Effect of HIPing on microstructure and properties of spray formed Al-Li alloy UL40
Authors: G. J. Reddy, N. Srinivasan, A. A. Gokhale, B. P. Kashyap
Source: Powder Metallurgy
Publisher: Maney Publishing
Abstract:
Spray formed billets of Al-4Li-0.14Zr (wt-%) were processed by a combination of hot isostatic pressing (HIPing), homogenisation, and solution treatment and aging. Extensive oxidation damage occurred after homogenisation in air, but could be alleviated by using controlled atmosphere or by prior HIPing. The microstructure and tensile properties were studied at various stages of processing. The volume fraction of AlLi (δ) decreased successively after HIPing, homogenisation and T6 temper, redistributing itself towards grain boundaries. The Al3Zr (β') phase was absent in the as formed condition, but precipitated after HIPing at 838 K/4 h and/or stepped homogenisation finishing at 838 K/4 h. Room temperature tensile properties were poor in the as spray formed condition, but improved after HIPing, homogenisation and T6 treatment successively. The tensile properties of the alloy were also evaluated between 648 and 848 K, for preliminary identification of optimum hot working parameters. HIPing did not affect high temperature yield strength significantly, but increased the ductility.Document Type:
DOI: 10.1179/174329009X380563
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