Al-5Zr中间合金初生Al_3Zr相三维形貌及其对浇注温度的依赖性

采用熔盐反应法制备了Al-5Zr中间合金并利用强碱腐蚀获得了初生Al_3Zr相的三维形貌,分析了Al_3Zr相的长大机理,研究了降温过程中浇注温度(1250、1050、950、800℃)对合金中初生Al_3Zr相三维形貌、尺寸及数量的影响,利用JMat Pro软件和面积法分别计算了Al-5Zr中间合金的理论固相率和实际固相率。结果表明:Al-5Zr中间合金中,Al_3Zr相的三维形貌呈现厚板状、薄片状、花瓣状及搭桥状等形貌,这些形貌的形成可以追溯到二维晶核和成分过冷综合作用机制。随着浇注温度降低,Al_3Zr相形貌由薄片状逐渐转化为厚板状,薄片相尺寸减小、数量减少;厚板相尺寸增大、数量增多,两种形貌相的总数量减少。利用JMat Pro软件计算的合金理论固相率与面积法计算的合金实际固相率基本吻合。从合金固相率看,随着浇注温度降低,厚板Al_3Zr相的相对含量增多。     

Al-9.0Zn-2.5Mg-2.5Cu-0.15Zr-0.2Sc合金中Al3(Sc,Zr)粒子的析出行为

采用金相显微镜、扫描电镜、透射电镜和能谱分析,研究了Al-9.0Zn-2.5Mg-2.5Cu-0.15Zr-0.2Sc合金中Al3(Sc,Zr)粒子的形貌及其细化合金铸态组织、提高合金性能的机理.从熔体中析出的一次Al3(Sc,Zr)粒子是α(Al)固溶体的有效形核剂,该粒子以亚稳的Ll2型Al3Zr为核心,形成富钪与富锆Al3(Sc,Zr)层相间排列的多层复合结构;铸态合金退火后,α(Al)基体内析出二次Al3(Sc,Zr)粒子,经450℃×3 2h退火,二次Al3(Sc,Zr)粒子尺寸为16 ～ 23 nm,与α(Al)基体完全共格,该粒子钉扎位错和亚晶界,阻碍合金再结晶过程,提高合金再结晶温度;合金经RRA处理后,抗拉强度、伸长率和电导率分别为:667.5 MPa、7.5％和37.8％ IACS,具有良好的综合性能.     

Al-Zn-Mg-Cu-Zr-Sc合金铸态Al3(Sc，Zr)相形貌的研究

采用金相显微镜、扫描电镜和能谱分析,研究Sc细化Al-Zn-Mg-Cu-Zr合金铸态组织的机制和一次Al3(Sc, Zr)粒子的形貌特征。结果表明：从熔体中析出的Al3(Sc, Zr)一次粒子是α(Al)固溶体的有效形核剂,该粒子以亚稳的L12型Al3Zr为核心,形成富钪与富锆Al3(Sc, Zr)层相间排列的多层复合结构。在Al-9.0Zn-2.5Mg-2.5Cu-0.15Zr合金中添加0.20%~0.60%（质量分数）的钪,合金的铸态组织由粗大的树枝晶变为等轴晶,随着钪含量的增加,合金铸态组织得到进一步细化。     

Al-Zn-Mg-Cu-Zr-Sc合金铸态Al3(Sc，Zr)相形貌的研究

采用金相显微镜、扫描电镜和能谱分析,研究Sc细化Al-Zn-Mg-Cu-Zr合金铸态组织的机制和一次Al3(Sc,Zr)粒子的形貌特征。结果表明:从熔体中析出的Al3(Sc,Zr)一次粒子是α(Al)固溶体的有效形核剂,该粒子以亚稳的L12型Al3Zr为核心,形成富钪与富锆Al3(Sc,Zr)层相间排列的多层复合结构。在Al-9.0Zn-2.5Mg-2.5Cu-0.15Zr合金中添加0.20%～0.60%(质量分数)的钪,合金的铸态组织由粗大的树枝晶变为等轴晶,随着钪含量的增加,合金铸态组织得到进一步细化。     

