Effect of temperature and pressure on the densification of titanium silicide compound

Abstract

Titanium silicide compound was synthesized from the mixture of titanium and silicon powder with atomic ratios of 60:40 and 70:30. The powders were mixed by ball milling and pressed by different methods: by using uniaxial pressing at 64 MPa, cold isostatic pressing (CIP) at 200 MPa, hot forging (HF) at 648 MPa, and hot pressing (HP) at 24 MPa. The samples were then sintered at 1300ºC or 1600ºC for 2 hours soaking time in argon atmosphere. The sintered samples were subsequently characterized for phase constitution using X-ray diffraction (XRD). Ti5Si3 was observed as main compound of mixtures with both ratios - 60:40 and 70:30. Archimedes’ method and scanning electron microscope (SEM) were used to measured density and investigate the microstructure of the sintered samples. It was found that the sample prepared from the mixture with ratio 70:30 has higher density than the sample of ratio 60:40 for all applied pressures. The density of samples prepared from the mixture of 70:30 and 60:40 sintered at 1300ºC are in the range of 53- 60% and 42-55%, respectively. It was found that densities of all samples sintered at 1300ºC were not much different when higher forming pressure was applied by using CIP and HF. This means that pores are created during sintering. However, the microstructure of samples formed by CIP and HF showed some big pores inside the sample body while the sample formed at lower pressure by uniaxial press showed a more uniform pore size. By increasing the sintering temperature to 1600ºC, the density of the uniaxial pressed sample was increased to 85%, and the pore size shrinks in comparison to the one sintered at 1300ºC. Applying a lower pressure during sintering the sample at 1600ºC by hot pressing, on the other hand, can produce a high density sample of 99% with a small amount of small closed pores.