纳米晶NiAl的机械合金化合成机理研究

采用机械合金化方法,以元素粉末为原料,对四种成分的NixA1100-x(x=25,30,40.50)进行不同球磨时间和球磨转速的机械合金化合成,制备纳米晶NiA1金属间化合物粉末.利用X射线衍射技术对球磨产物进行了物相分析,并对NiA1机械合金化合成机理进行了探讨.研究表明:NixAl100-x四种成分的元素粉末采用机械合金化方法均可以制备出纳米晶NiA1金属间化合物粉末;NiA1金属间化合物的机械合金化合成机理为燃烧合成反应.     

机械合金化制备Ta-10%Al纳米晶过饱和固溶体

利用机械合金化的方式制备了组成为Ta-10%Al(质量比)的纳米晶过饱和固溶体。以XRD和SEM为表征手段,研究了球磨时间对Ta-10%Al纳米晶过饱和固溶体产生的影响,并对Ta-10%Al纳米晶过饱和固溶体形成的热力学机理进行了研究。结果表明,随球磨时间增加,Al逐渐溶入Ta中。当球磨时间达到48 h后,Al完全固溶进Ta中形成Ta-10%Al纳米晶过饱和固溶体,晶粒尺寸和微观应力分别为84.3 nm和0.285%。延长球磨时间导致Ta-10%Al纳米晶过饱和固溶体晶粒细化且微观应力增加,过长的球磨时间可能引发合金粉末的团聚。以Miedema半经验模型为依据,建立了机械合金化过程中的热力学模型,计算结果显示,以机械合金化为手段制备Ta-10%Al纳米晶过饱和固溶体的主要驱动力来源于热力学驱动。     

机械合金化W-Ni-Fe纳米复合粉的制备及结构研究

W,Ni,Fe粉末按照91.16W6．56Ni2.26Fe和95W5Ni的成分配比进行了机械合金化(MA)．通过调整球磨转速、球磨时间等工艺参数研究了其对粉末结构的影响,并对机械合金化粉末的物相、合金化特性、晶粒尺寸、点阵畸变及粉末形貌和颗粒度作了测定和分析讨论.机械合金化使晶粒细化并产生孪晶和位错．有利于原子扩散形成过饱和固溶体和非晶；高的球磨能有利于形成非晶相、晶粒细化和点阵畸变，350r／min球磨20h后晶粒尺寸可达25nm；输入的球磨能不同．粉末粒度的变化路径不同，但都会经历长大，变小和稳定三个不同阶段.     

基于冷喷涂制备ZrC掺杂NiAl热障涂层粘结层

目的开发NiAl金属间化合物热障涂层粘结层。方法通过机械合金化技术制备了Ni/Al、Ni/Al+0.5%ZrC与Ni/Al+0.07%三种复合结构粉末。采用冷喷涂在镍基高温合金(IN738)基体上制备Ni/Al、Ni/Al+0.5%ZrC与Ni/Al+0.07%三种复合涂层,然后在保护气氛Ar气中进行热扩散制备这三种金属间化合物涂层。结果低温球磨8 h后可以获得具有亚微米层状结构的Ni/Al+ZrC复合结构粉末。喷涂态Ni/Al合金复合涂层保留了粉末的结构,经1080℃保温10 h后,形成了致密的NiAl金属间化合物涂层。结论掺杂ZrC(0.07%和0.5%)的Ni/Al粉末在球磨后比未掺杂ZrC的粉末更均匀。掺杂ZrC的粉末形成了部分NiAl金属间化合物,而没有掺杂ZrC的粉末则无NiAl金属间化合物形成。冷喷涂可以制备几乎无氧化Ni/Al粉末粘结层。热处理后原喷涂态涂层中的亚微米的层状结构已基本消失,变成了较为均匀的组织。     

