预变形对2197铝锂合金显微组织和力学性能的影响

通过力学性能测试,扫描电镜、透射电镜观察等手段,研究了固溶淬火后不同程度预变形对2197铝锂合金力学性能及显微组织的影响.结果表明:随着预变形量的增加,合金的时效响应加快,其强度达到峰值的时间逐渐缩短,且峰值强度明显提高.预变形的加入显著促进了基体中T1相的均匀、弥散析出,θ″/θ′相和δ′相析出受到抑制.     

Mechanical properties, corrosion behaviors and microstructures of 7075 aluminium alloy with various aging treatments

The influence of two novel aging treatments, T616 （130 ℃, 80 min ＋ 65℃, 240 h＋130℃, 18 h） and high-temperature pre-precipitation（HTPP） aging （445℃, 30 min＋120℃, 24 h） on the tensile properties, intergranular corrosion, exfoliation corrosion behaviors and microstructures of 7075 AI alloy was studied, which were compared with the T6, T73 and RRA treatments. Fine η＇ precipitate with high density was obtained in the alloy with the T6 and RRA treatments. The η＇ precipitate density in the HTPP aged alloy is decreased due to the formation of coarse particles during the pre-precipitation process at high temperature of 445℃. The 7075-T616 alloy possesses higher precipitate density and whole precipitate volume fraction within the grain than the 7075-T73 alloy, and its whole precipitate volume fraction is even greater than that of the 7075-T6 alloy. Compared with T6 treatment, the RRA, T73, T616 and HTPP aging treatments cause the discontinuous distribution of the η precipitates at the grain boundary, which decreases the intergranular corrosion and exfoliation corrosion susceptibility of the alloy. Meanwhile, the T616 and RRA treatments can keep the high strength of the 7075 AI alloy, but the studied HTPP aging and T73 treatments lower its strength.     

Nickel co-deposition with SiC particles at initial stage

The cyclic voltammetry and chronoamperometry were used to study the influence of SiC particles on the nucleation and growth of nickel deposition on copper matrix from acid sulphate solution. The surface morphology of Ni-SiC co-deposition at initial stage was observed with scanning electron microscope（SEM）. The results show that the nickel co-deposition with SiC particles may begin at -700 mV （vs SCE） under the experimental conditions, and the nucleation/growth mechanism of Ni-SiC co-deposition tends Seharifker--Hill with three-dimension model. In the case of low over-potential of -710--740 mV, the nucleation process of Ni-SiC co-deposition may follow the progressive nucleation mechanism of Scharifker--Hill. During higher over-potential of-770--800 mV, it trends to follow a 3D instantaneous nucleation/growth mechanism. With the increase of over-potential, the relaxation time tin, corresponding to the peak current Im of Ni-SiC co-deposition decreases regularly and is shortened apparently, compared with that of pure Ni deposition. The observation with SEM confirms that SiC particles can be considered as favorable sites for nickel nucleating. When certain amount of SiC particles are adsorbed （or cover） on cathode surface, especially under the condition of high overpotential, they may represent an external inhibition of the nickel electron deposition.     

Ni-SiC复合镀层电结晶初期动力学分析

利用循环伏安方法和恒电位阶跃技术研究Ni-SiC复合镀层电沉积行为。结果表明：Ni-SiC复合镀层和纯Ni镀层的形核／生长过程符合Scharifker-Hill三维成核模型;在低过电位下,Ni．SiC复合镀层形核／生长过程按三维连续成核机制;高过电位下,形核／生长过程遵循瞬时成核机制,与纯Ni镀层的形核／生长过程具有一致性;无论Ni-SiC复合镀层还是纯Ni镀层,形核弛豫时间‰随负电位的增大呈现有规律递减趋势,相应的厶值基本相近;SiC粉体的引入导致Ni形核的过电位正移和‰的显著减小。     

Ag，Mg合金化对Al-Cu-Li合金时效特性和显微组织的影响

通过力学性能测试和显微组织观察研究微量Ag和Mg对Al-3.5 Cu-1.0Li合金时效特性和显微组织的影响.结果表明:在175℃时效时,单独加Ag不影响合金的时效硬化效果,析出物形貌与Al-Cu-Li合金相似,峰值时效状态下均析出较粗大的T1相和θ'相;单独加Mg加快Al-Cu-Li合金的时效响应,提高合金的时效硬化效果,时效时析出GP区,θ'相和T1相;Ag和Mg同时添加的2050合金中,T1相的析出速度加快,析出密度增大,并以T1相为主要强化相,时效强化效果最大.Ag,Mg添加对合金的不同影响可通过溶质原子与空位、溶质原子与溶质原子之间的相互作用来解释.     

