Effect of aluminium on microstructure and shape memory effect in Cu-Al-Ag-Mn shape memory alloys

ABSTRACT

The objective of the present investigation is to synthesise and characterise the Cu-Al-Ag shape memory alloys with minor Mn addition. Synthesis of Cu-Al-Ag-Mn SMA was done by induction furnace and gravity die casting, with constant Ag/Mn ratio (5% Ag and 2% Mn), the aluminium composition is varied from 8% to 14%. The as-cast sample will be further subjected to thermo-mechanical treatment to produce a sheet which exhibits shape memory effect. This study is to determine the influence of Al content on shape memory characteristics, microstructure, and phase transformation temperatures. The phase fraction of β’₁ increased from 56% to 67% along with subsequent reduction of γ₁’ phase fraction from 23% to 17%, which is essential for improvement of shape memory properties with increase of aluminium constituent. X-ray diffraction revealed that the crystalline size decreased 79 to 32 nm and lattice strains increased from 0.24% to 0.69% with increase of Aluminium. With an increase in aluminium content, the martensite transformation temperature decreased from 386°C to 246°C, and the shape memory effect increased from 81 to 90% strain recovery. The ability to control shape memory characteristics by changing Al composition will improve the scope for this alloy in various shape memory applications.

KEYWORDS:

• Shape memory alloys
• Cu Al based
• transition temperature
• martensite
• X-ray diffraction studies
• phase transformation
• austenite
• shape memory effect
• hot rolling

Acknowledgments

The author acknowledges gratitude for Sophisticated Analytical Instrumentation Facility, NIT Raipur for providing the XRD and SEM facilities. Also, we are thankful to S. N. Bose National Centre for Basic Sciences for providing the DSC facility.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data Availability statement

The authors confirm that the data supporting the findings of this study are available within the article. Any further information can be obtained from the corresponding author, T Sai Vamsi Krishna (e-mail: [email protected]), upon request.

Additional information

Notes on contributors

T. S. Vamsi Krishna

T S Vamsi Krishna is currently working as Assistant professor at Gayatri vidya parishad college of engineering, Visakhapatnam. He has 10 years of teaching experience and 8 years of research experience. He is currently working on copper based shape memory alloys.

D. Srinivasa Rao

Dr. D. Srinivasa Rao is working a Professor at Gayatri vidya parishad college of engineering, Visakhapatnam. He has 33 years of teaching and research experience. He did his Ph.D in NIT Suratkal. Currently he is working on Tribology, fracture mechanics of smart materials