金属晶粒细化方法的研究现状

细化晶粒是提高材料性能的一种有效手段,本文将材料细化方法分为物理和化学两大类,评述了常见的细化方法如形变处理细化法、物理场细化法、快速冷却细化法、机械物理细化法及添加细化剂和变质剂等,对比了它们的优缺点。物理细化方法处理材料纯净度高,不会对金属熔体带来外来夹杂,细化效果好;化学添加剂法细化效果稳定、作用快、操作方便、适应性强,是目前最普遍的细化方法。     

自蔓延高温合成Al-TiC晶粒细化剂及其晶粒细化效果

采用自蔓延高温合成 (SHS)技术直接合成了Al 80 %TiC和Al 5 0 %TiC晶粒细化剂。研究了这两种细化剂的相组成、结构及对工业纯铝的晶粒细化效果 ,并与商用Al 5Ti 1B细化剂进行了对比。结果表明 :合成的细化剂由TiC和α (Al)两相组成 ,TiC粒子的尺寸和分布对细化剂的晶粒细化效果有显著影响。Al 80 %TiC细化剂中TiC粒子尺寸较大 (2～ 5 μm)且呈聚集成团分布 ,其晶粒细化效果较差。合成的Al 5 0 %TiC细化剂的晶粒细化效果略优于Al 5Ti 1B细化剂。加入 0 .1%的该细化剂就能使凝固试样的结构由粗大的柱状晶转变成细小的等轴晶 (平均晶粒尺寸 12 0 μm) ,且这种晶粒细化效果可保持 90min。SEM和TEM分析显示 ,Al 5 0 %TiC细化剂中原位合成的TiC粒子具有亚微米尺寸 (0 .4～ 0 .9μm) ,且在高温铝液中具有较强的稳定性 ,从而赋予该细化剂良好的晶粒细化效果和强的抗晶粒细化衰退能力     

铝合金晶粒细化剂的研究进展

晶粒细化剂是铝合金生产中常用的添加剂之一,能显著提高铝合金的力学性能和机械加工性能,对铝合金的生产具有十分重要的意义。本文阐述了铝合金晶粒细化剂的发展历史和研究现状,并简单介绍了晶粒细化剂的细化机理和目前工业生产中常用的晶粒细化剂。     

Al-Ti-B合金晶粒细化剂及细化机理的发展与现状

晶粒细化是提高材料强度和塑性,改善铸件质量的重要途径之一,其成功的关键在于形成高效、稳定、价廉的细化剂产品.在介绍Al-Ti-B合金晶粒细化剂的应用现状及生产方法的基础上,分析了晶粒细化剂的细化机理,明确了目前尚存在的问题,指出了今后的发展方向.     

铝钛硼晶粒细化剂的研究现状与发展趋势

简述了铝钛硼晶粒细化剂的发展历程,归纳了铝钛硼晶粒细化剂的细化机理并针对目前普遍采用的制备方法进行了简单介绍。重点介绍了高能超声、电磁搅拌、快凝技术等高品质铝钛硼晶粒细化剂制备新技术,并对铝钛硼晶粒细化剂的发展趋势进行了介绍和讨论。     

Ti6Al4V合金切削过程微观组织演化分析

针对切削钛合金(Ti6Al4V)在高温、高应变率的过程中发生微观组织的变化,进一步地探究切削参数和材料多物理场对钛合金切削过程晶粒细化及规律的影响,采用数值模拟与实验相结合的方法来研究钛合金切削过程中的有限元建模和微观组织演变过程。结果表明:所建立的基于Johnson-Mehl-Avrami-Kolmogorov模型的有限元仿真模型具有好的可信性,可用于探索加工过程中的微观组织演变和材料多物理场对晶粒细化的规律,预测主切削力、切屑形貌尺寸与实验结果对比的平均相对误差分别约为7%、8%,晶粒细化主要发生在第一变形区和第二变形区,已加工表面晶粒细化程度相对较弱,随着切削速度的不断增大,切屑和已加工表面的平均晶粒尺寸增大,而随着进给量的不断增大则平均晶粒尺寸减小,切屑平均晶粒尺寸明显小于已加工表面,切屑剪切区晶粒细化最明显,应变速率对切削加工过程中切屑和已加工表面的晶粒细化起主导作用。     

