反应放热法合成Al-Ti-C晶粒细化剂研究

以Al，Ti，C粉末为原料，在Al熔体中通过粉末间的强烈放热反应合成了AlTi5C0．2晶粒细化剂，并采用OM，XRD和SEM等分析手段。研究了中间合金的反应合成过程、TiC粒子的形成机制及其细化特性。结果表明：在670℃时，Ti(s)与Al(1)发生强烈的放热反应，在Al熔体中形成块状TiAl3粒子；反应释放的热量使反应区升温，TiAl3(s)粒子溶解于Al熔体中形成活性Ti，Ti通过扩散至C颗粒表面并与之反应形成TiC粒子，并呈现聚集形态；随保温时间的延长，TiAl3粒子由块状向针片状转变，TiC粒子的簇状分布特征明显增强，中间合金的细化能力略有降低。     

石墨与Al-Ti合金反应生成TiC粒子的机理

采用石墨粉加入到Al Ti熔体中的方法来制备Al Ti C晶粒细化剂。用金相显微镜、扫描电镜观察不同反应时间的Al Ti C合金微观组织 ,结合热力学和动力学的分析 ,研究了石墨与Al Ti合金熔体反应生成TiC粒子的机理。结果表明 :在 10 73～ 1173K温度范围内 ,将石墨加入Al 5 %Ti合金熔体中 ,石墨与Al液不会直接反应生成Al4 C3 ,石墨也不会转变成游离的碳原子而与Ti反应生成TiC。TiC由下面反应式生成 :Ti C石墨 →TiC、TiAl3 C石墨 →TiC 3Al     

原位反应法制备Al2O3-TiC/Al复合材料

通过向含Ti的Al-Si合金熔体中通入CO2气体制备Al2O3-TiC／Al复合材料的方法．研究了Al2O3-TiC／Al复合材料特性。用X射线衍射仪（XRD）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）对复合材料的组织进行了研究。研究表明，CO2与合金熔体中的Al、Ti原位反应生成Al2O3和TiC颗粒，Al2O3和TiC颗粒尺寸在0．2～1．0μm之间，均匀分布在基体中，反应生成的Al2O3和TiC颗粒数量与CO2的通入时间有关。     

Al-Ti-C晶粒细化剂的形核与衰减机理研究

通过SEM、XRD、EPA等分析手段，研究了液一固反应法制备的Al—Ti—C晶粒细化剂中间合金的组织特征，并结合热力学分析探讨了TiC粒子的形核与衰减机制。试验结果表明：TiC的形核机理是Ti原子以某种机制扩散至TiC粒子的表面形成富Ti，并接近TiAl3的成分，在凝固过程中TiAl3与周围Al液发生包晶反应形成α-Al；保温过程由于C从TiC向Al熔体中的扩散，使其稳定性降低及TiC向Al4C3转化，使α-Al晶格失配是细化效果衰减的主要原因。     

铸造Al-4.5%Cu合金熔体中TiCp的合成反应研究

通过预制块在铸造Al-4.5%Cu合金熔体中的自蔓延反应,制备了TiCp/Al-4.5%Cu原位复合材料,分析了TiC形成的热力学及其原位生成过程。试验结果表明,TiCp/Al-4.5%Cu原位复合材料的拉伸性能比基体合金有大幅度地提高;原位反应生成的TiC颗粒呈小圆片状,平均直径0.15μm,与基体结合良好,无界面有害相。提出了一种新的TiC颗粒合成机制:Al依次与Ti、C发生反应生成Al3Ti和Al4C3,同时放出大量的热引发了TiC的生成;Al3Ti和Al4C3作为中间反应产物,由于热力学上的不稳定,最终被TiC取代。     

Al—Ti—C中间合金的相组成及其细化特性

用专利方法制备出各种成分的Al-Ti-C中间合金作为铝及铝合金的晶粒细化剂。对该系列中间合金的组织和物相分析表明：在制备中间合金过程中,C与Ti反应充分,生成TiC和TiAl3两种管二相,且TiAl3析出量取决于中间合金的Ti含量和Ti/C含量比。用于纯铝的晶粒细化试验表明：与Al-Ti-C中间合金相比,Al-Ti-C中间合金的晶粒细化效率更高;Al-Ti-C中间合金只有在组织中TiC与TiAl3保持适当比例时,才能对纯铝产生良好的晶粒细化效果,不含TiAl3的Al-Ti-C中间合金的晶粒细化作用很微弱;用Al-Ti-C中间合金细化纯铝晶粒时,响应时间短,但衰退较快,且不能通过熔体搅拌法予以消除。分析和探讨了Al-Ti-C中间合金的晶粒细化机理,认为“碳化物理论” 不能充分解释Al-Ti-C的晶粒细化机理,提出“Ti在TiC或TiAl3颗粒表面富集引发包晶反应”的晶粒细化机制。     

