The Influence of Ti Additions on the Microstructure of 2090 Alloys Used in Aeronautical Constructions 2001-01-3378
The aluminium alloys with lithium content of 2090 type represent metallic materials of high technical interest, with radical perspectives in the aeronautical and spatial industries and in other technical domains. These interest are due first of all to the special characteristics of reduced specific masses and of mechanical resistance obtained through alloying with Cu and Mg, and through complex heat treatments.
The impurities and microadditions of alloying for the Al-Li system have a great influence on the structure and properties of these alloys and they determine decisively the hardening heat treatments results.
The present paper includes studies and experimental researches of optical and electronic microscopy regarding some aluminium-lithium base alloys of 2090 type supplementary alloyed with Ti for the finishing of the structure and improve the properties of these alloys which are used in aeronautical constructions.
The adding of 0.5%Ti on the 2090 alloy lead to a finishing of the grains of αAl solid solution from 17-50μm to 10-40μm and the polyhedralisation of these grains. The structure analysis present distinctive phases of Al7Cu3Mg6 and TiAl3 type of lens shape disposed at the grain limits and in conglomeration with copper and nickel, and inside the grain phase of Al3Zr and Mg2Si type.
Through X-ray diffraction analysis was observed that the addition of 0.5%Ti in the 2090 alloy lead to the apparition of star or polyhedral phase. The star phase of Al3Li type, metastable, coherent with matrix crystallize in cubic system.