机械球磨与反应烧结制备TiAl基合金

研究了机械球磨与反应烧结制备TiAl基合金的工艺,结果表明,Ti、Al单质混合粉末经机械球磨可得到具有Ti、Al相间层片结构的复合粉,且球磨时间越长,Ti/Al复合粉的层片结构越薄越均匀。将Ti/Al复合粉压坯在固相下进行扩散反应,Ti/Al之间的扩散反应随机械球磨时间的延长而加快,且球磨所得到的Ti/Al复合粉在固相下能够完全转变成Ti-Al金属间化合物。反应后得到的Ti-Al金属间化合物经过进一步的高温烧结,可以得到近全致密TiAl基合金,且得到了晶粒尺寸和层片厚度都比较小的典型的TiAl基合金组织。     

高能球磨Ti/Al复合粉体的反应烧结致密行为

研究高能球磨Ti/Al复合粉反应烧结过程的致密行为 ,并进行反应烧结热力学和动力学分析。结果表明 ,与增加烧结压力、提高烧结温度或延长烧结时间的作用相同 ,高能球磨对Ti/Al粉末体反应烧结过程的致密化具有促进作用 ,且效果更加显著。球磨时间越长 ,烧结体越致密。球磨 3h的Ti/Al复合粉坯料经6 30℃× 2h预烧、12 5 0℃× 8h无压烧结后 ,获得的TiAl基合金试样的致密度高达 99 87%。球磨对Ti/Al粉末体反应烧结时致密化的促进作用 ,主要是由于Ti、Al反应组元及其晶粒尺寸的细化 ,晶格畸变能增加 ,从而显著提高了烧结驱动力和烧结动力学因子 ,缩短了反应扩散距离 ,抑制了kirkendall孔隙的形成。     

Cu-C-Ti系和Cu-CuO-Al系合金粉末的机械合金化

将CU-C3.3%-Til3.3%和CU-Cu02.5%-Al11.1%(质量分数)二合金粉末分别进行机械合金化,结果发现,经20h球磨后,C的衍射峰已经消失,Ti、Al、CuO的衍射峰强度显著降低;60h球磨后,二合金粉末都形成了Cu基过饱和固溶体;100h球磨后,部分Ti、C、Al、O溶质元素脱溶析出,并反应生成TiC和Al₂O₃。机械合金化导致粉末细化、亚晶界和位错等缺陷产生是形成过饱和固溶体和促进第二相析出的重要原因。     

镍基高温合金粉末的高能球磨工艺研究

本研究采用机械合金化方法制备氧化物(Al2O3)弥散强化镍基高温合金预合金粉末.通过改变球磨工艺参数,分析了球磨转速和球料比对机械合金化过程的影响,对球磨后的粉末进行SEM分析、XRD分析、粒度测试和松装密度测试,得出最佳的球磨工艺参数。实验结果表明:Al2O3 弥散强化镍基高温合金机械合金化粉末尺寸随球磨转速的增加先减小后增大,当球磨转速为400rmp,球料比为20∶1时,合金粉末有较高的松装密度和较小的粉末粒度。     

粉末冶金制备的Ti35Nb2．5Sn5HA生物复合材料的组织与性能研究

采用高能机械球磨和脉冲电流活化烧结方法制备了一种新型的不含Al、V等有毒元素的口钛合金基体的Ti35Nb2．5Sn5HA生物复合材料。研究了不同机械球磨时间球磨的Ti35Nb2．5Sn5HA粉末以及用这几种粉末烧结制备的样品微观组织和显微硬度变化,球磨时间对烧结复合材料的微观组织和性能的影响。结果表明：随着球磨时间的增加,Ti35Nb2．5Sn5HA粉末的颗粒尺寸逐渐减小,Nh和Sn开始与Ti发生固溶,形成Ti的过饱和固溶体,而且α-Ti也开始向β-Ti转化。当球磨时间达到12h,球磨粉末中α-Ti完全转化为β-Ti,粉末颗粒的平均尺寸为500nm左右。12h球磨的粉末烧结制备的复合材料具有超细晶粒尺寸,晶粒平均尺寸为200nm,这种复合材料的维氏显微硬度可以达到10187．3MPa。     

