Formation of NiAl Intermetallic Compound by Cold Spraying of Ball-Milled Ni/Al Alloy Powder Through Postannealing Treatment

Ni/Al alloy powders were synthesized by ball milling of nickel-aluminum powder mixture with a Ni/Al atomic ratio of 1:1. Ni/Al alloy coating was deposited by cold spraying using N₂ as accelerating gas. NiAl intermetallic compound was evolved in situ through postspray annealing treatment of cold-sprayed Ni/Al alloy coating. The effect of annealing temperature on the phase transformation behavior from Ni/Al mechanical alloy to intermetallics was investigated. The microstructure of the mechanically alloying Ni/Al powder and NiAl coatings was characterized by scanning electron microscopy and x-ray diffraction analysis. The results show that a dense Ni/Al alloy coating can be successfully deposited by cold spraying using the mechanically alloyed powder as feedstocks. The as-sprayed alloy coating exhibited a laminated microstructure retained from the mechanically alloying powder. The annealing of the subsequent Ni/Al alloy coating at a temperature higher than 850 °C leads to complete transformation from Ni/Al alloy to NiAl intermetallic compound.     

添加剂对低压烧结Zr50Al15Ni10Cu25非晶态粉末力学性能的影响

以商业纯元素粉末为原料,用机械合金化方法在低真空条件下合成了以非晶态为主的Zr50Al15Ni10Cu25粉末。研究了一定量的外界添加剂C、Si3N4和SiC对体系热稳定性和晶化行为的影响。混合粉末用手工预压成形,然后在氩气氛下进行低压烧结。利用X射线衍射（XRD）、扫描电镜（SEM）、差热分析（DSC）和电子拉伸实验机对粉末样和块状样进行了测试。结果表明,合适的外界添加剂可以提高体系的析晶活化能,增强体系的热稳定性。适量的Si3N4能促进Zr50Al15Ni10Cu25非晶粉末的低压烧结性能,即有助于提高样品的烧结致密度和样品的抗弯强度。     

Effect of ball milling conditions on the microstructure and the transformation behavior of Ti−Ni and Ti−Ni−Cu shape memory alloy powders

Ti−50Ni and Ti−40Ni−10Cu (at.%) shape memory alloy poweders have been fabricated by the ball milling method. Their alloying behaviour and transformation behaviour were investigated by means of optical microscopy, electron microscopy, X-ray diffractometry and differential scanning calorimetry. As-milled Ti−Ni powders fabricated with a milling time of less than 20 hrs were a mixture of pure elemental Ti and Ni, and therefore we were unable to obtain alloy powders because the combustion reaction between Ti and Ni occurred during heat treatment. Since those fabricated with a milling time of more than 20 hrs were a mixture of Ti-rich and Ni-rich Ti−Ni solid solution, it was possible to obtain alloy powders without a combustion reaction during heat treatment. Clear exothermic and endothermic peaks appeared in the cooling and heating curves, respectively, in DSC curves of 20 hr and 30 hr milled Ti−Ni powders. On the other hand, in DSC curves of 1 hr, 10 hrs, 50 hrs and 100 hrs, the thermal peaks were almost discernible. The optimum ball milling time for fabricating Ti−Ni alloy powders was 30 hrs. Ti−40Ni−10Cu alloy powders were fabricated successfully by the optimum ball milling conditions deduced from Ti−50Ni alloy powders.     

非晶55Mg35Ni10Si块体的制备及力学性能

利用机械合金化方法制备55Mg35Ni10Si三元非晶合金粉末,以该非晶粉末为基础材料,采用真空热压法制备55Mg35Ni10Si非晶块体,利用显微硬度测试等手段考察其力学性能。DSC和XRD分析表明,粉体和块体材料中均出现一个明显的放热峰,结合高分辨电子显微镜观察证明,真空热压后块体材料总体上仍以非晶相为主并含少量纳米晶,而块体材料的晶化峰温度要略低于非晶粉末。力学性能测试表明,块体材料的显微硬度为7 834-8 048 MPa,且随载荷的增加而下降,与传统晶态材料的硬度-载荷依赖关系相似。块体材料的断口呈山峦状,没有明显塑性形变的特征,断裂裂纹扩展沿压痕对角线呈放射状。     

