β/γ三相钛铝合金Ti-43Al-8.5V-Y的应变疲劳性能

对Ti-43Al-8.5V-Y合金进行了常温、550℃和700℃高温应变疲劳试验,研究应变幅值对材料疲劳性能的影响。基于Manson-Coffin公式推导出应变幅与疲劳寿命之间的关系式,通过断口分析揭示材料的高温应变疲劳断裂机理。研究表明:Ti-43Al-8.5V-Y合金在高应变幅下呈现快速循环硬化特征,在低应变幅下有轻度的循环软化特征;随着环境温度的提高,材料塑性有所增加;高温下晶间的β相脆断是合金应变疲劳破坏的主要原因。     

拉伸断裂能与橡胶磨耗性能的关系研究

本论文以ESBR1500E、BR9000和NR为基体,采用不同的硫化体系(普通硫化体系、有效硫化体系、半有效硫化体系和平衡硫化体系),研究不同硫化体系下硫化胶的拉断断裂能与橡胶阿克隆磨耗和DIN磨耗体积的相关性。研究结果表明,无论是SBR、BR还是NR,硫化胶的DIN磨耗体积与其拉伸断裂能都有较好的线性关系,随拉伸断裂能的增加,硫化胶的DIN磨耗体积下降,耐磨性能提高。但对于阿克隆磨耗,拉断断裂能与磨耗体积没有明显的相关性。采用不同种类的炭黑补强ESBR1500E,研究硫化胶拉断断裂能与磨耗体积的关系。研究结果表明,硫化胶的拉伸断裂能与其DIN磨耗体积有较好的线性关系,但与阿克隆磨耗体积的线性关系较差。以上研究结果表明拉断伸长率与DIN磨耗体积的线性相关性具有一定的普适性。     

橡胶拉伸断裂能与磨耗性能的关系研究

以丁苯橡胶(SBR)、顺丁橡胶和天然橡胶为基体,研究采用普通硫化体系、有效硫化体系、半有效硫化体系和平衡硫化体系硫化胶的拉伸断裂能与磨耗性能的相关性。结果表明:硫化胶的DIN磨耗量与拉伸断裂能有一定的相关性,随拉伸断裂能的增大,DIN磨耗量下降;但拉伸断裂能与阿克隆磨耗量没有明显的相关性。采用不同种类的炭黑补强SBR研究得到相同的结果,表明拉伸断裂能与DIN磨耗量的相关性具有一定的普适性。     

Ti-6Al-4V钛合金脉冲阳极氧化工艺

研究了Ti-6Al-4V钛合金脉冲阳极氧化工艺,并对影响阳极氧化膜厚度的主要因素(如温度、电流密度、时间等)进行了研究,得到了满足膜厚要求的工艺参数。将优化得出的工艺参数应用于零件的仿形试件生产,得到厚度均匀的阳极氧化膜,并对其表面形貌、成分等进行了分析。     

Laser Assisted Nitriding of Ti-6Al-4V Alloy: Metallurgical and Electrochemical Properties

The surface properties of Ti-6Al-4V alloy, such as wear resistance, are inadequate for many applications. To improve the surface properties of the alloy, many techniques have been considered. One of the promising techniques is to form a nitride layer on the surface of the workpiece by a laser beam. In the present study, laser assisted nitriding of the Ti-6Al-4V alloy surface is carried out under a nitrogen gas flow environment. A CO₂ laser is used to irradiate the Ti-6Al-4V alloy surface while nitrogen is introduced co-axially with the laser beam onto the workpiece surface. The resulting surface cross section is examined metallurgically. SEM and XRD were carried out for material characterization. The study is extended to include the electrochemical response of the resulting surfaces. The surface morphology of the electrochemically treated workpieces are examined. It is found that in the laser treated region dendritic structures occur and TiN forms in the surface vicinity. The density of pit formation at the surface of the treated region reduces considerably.     

镁-锂合金稀土转化工艺的研究

对镁-锂合金表面稀土转化成膜工艺进行了初步研究。分析了稀土盐硝酸镧转化、稀土盐硝酸镧+高锰酸钾转化工艺对稀土转化膜的形貌及耐蚀性能的影响。扫描电镜分析了稀土转化膜表面形貌;极化曲线、电化学阻抗谱测试技术研究了转化膜的耐蚀性能。结果表明:当在2g/L的硝酸镧转化液中加入2g/L的高锰酸钾时,镁-锂合金表面获得了均匀致密、裂纹细小的稀土转化膜;转化成膜时间对膜的耐蚀性也有不同程度的影响。     

Corrosion susceptibility of implant materials Ti-5Al-4V and Ti-6Al-4Fe in artificial extra-cellular fluids

The paper is aimed at detecting the corrosion susceptibility (generated by the potential gradients, due to the pH changes) of implant materials Ti-5Al-4V and Ti-6Al-4Fe alloys exposed in extra-cellular fluids for long term (10 000 exposure hours) in comparison with pure titanium. The titanium and its ternary alloys exhibited spontaneous passivity in Ringer’s solutions of pH=6.98, 4.35 and 2.5, simulating the real situations that can arise in surgical applications. Potential gradients determined in presumptive extreme pH conditions indicate that there is no probability for local corrosion. Impedance spectra were fitted with one time constant equivalent circuit, typically for protective, compact oxide film. The fitting parameters indicate long-term stability of the passive layers in surgical implant conditions. Atomic force microscopy (AFM) and spectral infrared (IR) data are important arguments in supporting the conclusion that titanium and its ternary alloys have a very good corrosion resistance in long-term functional conditions.     