球磨时间对放电等离子烧结合成Ti_3SiC_2纯度的影响

本文采用原料配比为3Ti/Si/2C/0.2Al(摩尔比)的单质混合粉体为原料,进行机械合金化(MA)和随后的放电等离子烧结(SPS),以制备高纯Ti3SiC2陶瓷,研究了球磨时间对放电等离子烧结制备Ti3SiC2的影响。结果表明,机械合金化混合粉体后,粉体颗粒明显细化。球磨10h,单质混合粉体会发生化学反应,生成TiC,Ti3SiC2混合粉体。继续球磨至20h,生成物混合粉体会显著细化。球磨时间对SPS烧结合成Ti3SiC2有显著的影响。球磨10h,即反应刚刚完毕,最有利于SPS合成致密高纯的Ti3SiC2,球磨时间较短(5h),对Ti3SiC2陶瓷的烧结促进作用不显著,而反应后继续延长球磨时间至20h,会降低烧结体中Ti3SiC2的纯度。采用球磨10h的粉体为原料,经850℃放电等离子烧结可获得纯度高达96%(质量分数,下同)的Ti3SiC2疏松块体,烧结温度提高到1100℃,可获得纯度为99.3%、相对密度高达98.9%的TiSiC致密块体。     

机械球磨作用下Al/Ti混合粉末的组织和热稳定性

为探索一种制备高综合性能Al-Ti基金属间化合物的新方法，研究了机械球磨方法制备的Al-10％Ti(质量分数)混合粉末的组织和热稳定性。结果表明：在球磨作用下，Al、Ti粉末的颗粒尺寸得到有效细化，并且球磨时间越长，Al／Ti粉末储备能量越大，生成Al-Ti金属间化合物所需的反应激活能越低，内能的增加和扩散能力的提高是由于机械球磨导致了大量的晶格缺陷；经90h球磨的粉末在660℃下经6h热处理后生成Al3Ti，还有少量的Al2Ti，Al5Ti2生成。     

Al-Al_2O_3-TiB_2复合粉体的机械化学合成工艺研究

研究了Al-Ti O_2-B_2O_3系粉末在无过量Al以及过量Al为0%,5%,10%,15%,20%,25%(质量分数,下同)时,球磨时间对机械合金化及燃烧反应的影响规律,计算了不同成分时反应体系的理论绝热温度,对球磨后的粉末进行了X射线衍射(XRD)、差示扫描量热法(DSC)、扫描电镜(SEM)测试分析。结果表明:在球磨过程中,无过量Al以及过量Al为5%,10%,15%时,Al还原Ti O_2反应的理论绝热温度低于1800 K,Al还原B_2O_3反应远高于1800 K,反应产生的热量促使Ti O_2还原反应发生,生成Al_2O_3和Ti B_2。过量Al为20%,25%时,Al还原Ti O_2和B_2O_3反应的理论绝热温度都低于1800K这一临界反应温度,不能发生化学反应。随着球磨时间的增加,粉末的表面能、晶格畸变能、位错能以及晶界能增加,扩散通道缩短,促使自蔓延化学反应的点火温度下降,从未球磨的1000℃以上下降到600℃左右。在球磨过程中,粉末颗粒尺寸首先增加,超过一定时间后,粉末颗粒尺寸减小,发生化学反应后,粉末颗粒尺寸明显减小,达到微纳米级。     

高能球磨工艺对钨铜复合材料组织的影响

采用机械合金化方法将W-15%Cu混合粉末在行星式高能球磨机中球磨,研究了不同球磨时间对钨铜复合材料组织的影响,利用XRD及SEM分析了不同球磨时间的粉末和烧结后的样品,结果表明,随着球磨时间的延长,粉末的晶粒尺寸不断减小,烧结后样品的相对密度不断提高.球磨60h的混合粉末在1350℃烧结后的相对密度达到98.8%.     