控冷环缝电磁搅拌对Al-Zn-Mg-Cu合金初生Al3Zr相及组织的影响

通过对比施加与未施加控冷环缝式电磁搅拌(IC-AEMS)熔体均匀化处理技术,对Al-Zn-Mg-Cu合金初生Al3Zr相的析出行为以及组织细化的影响进行了研究。结果表明,施加IC-AEMS后,Al3Zr粒子形貌从大尺寸针状与板状变成细小弥散分布的块状;此外,相比未施加IC-AEMS处理的Al-Zn-Mg-Cu合金的凝固组织,施加IC-AEMS后,合金细化效果与组织均匀性得到提高,平均晶粒尺寸由387μm减小至218μm。     

Al-25％Si合金过热处理后的凝固行为和组织研究

研究了熔体过热温度、冷却速度及浇注温度对Al-25％Si合金凝固形核温度、初生硅尺寸和数量分布的影响.结果显示,过热温度增加、冷却速度增大均会影响初生硅形核温度.随过热温度升高,形核温度增加,直至1 000℃过热后形核温度降低.增加冷却速度使形核温度进一步升高.不同冷却速度下,初生硅相尺寸和数量随过热温度增加以相同规律变化,1 000℃时尺寸细化达到最小值,数量达到最大值.冷却速度对初生硅尺寸的影响与过热温度有关,低过热温度下,增加冷却速度有利于初生硅相尺寸细化,过热温度升高,冷却速度对尺寸的影响逐渐减小.熔体过热处理对初生硅相的影响还与浇注温度有关,降低浇注温度,初生硅尺寸粗化,同时硅颗粒数量减少.Al-25％Si合金熔体高温过热处理后在850℃浇注,能够将初生硅相尺寸细化至30μm以下.     

Al-Cu-Zr和Al-Cu-Zr-Ti-V合金中Al_3Zr析出相的析出行为

利用透射电子显微技术研究Al-Cu-Zr和Al-Cu-Zr-Ti-V合金中Al3Zr的沉淀析出行为。亚稳态的Al3Zr沉淀相在枝晶中心均匀形核并获得均匀分布。然而,在枝晶边缘区域的析出复杂,观察到由许多球形Al3Zr析出颗粒组成的螺旋状和条状的形貌。条状的沉淀团簇沿100铝方向优先排列,这可能与Al2Cu的亚稳态θ′和稳态θ析出相相关。添加铜有利于Al3Zr沉淀相从L12→D023的结构转变。     

微量元素Zr+Sc与凝固速度对铸造Al-Li-Cu-Mg合金组织性能的影响

通过控制微量元素Zr+Sc与凝固速度,对铸造Al-Li-Cu-Mg合金进行熔体处理,研究两种因素对合金微观组织及性能的影响。利用光学显微境、场发射扫描电镜、X射线衍射仪、万用拉伸机等分别对合金的微观组织标定及力学性能进行分析和测试。结果表明：向Al-5Li-4Mg-3.5Cu基础合金中加入Zr+Sc后,合金的铸态晶粒得到明显细化,基体晶粒形貌由树枝状转变为近似等轴晶。向基础合金中加入0.2%Zr+0.4%Sc时达到晶粒细化极值,继续添加Zr+Sc元素则会降低细化效果,恶化合金组织;经过力学性能测试可知,添加0.2%Zr+0.4%Sc的合金的力学性能有了较大的提高,相比于基础合金抗拉强度提高了约48.57%,伸长率提升了27.93%;快速凝固时,添加0.2%Zr+0.4%Sc合金仅有Al2MgLi、Al3Zr、Al3Sc和Al8.9Li1.1相的析出,析出相的数量很少且尺寸极小。     

微量Cr、Mn、Ti、Zr细化7A55铝合金铸锭组织的效果与机理

采用光学显微镜、扫描电镜及能谱分析术研究了复合添加微量Cr、Mn、Ti、Zr细化7A55合金铸锭组织的效果和机理.结果表明:复合添加0.04%Ti 0.17%Zr能在一定程度上细化7A55合金铸锭组织,复合添加0.20%Cr 0.20%Mn 0.03%Ti能够显著细化铸锭组织,其细化机理为含有Cr、Mn的原子团簇作为Al3Ti形核的基底促使α-Al成核;复合添加微量0.04%Cr 0.04%Mn 0.03%Ti 0.18%Zr产生了极强烈的晶粒细化效果,其细化机理为含有Cr、Mn的原子团簇作为Al3Ti、Al3Zr共同形核的基底使Al3(TixZr1-x)形核,Al3(TixZr1-x)使α-Al形核.随着Cr、Mn含量增加,铸锭晶粒向枝晶化、粗大化方向发展.     

