Features of compacting hydrogen-doped granules of a VT5-1kt titanium alloy

The effect of hydrogen on consolidation of granules of the VT5-1kt alloy, as well as the structure, mechanical characteristics, and fracture micromechanism of a compact produced by the hot-isostatic-pressing technique, is studied. It is established that hydrogen doping allows obtainment of a compact of the VT5-1kt alloy of 100% density with a high complex of properties in the course of a few minutes at such temperature-strength conditions in which the consolidation of granules is not realized. It is shown that the process of consolidation of hydrogenated granules proceeds more effectively in the (α + β) region.     

Surface chemistry of the titanium powder studied by XPS using internal standard reference

Surface chemistry of the titanium powder has particularly growing interest due to the increasing application of titanium components prepared by powder metallurgy, in particular metal injection moulding and additive manufacturing. Due to the high chemical activity, number of titanium oxides, calcium and complex Ca–Ti–oxides can be expected on the component/medical implant surface, depending on powder and component manufacturing and post-treatment, but are very difficult to analyse due to the lack of the experimental data and analysis methodology. Therefore, a methodology for the analysis of the surface chemistry of the Ti-powder by XPS utilising internal standard reference was developed. The obtained methodology was used for the surface analysis of titanium powder and identification of its surface oxide composition. The results show that the powder surface is covered by TiO₂ layer in the form of rutile with a thickness of 4.4?nm. Carbon and nitrogen impurities were also found present on the powder surface.     

Elevated-temperature oxidation behavior of titanium silicide and titanium silicide-based alloy and composite

The oxidation behavior of Ti₅Si₃ has been studied in air in the temperature range of 1200 °C to 1400 °C. The oxidation kinetics is slower than that predicted by the parabolic-rate law equation at 1200 °C, but is sharply enhanced beyond a temperature of 1300 °C. The oxidation kinetics of a Ti₅Si₃-8 wt pct Al alloy and a Ti₅Si₃-20 vol pct TiC composite at 1200 °C has also been investigated and compared to that of Ti₅Si₃. Alloying with Al does not alter the oxidation resistance much, but the presence of TiC reinforcements enhances the rate of oxidation significantly. The oxidation products have been identified and the mechanism of oxidation has been analyzed using thermodynamic and kinetic considerations.     

Substructure characteristics of titanium alloy weldments

The morphological characteristics of prior beta grain and subgrain boundaries in Ti-6 Al-6 V-2 Sn and Ti-6 Al-2 Sn-4 Zr-6 Mo fusion weldments have been studied using a unique decoration technique. Subgrain boundary characteristics were often found to differ from those of the more commonly observed microsegregation-revealed solidification substructure. Differences resulted both from alterations in the true cell boundary morphology and from the creation of secondary subgrain boundaries during weldment cooling. Decorated subgrain structures created during weldment cooling were often observed to be stable in weldments which had undergone super-transus post-weld heat treatment, and consequently which had experienced several allotropic transformations. Although a complete understanding of the decoration technique remains elusive, conclusions obtained concerning the validity of the subgrain decoration technique and weldment substructure characteristics were found to be complementary.     

Sintered alloy obtained from titanium waste

Translated from Poroshkovaya Metallurgiya, No. 2(302), pp. 97–101, February, 1988.     

TA15钛合金高温氧化行为

研究TA15钛合金在750~950℃,空气中氧化1~150 h的氧化动力学规律,采用SEM、XRD及EPMA测试技术分析该合金氧化层的显微组织形貌、相组成和复合结构,并对氧化膜的生成机理进行探讨。结果表明:合金在750、850和950℃温度下的氧化行为均符合抛物线规律,但在950℃以上随氧化温度的升高和保温时间的延长,氧化质量增加值持续升高,并远大于750℃和850℃时的氧化质量增加。750℃和850℃下氧化150 h后,合金氧化层结构为TiO2/Al2O3/TiO2/基体;950℃下氧化150 h后合金的氧化层结构为TiO2/Al2O3/TiO2/Al2O3/TiO2/Ti3Al/基体。     

钛及钛合金标准中规定残余伸长应力的探讨

通过对钛及钛合金标准中规定残余伸长应力表述的分析和探讨,从标准几次修订描述过程来探讨目前国家标准和国家军用标准中对规定残余伸长应力测试存在的问题,并对今后标准再次修订中的修改提出建议。     

Shrinkage and dimensional accuracy of sintered titanium alloy components

Conclusions As shrinkage increases, the inherent scatter in its values increases, that is, the mean-square error increases. In order to improve the dimensional accuracy of sintered components, it is essential to develop a production technology with a minimum sintering shrinkage. Here, the accuracy of sintered components is assessed not by the absolute shrinkage value, but by the mean-square error of its values.Translated from Poroshkovaya Metallurgiya, No. 4, pp. 97–99, April, 1992.