High end sports cars use titanium connecting rod to reduce weight and improve performance.
Powder metallurgy titanium has been challenged for 40 years to compete with wrought Ti on cost, performance, and performance to cost ratios. To date, there is no PM Ti that can compete wrought Ti on both. We have developed a new powder metallurgy process called Hydrogen Sintering and Phase Transformation (HSPT) for making Ti-6Al-4V with wrought-like microstructure and mechanical properties. HSPT is a pressureless sintering process, in which Ti hydride or partially hydrogenated Ti powder is blended with master-alloy or elemental alloying element powders and sintered under a dynamically controlled hydrogen atmosphere. After sintering, residual hydrogen is removed by annealing under vacuum or inert gas. HSPT takes advantage of the phase transformations in the (Ti-alloy)-H alloy systems to simultaneously refine the microstructure during the thermal cycle of sintering. The fine misstructure allows for subsequent pressure less heat treatment steps to produce very fine wrought-like microstructures without thermomechanical processing (TMP).
Owing to the microstructures, HSPT Ti-6Al-4V has been shown to have wrought-like mechanical properties as well. As-sintered UFG HSPT Ti-6Al-4V typically has strength exceeding 1 GPa and ductility exceeding 15 %EL. The properties may be application-tailored via simple heat treatments to increase the ductility beyond 20 %EL or strength exceeding 1100 MPa. Additionally, HSPT has been shown to have fatigue properties competitive with wrought Ti-6Al-4V.
- Z. Zak Fang et al., Powder metallurgy methods for the production of fine and ultrafine grain Ti and Ti alloys, US patent 9,816,157 B2
- Z. Zak Fang et al., Hydrogen Sintering of Titanium to Produce High Density Fine Grain Titanium Alloys, Advanced Engineering Materials, 14 (2012): 383-387.
- Pei Sun et al., An Experimental Study of the (Ti-6Al-4V)-xH Phase Diagram using in situ Synchrotron XRD and TGA/DSC Techniques, Acta Materialia 84(2015):29-41.
- Pei Sun, et al., Phase Transformations and Formation of Ultra-fine Microstructure during Hydrogen Sintering and Phase Transformation (HSPT) Processing of Ti-6Al-4V, Metallurgical and Materials Transactions A, 46(2015):5546-5560.
- James Paramore et al., A powder metallurgy method for manufacturing Ti-6Al-4V with wrought-like microstructures and mechanical properties via hydrogen sintering and phase transformation (HSPT), Scripta Materialia, 107(2015): 103-106.
- James Paramore et al., Hydrogen-enable Microstructure and Fatigue Strength Engineering of Titanium Alloys, Scientific Reports, 7(2017):41444.
- Matthew K. Dustan et al., The effects of microstructure and porosity on the competing fatigue failure mechanisms in powder metallurgy Ti-6Al-4V, International Journal of Fatigue, 116(2018): 584-591
Approximately 14% of Boeing 787 is made of titanium.