn-Mg-Cu合金纳米晶粉末,并采用X射线衍射(XRD)对材料在球磨过程中的晶粒尺寸和微观应变进行了研究,利用扫描电镜(SEM)、透射电镜(TEM)和差热分析(DSC)等测试方法研究了材料的固态相变以及热稳定性.研究表明,粉末晶粒尺寸随着球磨的进行逐渐减小,球磨10h后晶粒尺寸达到45nm;微观应变随着球磨的进行逐渐增大.粉末球磨过程中,MgZn2相逐渐减少,合金元素过饱和固溶于α-Al晶格之中.球磨10h后仅有少量的MgZn2相存在.制备的Al-Zn-Mg-Cu纳米晶粉末在低于709K下加热,粉末晶粒长大速度较慢,表明Al-Zn-Mg-Cu纳米晶粉末具有较高的热稳定性.     

铸造高铌TiAl合金双态组织转变过程

通过对Ti-46Al-8Nb-2Mn-0.2B合金的铸态组织和经过a γ双相区热处理后的组织进行光学和扫描电镜进行观察,发现原始铸态组织的γ相偏析处不是片层的晶界,而是片层穿越的区域.由于γ相偏析区域的Al含量比片层基体高,因此阻碍了后续回火过程中该偏析部位片层的分解.通过先得到近γ组织,然后经过a γ双相区保温,最终得到晶粒为40μm的双态组织;但组织中有少量的β相没有得到消除.     

含合金元素γ-Fe晶胞价电子结构及其对相变过程的影响

利用固体与分子经验电子理论,对奥氏体中含合金元素γ-Fe晶胞的价电子结构进行了计算分析.结果表明,合金元素溶入γ-Fe晶胞后,其价电子结构发生了较大变化,Fe原子杂化态向较高杂阶迁移,其相结构因子均有不同程度的增加.同时晶胞内形成了由强键组成的八面体结构,阻碍了原子的移动,使得γ-Fe晶胞在相变过程中产生"类拖曳效应",提高过冷奥氏体的稳定性,亦会延缓马氏体相变的进程.     

钛合金深冷及冷-热循环处理研究

通过模拟空间特殊环境,对纯钛、TA7,TC4和TC10钛合金在深冷处理及冷-热循环处理环境下的显微组织及力学性能进行了研究;并进行了维氏硬度观察及金相组织、XRD,扫描电镜分析.结果表明:深冷及冷热循环处理可以改善钛合金的显微组织,也可以提高其力学性能,同时冷-热循环处理可以引起纯钛孪晶增生的现象.     

Microstructural characteristics and mechanical properties of Al-2024 alloy processed via a rheocasting route

This article reports the effects of stirring speed and T6 heat treatment on the microstructure and mechanical properties of Al-2024 alloy synthesized by a rheocasting process. There was a decrease in grain size of α-Al particles corresponding to an increase in stirring speed. By increasing the stirring speed, however, the globularity of matrix particles first increased and then declined. It was also found that the hardness, compressive strength, and compressive strain increased with the increase of stirring speed. Microstructural studies revealed the presence of nonsoluble Al₁₅(CuFeMn)₃Si₂ phase in the vicinity of CuAl₂ in the rheocast samples. The required time for the solution treatment stage was also influenced by stirring speed; the solution treatment time decreased with the increase in stirring speed. Furthermore, the rheocast samples required a longer homogenization period compared to conventionally wrought alloys. Improvements in hardness and compressive properties were observed after T6 heat treatment.     

Effect of rheo-diecast process on the mechanical properties of A390 alloy by serpentine channel

In this paper, the effects of rheo-diecast process parameters and T6 heat treatment on the microstructure and mechanical properties of the rheo-diecasting (RDC) semi-solid A390 alloy prepared through pure copper serpentine channel were investigated. The results indicate that the mechanical properties of the RDC samples change with the pouring temperature and injection pressure. In this case, a lower pouring temperature results in better tensile strength and elongation of the RDC A390 alloy; however, the tensile strength and elongation decrease when the pouring temperature decreases to 660°C. Higher injection pressures result in the improved mechanical properties of the RDC A390 alloy. To some extent, T6 heat treatment improves the tensile strength and ductility of the RDC A390 alloy compared to those of the non-heat treated alloy. However, when the pouring temperature and injection pressure are greater than 670°C and 70 MPa, respectively, the mechanical properties are sharply diminished.