Al-Al_4C_3-TiC中间合金对Mg-Al系合金的晶粒细化

通过熔体原位反应法制备了一种Al-Al4C3-TiC中间合金。在该中间合金中,Al4C3颗粒被TiC颗粒包围,Al4C3颗粒和TiC颗粒尺寸分别在2.5~8.0μm和0.5~1.5μm之间。试验表明,该中间合金对AZ31有良好的细化作用。当加入1%的中间合金时,AZ31的晶粒尺寸由原来的1050μm减小到260μm。Al4C3颗粒或者Al4C3颗粒团簇充当了α-Mg的异质形核核心,这导致了明显的晶粒细化。     

钛合金表面激光熔覆原位生成TiC增强复合涂层

利用Cr3C2和TiC生成自由能和稳定性的差异,通过激光熔化法在Ti6Al4V表面制备TiC颗粒增强钛基复合材料涂层,结果表明：选择合适的激光处理工艺,可使Cr3C2和Ti合金粉末通过原位结晶置换反应生成TiC/Ti复合材料熔覆层。亚微米级的TiC颗粒均匀地分布于复合材料的基体中,复合材料的基体组织随合金粉末的成分不同而改变。     

工艺参数对Al-Ti-C中间合金第二相粒子及细化效果的影响

研究了铝含量和铝液温度对热爆法合成Al-Ti-C中间合金第二相粒子形成规律及细化效果的影响.结果表明:预制块铝含量对第二相粒子TiAl3和TiC的生成有重要影响.铝液温度影响反应生成的中间合金中TiAl3、TiC的形态和分布,并影响其晶粒细化能力.当Al:Ti:C的原了比为3.4:1.8:1、铝液温度为780℃时,合成的中间合金中大量TiAl3和TiC粒子在铝基体上均匀分布,晶粒细化效果最佳,并讨论了晶粒细化机理.     

铝硅合金晶粒细化剂Al-Ti-C-P的研制

采用自蔓延＋熔铸法制备了Al-Ti—C-P晶粒细化剂，探讨了其对共晶铝硅合金的变质效果。通过扫描电镜（SEM）、光学显微镜（OM）、能谱分析（EDS）和X射线衍射仪（XRD）等手段，研究了Al—Ti—C—P晶粒细化刺的显微组织。结果表明：Al—Ti—C—P晶粒细化剂的主要相组成为TiAl3、TiC、AlP，对共晶铝硅合金具有优良的变质效果。晶粒细化剂中的TiAl2和TiC颗粒促进了AlP时共晶铝硅合金的变质效果。     

Grain refining action of Al–5Ti–C and Al–TiC master alloys with Al–5Ti master alloy addition for commercial purity aluminium

Al–Ti–C master alloys have a great potential as efficient grain refiners for aluminium and its alloys. In the present work, the Al–5Ti–C, Al–TiC and Al–5Ti master alloys have been successfully prepared by a method of liquid solidification reactions. While the Al–5Ti–C master alloy consists of some strip- or needle-like TiAl₃, and in addition to TiC particles in the Al matrix, the Al–TiC master alloy revealed the presence of only TiC particles, and the Al–5Ti master alloy consists of only some blocky TiAl₃ particles. A united refinement technology by Al–5Ti–C+Al–5Ti and Al–TiC+Al–5Ti master alloys was put forward in this paper. The blocky TiAl₃ particles in Al–5Ti master alloy can not only improve the grain refinement efficiency of Al–5Ti–C and Al–TiC master alloys but also reduce the consumption because the blocky TiAl₃ particles improve the grain refinement efficiency of TiC particles in Al–5Ti–C and Al–TiC master alloys.     