放电等离子烧结-非晶晶化法合成Ti7oNb7.8Cu8.4Ni7.2Al6.6复合材料

采用机械合金化制备不含和含2%(体积分数)B4C的钛基非晶合金粉末,随后采用放电等离子烧结-非晶晶化法合成不含／含(TiB+TiC)的Ti7oNb7.8Cu8.4Ni7.2Al6.6超细晶／细晶钛基复合材料;运用X射线衍射分析(XRD)、差示扫描量热分析(DSC)、扫描电子显微镜(SEM)和万能材料试验机等对制备的钛基非晶粉末和超细晶／细晶钛基复合材料进行表征.结果表明高能球磨80h的钛基粉末中主要为非晶相,B4C颗粒的加入对钛基粉末的玻璃转变温度、晶化温度和晶化焓有显著的影响.另外,不含／含(TiB+TiC)的复合材料的显微硬度分别为5.47和5.33GPa;以50K/min升温到1223K并保温10min获得的Ti70Nb7.8Cu8.4Ni7.2Al6.6块体试样的断裂强度和断裂应变分别为2098MPa和11.5%.     

Formation of Fe-19 wt%Cr-9 wt%Ni Nanocrystalline Alloy with Excellent Corrosion Resistance: Phase Transition and Microstructure

In this paper, microstructure characteristics and phase transitions of Fe-19 wt%Cr-9 wt%Ni nanocrystalline alloy are comprehensively studied during the mechanical alloying and hot pressing sintering processes. Corrosion resistance of the sintered Fe-19 wt%Cr-9 wt%Ni nanocrystalline alloy samples is further analyzed. During the mechanical alloying process, Fe-19 wt%Cr-9 wt%Ni nanocrystalline alloy powders mainly composed of metastable ferrite phase are obtained after mechanical alloying for 8, 16 and 24 h, respectively. In the subsequent hot pressing sintering process, the phase transitions(from ferrite to austenite) occur from 650 to 750 °C for Fe-19 wt%Cr-9 wt%Ni alloy powders milled for 24 h. When the sintering temperature is raised to 1050 °C for 1 h, the ferrite phase has transformed into austenite phase completely, and the obtained grain size of sintered Fe-19 wt%Cr-9 wt%Ni alloy is around 40 nm. Electrochemistry test of the sintered Fe-19 wt%Cr-9 wt%Ni alloy has been operated in 0.5 mol L~(-1) H_2SO_4 solution to show the corrosion resistance properties. Results show that the sintered Fe-19 wt%Cr-9 wt%Ni alloy exhibits excellent corrosion resistance, which is proved by higher self-corrosion potential, lower self-corrosion current density and larger capacitive reactance, compared with that of commercial 304 stainless steel.     

Characteristics of mechanical alloyed Ni-Al powder for sintering

Mechanical alloying was employed to obtain high-activity Ni-AI powder. The effects of mechanical alloying on the microstructure and characteristics of milled powder with a normal composition of Ni-22.89 at.% AI-0.5 at.% B were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The results show that a solution Ni （AI） was obtained after milling. During mechanical alloying, the milled powder obtains extra surface energy and crystalline energy because the crystallite size becomes free and the lattice strain increases with the milling time prolonging. Furthermore, about 0.5 mol% oxide in the particles were formed after milling, and this kind of dis- persed oxide is effective to improve the properties of the sintered alloy by dispersion strengthening. It is confirmed that Ni3AI alloy with outstanding properties has been prepared with mechanical alloyed powders.     

SYNTHESIS AND SOLID STATE SINTERING OF W-Ni-Fe NANO-COMPOSITE POWDERS

1.IntroductionTungstenheavyalloyisakindoftwo-phasecompositecharacterizedbyhighdensity,highstrengthandgoodductilityl1].Themicrostructureconsistsoftungstengrainsem-beddedinanalloymatrix.FullydenseW-Ni-FeheavyalloysaretypicallyprocessedfromWpowderblendedwithNiandFeelementalpowdersthroughliquid-phasesinteringat15oth155oop.Theliquidinitiallyformsatatemperaturenearl465rol2].Therelativelyhighprocessingtemperatureandlongexposuresresultinacoarsefinalmicrostructure(4O-6opmingrainsize)andprogressivec…     

Neutron diffraction study in amorphous Ni30Ta70 alloy powders by mechanical alloying

A mixture of elemental Ni and Ta powders with an atomic ratio of 3∶7 was subjected to mechanical alloying (MA). An amorphous Ni₃₀Ta₇₀ alloy was formed after 80 hrs of milling, the amorphization by rapid quenching technique of which has not been reported. The atomic structural changes were observed by neutron diffraction in the amorphization process during MA. The radial distribution function RDF(r) shows that peaks of fcc-Ni and bcc-Ta crystal broaden first and gradually approach those characteristic of an amorphous phase with increasing MA time. A local atomic environment around Ni and Ta atoms was studied by analyzing the first peak in the total pair distribution function g(r) after the completion of amorphization. We reach our conclusion from this analysis that the amorphization in the Ni₃₀Ta₇₀ alloy takes place by the penetration of smaller Ni atoms into the bcc-Ta lattice.     

