Spray forming of Ti 48.9Al (at.%) and subsequent hot isostatic pressing and forging

Abstract

Binary Ti 48.9Al (at.%) has been processed via two different processing routes, both comprising the spray forming technology: (i) spray forming followed by hot isostatic pressing (HIP) and subsequent thermal treatments and (ii) spray forming and subsequent high temperature forging. After each process step, the material is characterized by porosity measurements, microstructural investigations and tensile tests. The as sprayed state is characterized by a porosity of 1.0%. Both, HIP and forging yield a further reduction in porosity to 0.06 and 0.04%, respectively. The as sprayed microstructure is of high homogeneity, which is maintained during all subsequent treatments. High strength (UTS=470 MPa) and a plastic elongation of 0.9% have been measured for the nearly lamellar as sprayed microstructure. The duplex microstructure, which has been established by a specific heat treatment subsequently to HIP provides the highest plastic elongation of 2.7%. The fine near gamma microstructure after forging shows at 2%-plastic elongation the highest strength (UTS=520 MPa) among the various microstructures.