Al-5．8Mg—Mn-Sc—Zr合金的再结晶行为

采用活性熔剂保护熔炼,水冷铜模激冷铸造技术制备了Al-5.8Mg-0.4Mn-0.25Sc-0.1Zr（质量分数,%）合金板材。通过显微硬度测试、光学显微镜和透射电镜观察等分析手段研究了该合金的再结晶温度和再结晶形核机制。结果表明：通过添加微量的Sc和Zr元素使Al-Mg-Mn合金的抗再结晶能力得到显著提高,即添加了Sc和Zr的Al-Mg-Mn合金再结晶温度（450℃）比没有添加的合金（150℃）的高。Al-Mg-Mn-Sc-Zr合金的再结晶温度较高的主要原因是细小、弥散的Al 3（Sc,Zr）粒子对位错和亚晶界的钉扎作用。合金的再结晶形核机制为亚晶合并和亚晶长大的双重机制。     

Zr的两种添加方式对Al-Zn-Mg合金铸锭质量的影响

介绍了在某Al-Zn-Mg合金中分别使用Al-5Zr和Mg-25Zr两种中间合金添加Zr对铸锭质量的影响。铸锭质量全分析结果表明,使用优质的Al-5Zr、Mg-25Zr中间合金向Al-Zn-Mg合金添加Zr对铸锭的表面质量影响不大,但前者铸锭的综合性能要优于后者的,且Mg-25Zr中间合金存在不易保存,加入温度高,恶化铝合金熔体质量,生产成本高等缺点。     

Temperature-induced anomalous structural changes of Al-12wt.%Sn-4wt.%Si melt and its influence on as-cast structure

The temperature dependence of the viscosity of liquid Al-12wt.%Sn-4wt.%Si was studied with a high-temperature viscosity apparatus. Anomalous changes of viscosity of the melt were found at 1,103 K and 968K in the cooling process, which indicates anomalous structural changes of the melt. It is calculated that the anomalous structural change is associated with an abrupt decrease of atomic clusters' size and activation energy in the melt.According to the temperature of the anomalous structural changes, melt heat treatment process (quenching from superheat to pouring temperature)was performed on Al-12wt.%Sn-4wt.%Si melt prior to pouring, aimed to keep the small atomic clusters from higher temperature to lower pouring temperature. The results suggest that relatively small atomic clusters at the pouring temperature in the melt could generate a deep under-cooling of nucleation in the subsequent solidification process, and refine the as-cast structure. After being quenched from superheating to pouring temperature, the relatively small atomic clusters, especially the Si-Si clusters in the melt will grow to equilibrium state (relatively big atomic clusters) with holding time, resulting in the prominent coarsening of the Si morphology in the as-cast structure.     

微量元素Sc和Zr对过共晶Al-5%Fe合金组织和性能的影响

二元过共晶Al-5%Fe合金中的初生Al3Fe相为粗大的针片状。微量元素Sc和Zr加入到过共晶Al-5%Fe合金中,合金的初生Al3Fe相形貌发生显著变化。其细化作用在Sc、Zr加入量分别为0.3%和0.1%时效果较好,合金的初生Al3Fe相转变为细小的针状、粒状和花朵状。合金的抗拉强度达到266.8 MPa,提高了119.8%。讨论了Sc、Zr联合添加对过共晶Al-5%Fe合金初生Al3Fe相的作用机理。     

Temporal evolution of the nanostructure of Al(Sc,Zr) alloys: Part II-coarsening of Al3(Sc1−xZrx) precipitates

The coarsening behavior of four Al(Sc,Zr) alloys containing small volume fractions (<0.01) of Al₃(Sc_1−xZr_x) (L1₂) precipitates was investigated employing conventional transmission electron microscopy (CTEM) and high-resolution electron microscopy (HREM). The activation energies for diffusion-limited coarsening were obtained employing the Umantsev–Olson–Kuehmann–Voorhees (UOKV) model for multi-component alloys. The addition of Zr is shown to retard significantly the coarsening rate and stabilize precipitate morphologies. HREM of Al(Sc,Zr) alloys aged at 300 °C reveals Al₃(Sc_1−xZr_x) precipitates with sharp facets parallel to {1 0 0} and {1 1 0} planes. Coarsening of Al-0.07 Sc-0.019 Zr at.%, Al-0.06 Sc-0.005 Zr at.% and Al-0.09 Sc-0.047 Zr at.% alloys is shown to be controlled by volume diffusion of Zr atoms, while coarsening of Al-0.14 Sc-0.012 Zr at.% is controlled by volume diffusion of Sc atoms.     