机械合金化制备Ni-B-Si合金粉末

本实验选取成分为92%Ni-4%B-4%Si的混合粉末进行机械合金化,并每隔一定时间定量取粉进行SEM、XRD及DSC分析。实验结果表明,当球磨至30 h时,粉末形貌趋于球状,微量元素B和Si已经完全向镍中固溶,此时起始熔化温度降至1038℃;继续延长球磨时间粉末发生团聚,并在球磨至80 h时,趋于非晶化转变;将球磨40 h的合金粉末与松装镍粉在1100℃进行熔渗烧结时,发现其与镍粉发生冶金结合并形成致密的烧结体。     

机械合金化法制备Fe—Ni—P—B磁性非晶合金的研究

用机械合金化法研究制备Ｆｅ－Ｎｉ－Ｐ－Ｂ系磁性非晶材料,用Ｘ射线衍射仪,扫描电子显微术和透射电子显微术对不同球磨工艺处理的Ｆｅ４０Ｎｉ４０Ｐ１４Ｂ６成分的粉末进行了分析,结果表明,成分为Ｆｅ４０Ｎｉ４０Ｐ１４Ｂ６的粉末,可通过机械合金化使其非晶化。     

Ni3Al基复合材料的组织与性能

通过机械法将ＮｉＡｌ粉、Ｎｉ粉ＷＣ粉混合后烧结，堆焊制备成Ｎｉ３Ａｌ＋ＷＣ复合材料。研究结果表明，该复合材料在堆焊过程中，可促使大部分ＷＣ不溶入熔池而直接以颗粒状分布于Ｎｉ３Ａｌ基体上，在ＷＣ的抗磨特性和基体的抗汽蚀性能联合作用下，使该复合材料具有高的硬度及较好的抗汽蚀和抗水砂磨损的性能。     

Mg_2Ni系贮氢合金制备方法的研究进展

本文综述了熔炼法、机械合金化法、烧结法、扩散法、氢化燃烧合成法、表面处理法等制备Mg2Ni合金的基本原理和主要工艺。介绍了扩散法和球磨法等制备技术的联用,总结并讨论了这些合金制备技术制取的合金的充放氢性能和电化学性能及其对合金性能的影响。较先进的机械合金化法制备Mg2Ni系贮氢合金复合材料是比较理想的途径。     

低W-W连接度65W-25Cu-10Ni合金的制备及准静态力学性能研究

利用W颗粒表面化学镀Ni结合SPS的方法,制备了低W-W连接度65W-25Cu-10Ni合金,并开展了准静态力学性能研究。结果表明,制得的Ni包W复合粉中Ni包覆层分布均匀且与W结合良好;以Ni包W复合粉和Cu粉为原料制备的65W-25Cu-10Ni合金组织均匀且致密。在准静态压缩加载条件下,与65W-35Cu合金相比,65W-25Cu-10Ni合金的强度及塑性均大幅度提高;在准静态拉伸加载条件下,与65W-35Cu合金相比,65W-25Cu-10Ni合金的强度较高,塑性没有明显提高。机理分析表明,与65W-35Cu合金相比,65W-25Cu-10Ni合金中W-W连接度较低、粘结相由Cu相转变为Cu0.81Ni0.19固溶体,且W与粘结相之间形成了冶金结合,以上三个因素共同导致65W-25Cu-10Ni合金强度的提高;此外,W-W连接度的降低以及W-粘结相界面结合强度的提高是65W-25Cu-10Ni合金在准静态压缩加载条件下塑性提高的原因。     

机械合金化制备Cu-Cr合金时效强化特性的研究

采用机械合金化工艺制成Cu—Cr合金粉末,然后热压成形制备铜铬合金。采用XRD、TEM分析机械合金化过程中Cu-Cr合金粉末的显微组织和晶粒大小,测试了热压成形后Cu—Cr合金的力学和电学性能,探讨了材料的强化机制和热压温度对组织性能的影响。结果表明,Cu—Cr合金粉末可通过机械合金化获得过饱和固溶体,热压成形后,组织细小均匀,具有优良的综合性能。该合金经840℃热压并保温2h后,其强度达最大值,显微硬度为205．3HV,抗拉强度633．5MPa,电导率为80．4％IACS。合金中过饱和的Cr原子的作用是使合金沉淀强化。     

