OCTOBER 19-20, 2012 - YMCA University of Science & Technology

9 Titanium(ins
ert)/aluminiu
m–silicon
Ti/Al–7Si
Insert
moulding
Proceedings of the National Conference on
Trends and Advances in Mechanical Engineering,
YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, 2012
approaches to joining light metals
• Bimetallic specimen test pieces
of an AS-7 matrix locally
reinforced with a titanium insert
that have been produced using an
experimental procedure allowing
the control of both the interfacial
reaction layer and the
metallurgical health of the matrix
(directional solidification).
• The results obtain under push-out
solicitation highlight the potential
of the joining process for
producing castings with high
mechanical performances.
• Push-out test and a
variant that is the
circular-bending test
to investigate the
mechanical strength.
• Characterization of
the interfacial zone
by Optical
Microscopy (OM),
Scanning Electron
Microscopy (SEM)
and Electron
Micropobe Analyses
(EPMA).
• When a chemical bond is
established at the Ti/AS-7
interface an important rise of
mechanical properties for the
bimetallic assembly is observed:
the mean shear strength value is
about 120 MPa whereas it is of
48 MPa for simply fretted
specimens.
• Finite Element
Modeling (FEM)
was performed to
describe the stress
distribution in a
bimetallic slice
during push-out test
at different load
level.
• A three steps failure sequence
proposed is both characterized by
crack propagation from bottom to
top and matrix yielding from top
to bottom.
10 S45C steel
insert to
copper
Cast
welding or
compound
casting
• Heat treatment formed reacted
layers in the interface. The layer
near the S45C steel matrix was
the cast welding layer; another
close to the copper matrix was
the irregular layer, and the other
between these two layers was the
middle layer.
• The microstructure
of the compound
casting was
observed by OM
(optical microscope)
and SEM (scanning
electron
microscope).
• EPMA proved that most of the
iron atoms diffused into the
copper matrix and only a few
copper atoms diffused into the
iron matrix during diffusion
occurred between two matrices.
X-ray diffraction showed that the
chemical compounds of the
interface were CuFeO2 and C.
• Furnace-cooling yielded the
largest interface shear strength,
and water quenching yielded the
least.The fractured region was
near the S45C steel matrix in the
cast welding layer.
• The interface phase
was analyzed by X-
ray diffraction and
the composition was
determined using
EDS and EPMA
(electron probe
micro-analysis).
• A push-out test was
used to determine
the interface shear
strength
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