Al-Li-Mg系合金の凝固および熱処理組織に及ぼすSi量の影響 Effect of Si content on solidified and heat treated structure of Al-Li-Mg casting alloys
The effects of Li and Si contents on the solidified and heat treated structures of Al–2.5~5 mass%Li–O.7~7 mass%Si–1 mass%Mg alloys cast into metal and sand molds were investigated by scanning electron microscopy, specific heat curve measurement, X-ray diffraction and micro-vickers hardness measurement. AlLiSi compounds crystallize as primary and eutectic phases and disperse at the inter-dendrite arm, and they remaind intact after solution treatment at 803 K for 36 ks. The crystallization of primary and eutectic Si phases, and Mg<sub>2</sub>Si phases were not observed. The morphology of the AlLiSi phase is triangular plate-like in the alloys contained more than 3 mass%Si, is needle-like in the alloys contained 1~3 mass%Si and changed to small rod-like in the alloys contained less than 1 mass%Si. By the amount decrease in the solubility of Li in the matrix the crystallization of AlLiSi phase decreases and brings the decrease or retardation in age hardening by δ' (Al<sub>3</sub>Li) precipitation. The mechanical strength becomes higher with decreasing the amount of AlLiSi phase and δ (AlLi) equilibrium phase.
軽金属 47(3), 158-163, 1997-03-30
The Japan Institute of Light Metals