CuxBy表面修饰对Mg50Ni50合金循环稳定性的影响

用机械合金化法合成了CuxBy合金和非晶态Mg50Ni50储氢合金.用同样的方法以CuxBy对非晶态Mg50Ni50合金进行表面修饰.探索了不同组成的CuxBy合金、同一组成不同比例(质量比,下同)的修饰对Mg50Ni50合金电极循环稳定性的影响.结果表明:不同组成的CuxBy合金对Mg50Ni50合金的表面修饰,都不同程度地提高了Mg50Ni50合金电极的循环稳定性.同一组成不同比例的修饰,对Mg50Ni50合金电极循环稳定性改性效果差异较大.当Mg50Ni50:Cu0..9B0.1=5:1时,初始放电容量为465 mAh·g-1,第50个循环放电容量为222 mAh·g-1.在保持高放电容量的前提下,有效地提高了非晶态Mg50Ni50合金电极的循环稳定性.     

机械合金化对Mg_2Ni相形成的影响

用两步法 (即由机械合金化和压制烧结两个步骤组成 )制备了Mg2 Ni合金。实验证明 :混合粉经机械合金化后 ,晶粒细化 ,增加了固态扩散的能力 ,有利于固相反应进行 ,使Mg2 Ni产率明显提高。不同温度烧结处理的结果表明 :烧结温度是影响Mg2 Ni相形成的重要因素 ,烧结温度达到 843K ,Mg Ni粉基本能完全转变为Mg2 Ni相。     

Influence of process control agents on the performance of Ni3Al by mechanical alloying

The influence of process control agents (PCAs) on the mechanical properties of Ni3Al intermetallic compounds by mechanical alloying was in- vestigated in order to develop oxide deposition reinforced intermetallics. The PCAs in mechanical alloying were pure ligroin, 75 vol.% ligroin 25 vol.% alcohol, 50 vol.% ligroin 50 vol.% alcohol, 25 vol.% ligroin 75 vol.% alcohol, and pure alcohol. The normal composition is Ni-22.9at.%Al-0.5at.%B, the ball-to-powder weight ratio is 10:1, and the milling time is 30 min. Then, the powders were sintered by spark plasma sintering under 40 MPa for 5 min at 1000°C. The results show that a higher bending strength and a higher hardness were obtained when the PCAs were 75% ligroin 25% alcohol in mechanical alloying. The bending strength is about 2700 MPa and the hardness (HV) is more than 6 GPa.     

掺Pd改性纳米晶Mg2Ni吸放氢氘特性研究

采用机械合金化法制备了Mg2Ni-1．0％Pd（质量分数，下同）合金粉末，用XRD及AFM等分析表征了球磨20h后粉末的相结构和微观形貌，测定了Mg2Ni-1．0％Pd合金吸放氢氘的P-C-T曲线和动力学曲线。结果表明，机械合金化制备的Mg2Ni-1．0％Pd合金粉末粒度在10nm～50nm之间；同熔炼法制备的Mg2Ni合金相比，纳米Mg2Ni-1．0%Pd合金吸氢时的焓变值减小，放氢时焓变值增大，可逆贮氢容量为1．06（H／M,原子比，下同）；与吸放氢相比，在相同温度下合金吸放氘的坪台压升高，焓变值减小，具有显著的同位素效应。纳米Mg2Ni-1．0％Pd合金的吸氢速率和吸氘速率与温度的关系在573K附近发生变化。     

Effect of grain size on high-temperature oxidation behavior of Cu-80Ni alloy

1　INTRODUCTIONTheoxidationofunalloyedcopperandnickelhasalreadybeenstudiedindetail.Whilethehigh tem peratureoxidationofCu Nialloys ,alsostudiedanumberoftimestodate[13] ,isanexampleofarela tivelysimpleclassofscalingofbinaryalloysbyasin gleoxidant,becausethemetalsformacontinuousse riesofsolidsolutions ,whiletheiroxides ,CuO ,Cu2 OandNiO ,exhibitsmallmutualsolubilitiesandshowsignificantdifferencesinthethermodynamicstabilityandparabolicgrowthrates .Thus ,copper richalloysformexternalscales…