Abstract
Compression tests at very low temperature down to 4.2 K and conventional transmission electron microscopy were conducted to investigate the twinning behavior of the C15 HfV 2+Nb Laves phase. We chose two phase C15/bcc alloys to improve the ambient temperature ductility since the single Laves phase intermetallic compound is brittle. Transmission electron microscopy revealed that substantial mechanical twinning takes place in the C15 Laves phase matrix at room temperature and 77 K. A deep minimum in the flow stress, with a drop of nearly 500 MPa, appears at around 77 K in the C15/bcc two-phase alloy with C15 matrix. Since no such anomaly is seen in the bcc phase, we believe that the cause of this can be attributed to mechanical twinning in the C15 Laves phase. Twin bands observed in the C15 matrix of deformed samples at both 298 and 77 K can be classified into three categories by their thickness; coarse twin bands about 10 nm to several hundred nm thick, fine twin bands around 3–10 nm thick, and ultra fine twin bands with average thickness of 1.5 nm. A high density of ultra-fine twin bands is the characteristic feature of twinning in the C15 matrix. They belong to the 〈112〉(111) twinning system and commonly intersect with each other.
Published Version
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