ZHPbD59-1铸造铅黄铜锭的研制

在直接生产铅黄铜锭的工业试验条件下,进行了AZ-1高效环保黄铜细化剂与稀土细化剂对铜锭晶粒细化及其铜液流动性的对比试验研究;结果表明:AZ-1高效环保细化剂具有显著的晶粒细化和增强铜液流动性的作用,其效果明显优于稀土细化剂;并分析了开发高档ZHPbD59-1铸造铅黄铜锭的关键生产工艺及其质量控制。     

Al-Ti-B合金昌粒细化剂及细化机理的发展与现状

晶粒细化是提高材料强度和塑性,改善铸件质量的重要途径之一,其成功的关键在于形成高效、稳定、价廉的细化剂产品。在介绍Al-Ti-B合金晶粒细化剂的应用现状及生产方法的基础上,分析了晶粒细化剂的细化机理,明确了目前尚存在的问题,指出了今后的发展方向。     

Al-Ti-C晶粒细化剂对工业纯铝的晶粒细化

采用自制的Al-Ti-C晶粒细化剂，检验了Al-Ti-C晶粒细化剂对工业纯铝的晶粒细化能力，研究了Al-Ti-C的含碳量、添加量、保温时间、浇注温度等对工业纯铝晶粒细化效果的影响。结果表明，对于工业纯铝添加质量分数为0.2％的Al-5.14Ti-0.3C晶粒细化剂，在725℃的铸造温度下保温2.5min，所得的铸锭晶粒细化效果最好。     

TiN/Ti复合细化剂对工业纯铝细化效果的影响

利用高能球磨制备了一种金属钛包覆纳米TiN的复合晶粒细化剂(TiN/Ti),研究了该细化剂对工业纯铝的细化效果及其抗衰退性能.结果表明,TiN/Ti复合细化剂对工业纯铝具有良好的晶粒细化效果,当加入量仅为0.025％时,试样组织由粗大的柱状晶转变为等轴晶;当加入量为0.2％时,纯铝的晶粒平均尺寸为82μm.该细化剂在725℃铝液中保温30、60和120 min后,试样的晶粒尺寸分别为101、153和327 μm.相对纯钛粉,TiN/Ti细化剂表现出良好的抗衰退性能,其抗衰退性来源于金属钛包覆纳米TiN在铝液中的分散性和稳定性.     

Effects of grain refinement on cast structure and tensile properties of superalloy K4169 at high pouring temperature

In order to improve the filling ability of large complex thin wall castings, the pouring temperature should be increased, but this will result in the grain coarsening. To overcome this problem, two kinds of grain refiners of Co-Fe-Nb and Cr-Fe-Nb ternary alloys, which contain high stability compound particles, were prepared. The effects of the refiners on the as-cast structures and tensile properties of the K4169 superalloy with different casting conditions were studied by analyzing specimens 110 mm long and 20 mm in diameter.Results showed that the mixture addition of the two refiners in the melt of K4169 can reduce the columnar grain region and decrease the equiaxed grain size greatly. After refinement, the amount of Laves phase decreases and its morphology changes from island to blocky structure. The carbides in the fine grain samples are fine and dispersive. Meanwhile, the porosity in specimens is decreased due to grain refinement. As a result, the yield strength, ultimate strength and the elongation of the specimens are increased. The grain refinement mechanisms are also discussed.     

Microstructural evolution of AA7449 aerospace alloy refined by intensive shearing

Many aerospace alloys are sensitive to their composition thus cannot be chemically grain refined. In addition, only 1% grain refiners can act as nuclei for refining the structure. In this paper, physical refinement by intensive shearing above liquidus as an alternative technique will be investigated for AA7449 aerospace alloy. The results can open a new gateway for aerospace industry for refining their microstructure.     

铝合金用晶粒细化剂的探讨

综述用于铝合金晶粒细化的中间合金研究应用现状及细化机理，并就其发展历史、分类和生产方法进行介绍。结果表明：在铝熔体中添加细化剂是晶粒细化最简便有效的方法，对已开发的细化荆应加强细化机理及稳定性研究，提高细化效果和能力，并指出了铝合金晶粒细化剂的发展方向。     

