Simultaneous grain refinement and nanoscale spinodal decomposition of β phase in Ti-Nb-Ta-Zr alloy induced by ultrasonic mechanical impacts

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>It was found that ultrasonic nanocrystal surface modification (UNSM) treatment performed on Ti-Nb-Ta-Zr (TNTZ) alloy surface to produce a gradient nanostructured surface layer also resulted in the nano-scale spinodal decomposition of β phase. For the first time, nano-scale spinodal decomposition of β phase induced by ultrasonic mechanical impacts was observed in a short time without any age treatment. The peak shift of XRD to lower angles, (110) β XRD peak splitting, overlapped and asymmetric XRD peaks, satellite reflections in the SAED pattern, and lattice straining in HR-TEM images confirmed nano-scale spinodal decomposition of β phase in the TNTZ alloy induced by UNSM treatment. Nano-scale EDS line-scan probe analysis revealed the β phase separation into nano-scale domains of Ti-rich (β<SUB>1</SUB>) and Ti-depleted (β<SUB>2</SUB>) phases. HR-TEM images showed the semi-coherent arrangement of Ti-rich (β<SUB>1</SUB>) and Ti-depleted (β<SUB>2</SUB>) regions. Nanosized grain formation and spinodal decomposition of β phase were induced simultaneously by UNSM treatment. The nano-scale grains, high dislocation density, and semi-coherent interface between the spinodally separated phases contributed to the high hardness of the UNSM-treated TNTZ alloy specimen.</P> <P><B>Highlights</B></P> <P> <UL> <LI> UNSM is a method that applies ultrasonic impacts to generate nanostructured surface. </LI> <LI> UNSM was applied to the surface of TNTZ alloy. </LI> <LI> Gradient nanostructured layer was produced in the top surface. </LI> <LI> Nano-scale spinodal decomposition of β phase induced by ultrasonic impacts. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>