The Durability of Adhesively-bonded Ti-6Al-4V

The durability of chromic acid-anodized Ti-6Al-4V alloy, adhesively-bonded with FM-5 supported polyimide adhesive has been studied. The performance tests compared titanium samples that had been thermally treated and bonded, and samples that were bonded and thermally treated. Following the thermal treatment, the durability was examined (1) by immersing wedge-type specimens in boiling water and measuring the crack growth and (2) by measuring the lap shear strength for single lap specimens. In the wedge tests, failure occurs within the adhesive for specimens treated at temperatures below 371°C for less than one hour. For treatments at higher temperatures and for longer periods of time, failure occurs within the anodic oxide. From the lap shear tests, the principal finding is that the lap strength decreases with increasing treatment time at constant temperature and with increasing temperature at a fixed time. For the lap specimens, failure occurs to a greater extent within the oxide as the treatment time and temperature increase. Surface analysis results indicate the formation of an aluminum fluoride species. It is reasoned that the formation of fluorine-containing materials weakens the oxide and promotes failure within the anodic oxide.     

The Durability of Adhesively-bonded Ti-6Al-4V

The durability of chromic acid-anodized Ti-6Al-4V alloy, adhesively-bonded with FM-5 supported polyimide adhesive has been studied. The performance tests compared titanium samples that had been thermally treated and bonded, and samples that were bonded and thermally treated. Following the thermal treatment, the durability was examined (1) by immersing wedge-type specimens in boiling water and measuring the crack growth and (2) by measuring the lap shear strength for single lap specimens. In the wedge tests, failure occurs within the adhesive for specimens treated at temperatures below 371°C for less than one hour. For treatments at higher temperatures and for longer periods of time, failure occurs within the anodic oxide. From the lap shear tests, the principal finding is that the lap strength decreases with increasing treatment time at constant temperature and with increasing temperature at a fixed time. For the lap specimens, failure occurs to a greater extent within the oxide as the treatment time and temperature increase. Surface analysis results indicate the formation of an aluminum fluoride species. It is reasoned that the formation of fluorine-containing materials weakens the oxide and promotes failure within the anodic oxide.     

Ti-6Al-4V合金表面激光熔覆NiCrBSi＋5%BN涂层组织和性能

Ti-6Al-4V合金具有比强度高、耐蚀性能好等优点,在航天、航空、石油和化工等新科技工业部门广泛使用。在表面激光熔覆金属-陶瓷复合涂层是改善钛合金性能的重要方式,利用XRD、SEM和EDS等分析手段对NiCrBSi＋5%（质量分数）BN熔覆层的微观组织进行分析。利用HV-1000型显微维氏硬度计测试激光熔覆试样的硬度。     

Optimization of SiC Abrasive Parameters on Machining of Ti-6Al-4V Alloy in AJM Using Taguchi-Grey Relational Method

Silicon - In this research, multi response Taguchi-grey relational approach was employed to optimize the machining parameters of Ti-6Al-4V alloy in abrasive water jet process. The main aim of this...     

Corrosion behaviour of Ti-6Al-4V in phosphoric acid

Ti-6A1-4V shows distinct active-passive behaviour in phosphoric acid over a wide concentration range. The cathodic polarization curves are similar over a wide range of acid concentration and temperatures. The alloy undergoes active dissolution and turns passive in the negative potential region followed by a wide range of passivity at all acid concentrations at different temperatures. Increasing acid concentration up to 11 M results in an increase in critical current density (i _cr). The passive current density (i _p) increases up to an acid concentration of 9 M while at 13 M i _cr and i _p decrease appreciably. A significant increase in both i _cr and i _p occurs with increase in solution temperature. The passive specimen remained stable for a long time when exposed to phosphoric acid under open circuit conditions.     

Experimental Study of Fracture of Glass:I, The Fracture Process

A concept of fracture is developed from experimental data. Fractures are found to originate at flaws or cracks of finite size, most of which are at the surface. The mechanism is one of crack propagation which begins when the local stress at the crack exceeds a minimum value. The rate of propagation increases with crack growth until a critical stress is reached at the crack tip which coincides with a limiting crack velocity. This limiting condition is identified with the boundary of the mirror surface of the fracture. From calculations to be presented in Part 11, the critical stress is estimated to be several million pounds per square inch.