A Study of the Dependence of Microsegregation on Critical Solidification Parameters in Rapidly-Quenched Structures.
Abstract
Mechanically-blended powder alloys of Ti-6Al-4V, Ti-6Al-4V blended with less than or = 3Er, Y or Nd, and Ti-6Al-2Sn-4Zr-6Mo-1Er (wt %) were laser-consolidated and rapidly solidified by the LAYERGLAZESM process. This procedure was used to form the fusion zones of butt welds in Ti-6AL-4V plate, premachined with straight-sided 3 mm gaps, which were filled with sequential layers of laser-melted powder feedstock. After melting, the rare-earth elements reacted with dissolved oxygen in the titanium to form a dispersion of equilibrium-structure oxides. The as-solidified microstructure of each alloy consisted of large, columnar rains of acicular alpha HCP martensite. The largest rare earth oxide size and spatial dispersions were observed in alloys LAYERGLAZED from Ti-6Al-4V-3Nd powder; the finest, in those made from Ti-6Al-4V-1.5Er. The largest oxide particles were located at interdendritic and, in the case of Ti-6Al-4V-1.5Er, at intergranular sites. The erbium oxide size distribution was bimodal, with mean sizes of 280 and 40 nm. The oxide structures were identified by analysis of selected area and convergent beam diffraction patterns, obtained from particles determined to contain the appropriate rare earth element by EDS. Neither the ambient temperature tensile strength nor the microhardness of either aged (800 C, 75 min) or as-LAYERGLAZED alloys were significantly improved by the oxide dispersions.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1984
- Accession Number
- ADA142293
Entities
People
- D. B. Snow
Organizations
- United Technologies Corporation