'Age-hardening' caused by solid state reactions in mechanically alloyed aluminum based materials

摘要

With an aim of obtaining in situ formation ofnano-structured dispersoids in aluminum based materials,aluminum and its alloys were mechanically alloyed withaddition of various metal oxides and carbides. Solid statereactions during and after mechanically alloying were studiedmainly by X-ray diffraction. Hardness changes caused by solidstate reactions were examined. It was found that some of themechanically alloyed materials showed "age-hardening" whenheated after consolidation at very high temperatures, such as773 or 873K. The hardness increases were considered to becaused by in situ formation of dispersoids. By applying such"age-hardening", aluminum based materials of higher strengthat room and elevated temperatures can be obtained. Thematerials which showed "age-hardening" include the followingcombinations of the starting materials; Al/carbide (Al/VC,Al/NbC, Al/TaC), Al/oxide (Al/V2O5, Al/Nb2O5, Al/Ta2O5,) andAl-Mg/oxide (Al-Mg/Fe2O3, Al-Mg/V2O5, Al-Mg/Nb2O5,Al/Ta2O5). Hardening in Al/carbide materials is caused bydecomposition of the carbide and formation of aluminumcarbide and intermetallic aluminide compound. In Al/oxidematerials, hardening occurs due to decomposition of the oxideand formation of Al2O3 and aluminide compound. In case ofAl-Mg/oxide, solute Mg was oxidized in preference to Al.Hardening in these materials occurs at much highertemperatures than conventional age-hardening of aluminumalloys, and hence microstructures of the "age-hardened"materials are considered to be thermally very stable.