Effect of Ta content on martensitic transformation behavior of RuTa ultrahigh temperature shape memory alloys

Effects of Ta content on martensitic transformation (MT) behavior of Ru_100-x Ta_x (x = 46-54 at.%) alloys have been investigated by differential scanning calorimetry, dilatometry, X-ray diffraction and optical microscopy. Ta content significantly affects the MT behavior of RuTa alloys. The one-stage reservible MT occurs in Ta-poor RuTa alloys with Ta content less than 49 at.%. The two-stage reservible MT takes place in near-equiatomic RuTa alloys. No reservible MT is observed in Ta-rich alloys with Ta content more then 52 at.% Ta. The MT temperatures and hysteresis of RuTa alloys decrease with increasing Ta content. The aged and thermal cycled processes are nearly no effect on the MT behavior of these alloys. The deforming way of RuTa alloys is twinning. The Ru₅₀ Ta₅₀ alloy is of the most excellent MT behavior among these RuTa alloys.