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 mea-suring the magnitude of enthalpy of relaxation(△Hrel)via differential scanning calorimetry(DSC).This is further validated by examining the strain-to-failure(ef)in compression tests.Mode I fracture behaviour of the as-cast embrittled BMGC and the CTC treated BMGC,which exhibits maximum plasticity,is exam-ined.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 signa-tures of plasticity in nanoindentation and higher △Hrel 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.

Department of Mechanical Engineering,Indian Institute of Technology Bombay,Powai,Mumbai,400076,India;Department of Mechanical and Aerospace Engineering in Nanyang Technological University,Singapore 637331,Republic of Singapore;Department of Materials Science and Engineering,Indian Institute of Technology Delhi,Hauz Khas,New Delhi,110016,India;Shi-changxu Innovation Center for Advanced Materials,Institute of Metal Research,Chinese Academy of Sciences,Shenyang,110016,China;Institute of Materials Research and Engineering,Agency for Science,Technology and Research(A *STAR),Singapore 138634,Republic of Singapore

[1]Devashish Rajpoot;R.Lakshmi Narayan;Long Zhang;Punit Kumar;Haifeng Zhang;Parag Tandaiya;Upadrasta Ramamurty-.Fracture toughness of a rejuvenated β-Ti reinforced bulk metallic glass matrix composite)[J].材料科学技术（英文版）,2022(11):225-235

BMGC,cryothermal,Hrel,embrittled,BMGCs,KQJ,tougher,signa,reassessing

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