Study of the Dependence of Microsegregation on Critical Solidification Parameters in Rapidly-Quenched Structures.
Abstract
Laser welds of 1.27 and 2.54 cm thick Ti-6Al-4V (wt%) plate separated by a 4 mm straight-sided gap were achieved with the aid of the addition of solution blend Ti-6Al-4V powder to the weld gap (the powder-feed LAYERGLAZE process). A continuous C02 laser was utilized in the unstable resonator mode with a set beam power of 5 kW, focused by a copper mirror of 45.7 cm focal length. Each successive layer of feedstock filled the gap width, and was overlaid by another until the gap was filled. Ambient temperature tests of cross-weld tensile and impact specimens revealed no fusion zone strength reduction but a somewhat decreased toughness with respect to the annealed base metal. The average fusion zone microhardness was 417 VHN vs 342 outside the HAZ, due primarily to an increase in oxygen content in the fusion zone. The fusion zone grain structure was distinctively columnar, with grains traversing many successive deposited layers. No grain boundary alpha phase was detected; the grains consisted entirely of fine alpha HCP martensite, internally twinned and faulted, with a wide range of lath lengths and a high dislocation density. No grain boundary or interdendritic segregation was detected by TEM/STEM EDS analysis. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1982
- Accession Number
- ADA122539
Entities
People
- David B. Snow
- Edward M. Breinan
Organizations
- United Technologies Corporation