TY - JOUR

T1 - Thermal stability and latent heat of Nb–rich martensitic Ti-Nb alloys

AU - Bönisch, Matthias

AU - Panigrahi, Ajit

AU - Calin, Mariana

AU - Waitz, Thomas

AU - Zehetbauer, Michael

AU - Skrotzki, Werner

AU - Eckert, Jürgen

PY - 2017/3/15

Y1 - 2017/3/15

N2 - Ti-Nb-based alloys are candidate materials for load-bearing and for functional biomedical implant components. For these applications alloy compositions with relatively low martensitic transformation (MT) temperatures are of highest interest. In this work we examine the thermal stability and the temperature-induced β ↔ α″ MT of Nb-rich martensitic and partially martensitic Ti-Nb alloys exhibiting martensite start temperatures Ms < 300°C. The first part of this article investigates the phase transformations and precipitation reactions occurring during isochronal cycling in dependence of the Nb content using differential scanning calorimetry and dilatometry in combination with X-ray diffraction. The second part studies the temperatures, thermal hysteresis and transformation interval of the β ↔ α″ MT. The latent heat, elastic and irreversible energy contributions of the thermoelastic energy balance are quantified in dependence of Nb content in the remaining parts. All energy contributions decrease with increasing Nb content and the latent heat becomes very small (< 5 J/g) for the Nb-richest martensitic compositions. Above a critical Nb concentration the β → α″ MT is incomplete.

AB - Ti-Nb-based alloys are candidate materials for load-bearing and for functional biomedical implant components. For these applications alloy compositions with relatively low martensitic transformation (MT) temperatures are of highest interest. In this work we examine the thermal stability and the temperature-induced β ↔ α″ MT of Nb-rich martensitic and partially martensitic Ti-Nb alloys exhibiting martensite start temperatures Ms < 300°C. The first part of this article investigates the phase transformations and precipitation reactions occurring during isochronal cycling in dependence of the Nb content using differential scanning calorimetry and dilatometry in combination with X-ray diffraction. The second part studies the temperatures, thermal hysteresis and transformation interval of the β ↔ α″ MT. The latent heat, elastic and irreversible energy contributions of the thermoelastic energy balance are quantified in dependence of Nb content in the remaining parts. All energy contributions decrease with increasing Nb content and the latent heat becomes very small (< 5 J/g) for the Nb-richest martensitic compositions. Above a critical Nb concentration the β → α″ MT is incomplete.

KW - Differential scanning calorimetry

KW - Dilatometry

KW - Hysteresis

KW - Omega-phase

KW - Precipitation

UR - http://www.scopus.com/inward/record.url?scp=85006802905&partnerID=8YFLogxK

U2 - 10.1016/j.jallcom.2016.12.108

DO - 10.1016/j.jallcom.2016.12.108

M3 - Article

AN - SCOPUS:85006802905

VL - 697.2017

SP - 300

EP - 309

JO - Journal of alloys and compounds

JF - Journal of alloys and compounds

SN - 0925-8388

IS - 15 March

ER -