航空铝合金耐疲劳损伤特征微结构研究现状

铝合金疲劳裂纹易沿粗大的杂质相粒子萌生,而合金的晶粒结构、晶界和晶粒取向、析出相等本征微观特征影响疲劳裂纹的扩展行为.从疲劳裂纹的萌生和扩展两方面较系统地分析了航空铝合金耐疲劳损伤性能与本征微结构之间的关系和作用机制以及最新的研究进展,并在此基础上提出了需要进一步研究的问题.     

燃烧合成(W,Ti)C在硬质合金中的应用

研究了保护性气氛Ar气压力对燃烧合成TiC:WC=5:5的单相（W,Ti)C碳含量的影响。研究表明,在0．1－0．3MPaAr气压力范围内,增加Ar气压力,可阻碍燃烧坯体的膨胀或裂纹的出现,从而提高（W,Ti)C中的合成碳含量,并有利于其中游离碳含量的控制,当预热温度为800℃、Ar气压力为0．2和0．3MPa时,（W,Ti)C中游离碳含量分别为0．062％、0．32％。以0．3MPaAr气压力下合成的（W,Ti)C粉末与WC及Co粉为原料烧结制备YT15硬质合金时,WC在（W,Ti)C中有一个继续固溶过程,烧结后的合金硬度为92．1HRA、横向断裂强度为13251．9MPa。     

高性能航空铝合金结构材料的动态研究

随着航空工业的发展,对航空铝合金材料性能的性能提出了更高的要求,本文分析研究了高性能航空铝合金结构材料的动态和发展趋势。调整合金的化学成分、降低杂质元素含量、改进材料制备、加工和热处理工艺是提高航空铝合金性能的主要手段,而发展超高强铝合金、高强高韧铝合金、低密高强高刚Al-Li合金、高强耐热铝合金、高强超塑性性铝合金和铝基复合材料等是发展航空铝合金结构材料的主要目标。     

Ti-W-C体系的自蔓延高温合成与反应机理

研究了Ti-W-C体系自蔓延高温合成(SHS)的燃烧温度和燃烧速度与W含量、Ti粉粒度及预热温度的关系。分析了不同W含量和预热温度时SHS产物的相组成,并对体系的SHS反应机理进行了研究。结果表明:W/(Ti+W)≤ 0.3时,基本能合成单相(W/Ti)C;而预热可促进(W,Ti) C的SHS合成;体系的SHS反应过程中存在两种反应机制,即溶解-析出机制和扩散-固溶机制     

耐高温聚氨酯改性TDE-85/E-51环氧树脂胶粘剂的制备和性能

以混合芳胺为固化剂,通过聚氨酯(PU)对4,5-环氧环己烷-1,2-二甲酸二缩水甘油酯(TDE-85)与二酚基丙烷缩水甘油醚(E-51)环氧树脂的改性,制备了一种高强高韧的耐高温环氧树脂结构胶粘剂。通过改变E-51、TDE-85、PU及固化剂之间的配比,探讨了各个组分对胶粘剂力学性能的影响。通过SEM分析,研究了PU增韧环氧树脂的机理。结果表明,TDE-85和E-51的配比为1∶1,PU添加量为环氧树脂的19%,芳胺固化剂添加量为20%时,胶粘剂具有最佳的耐热性和力学性能。制备的PU改性TDE-85/E-51结构胶粘剂室温拉伸剪切强度达到25.81 MPa,160℃高温拉伸剪切强度为12.85 MPa,剥离强度达到51.68 N/cm。