机械合金化制备TiB2-Ni(Al)复合粉末组织结构研究

目的通过原位合成技术获得TiB_2-Ni(Al)复合粉末。方法采用机械合金化方法在不同球磨时间的条件下,制备不同体积含量的TiB_2陶瓷相增强Ni(Al)基复合粉末,其中Ni粉和Al粉的摩尔比为1:1。采用扫描电子显微镜(SEM)以及X-射线衍射仪(XRD)分析球磨后粉末的显微组织结构及物相,研究不同球磨时间对制备TiB_2-Ni(Al)复合粉末物相演变、组织结构及粒子间界面结合状态的影响。结果在球磨过程中,球磨时间越长,Ni/Al间的塑变有利于原子之间的扩散,TiB_2陶瓷相颗粒逐渐变小。当球磨时间增长到一定程度时,延展性好的Al粉颗粒发生扁平化且其表面积不断增大,使得碎化后的Ni粉颗粒不断嵌入Al粉颗粒中,最终形成Ni(Al)固溶体。同时根据XRD分析发现,随着球磨时间的延长,TiB_2-Ni(Al)复合粉末中的Al峰逐渐减小,说明Al不断固溶到Ni中,形成了一定量的Ni(Al)固溶体。结论通过机械球磨技术在球磨一定时间后可原位合成Ni(Al)固溶体,这说明随着Ni与Al之间的相互扩散有利于形成Ni(Al)固溶体。     

机械合金化制备纳米晶Al65Fe25Ni10合金粉

采用X射线衍射（XRD），扫描电子显微镜（SEM）和差热分析仪（DTA）等研究了Al65Fe25Ni10元素混合粉末在机械合金化过程中的结构演变及热稳定性。结果表明：球磨5h后的粉末样品退火处理后生成Al5Fe2和Al3Ni2金属间化合物。球磨500h后得到纳米尺寸的Al（Fe，Ni）无序相。     

机械合金化制备铜碳过饱和固溶体

采用机械合金化方法制备Cu-4wt%C过饱和固溶体,通过SEM和XRD分析研究了机械合金化中Cu-C复合粉末的形貌变化及碳在铜中的固溶度扩展问题.结果表明,机械合金化过程中Cu粉和C粉形成了层状复合粉末;随着球磨时间的增加,C的衍射峰逐渐消失,Cu的衍射峰逐渐宽化,并且位置发生偏移;球磨24h后,C原子固溶到Cu中,Cu的点阵常数达到0.3620nm,晶格膨胀了0.15%.     

原位TiB2/Fe3Al基纳米复合材料的合成及其晶粒生长动力学(Ⅰ)--Fe-Al-Ti-B四元粉体的机械合金化

研究了机械合金化过程中Fe-Al-Ti-B四元粉体的结构演变,讨论了其合金化机制.研究表明,Fe-Al-Ti-B四元粉体的机械合金化通过Al、Ti、B原子向Fe晶格中扩散形成Fe（Al,Ti,B）过饱和固溶体.在机械合金化的早期（＜10h）,形成包覆结构的复合颗粒,合金化尚未进行.在机械合金化的中期（10-60h）,首先形成具有几个同心圆环结构的复合颗粒,然后环状结构消失,同时Fe（Al,Ti,B）晶格常数迅速增加,但成分均匀化过程缓慢.在机械合金化的后期（60-80h）,主要发生复合颗粒内部的成分均匀化过程,球磨80h后,复合颗粒内部各组元的成分已经非常均匀.Fe（Al,Ti,B）晶粒细小（6.8nm）,晶格畸变严重,具有近似非晶态的结构.由于Ti、B元素的添加,Fe-Al-Ti-B四元粉体晶粒细化速率更快,但合金化速率明显降低.     

