Effect of the formation process of transient liquid phase （TLP） on the interface structure of TiAl joints

TiAl has been joined employing the transient liquid phase （TLP） bonding with Ti combined with Cu, Ni or Fe foils. Experimental results showed that though the interface structures of the joints are quite different, all the joined zones are composed of five sublayers, i.e. two diffusion zones, two interfacial zones and an interlayer. It has been convinced that the formation process of the transient liquid phase controls the diffusion behavior of melting point depressant （MPD） Cu, Ni, and Fe atoms, which leads to form different interface structures of the joints.     

连接温度对氮化硅陶瓷/镍基高温合金部分液相扩散连接接头性能的影响

采用部分液相扩散连接方法 ,利用Nb/Cu/Ni复合层作中间层 ,在连接压力、连接时间、冷却速度一定 ,连接温度变化的条件下对氮化硅陶瓷 /镍基高温合金进行了部分液相扩散连接试验 .通过剪切试验评价连接温度对接头强度的影响和采用SEM研究连接温度对接头微观组织的影响 ,分析了连接温度对氮化硅陶瓷 /镍基高温合金连接接头性能影响的规律     

Spark Plasma Sintering Preperties of Ultrafine Ti （ C, N）-based Cermet

Ultrafine Ti( C, N)-based cermet was sintered by SPS from 1050℃ to 1450℃ and its sintering properties, such as porosity, mechanical properties and phase transformation , were investigated by optical microscopy ( OM ), scanning electron microscopy (SEM), X-ray diffraction ( XRD ), and differential scanning calorimeter (OSC). It is found that the spark plasma sintering properties of Ti ( C, N )-based cermet differ from those of conventional vacuum sintering. The liquid phase appearance is at least lower by 150℃ than that in vacuum sintering. The porosity decreases sharply belove 1200℃ and reaches minimum at 1200℃ , and afterwards it almost keeps invariable and no longer increases. SPS remarkably accelerates the phase transformation of Ti ( C, N )-based cermet and it has a powerful ability to remorse oxides in Ti( C, N)-based cermets. Above 1350℃, denitrification occurred. Fresh graphite phase formed above 1 430℃ . Both the porosity and graphite are responsible for the poor TRS.     

Effect of Various Carbides on the Wettability in Ni/Ti（C,N） System

The wettability in Ni / Ti （ C, N ） systems with various carbides additions was investigated by the sessile drop technique. The substrates prepared by HP at 2073 K for 1 h before and after wetting were characterized by XRD . The microstructure ca metall ceramics interfaces was observed via SEM in a back scattered mode. Furthermore , an X-ray energy-dispersive spectrometer （ EDS ） attached to SEM was used to study the element diffusion in interfacial regions. The resalts reveal that reactive wetting takes place in the system in high tempercature wetting procedure , which is controlled by diffusion and dissolution mechanism. Results also show that the contact angles decrease with various carbides additions, iuelnding WC , Mo2 C, TaC , NbC and VC , and decrease continuously with the increasing of additions. The order of the contact angles in Ni/Ti （ C, N ） systems with 10 wt% carbides acMitions is Mo2 C 〈 TaC 〈 WC 〈 VC 〈 NbC. The enhancement of the wettability is due to an alloying procedure during high temperature wetting when metallic atoms diffuse into Ni phase, which decreases the interfacial energy of Ni/ Ti （ C, N） systems.     

梯度(Ti,Al)N涂层的微观结构与机械性能研究

利用电弧离子镀技术在航空发动机压气机用1Cr11Ni2W2MoV在不锈钢上沉积了（Ti,Al）N梯度涂层,X射线衍射的结果表明涂层为B1型（Nacl）单相结构,具有（220）择优取向．扫描电镜观察表明,涂层均匀致密,与基体结合良好．电子探针元素线分析和截面面分布表明,所制备的涂层是内层富TiN、外层富（Ti,Al）N的梯度涂层,试验结果表明,（Ti,Al）N梯度涂层具有良好的耐磨性等机械性能．     

基于荧光标记的亲水修饰聚N,N-二乙基丙烯酰胺构象转变研究

基于荧光的光物理技术,考察了苊烯标记聚N,N-二乙基丙烯酰胺(PDEA)和N-羟甲基丙烯酰胺(NHMAA)与DEA的温敏性共聚物P(DEA-co-NHMAA)稀水溶液相分离过程。结果表明,经亲水修饰后,最低临界溶解温度升高,相分离过程趋缓。PDEA和P(DEA-co-NHMAA)稀水溶液相分离属渐变过程的构象发生了从伸展线团到蜷曲球的转变。     

Ti(C,N)基金属陶瓷与3Cr13不锈钢的真空钎焊

采用AgCuZnNi钎料对Ti(C,N)基金属陶瓷和3Cr13不锈钢进行真空钎焊。研究了钎焊温度和钎焊时间对钎焊接头剪切强度的影响,通过SEM和EDS对Ti(C,N)基金属陶瓷/3Cr13不锈钢接头的显微组织、元素分布及断口形貌进行分析。研究表明:随着钎焊温度和钎焊时间的增加,钎焊接头的剪切强度先增大后减小。在钎焊温度为820℃,钎焊时间为10 min的工艺条件下,钎焊接头的结合强度达到最大,其剪切强度为154 MPa。Ti(C,N)基金属陶瓷/3Cr13不锈钢焊缝由Ag基固溶体和Cu基固溶体构成。Ag基固溶体主要集中在焊缝的中部,而Cu基固溶体大多数分布在焊缝两侧与母材结合。Ti(C,N)基金属陶瓷/3Cr13不锈钢接头断裂主要发生在Ti(C,N)基金属陶瓷侧,其断裂方式为脆性断裂。     