铸造工艺参数和细化剂对K4169高温合金铸态组织的影响Ⅰ.晶粒组织及晶粒细化机理

研究了K4169高温合金在各种工艺条件下及向熔体中加入复合细化剂时的晶粒组织。结果表明，降低浇注温度和加入复合细化剂可以明显细化冷凝后基体的晶粒和提高铸件断面等轴晶的比例。在通常的浇注温度1400℃下加入复合细化剂。对合金熔体进行或不进行过热处理时，可使圆柱锭的晶粒分别细化至ASTM1.7级和ASTM3.2级；断面等轴晶的比例分别达96％和99％以上。当浇注温度为1420℃、加入复合细化剂并对合金熔体进行过热处理时。可使圆柱锭晶粒细化至ASTM M10.5级，断面等轴晶的比例达90％以上。提出了晶粒细化的机理并对晶粒细化后断面等轴晶比例增大的现象进行了分析。     

Structural heredity of TiC and its influences on refinement behaviors of AlTiC master alloy

1　INTRODUCTIONPreparationofmostalloysisachievedthroughprocessinginthreestages :solid liquid solid .Duringeveryprocessingstage ,processingmethodsorparam etersmayresultinsomechangesinthemicrostruc turesorpropertiesofthealloywhichwillbetrans ferredstablytothesubsequentstagesandinfluencepropertiesoftheultimateproduct ,andthismaybecalledhereditaryphenomenonofmicrostructuresandproperties .Heredityphenomenoninmetalalloyshasbeennoticedasearlyasin 192 0 [1] ,recentlyworkswerecarriedouttostudyitsre…     

Al3Zr和Al3Nb作为铝合金晶粒细化剂的晶体学研究

利用edge-to-edgematching模型从晶体学角度研究Al3zr和Al3Nb两种金属间化合物作为铝合金晶粒细化剂的有效性。结果表明,Al3zr和Al3Nb两种金属间化合物和铝之间的原子间距错配和面间距错配值都很小。此外,模型预测Al3zr和Al3Nb两种金属间化合物与铝之间存在良好的晶粒取向关系。根据模型理论可以从晶体学角度证明这两种金属间化合物对铝合金是有效的晶粒异质形核细化剂。本晶体学研究为包晶铝合金Al-Zr和Al-Nb中出现的明显晶粒细化现象提供了合理解释,同时为理解晶粒细化机理提供了新方法。     

Microstructure and properties of a beta-solidifying TiAl-based alloy with different refiners

This study systematically compared the influences of yttrium(Y),boron(B),and carbon(C) on the microstructural refinement and properties of a Ti-43Al-5Nb alloy.The microstructural refinement effect in the TiAl alloy closely depends on the refiner used.The refinement effects of the three elements on colony size and lamellar thickness can be arranged as B Y C and Y C B,respectively.Moreover,a microstructure with a small grain size and ultra-fine lamellar spacing can be obtained by adding B and Y or B and C.The mechanical properties of TiAl alloy are also influenced by the refiners.TiAl alloys with proper B and Y contents exhibit favorable hot workability,tensile properties,and fracture toughness,whereas the C-containing alloy displays poor tensile properties and low fracture toughness.These results indicate that Y and B are more suitable microstructure refiners than C.This study may serve as a reference for practical alloying design.     

Grain refinement of AZ31 by (SiC)P: Theoretical calculation and experiment

Grain refinement of gravity die-cast Mg-alloys can be achieved via two methods: in situ refinement by primary precipitated metallic or intermetallic phases, and inoculation of the melt via ceramic particles that remain stable in the melt due to their high thermodynamic stability. In order to clarify grain refinement mechanisms and optimize possible potent refiners in Mg-alloys, a simulation method for heterogeneous nucleation based on a free growth model has been developed. It allows the prediction of the grain size as a function of the particle size distribution, the volumetric content of ceramic inoculants, the cooling rate and the alloy constitution. The model assumptions were examined experimentally by a study of the grain refinement of (SiC)_P in AZ31. Additions of (SiC)_P result in significant grain refinement, if appropriate parameters for ceramic particles are chosen. The model makes quantitatively correct predictions for the grain size and its variation with cooling rate.     

评价溶质元素细化晶粒能力的参数

推导了凝固界面前沿液相一侧的液相线温度梯度,并由此梯度提出了评价溶质元素细化晶粒能力大小的参数H。对铝基合金的实验结果表明:H参数数值越大,铸态晶粒尺寸越小。因此,H参数可用于指导晶粒细化剂的选择。     

中间合金对铝合金细化处理的现状分析与初探

分析讨论了中间合金对铝合金晶粒细化处理的研究与应用现状及其细化机理;并对新型细化剂AITiBRE中国合金的细化效果进行初探,结果表明该中间合金是一种高效、长效的晶粒细化剂,对压力罐用铝材具有显著的细化作用,其效果优于进口的A15TilB细化剂。