Effect of laser remelting and heat treatment on microstructure and wear resistance of 2A97 Al-Li alloy

Abstract

Effects of laser surface remelting and heat treatment on microstructure and wear resistance of 2A97 Al-Li alloy were studied. The results show that hardening layer with fine grain and small size eutectic phase is easily prepared by laser remelting technique with rapid solidification characteristics. The cross section of molten pool after laser remelting is mainly composed of fine equiaxed grains (about 10 μm in size) close to fusion line, elongated columnar grains and coarse equiaxed grains on top of molten pool. Divorced eutectic phase Al2Cu is formed at grain boundary, and T2 phase (Al6CuLi3) with five times symmetric axis is observed. Fine grain strengthening and solution strengthening are main reasons for higher microhardness (105 HV) of remelting sample than that of matrix (85 HV). Hardness and wear resistance of remelting alloy are improved significantly by simple heat treatment. After 520 °C/1.5 h + 175 °C/24 h, discontinuous Al2Cu eutectic phase is no longer reticular distribution, and the size is greatly reduced. δ' phase (Al3Li), T1 phase (Al2CuLi) and σ (Al5Cu6Mg2) phase are precipitated during aging. Due to precipitation of reinforcements, microhardness of laser remelted Al-Li Alloy is increased from 105 HV to 142 HV, and elastic modulus is increased from 79.734 GPa to 91.962 GPa. The wear forms of Al-Li alloy are mainly abrasive wear and adhesive wear. Simple heat treatment significantly improves wear resistance of remelted Al-Li alloy, and wear rate is only 39.62 % of matrix.