Metallurgical and Materials Transactions A

, Volume 32, Issue 5, pp 1189–1200

A process model for friction stir welding of age hardening aluminum alloys

  • Ø. Frigaard
  • Ø. Grong
  • O. T. Midling
Article

DOI: 10.1007/s11661-001-0128-4

Cite this article as:
Frigaard, Ø., Grong, Ø. & Midling, O.T. Metall and Mat Trans A (2001) 32: 1189. doi:10.1007/s11661-001-0128-4

Abstract

In the present investigation, a numerical three-dimensional (3-D) heat flow model for friction stir welding (FSW) has been developed, based on the method of finite differences. The algorithm, which is implemented in MATLAB 5.2, is provided with a separate module for calculation of the microstructure evolution and the resulting hardness distribution. The process model is validated by comparison with in-situ thermocouple measurements and experimental hardness profiles measured at specific time intervals after welding to unravel the strength recovery during natural aging. Furthermore, the grain structure within the plastically deformed region of the as-welded materials has been characterized by means of the electron backscattered diffraction (EBSD) technique in the scanning electron microscope (SEM). Some practical applications of the process model are described toward the end of the article.

Appendix I List of Symbols

A0

material constant related to the potency of the heterogeneous nucleation sites in actual alloy (J mol−1)

a

thermal diffusivity (m2 s−1)

Co

total alloy content (wt pct)

Cmo

matrix solute content in stabilised base material (wt pct)

Cp

solute concentration within the particle (wt pct)

D0

diffusion coefficient (m2 s−1)

ds

subgrain diameter (m)

dx, dy, dz

discretization parameters in x, y, and z directions (m)

f0

initial volume fraction of precipitates in base material

fm

maximum possible volume fraction of hardening precipitates that can form at absolute zero

HVmax

hardness in the temper condition (VPN)

HVmin

hardness in the fully reverted condition (VPN)

M

interfacial torque (Nm)

N

rotational speed (rot·s−1)

P

pressure (Pa)

P(r)

pressure distribution across the interface (Pa)

Q

activation energy for diffusion (J mol−1)

Qd

activation energy for diffusion of Mg in Al (J mol−1)

Qs

activation energy for diffusion of the less mobile constitutive atom of the precipitates (J mol−1)

q0

net power (W)

R

tool radius (m)

r

two-dimensional radius vector (m)

r0

initial particle radius (m)

Smax0

hardness or strength in age-hardened base material (VPN or Pa)

Smin0

hardness or strength in fully reverted condition (VPN or Pa)

T

temperature (°C or K)

Tmax

maximum temperature (°C or K)

Ts

peak temperature (°C or K)

Ts

phase boundary solvus temperature (°C or K)

t

time (s)

t*r1

maximum hold time for complete dissolution at reference temperature (s)

t*r2

time taken to precipitate a certain fraction of β′-Mg2Si at a chosen reference temperature (s)

v

welding speed (m s−1)

V

unit volume (m3)

Vm

molar volume (m3 mol−1)

x

x-axis/welding direction (m)

y

y-axis/transverse direction (m)

Zh

Zener-Hollomon parameter (s−1)

z

z-axis/thickness direction

ρc

volume heat capacity (J m−3 °C−1)

ɛ

strain rate (s−1)

γ

interfacial energy (J m−2)

μ

friction coefficient

ω

angular velocity (rad/s)

Download to read the full article text

Copyright information

© ASM International & TMS-The Minerals, Metals and Materials Society 2001

Authors and Affiliations

  • Ø. Frigaard
    • 1
  • Ø. Grong
    • 2
  • O. T. Midling
    • 3
  1. 1.the Material Command, Analytical LaboratoryRoyal Norwegian AirforceKjellerNorway
  2. 2.Department of Materials Technology and ElectrochemistryThe Norwegian University of Science and TechnologyTrondheimNorway
  3. 3.Hydro Aluminium Maritime ASAvaldsnesNorway

Personalised recommendations