Effect of hypoeutectic boron modification on the dynamic properties of Ti-6Al-4V alloy
- PDF / 877,662 Bytes
- 13 Pages / 584.957 x 782.986 pts Page_size
- 104 Downloads / 165 Views
Shibayan Roya) Department of Materials Engineering, Indian Institute of Science, Bangalore 560012, India; and Materials Science Centre, Indian Institute of Technology, Kharagpur 721302, India
Satyam Suwas Department of Materials Engineering, Indian Institute of Science, Bangalore 560012, India (Received 1 March 2016; accepted 26 May 2016)
The effect of boron on the room-temperature dynamic properties of Ti-6Al-4V alloy with and without boron addition in as-cast and b-forged conditions is studied by varying number of loading cycles, frequency of loading, and strain amplitude. Boron addition seems to lower the complex modulus and increases the damping of the base Ti-6Al-4V alloy. TiB precipitates in boron modified alloys play a key role in improving the damping through dislocation pinning (at all frequencies) and grain boundary pinning (at high frequencies). These effects are more prominent after b-forging wherein arrangement of TiB particles is found to be a deciding factor. Strain amplitude variation of damping shows trend reversal between 10 and 87 Hz frequencies; damping increases with strain amplitude at 10 Hz but reduces with strain amplitude at 87 Hz. A damping peak occurs near the 50 Hz frequency, and cycling through this range results in a significant improvement in damping (21% for as-cast and 93% for b-forged alloys).
I. INTRODUCTION
The workhorse among titanium alloys, Ti-6Al-4V is an actively researched material due to its numerous applications in the aerospace, automotive, and biomedical industries.1 These applications necessitate, amongst other properties, high specific strength, fracture toughness, fatigue, and corrosion resistance. Whereas, the coarse microstructure and strong crystallographic texture of ascast Ti-6Al-4V ingots are a major limitation and thereby, warrants secondary processing,2 significant microstructural refinement is achieved through boron modification.3 Boron addition in hypoeutectic quantities (typically ;0.1 wt%) enhance most of the mechanical properties of Ti-6Al-4V alloy.47 These improvements are attributed to formation of TiB particles, which surround the prior b-grain boundaries and increase stiffness of the alloy.8 Boron modified alloys have also shown significant improvement in secondary processing response of Ti-6Al-4V alloy, whether in the b9 or (a 1 b)-phase fields.10–17 Following these findings, the interest in boron modified Titanium alloys in general, and Ti-6Al-4V in
Contributing Editor: Eric Wuchina a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.227
particular, has increased over the time. Despite significant advances in various mechanical and thermo–mechanical aspects, little attention has been directed towards the dynamic properties of boron modified alloys. The only available study from Sen and Ramamurty18 have used dynamic mechanical analysis (DMA) to estimate the elastic modulus of Ti-6Al-4V alloy with varying boron content. This study has not, however, shed any information about the dynamic properties like
Data Loading...