WC和Mo2C添加对Ti(C,N)基金属陶瓷切削性能的影响

传统的Ti(C,N)基金属陶瓷刀具材料广泛采用Mo2C来改善粘结相对硬质相的润湿性,近年来Mo的价格不断上涨,寻找低成本金属代替Mo已成为Ti(C,NEDS)基金属陶瓷的发展趋势。为了探讨WC代Mo2C添加的可行性及其效果,研究了WC和Mo2C添加对Ti(C,N)基金属陶瓷切削性能的影响,采用电子扫描显微镜（SEM）观察刀具的磨损形貌,通过能谱分析（EDS）分析磨损表面的元素分布,并对刀具的主要磨损机理进行分析。实验结果表明,添加WC的金属陶瓷的切削长度和添加Mo2C的相当,将原始WC粉末粒度细化后,不仅切削长度显著增加,切屑也由带状缠乱型变为螺旋型,并且大大减少积屑瘤的形成,有利于切削的进行。切削磨损机理主要为扩散磨损和氧化磨损,伴有轻微的磨粒磨损。     

TA1表面制备Ni/Al涂层的反应扩渗及抗氧化行为

为了提高纯钛的高温抗氧化性能,采用电弧喷涂和等离子喷涂方法在纯钛表面制备Ni/Al涂层.对试件进行900 ℃×5 h热处理后,再进行900 ℃×40 h连续氧化实验,探索其高温抗氧化行为.结果表明,经过表面改性处理的Ni/Al涂层可以显著提高纯钛的高温抗氧化性.在热处理过程中Ni/Al涂层中的Al发生熔化扩散并与Ni和Ti形成以NiAl与TiAl₃相为主的扩散层.在氧化过程中Ni/Al涂层表面形成连续且致密的α-Al₂O₃,同时表面扩散层中的富铝相可为涂层表面提供充足的Al元素,进而对纯钛基体提供有效的高温抗氧化保护作用.     

Precipitation and Hetero-nucleation Effect of V(C,N)in V-Microalloyed Steel

The precipitation behavior of V(C,N) in steels microalloyed with vanadium was researched using a thermal simulator during single-pass deformation at 800-750 ℃.The V(C,N) precipitates and its nucleation effect on ferrite were investigated by TEM and EDS.The experimental results show that there are two remarkable heterogeneous nucleation effects of V(C,N) particles precipitated before y→αphase change:primary reason is that high coherency between V(C,N) and ferrite promotes V(C,N) to become a nucleating center of intragranular ferrite;secondary reason is that the coarsening of V(C,N) causes locally solute-poor region in austenite,thus expedites the nucleation of intragranular ferrites further.Furthermore,the relationship between the size and shape of V(C,N)was studied,and identification method was provided for distinguishing interphase precipitation and general precipitation to avoid erroneous judgment and misguide.     

聚甲基丙烯酸-N,N-二甲氨基乙酯的紫外光引发溶液聚合及性能研究

采用紫外光引发溶液聚合得到了甲基丙烯酸-N，N-二甲氨基乙酯(DMAEMA)聚合物，研究了聚合过程中引发剂安息香乙醚(BE)用量、单体浓度、光引发时间对聚合速率、产率及分子量的影响，实验确定了制备线型聚甲基丙烯酸-N，N-二甲氨基乙酯聚合物(PDMAEMA)的工艺及方法。采用膨胀计法研究了聚合反应，结果表明：DMAEMA单体可能同时参与了光引发过程。通过对PDMAEMA水溶液性能研究发现，PDMAEMA水溶液具有明显的温度及pH敏感性。     

Fabrication and magnetic properties of Sm3(Fe,Ti)29Nx/α-Fe dual-phase nanocomposite permanent magnetic material

Sm3(Fe,Ti)29Nx/α-Fe dual-phase nanometer magnetic material was fabricated through rapid solidification, crystallization and nitridation of Sm-Fe (Ti) alloy. The effect of combination of rapid solidification and Ti alloy addition on the phase formation and microstructure of the Sm-Fe alloy is investigated in this paper. The microstructure of amorphous phase and dual-phase nano-grain crystals before and after crystallization annealing were observed using a high-resolution transmission electron microscope (HREM). The dual-phase nano-grains after annealing were compacted together with a clear interface with the direct exchange-coupling mechanism. Different annealing processes were used to examine the melt-spun alloy. Comparison of the images of SEM showed that annealing at 750℃ for 10 min was most suitable to get homogeneous and nano-grains. No obvious kink was detected in the second quadrant of the hysteresis loop like a single hard magnet, and strong exchange coupling was found between hard magnets and soft magnets.