机械合金化-加压烧结制备Fe3Al金属间化合物

采用机械合金化-加压烧结在1250℃制备相对密度为99%、晶粒尺寸为300～700nm的Fe3Al烧结体材料.研究了球磨过程中Fe-Al粉末的结构转变及烧结体Fe3Al的微观结构和力学性能.Fe3Al材料的室温压缩屈服强度和压缩应变分别为1900MPa和14%,硬度61HRC,横向断裂强度和断裂韧度KIc分别高达1300MPa和49 MPa·m1/2.Fe3Al材料优异的室温力学性能来源于晶粒细化、组织均化效应.     

铝与K2TiF6混合粉末的高能球磨反应

以Al粉和K2 TiF6 混合粉末为原料 ,利用高能球磨法制备Ti Al基金属间化合物。采用XRD ,SEM ,EPMA和DTA等方法对球磨 1,2 5 ,5 ,8h的粉末进行分析 ,在球磨时间超过 2 .5h的粉末中有TiAl3,TiAl出现 ,并伴有副产物KAlF4 和K3AlF6 生成。随着反应的进行 ,产物中TiAl相含量逐渐增加 ,产物粒度可达纳米级。     

Ti6Al4V和Al2A12的扩散连接界面组织及力学性能

采用热等静压(HIP)工艺连接Al12A12和Ti6Al4V两种不同的航空航天用材料.利用扫描电镜、能谱仪和X射线衍射仪观察连接过渡区的微观组织和组成的演化,并测试其主要的力学性能.结果表明:采用热等静压制备这两种材料的界面连接好;Ti/Al反应层界面处形成了不同的金属间化合物,例如,Al₃ Ti、TiAl₂和TiAl;连接接头处硬度为163 HV,界面连接处剪切强度达到了23 MPa,比只添加镀层而无中间层的连接强度提高了约17.9%,但低于带有中间层的连接强度.由于过烧和孔隙的形成使得断裂方式是脆性断裂.由此可知,在热等静压成形过程中异种材料的元素发生了相互扩散,在扩散连接处形成了不同的金属间化合物,这些金属间化合物影响连接处的力学性能.      

Preparation of TiAl15Si15 intermetallic alloy by mechanical alloying and the spark plasma sintering method

This work is devoted to the preparation of alloys based on intermetallic compounds in the Ti–Al–Si system by powder metallurgy using mechanical alloying and the spark plasma sintering (SPS) method. The aim was to describe the formation of intermetallic phases during mechanical alloying of TiAl15Si15 (wt-%) alloy and to consolidate the powder prepared by optimised conditions. Phase composition, microstructure and hardness of compacted alloy were determined. Four hours of mechanical alloying is sufficient time for preparation of pure elements free material composed only of intermetallic phases. After consolidation, the TiAl15Si15 alloy has a homogeneous structure composed of silicide (Ti₅Si₃) in aluminide (TiAl) matrix. The hardness of the material reaches 865?±?42 HV 5.     

元素粉末冶金方法制备TiAl基合金

详细介绍了采用元素粉末冶金方法制备TiAl基合金的机理、工艺方法及材料性能,元素Ti,Al粉末在一定温度下的反应合成主要由扩散控制,包括产生TiAl_3相和TiAl_2相的中间化过程,元素粉末冶金TiAl合金的工艺方法有元素粉末Ti,Al的反应烧结、热压或热等静压,热爆合成,元素TiAl箔片的反应合成等,采用这些方法制备的TiAl基合金具有均匀、细小的组织,但其力学性能受氧含量及孔隙的严重影响。     

元素粉末法制备TiAl基合金

详细综述了采用元素粉末法制备TiAl基合金的机理研究,工艺方法及材料性能。元素里,则在一定温度下的反应合成主要由扩散控制,包括产生TiAl₃相和TiAl₂相的中间化过程。由元素粉末制备TiAl合金的工艺方法有Ti,Al元素粉末的反应烧结、热压或热等静压、热爆合成、元素Ti、Al箔片的反应合成等。采用这些方法制备的TiAl基会金具有均匀、细小的组织,但其力学性能受氧含量及孔隙的严重影响。.     

