Papers by Keyword: Evaporation of Al

Abstract: Titanium alloys belong to a group of the most advanced metal materials with increasing applications observed in recent years, mainly in the aircraft, shipbuilding, automotive and chemical industries as well as in medicine. In the paper, results of the study on changes in aluminium content in binary Ti-Al alloys during smelting in the vacuum induction melting (VIM) furnace are presented. The experiments were performed at 5 Pa and 1000 Pa, 1973 K and 2023 K. The investigations were conducted for alloys containing up to 49%mass Al. Each experiment began with loading an alloy sample (about 1000 g) into the graphite crucible placed in the induction coil of the furnace. After closing the furnace chamber, the pre-specified vacuum was generated with the use of a pump system. When the pressure level was stabilised, the crucible was heated up to the required temperature and the metal bath was held for 600 sec. During each smelting experiment, metal samples were collected and subjected to a chemical analysis. The Al loss rate in each experiment was not higher than 21%; it increased with temperature and reduced pressure in the device. It is assumed that the observed loss of aluminium during smelting is the effect of evaporation. The obtained values of Al concentration in the investigated alloys ensured that the aluminium overall mass transfer coefficient in the process could be estimated. The values of overall mass transfer coefficient were 0.88 to 1.66×10^-5 [m·s^-1]. Lack of clear effects of the alloy composition on the analysed process rate proves that it is not controlled by mass transfer in the liquid phase.

Abstract: A high purity of Ti₂AlC powder has been synthesized by pressureless sintering a mixture of Ti-Al-TiC-Sn (Sn as an additive) powders. Four recipes with different mole ratios of Ti-Al-TiC-Sn were examined at sintering temperature from 1400°C to 1480°C. A high purity of Ti₂AlC powder can be obtained by sintering all these four recipes at temperature 1450°C for 10 min in an Ar atmosphere. The synthesis of Ti₂AlC on this large mole ratio scale of starting materials is associated with the evaporation of Al at high temperature and the structure stability of Ti₂AlC. From the X-ray diffraction analysis, a reaction path for the Ti₂AlC formation is proposed. Scanning electron microscopy was also used to characterize the samples.