Characterisation, Consolidation and Mechanical Properties of TiAl Alloy Produced Using Titanox Powders
Parmar, B. (2007). Characterisation, Consolidation and Mechanical Properties of TiAl Alloy Produced Using Titanox Powders (Thesis, Master of Engineering (ME)). The University of Waikato, Hamilton, New Zealand. Retrieved from http://hdl.handle.net/10289/6060
Permanent Research Commons link: http://hdl.handle.net/10289/6060
Characterization of the three different as- received TiAl powders, namely Tax1, Tax2 and Tax3 produced by Titanox development Ltd has been done. Predominate TiAl phase was observed in all the three compositions .The powder particles were very fine with average particle size of 12μm, 5μm and 10μm respectively for Tax1, Tax2 and Tax3.Chemical analysis of the powders showed high oxygen content in all the three compositions of the powders .Bulk samples were produced from Tax1, Tax2 and Tax3 powders by hot isostatic pressing at 1200 C under a pressure of 200Mpa for two hours .The pressurization gas used for the process was argon. The relative density of Tax1, Tax2 and Tax3 HIPped samples was 96%, 86% and 93%and respectively. The characterization of the HIPped samples showed that the predominate phase was γ-TiAl phase in all the three HIPped samples .A small fractions of Ti3Al and TiAl3 was also observed in tax1 and Tax3 HIPped material. Also some of the dark Al rich phases was Al2O3 phase in Tax1 and Tax3 HIPped samples. High oxygen content of the powder and air leaking in the can during the process of press-seal and welding of the end of the tube of the can prior to HIPping lead to poor consolidation of Tax2 which eventually resulted in high porosity and formation of Ti2O and Al2O3. Half of the Tax2 HIPped sample was canned and heated to 1160 C and was subjected to open die hammer forging with a high strain and a total reduction of height by 66% .The forging produced a pancake shaped sample without breaking of the sample.Tensile specimens were cut from the Tax1 and Tax3 HIPped sample and one from the Tax2 forged sample using electrical discharge machine (EDM) wirecutting. Tax1 HIPped material showed the average fracture strength of 204MPa, 256MPa and 197MPa at room temperature, 800 C and 900 C respectively., Whereas Tax3 HIPped material showed average fracture strength of 103MPa and 234MPa respectively at room temperature and 800 C respectively. The HIPped and the forged Tax2 sample showed low fracture strength of 91MPa because of the micro-cracks produced during forging.
The University of Waikato
- Masters Degree Theses