Samples of Ti6Al4V have been held at 500℃ for times up to 5 weeks and in agreement with phase diagram calculations and with earlier work it has been confirmed that particles of alpha 2 are formed under these conditions. Transmission electron microscopy (TEM) and atom probe have been used to characterise the alpha 2 precipitates. In addition the fraction of beta present after these long heat treatments was measured and found to be significantly higher than phase diagram predictions. The fatigue and tensile properties of exposed samples have been compared with those of samples slowly cooled from above the transus and TEM is being carried out in order to understand the observed properties. Some work has also been carried out on an alloy developed recently by Timet,Ti-5Al-4V-0. 6Mo-0.4Fe and alpha 2 is also seen in heat treated samples of this alloy. At the SEM level the volume fraction of beta is again far higher than is predicted from modelling work.
Titanium 64 long range order tensile and fatigue properties
Zhiwei Wu Michael H Loretto V. Venkatesh Hamish L. Fraser R. E. A. Williams G. B. Viswanathan S. Nag Rajarshi Banerjee Matthew Thomas
GE Research Centre,Shanghai,China IRC in Materials,The University of Birmingham,Edgbaston B15 2TT,,UK Henderson Technical Laboratory,T Henderson Technical Laboratory,TIMET,Henderson,NV 89015,USA Dept. of Materials Science and Engineering,2041 College Road,Columbus,OH,USA UES Inc.,Dayton OH,USA Dept. of Materials Science and Engineering,University of North Texas,Denton,TX USA Timet UK,POBOX 704,Witton,Birmingham,BS 7UR