Zr对Ni3Al晶界及力学性能的影响

对不同Ｚｒ含量Ｎｉ３Ａｌ的力学性能及晶界的研究结果表明：随Ｚｒ含量的增加，合金的屈服强度和抗张强度不断提高；当Ｚｒ≤０．７ａｔ．－％时，塑性随Ｚｒ含量的增加而提高；但Ｚｒ含量达１．２ａｔ．－％时，Ｚｒ的增塑效果下降．Ａｕｇｅｒ能谱分析表明：Ｚｒ在晶界有偏聚，偏聚因子约为３．断口观察显示：不含Ｚｒ或Ｚｒ含量为１．２ａｔ．－％的Ｎｉ－２４．０Ａｌ合金均为沿晶断裂，其余含Ｚｒ合金的断裂方式为穿晶、沿晶混合断裂．这表明：含Ｚｒ的Ｎｉ３Ａｌ塑性和Ｚｒ在晶界的偏聚有密切关系．     

Al-Ti-C与Al-Ti-B晶粒细化剂的Zr中毒机理

通过采用扫描电镜(SEM)、能谱仪(EDS)、X射线衍射(XRD)等对Al-Ti-Zr-C与Al-Ti-Zr-B试验合金中Al3Zr、Al3Ti、TiC或TiB2等第二相粒子结合情况的观察,研究晶粒细化剂的Zr中毒机理。结果表明:两种实验铝合金的凝固组织中Al3Zr均容易与Al3Ti结合形成聚积体,从而抑制了Al3Ti异质形核、细化晶粒的作用,出现所谓晶粒细化剂的Zr中毒现象;而TiC、TiB2粒子基本不与Al3Zr结合,但受Al3Zr的影响出现了团聚现象。根据边-边匹配晶体学模型(E2EM)计算表明:Al3Zr与Al3Ti、α-Ti具有多种可能的共格位向关系,而与TiC/TiB2粒子均只有一种可能的共格位向关系。母相-新相的共格位向关系的多少可作为晶粒细化剂设计的晶体学理论参考。     

Interdiffusion and reaction between Zr and Al alloys from 425° to 625 °C

Zirconium has recently garnered attention for use as a diffusion barrier between U–Mo nuclear fuels and Al cladding alloys. Interdiffusion and reactions between Zr and Al, Al-2 wt.% Si, Al-5 wt.% Si or AA6061 were investigated using solid-to-solid diffusion couples annealed in the temperature range of 425° to 625 °C. In the binary Al and Zr system, the Al₃Zr and Al₂Zr phases were identified, and the activation energy for the growth of the Al₃Zr phase was determined to be 347 kJ/mol. Negligible diffusional interactions were observed for diffusion couples between Zr vs. Al-2 wt.% Si, Al-5 wt.% Si and AA6061 annealed at or below 475 °C. In diffusion couples with the binary Al–Si alloys at 560 °C, a significant variation in the development of the phase constituents was observed including the thick τ₁ (Al₅SiZr₂) with Si content up to 12 at.%, and thin layers of (Si,Al)₂Zr, (Al,Si)₃Zr, Al₃SiZr₂ and Al₂Zr phases. The use of AA6061 as a terminal alloy resulted in the development of both τ₁ (Al₅SiZr₂) and (Al,Si)₃Zr phases with a very thin layer of (Al,Si)₂Zr. At 560 °C, with increasing Si content in the Al–Si alloy, an increase in the overall rate of diffusional interaction was observed; however, the diffusional interaction of Zr in contact with multicomponent AA6061 with 0.4–0.8 wt.% Si was most rapid.     

A Zr-RICH LOW MELTING POINT PHASE IN Ni_3Al ALLOY WITH Zr

A Zr-rich phase,Ni_5Zr,with low melting point has been fouhd in an Ni_3Al alloy doped withZr(1.2at.-%).It will cause the incipient melt of the alloy after being homogenized at 1300℃.This makes it difficult to homogenize the coarse casting structures completely and limits thefurther improvement of properties of the Ni_3Al alloy.