TiC-Al金属陶瓷自蔓延高温合成中的显微组织转变

用燃烧波淬熄法研究了TiC-Al金属陶瓷自蔓延高温合成中显微组织的转变,淬熄试样中保留了未反应区、反应区及反应完成区.用扫描电子显微镜观察了燃烧反应中的显微组织转变过程,用能谱仪分析了各微区的成分变化,测量了燃烧温度和燃烧波蔓延速度,并用XRD分析了反应产物相的组成.结果表明,Ti-C-Al系燃烧反应起始于铝粉熔化后与固态钛粉反应生成Al3Ti,并随着反应温度的升高,TiC颗粒从溶有钛和碳的铝熔体中析出;当Al3Ti熔化后,从熔体中也析出TiC颗粒,最终产物组织中除大量的TiC颗粒分布于铝基体中外,还发现有少量的Al3Ti存在,可能与使用的钛粉和铝粉的原料颗粒较粗有关.     

REACTION MODEL IN Al-Ti-C SYSTEM

ＲＥＡＣＴＩＯＮＭＯＤＥＬＩＮＡｌ－Ｔｉ－ＣＳＹＳＴＥＭ￥ＷＡＮＧＺｉｄｏｎｇ;ＨＵＨａｎｑｉ（ＵｎｉｖｅｒｓｉｔｙｏｆＳｃｉｅｎｃｅａｎｄＴｅｃｈｎｏｌｏｇｙＢｅｉｊｉｎｇ．Ｂｅｉｊｉｎｇ,Ｃｈｉｎａ）ＬｉＱｉｎｇｃｈｕｎ（Ｈａｒｂｉｎｉｎｓｔｉｔ...     

Grain refinement of AZ31 magnesium alloy by new Al-Ti-C master alloys

New Al₄C₃-containing Al-Ti-C master alloys (Al-0.6Ti-1C and Al-1Ti-1C) were developed by introducing Ti element into Al-C melt using melt reaction method, in which most of the TiC particles distribute around Al₄C₃ particles. It is believed that most of the C firstly reacts with Al melt and form Al₄C₃ particles by the reaction Al(l)+C(s)→Al₄C₃(s), and after adding Ti into the Al-C melt, the size of Al₄C₃ particles is decreased and the distribution of Al₄C₃ is improved through the reaction Ti(solute)+Al₄C₃(s)→TiC(s)+Al(l). With the addition of 1% Al-1Ti-1C master alloy, the average grain size of AZ31 is reduced sharply from 850 μm to 200 μm, and the grain morphology of α-Mg transits from a fully-developed equiaxed dendritic structure to a petal-like shape. Al-C-O-Mn-Fe compounds are proposed to be potent nucleating substrates for primary Mg. Appropriate addition of Ti is believed to increase the grain refinement efficiency of Al₄C₃-containing Al-Ti-C master alloys in AZ31 alloy.     

Microstructure and refinement performance of Al-Ti-C master alloy: Effect of excess Ti on the growth and nucleating ability of TiC particles

Al-5Ti-0.2C, Al-0.8Ti-0.2C, Al-8Ti-2C, and Al-10Ti master alloys were prepared and used to investigate the influence of excess Ti on the growth of TiC particles and its ability to nucleate Al-grains. The results of a microstructure analysis of TiC-containing alloys and refined CPAl were interrelated to the results of a refinement test. It was found that the presence of excess Ti is essential at the stage of master alloy preparation, as it facilitates the growth and uniform distribution of TiC within the structure. In Al-5Ti-0.2C alloy containing excess Ti, carbide particles grow faster and to a higher extent (from 0.29 μm to 0.44 μm) compared to Al-0.8Ti-0.2C alloy produced without excess Ti (from 0.29 μm to 0.32 μm). The results support the “Ti-transition zone theory” as the mechanism of grain refinement by TiC-containing master alloys. The refinement performance of Al-5Ti-0.2C is superior compared to the one achieved by adding Al-8Ti-2C and Al-10Ti master alloys in corresponding concentrations. For the TiC particles to become favourable nucleating sites, they must undergo certain interaction with excess Ti at the stage of master alloy preparation.     

PHASE CONSTITUTE AND MICROGRAPHY OF REACTION SYNTHESIS OF Al+Ti+C SYSTEM

ＰＨＡＳＥＣＯＮＳＴＩＴＵＴＥＡＮＤＭＩＣＲＯＧＲＡＰＨＹＯＦＲＥＡＣＴＩＯＮＳＹＮＴＨＥＳＩＳＯＦＡｌ＋Ｔｉ＋ＣＳＹＳＴＥＭ￥ＺＨＡＮＧＥｒｌｉｎ;ＺＥＮＧＳｏｎｇｙａｎ;ＺＥＮＧＸｉａｏｃｈｕｎ;ＬＩＱｉｎｇｃｈｕｎ（Ｈａｒｂｉｎｉｎｓｔｉｔｕｔ...     

