| The ultra high temperature structural intermetallic molybdenum and its alloys were studied for their thermal properties and correlated to the material microstructure. Thermal expansion tests were carried out using thermo-mechanical analyzer (TMA). Thermo cycling tests were conducted around 650°C for spinel dispersed molybdenum alloys with 3% wt of spinel or 6% wt of spinel (MgAl 2O4) particles. Results show that the coefficient of thermal expansion (CTE) value decreases with the addition of spinel and silicide particles. Furthermore, pure molybdenum alloys with different processing method also affect the CTE values. Thermo cycling tests show that molybdenum alloy with 6% wt of spinel (MgAl2O4) develops microcracks which are related to the number of cycles. The microcracks are caused by the thermal expansion mismatch between the spinel particles and molybdenum matrix, as well as the processing conditions. After the tests, the specimen was polished suitable to examine them using Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) and the micro cracks were detected, which were developed due to the thermal stresses. |
