超微細結晶粒材料の作成と物性 非周期構造をもつナノ粒子分散Ａｌ‐Ｍ（Ｍ＝Ｃｒ，Ｖ，Ｔｉ）系合金の作製と機械的性質

Abstract

We examined the structure in rapidly solidified Al-M (M=Mo, V, Cr, Mn, Fe, Co, Ni) binary alloys and noticed that a quasicrystalline phase is formed in the M=V, Cr and Mn alloys. The fcc-Al plus quasicrystalline structure was formed in the range of 4 to 16 at%Cr or 6 to 23 at%Mn, and having almost single quasicrystalline phase in the vicinity of 14.0 at%V, 15.4 at%Cr or 22.5 at%Mn. The Vickers hardness values of the Al86V14, Al84.6Cr15.4 and Al77.5Mn22.5 alloys with having almost single quasicrystalline phase were 735, 1010 and 710, respectively and the grain size of the quasicrystalline phase was 200, 450 and 650 nm, respectively. The addition of Ce in the Al-Cr binary alloys was effective for the extension of the solute concentration range of quasicrystalline phase to a lower solute concentration range. The particle size and volume fraction of the quasicrystalline phase in the A194Cr5Ce1 alloy were about 200 nm and 70 %, respectively and the tensile fracture strength (σf) was 650 MPa. The σf increased to 1080 MPa for the Al95Cr3Ce1Co1 alloy in which the particle size and volume fraction were about 50 nm and 70 %, respectively. The σf of the Al94V4Fe2 alloy was 1390 MPa and the particle size and volume fraction were about 13 nm and 50 %, respectively. Similarly, the of of the Al93Ti4Fe3 alloy was 1320 MPa and the particle size and volume fraction were about 12 nm and 30 %, respectively. In aluminum alloys containing nanoscale quasicrystalline and amorphous particles, the 0.2 % proof stress (σ0.2) increased with decreasing particle size up to about 25 nm. When the particle size decreased further to was less than about 25 nm, the σ0.2 decreased with decreasing particle size. The transition from Hall-Petch relation to inverse Hall-Petch relation was recognized to occur in the vicinity of 25 nm.