Al-20% Sn-4.5% Cu合金在高能球磨和烧结中的组织

利用机械合金化方法制备Al-20%Sn-4.5%Cu合金粉末,将之压制成型后进行烧结.用X射线衍射仪(XRD)、扫描电镜(SEM)和差示扫描量热仪(DSC)分析了Al-20%Sn-4.5%Cu合金在高能球磨和烧结过程中的组织变化.结果表明,该合金粉末经40 h球磨后,可以获得纳米级Sn颗粒均匀弥散分布在Al基体上的组织,并且形成了Al(Cu)过饱和固溶体;在随后的烧结过程中,Sn相尺寸仍保持在200 mm左右,Al(Cu)过饱和固溶体则以CuAl2相的形式脱溶析出.     

低温高能球磨Ti/Al复合粉显微组织结构演化

采用低温高能球磨法制备了两种Ti/Al复合粉末,粉末组成为Ti-47Al(at%),Ti-45Al-2Cr_2Nb-1B-0.5Ta(at%).研究两种粉末在球磨过程中显微组织结构演化、形貌变化.结果表明,降低球磨温度能够有效控制球磨颗粒尺寸,低温条件及合金元素共同作用可以获得高质量的细晶均匀化复合结构粉末.在低温(-140-5)℃不加过程控制剂条件下球磨12 h,Ti-45Al-2Cr-2Nb-1B-0.5Ta(at%)粉末粒度得到有效细化,表现出精细均匀化复合结构粉末,Ti与Al晶粒尺寸分别约为16 nm,9 nm.在相同条件成分为Ti-47Al(at%)球磨5.2 h,Ti与Al元素没有很好复合及成分均匀化,两种成分球磨条件下均未有新相生成.在不加过程控制剂条件下,低温环境球磨和合金元素添加对机械合金化过程具有十分重要影响.     

Synthesis of nanocrystalline NiAl by mechanical alloying

The nanocrystalline NiAl intermetallic compound was synthesized by mechanical alloying of the elemental powders. The structural changes of powder particles during mechanical alloying were studied by X-ray diffractometery, scanning electron microscopy and microhardness measurements. The mechanical alloying resulted in the gradual formation of nanocrystalline NiAl with a grain size of 20 nm. It was found that NiAl phase develops by continuous diffusive reaction at Ni/Al layers interfaces. The NiAl compound exhibited high microhardness value of about 1035 Hv.     

Effect of CNT addition approach on the microstructure and properties of NiAl-CNT nanocomposites produced by mechanical alloying and spark plasma sintering

An approach was offered to synthesize NiAl-CNT intermetallic matrix nanocomposite by mechanical alloying (MA) to ensure the effective distribution of carbon nanotubes (CNTs) within the matrix. For this purpose 0.5 and 1 wt% of CNTs were added to the powder mixture before the completion of reaction between Ni and Al. The resultant powders were compared to the powders obtained from MA of ex situ synthesized NiAl intermetallic compound with CNTs. Bulk samples were fabricated by spark plasma sintering (SPS) that retained the integrity of CNTs in the matrix. Structural evolutions were investigated by X-ray diffractometery (XRD). Field emission scanning electron microscopy (FESEM) micrographs showed that the offered MA approach caused the CNTs to uniformly embed in the in situ synthesized NiAl matrix. Meanwhile better distribution of CNTs resulted in higher density of SPSed bulk nanocomposite as well as higher hardness up to 5.6 GPa compared to 5.41 of NiAl intermetallic obtained from the same MA time. Fracture toughness showed more than 6.4% increase with bridging and pull out of CNTs and deflection of cracks as toughening mechanisms.     

纳米金属间化合物NiAl的机械合金化合成及性能

利用机械合金化和高温热压工艺制备ＮｉＡｌ纳米晶体材料,并研究了材料的微观组织和力学性能。结果表明,ＮｉＡｌ的反应生成归结于机械碰撞诱发的爆炸反应机制,采用高温热压工艺可制备接近完全致密的纳米晶ＮｉＡｌ块体材料。ＮｉＡｌ纳米晶体材料的室温强度和塑性都高于铸态ＮｉＡｌ,纳米晶ＮｉＡｌ的高温强度依赖于应变速率,变形受扩散机制控制。     

Partial martensitic transformation of nanocrystalline NiAl intermetallic during mechanical alloying

Nanocrystalline NiAl intermetallic powders were synthesized by mechanical alloying (MA) in a planetary ball mill. Microstructural characterization was accomplished using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The nanocrystalline NiAl powders were formed by a gradual exothermic reaction mechanism during MA. Prolonged milling resulted in partial martensitic transformation of B2-NiAl to tetragonal L1₀-NiAl structure. It is believed that the martensitic transformation is induced by mechanical stress during MA.     

