J. Mater. Sci. Technol. ›› 2022, Vol. 106: 225-235.DOI: 10.1016/j.jmst.2021.09.001

• Research Article • Previous Articles     Next Articles

Fracture toughness of a rejuvenated β-Ti reinforced bulk metallic glass matrix composite

Devashish Rajpoota,b, R. Lakshmi Narayanc,*(), Long Zhangd,*(), Punit Kumarb, Haifeng Zhangd, Parag Tandaiyaa, Upadrasta Ramamurtyb,e   

  1. aDepartment of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
    bDepartment of Mechanical and Aerospace Engineering in Nanyang Technological University, Singapore 637331, Republic of Singapore
    cDepartment of Materials Science and Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, 110016, India
    dShi-changxu Innovation Center for Advanced Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016, China
    eInstitute of Materials Research and Engineering, Agency for Science, Technology and Research (A *STAR), Singapore 138634, Republic of Singapore
  • Received:2021-07-28 Revised:2021-09-01 Accepted:2021-09-03 Published:2022-04-20 Online:2021-10-06
  • Contact: R. Lakshmi Narayan,Long Zhang
  • About author:zhanglong@imr.ac.cn (L. Zhang).
    *E-mail address: rlnarayan@mse.iitd.ac.in (R.L. Narayan),

Abstract:

A β-Ti dendrite reinforced Zr-based bulk metallic glass composite (BMGC) was found to be brittle when cast in a large size. The reasons for the embrittlement and the effectiveness of the cryothermal cycling (CTC) treatment in restoring the mode I fracture toughness are examined. Plasticity in all the CTC treated BMGC is estimated from the distribution and occurrence of pop-ins in nanoindentation tests and by measuring the magnitude of enthalpy of relaxation (ΔHrel) via differential scanning calorimetry (DSC). This is further validated by examining the strain-to-failure (εf) in compression tests. Mode I fracture behaviour of the as-cast embrittled BMGC and the CTC treated BMGC, which exhibits maximum plasticity, is examined. Results show that both BMGCs are equally brittle and exhibit 5 times lower notch toughness (KQJ) than their tougher counterpart. Post-facto imaging of the side surfaces reveals the absence of notch-tip plasticity in both BMGCs. The lack of notch tip plasticity of CTC treated BMGC, despite exhibiting signatures of plasticity in nanoindentation and higher ΔHrel is rationalized by reassessing the origin of pop-ins in nanoindentation tests and describing the variations in chemical and topological short range ordering during CTC, respectively. Implications of these results in terms of improving the fracture toughness of structurally relaxed BMGCs via CTC are discussed.

Key words: Bulk metallic glass composites, Fracture, Rejuvenation, Shear bands, Microsegragation