11/2 Speech

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建立於 2016-10-04, 週二 10:29

最近更新於 2016-10-04, 週二 10:58

發佈於：2016-10-04, 週二 10:49

點擊數：2600

Speaker：Dr. C.T. Liu
Topic：FCC high entropy alloys strengthened by intermetallic precipitates

 

Speaker: Dr. Chain Tsuan Liu

Organization:  Distinguished Professor, Department of Mechanical Engineering, City University of Hong Kong

Topic: FCC high entropy alloys strengthened by intermetallic precipitates

Date: 10:00 , 2016.11.2

Location: Room 228, College of Engineering

Abstract：

Face-centered-cubic (FCC) based high entropy alloys (HEAs) generally exhibit outstanding ductility even at cryogenic temperatures, but they are relatively weak in strength which is far from the requirements for practical structural applications. One of the general concepts employed previously in alloy design is the suppression of 'brittle' intermetallic compound formation which usually leads to a serious embrittlement. In the current study, it is interesting to point out that the precipitation of γ', σ and μ intermetallic phases substantially strengthened FeCoNi, FeCrNiCo- and FeCrNiMn-based HEAs but without causing a serious embrittlement. These particle-strengthened HEAs exhibit a tensile strength easily above 1 GPa and a tensile ductility as high as 20-50 % at ambient temperature. A careful study of the deformation behavior reveals that the fcc matrix exhibits a high work hardening exponent, which effectively suppresses the propagation of microcracks originated at these intermetallic particles. Our work has demonstrated the feasibility of hardening these FCC HEA systems by precipitation of these intermetallic particles. The low and negative formation energies of stacking faults and micro-twins in these alloys at low temperatures will also be discussed. This research is supported from the Hong Kong Government through the General Research Fund (GRF) with the account number of CityU 11209314.