High-pressure sintering of the amorphous TiAl powder (特集各種粉末の焼結機構と新しい焼結技術の展開)

概要

論文の詳細を見る
In order to manufacture a pore free amorphous Ti50Al50 product, a pulse electric current sintering of the mechanically alloyed amorphous powder under high-pressure is proposed, with which one can obtain full densification at low temperatures prior to glass transition to a supercooled liquid. The compressibility (Cm) of the amorphous Ti50Al50 powder follows a simplified Cooper-Eaton equation of Cm =Aexp(-k/P) under the applied stress of up to 600 MPa at room temperature, indicating that the powder compaction proceeds mainly via local plastic deformation at their contacted area with nearly non-strain hardening. When a high applied pressure of 600 MPa is used with a specially designed WC die, the amorphous Ti50Al50 powder can be consolidated at a full-density up to 939 K below a glass temperature, avoiding major crystallization; its densification during electric current heating is fairly well expressed with a commonly used equation of Non-Newtonian flow: ε=ε0 sin h(cσeff/kT)exp(-Hp/kT) with a decreased value of 50 kJ mol-1 for the apparent activation energy, Hp. Dynamic nanoindentation is used to give the value of 0.65 GPa for the level of yield stress for the fully dense amorphous Ti50Al50 sample.
2011-01-15