SYNTHESIS OF Ni-Mo ALLOYS BY MECHANICAL ALLOYING

Ni_(100-x)Mo_x(x=20,30,38)alloys have been synthesized by mechanical alloying.Thestructure evolution of powders in mechanical alloying process has been monitored byX-ray diffraction,scanning electron microscopy and transmission electron microscopyanalyses.The results show that the Ni_(62)Mo_(38)sample becomes partially amorphous afterhigh energy ball milling,while the Ni_(80)Mo_(20)and Ni_(70)Mo_(30)become non-equilibriumnanocrystals.     

机械合金化合成Ni—Mo合金

采用机械合金化方法制备Ni_(100-x)Mo_x(x=20,30,38)合金,并采用X-射线衍射,扫描电镜,透射电镜研究该机械合金化过程合金的结构变化结果表明Ni_(62)Mo_(38)试详经高能球磨后产生了部分非晶化,而Ni_(80)Mo_(20)和Ni_(70)Mo_(30)都形成了非平衡的纳米晶体     

Formation of NiAl intermetallic by gradual and explosive exothermic reaction mechanism during ball milling

NiAl intermetallic has been produced by mechanical alloying in a high energy vibrator mill using elemental Ni and Al powder mixture. The NiAl powders were formed in two ways. One by a gradual exothermic reaction mechanism during a long time continuous milling and the other by explosive exothermic reaction mechanism that occurred when opening the milling vessel to the air atmosphere after a short time milling. Prolonged milling for both cases resulted in change of morphology and refinement of grain size down to nano scale.     

脉冲放电等离子烧结NiAl金属间化合物的组织与性能

通过脉冲放电等离子烧结技术对经机械合金化法合成的NiAl金属间化合物粉末进行了烧结,研究了NiAl金属间化合物的微观组织和力学性能。结果表明,在较低温度下可制备接近完全致密的NiAl金属间化合物块体材料。     

Al-W二元系的机械合金化

用机械合金化方法由元素粉末制备了Ａｌ１ － ｘ Ｗｘ（ ｘ ＝ ０ ．１ ,０ ．２ ,０ ．５ ,０ ．９） 合金。用Ｘ 射线衍射法对球磨后的粉末进行了分析, 并用扫描电镜和透射电镜观察了形貌并研究了晶相结构。结果表明, 球磨后Ａｌ 在Ｗ 中的固溶度大大扩展, 但球磨到２５０ｈ 该系统仍未形成非晶; Ａｌ０ ．５ Ｗ０ ．５ 粉末经２５０ ｈ球磨后出现一结构为体心四方的新相。热力学计算表明该系统不能形成非晶     

MICROSTRUCTURE AND COMPRESSIVE PROPERTIES OF REACTION-MILLED NiAl-10wt%TiC COMPOSITE

1.IntroductionTheB2structuralintermetallicc0mp0undNiAlhasemergedaspotentialstructuralmaterialsf0rhightemperatureapplicati0n.However,thelack0fr00mtemperatureduc-tilityandpoorhightemperaturestrengthimpedesitsuse.Lackofambientductilityhasbeenattributedt0theabsence0fslipsystems(0nlydislocationhasbeenf0undinpolycrystallinematerialdeformedatr00mtemperature)['-'].Severalattemptshavebeenmadet0res0lveitsroomtemperaturebrittleness,includingmodification0fslipsystems,microalloying,grainb0undaryelim…