Ti-Al-BN混合粉末の燃焼反応プロセスにより作製したTiAl-(TiB_2+Ti_2AlN)複合材料の組織と機械的性質 Microstructure and mechanical properties of TiAl-(TiB_2+Ti_2AlN) composites produced by combustion reaction process of Ti-Al-BN powder mixtures
To improve low room-and high-temperature strength of titanium alminides, TiAI based composites reinforced with TiB<SUB>2</SUB> and Ti<SUB>2</SUB>AIN particles were made by combustion reaction process using Ti-AI-BN powder mixtures, and arc-melted for densification. The powder compositions included Ti<SUB>47.4</SUB>Al<SUB>44.2</SUB>(BN)<SUB>8.4</SUB>, Ti<SUB>49.0</SUB>Al<SUB>42.6</SUB>(BN)<SUB>8.4</SUB> and Ti<SUB>50.5</SUB>Al<SUB>41.1</SUB>(BN)<SUB>8.4</SUB> in at%, corresponding to matrix composition of Ti<SUB>48</SUB>A<SUB>l52</SUB>, Ti<SUB>50</SUB>Al<SUB>50</SUB> and Ti<SUB>52</SUB>Al<SUB>48</SUB>, respectively. The volume fraction of reinforced particles was about 18%. The as cast specimens had a matrix of TiAl(γ) with a lamellar structure of Ti<SUB>3</SUB>Al(α<SUB>2</SUB>). In the annealed specimens, such lamellar structures were completely or partially disappeared, while smaller particles (about 100-200nm) were observed in the matrix of all specimens. These particles were found to be MAIN and mainly formed in place of disappeared Ti<SUB>3</SUB>Al in the lamellae. The formation of these particles was attributed to different solubility limit for nitrogen in yand α<SUB>2</SUB> and solutionizing α<SUB>2</SUB> phase by heat treatment. It was found that the composite materials had a high strength at both room and elevated(1173K) temperatures; 800-1100MPa and about 600MPa, respectively. The bending and fracture toughness tests also proved that the composite annealed is better than the as cast, and values were about 0.4% in ductility and 13-15 MPam in fracture toughness.
粉体および粉末冶金 45(4), 336-340, 1998-04-15
Japan Society of Powder and Powder Metallurgy