In-situ production and microstructures of iron aluminide/TiC composites

In this study we have tried to produce the titanium carbide reinforced iron aluminide composites by in-situ reaction between titanium and carbon in liquid iron–aluminum alloy doped with titanium and carbon. A homogeneous distribution of titanium carbide particles in the iron aluminide matrix up to about 16 vol% of titanium carbide was intended without agglomeration. The composition of TiC formed during in-situ reaction was investigated by ICP analysis and the Combustion-Infrared Absorption method after chemical dissolution of the iron aluminide matrix. It is found that the composition of titanium carbide formed during melt processing is an average of Ti–48.4 mol% C. In addition, titanium carbide has very low solubility of Fe and Al. The microstructure of composites consists of three different regions; primary large TiC particles of 5–40 μm, matrix with small dendritic TiC particles of about 1 μm and particle-free regions around primary large TiC particles. The formation of this complex microstructure can be explained by assuming the Fe₃Al–TiC pseudo-binary system containing the eutectic reaction. Particle-free regions are halos of iron aluminide phase and the formation of halos is explained by coupled zone concept. Subsequent heat treatment at 1373 K for 48 h induces spheroidization and/or coarsening of small TiC particles, while microstructure after heat treatment at 973 K for 48 h exhibits the additional formation of small TiC precipitates. Though excess 1 mol% Ti addition over the Ti content for TiC formation is soluble to Fe–28 mol% Al, excess 1 mol% C addition forms the secondary Fe₃AlC phase during melt processing.     

铸造Al-Si合金熔体处理——晶粒细化

对亚共晶Ａｌ－Ｓｉ铸造合金进行细化处理已成为一种基本操作。中间合金（Ａｌ－Ｔｉ,Ａｌ－Ｔｉ－Ｂ和Ａｌ－Ｂ合金）在亚共晶Ａｌ－Ｓｉ铸造合金中与在工业纯铝和变形铝合金中的晶粒细化行为存在较大的差异。Ａｌ－３Ｔｉ－３Ｂ,Ａｌ－３Ｂ中间合金在Ａｌ－Ｓｉ铸造合金中表现出优异的晶粒细化效应,Ｓｉ与晶粒细化剂的交互作用在其中扮演着重要的角色。通过炉前对熔体进行快速热分析可以对晶粒细化效果和变质程度进行评价和预测,继而控制熔体处理的质量。对于亚共晶Ａｌ－Ｓｉ铸造合金,归纳起来有四种晶粒细化机理：包晶反应理论、共晶反应理论、硼化物颗粒理论和超形核理论。仅对Ａｌ－Ｓｉ铸造合金细化处理的最新进展、Ｓｉ与晶粒细化剂的交互作用和晶粒细化机理进行综合评述     

Effects of solid deformation and melt vibration on structure and refining performance of Al5Ti1B master alloy

1　ＩＮＴＲＯＤＵＣＴＩＯＮＧｒａｉｎｒｅｆｉｎｅｍｅｎｔｏｆｆｅｒｓｓｕｂｓｔａｎｔｉａｌｂｅｎｅｆｉｔｓｉｎｂｏｔｈｃｏｎｔｉｎｕｏｕｓｃａｓｔｉｎｇｂｙｄｉｒｅｃｔｃｈｉｌｌ (ＤＣ)ａｎｄｉｎｃａｓｔ ｔｏ ｓｈａｐｅｐｒｏｄｕｃｔｓ[1].Ａｌ 5%Ｔｉ 1 %Ｂｍａｓｔｅｒａｌ ｌｏｙ ,ｗｈｉｃｈｍａｉｎｌｙｃｏｎｔａｉｎｓＴｉＡｌ3ａｎｄＴｉＢ2 ｐａｒｔｉｃｌｅｓｉｎＡｌｍａｔｒｉｘ[2 ,3]ｈａｓｂｅｅｎｐｒｏｖｅｎｔｏｇｉｖｅｔｈｅｂｅｓｔｇｒａｉｎｒｅｆｉｎｅｍｅｎｔ[4 ,5 ].Ａｄｄｉｔｉｏｎｏｆ 0 …