Structural evolution in mechanically alloyed Al-Fe powders

The structural evolution in mechanically alloyed binary aluminum-iron powder mixtures containing 1, 4, 7.3, 10.7, and 25 at. pct Fe was investigated using X-ray diffraction (XRD) and electron microscopic techniques. The constitution (number and identity of phases present), microstructure (crystal size, particle size), and transformation behavior of the powders on annealing were studied. The solid solubility of Fe in Al has been extended up to at least 4.5 at. pct, which is close to that observed using rapid solidification (RS) (4.4 at. pct), compared with the equilibrium value of 0.025 at. pct Fe at room temperature. Nanometer-sized grains were observed in as-milled crystalline powders in all compositions. Increasing the ball-to-powder weight ratio (BPR) resulted in a faster rate of decrease of crystal size. A fully amorphous phase was obtained in the Al-25 at. pct Fe composition, and a mixed amorphous phase plus solid solution of Fe in Al was developed in the Al-10.7 at. pct Fe alloy, agreeing well with the predictions made using the semiempirical Miedema model. Heat treatment of the mechanically alloyed powders containing the supersaturated solid solution or the amorphous phase resulted in the formation of the Al₃Fe intermetallic in all but the Al-25 at. pct Fe powders. In the Al-25 at. pct Fe powder, formation of nanocrystalline Al₅Fe₂ was observed directly by milling. Electron microscope studies of the shock-consolidated mechanically alloyed Al-10.7 and 25 at. pct Fe powders indicated that nanometer-sized grains were retained after compaction.     

Phase transformation,structural evolution and mechanical property of nanostructured FeAl as a result of mechanical alloying

Objective of the work was to synthesize nanostructured FeAl alloy powder by mechanical alloying (MEA). The work concentrated on synthesis, characterization, structural and mechanical properties of the alloy. Nanostructured FeAl intermetallics were prepared directly by MEA in a high energy rate ball mill. Milling was performed under toluene solution to avoid contamination from the milling media and atmosphere. Mixtures of elemental Fe and Al were progressively transformed into a partially disordered solid solution with an average composition of Fe—50 at % Al. Phase transformation, structural changes, morphology, particle size measurement and chemical composition during MEA were investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDS) respectively. Vickers micro hardness (VMH) indentation tests were performed on the powders. XRD and SEM studies revealed the alloying of elemental powders as well as transition to nanostructured alloy, crystallite size of 18 nm was obtained after 28 hours of milling. Expansion/contraction in lattice parameter accompanied by reduction in crystallite size occurs during transition to nanostructured alloy. Longer milling duration introduces ordering in the alloyed powders as proved by the presence of superlattice reflection. Elemental and alloyed phase coexist while hardness increased during MEA.     

Microstructural analysis of multilayered titanium aluminide sheets fabricated by hot rolling and heat treatment

This study is concerned with the microstructural analysis of multilayered or bulk Ti aluminide sheets fabricated by the self-propagating high-temperature synthesis (SHS) reaction using hot rolling and heat treatment. Multilayered Ti/Al sheets were prepared by stacking thin Ti and Al sheets alternately, and a good Ti/Al interfacial bonding was achieved after rolling at 500 °C. When these sheets were held at 1000 °C, spheroidal TiAl₃ phases were formed by the SHS reaction at Ti/Al interfaces and inside Al layers. Microstructural analysis on the hot-rolled, multilayered Ti/TiAl₃ sheets revealed that intermetallic phases such as TiAl₂, TiAl, and Ti₃Al were formed at Ti/TiAl₃ interfaces due to interaction between Ti and TiAl₃ and that pores formed in the TiAl₃ layer were significantly reduced during hot rolling. When multilayered Ti/Ti aluminide sheets were heat treated at 1000 °C, Ti₃Al, TiAl, and TiAl₂ were grown as Ti and TiAl₃ were consumed. As the heat treatment proceeded, TiAl grew further, eventually leading to the fabrication of multilayered sheets composed of Ti₃Al and TiAl. Bulk Ti aluminide sheets, having a lamellar structure of Ti₃Al and TiAl, instead of multilayered sheets, were also fabricated successfully by heat treatment at 1400 °C. This fabrication method of the bulk sheets had several advantages over the method by hot forging or rolling of conventional cast Ti aluminides. From these findings, an idea to fabricate multilayered or bulk Ti aluminide sheets by hot rolling and heat treatment is suggested as an economical and continuous fabrication method, and the formation and growth mechanisms of interfacial phases are elucidated in this study.