Analysis of heat treatment on the thermal conductivity of Ti6Al4V parts manufactured via laser-based powder bed fusion
摘要
The advantages of AM such as unlimited design freedom, less material waste and better customization along with Ti6Al4V’s merits of high strength to weight ratio, good corrosion resistance and excellent fracture toughness make AM of Ti6Al4V an enormously promising choice for manufacturing aerospace parts. In this research the effect of sub-transus post heat treatments on thermal conductivity of additively manufactured Ti6Al4V through LPBF have been studied through comprehensive microstructure analysis. Moreover, the effect of LPBF built and scan orientation on thermal conductivity has been analyzed. The heat treatments were performed at three different temperatures i.e. 900 °C, 930 °C and 950 °C and hot isostatic pressing (HIP) treatment was performed at 920 °C with 100 MPa pressure. Thermal conductivity of heat treated and hot isostatically pressed samples was also analyzed at elevated temperatures from room temperature (RT) to 300 °C. Findings showed that these heat treatments improved the thermal conductivity at RT from 2.33 to 2.41 W/mK to 2.47–2.85 W/mK. Hot isostatically pressed Ti6Al4V has significantly enhanced the thermal conductivity to 2.85 W/mK with a relative density of 99.5%. Heat treatment at 900 °C (specimen CHP-HT900-2) has improved thermal conductivity relatively more than other heat treatments. The thermal conductivity of stress relieved Ti6Al4V in scan orientation (specimen AVP-SR) achieved higher values of 2.98 W/mK as compared to 2.33 W/mK in built orientation (specimen BHP-SR). Thermal conductivity of heat treated Ti6Al4V increased almost linearly from 2.47 W/mK to 4.86 W/mK with an increase in temperature from RT to 300 °C. Overall, the additively manufactured Ti6Al4V via LPBF in scan orientation has the capability to give highest thermal conductivity for aerospace applications but with a compromise in strength due to layered manufacturing.