Accession Number:

ADA142293

Title:

A Study of the Dependence of Microsegregation on Critical Solidification Parameters in Rapidly-Quenched Structures.

Descriptive Note:

Final rept. Aug 79-Mar 84,

Corporate Author:

UNITED TECHNOLOGIES RESEARCH CENTER EAST HARTFORD CT

Personal Author(s):

Report Date:

1984-03-01

Pagination or Media Count:

65.0

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.

Subject Categories:

  • Properties of Metals and Alloys

Distribution Statement:

APPROVED FOR PUBLIC RELEASE