Ti-Al系急冷凝固粉末の性状と強度特性

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The objective of this work was mainly to elucidate the potential of Ti-Al type P/M intermetallics for higher temperature structural applications. Investigations were made firstly on titanium aluminides for Al; 26-80% and then on TiA1-B(-Si) type intermetallics containing B and Si of less than 0.124 and 4.6%, respectively. The results were summarized as follows: (1) Morphologies of titanium aluminides such as Ti3Al, TiAl and TiAl3 are highly varied under the influence of Ti-Al binary equilibrium diagram. They, mostly meta-stable as rapidly quenched, fairly change in Ti3Al/TiAl phase boundary and other microstructures of particles after heat-treated and hence from Ti3Al/TiAl>TiAl3>TiAl (S) to TiAl3>TiAl (S)>TiAl in the order of microhardness. (2) Titanium aluminide specimens (of full density) are successfully prepared by specific double-stage HIP process, with the view of preventing titanium alloy powders from metallurgically reacting with HIP container materials. They, HIPed in such a way, show a minimum microhardness and relatively, nonbrittleness for the stoichiometric TiAl (γ). (3) Hot ductility of TiAl (at 900°C) may be appreciably improved by the B-addition of about 0.05% (hot tensile strength ge; 30 kgf/mm2), although greatly dependent on HIP temperature. On the other hand, tensile strength at ambient temperature (RT) proves to be more than 40 kgf/mm2. (4) Hot ductility of TiAl firstly increases with Si-addition and then reaches a maximum elongation of almost 50% in the vicinity of Si: 3%, while hot tensile strength keeps nearly 30 kgf/mm2. Excess Si-additive leads to a salient decline of hot ductility and also RT tensile strength possibly due to TiSi type precipitates.
社団法人粉体粉末冶金協会の論文

Ti-Al系急冷凝固粉末の性状と強度特性

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