In situ detection of stability limit of ω phase in Ti–15Mo alloy during heating. Issue 5 (6th September 2019) - Zháňal, Pavel
Abstract : Synchrotron X‐ray diffraction has allowed the determination of the microstructure evolution during linear heating in a single crystal of a metastable titanium alloy (Ti–15Mo). The results were compared with electrical resistance evolution. The dissolution of the ω phase during heating of Ti–15Mo with a heating rate of 5 K min −1 occurs by ω → β transformation rather than ω → α. Abstract : Phase transitions in a single crystal of a metastable β‐titanium alloy (Ti‐15Mo) were investigated in situ during heating by synchrotron X‐ray diffraction. The results were compared with previous measurements of electrical resistance. Single‐crystalline samples allowed different crystallographic families of ω‐Ti and α‐Ti phases to be distinguished. The observed evolution of the intensity of the reflections of the ω phase during heating is consistent with the evolution of electrical resistance, which proves that the resistance is affected by the presence of ω‐phase particles. Between approximately 673 and 833 K, both the resistance and the intensity of ω peaks sharply decrease. At 833 K, ω reflections disappear, indicating a complete dissolution of the ω phase due to achieving the solvus temperature of the ω phase in the Ti–15Mo alloy. The synchrotron X‐ray diffraction experiment proved that the disappearance of the ω phase during heating of Ti–15Mo with a heating rate of 5 K min −1 occurs by its dissolution back to the β phase and not by ω → α transformation.