Los Alamos National LaboratoryGo to the Lab's home pageSearch for people in the Lab's phone book
     
  logo

Applications: Titanium Friction Stir Weld

 
transparent spacer
 
HOME
Principle
   - make cut
   - measure surface
   - calculate stress
Validations
Applications
   - bent beam
   - weld plate
   - quenched steel
   - impacted plate
   - alum. forging
   - friction stir weld
>    - Ti FSW
   - Railroad rails
Publications
More info
 
Residual Stress
Conferences
Vertical Linetransparent spacer

M.B. Prime, T.J. Lienert, W.L. Stellwag, R.S. Casey, “Residual Stress Measurement in Friction Stir Welded Ti-6Al-4V,” Fabtech International and AWS Welding Show 2005, November 13–16, 2005, Chicago, Illinois. (LA-UR-05-8693)

Results:

Residual longitudinal stresses

  • Looks more like fusion welding stresses than the two peak distribution typical of FSW of aluminum alloys
  • The stir zone or nugget exhibited residual tensile stress. A single peak of tensile stresses > 400 MPa was observed slightly below the surface corresponding to the shoulder of the tool.
  • The stresses were asymmetric with higher stresses on the advancing side of the weld.

Friction Stir Welding:

  • 0.285” thick Ti-6Al-4V plate - mill annealed
  • FSW at 3.75 ipm and 275 RPM using inert gas box with sliding top.
  • CP Tungsten tool with 0.75” diameter shoulder & 0.31” diameter pin (no threads). Cooled tool holder.
FSW of Ti

 

Macro metallography :

  • Weld region displayed three microstructurally distinct zones
    • Stir zone or nugget.
    • HAZ (Heat-Affected Zone) or TMAZ (Thermo-Mechanically Affected Zone)
    • Base metal
  • Some Tungsten from tool observed
Macro regions

Microstructure:

Base metal microstructure

  • Base metal
  • Fine equiaxed grains of α
    phase
  • with small amounts of intergranular β phase

Stir/HAZ Boundary

  • Stir zone/HAZ boundary

Stir zone microstructure

  • Stir zone:
  • GB α phase
  • with fine
    acicular α in prior β grains

 

Microhardness :

  • 1 kg load & 15 seconds dwell
  • Higher hardness in stir zone
Hv Microhardness map

 

Contour Experiment:

  • Part was clamped in special fixture to minimize movement during cutting (see on picture on cutting page)
  • Cut in wire EDM machine using 50 µm (0.002") diameter tungsten wire.
  • Surface contour measured using laser scanner
  • Peak-to-valley about 190 µm not including noise in data:
Measured surface contour

Calculate Stress using FEM

  • Make 3-D model of plate after cut
  • Start with flat surface
  • Using displacement boundary conditions, force cut surface to opposite of measured contour
  • Extract stresses normal to surface.
Deformed 3D FE model

 

 

 

transparent spacer       transparent spacer
   

Managed by Triad National Security, LLC Los Alamos National Security, LLC for the U.S. Department of Energy's NNSA
contact: Mike Prime at prime@lanl.gov | Copyright & Disclaimer
U.S. patent 6,470,756 | Last Modified: November 23, 2009

spacer spacer spacer spacer