Mechanical Properties of Ti-15Mo Alloy Prepared by Cryogenic Milling and Spark Plasma Sintering

Anna Veverková,Cinthia Antunes Corrêa,Josef Stráský,Jiří Kozlík,Tomáš Chráska,Kristína Bartha

doi:10.3390/met9121280

Anna Veverková, Cinthia Antunes Corrêa + Show 4 more

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https://doi.org/10.3390/met9121280

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Abstract

Metastable β-Ti alloy Ti-15Mo was prepared by cryogenic ball milling in a slurry of liquid argon. Material remained ductile even at low temperatures, which suppressed particle refinement, but promoted intensive plastic deformation of individual powder particles. Repetitive deformation of powder particles is similar to the multidirectional rolling and resembles bulk severe plastic deformation (SPD) methods. Initial and milled powders were compacted by spark plasma sintering. Sintered milled powder exhibited a refined microstructure with small β-grains and submicrometer sized α-phase precipitates. The microhardness and the yield tensile strength of the milled powder after sintering at 850 °C attained 350 HV and 1200 MPa, respectively. Low ductility of the material can be attributed to high oxygen content originating from the cryogenic milling. This pioneering work shows that cryogenic milling followed by spark plasma sintering is able to produce two-phase β-Ti alloys with refined microstructure and very high strength levels.

Highlights

Metastable β-alloys constitute a specific group of Ti alloys in which none of the α-phase, α’-phase or α”-phase form after quenching from a temperature above the temperature of β-transus (774 ◦ C forTi-15Mo [1]). β-Ti alloys are widely used in the aircraft industry due to their high specific strength [2].Utilization of these alloys in biomedicine is expected [3]
In our previous study we proved that deformation by ball milling resembles the multi-directional forging and causes grain refinement [24]
The powder was compressed by a pressure of 80 GPa and heated 50 ◦ C below the desired temperature always in one minute

Summary

Introduction

Β-Ti alloys are widely used in the aircraft industry due to their high specific strength [2]. Utilization of these alloys in biomedicine is expected [3]. Ti-6Al-4V is a commonly used alloy for biomedical implants manufacturing, despite vanadium being considered as a toxic element [4]. Ti-15Mo, which contains only biocompatible elements, is a perspective biocompatible alternative. Mechanical properties of metastable β-Ti alloys can be further improved by thermomechanical treatment. Both microstructure refinement and precipitation of α-phase increase the strength of the alloy

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Conclusion