Materials Characterization,
Год журнала:
2023,
Номер
206, С. 113452 - 113452
Опубликована: Ноя. 4, 2023
Achieving
equiaxed
grain
structure
is
highly
sought
after
in
metal
processing
for
most
critical
structural
applications
but
it
seldom
realized
Ti-6Al-4
V
additively
manufactured
(AM)
by
laser
powder-bed
fusion
(LPBF)
due
to
its
unique
thermal
environment
favor
of
columnar
growth.
To
convert
grains
into
equiaxed,
post
heat
treatment
the
β
phase
field
often
adopted
initiate
recrystallization
prior-β
grains.
This
study
demonstrates
achievement
situ
LPBF
via
epitaxial
mediated
α
→
transformation
taking
place
rapid
heating
stage
cycling.
In
this
reverse
process,
new
nuclei
distinct
variants
their
parent
nucleate
directly
on
matrix
accordance
with
Burgers
orientation
relationship
and
grow
towards
surrounding
while
transforming
within
a
specific
grain.
hypothesis
strongly
supported
experimental
evidence
that
significant
fraction
β/β
boundaries
are
featured
misorientations
near
60°
both
as-built
those
subjected
treatment.
essentially
excludes
conventional
as
mechanism
responsible
evolution
state.
The
finding
unveils
role
cycling
associated
microstructure
paves
way
development
high-quality
AM
reduced
performance
anisotropy.
Materials & Design,
Год журнала:
2024,
Номер
241, С. 112926 - 112926
Опубликована: Апрель 9, 2024
The
laser
powder
bed
fusion
manufactured
Ti-6Al-4
V
alloy
predominantly
consists
of
α'
martensite,
resulting
in
excellent
strength
but
limited
ductility,
hinders
widespread
application.
Therefore,
it
is
crucial
to
achieve
the
decomposition
martensite
and
improve
ductility.
However,
reverse
transformation
behavior
its
mechanism
β
phase,
as
well
stability
remain
unclear.
Our
findings
demonstrate
that
phase
follows
a
diffusion-controlled
process.
into
α
+
initiates
at
approximately
550
℃,
while
from
occurs
around
870
℃.
Increasing
temperature
leads
an
increase
reverse-transformed
phase.
retention
these
phases
room
also
depends
on
their
stability,
which
exhibits
significant
correlation
with
element
partitioning.
Additionally,
this
study
reveals
critical
(840
℃)
maximum
volume
fraction
(18.6
%)
retained
obtained,
exhibiting
exceptional
mechanical
properties,
particularly
uniform
elongation
surpassing
those
observed
as-printed
microstructure
LPBF-ed
alloy.
Materials,
Год журнала:
2023,
Номер
16(21), С. 6947 - 6947
Опубликована: Окт. 29, 2023
Selective
laser
melting
(SLM)
can
effectively
replace
traditional
processing
methods
to
prepare
parts
with
arbitrary
complex
shapes
through
layer-by-layer
accumulation.
However,
SLM
Ti-6Al-4V
alloy
typically
exhibits
low
ductility
and
significant
mechanical
properties
anisotropy
due
the
presence
of
acicular
α'
martensite
columnar
prior
β
grains.
Post-heat
treatment
is
frequently
used
obtain
superior
by
decomposing
into
an
equilibrium
α
+
phase.
In
this
study,
microstructure
tensile
before
after
various
heat
treatments
were
systematically
investigated.
The
as-fabricated
sample
was
composed
grains
martensite,
which
led
high
strength
(~1400
MPa)
but
(~5%)
as
well
significantly
anisotropy.
single
samples
lamellar
exhibited
improved
elongation
6.8-13.1%
a
sacrifice
100-200
MPa,
while
weakened.
A
trimodal
achieved
multi-step
high-to-low-temperature
(HLT)
treatment,
resulting
in
excellent
combination
(~1090
(~17%),
almost
eliminated.
comprehensive
HLT
that
conventional
manufactured
alloy.
Results in Physics,
Год журнала:
2024,
Номер
61, С. 107781 - 107781
Опубликована: Май 21, 2024
In
this
study,
selective
laser
melting
(SLM)
technology
was
utilized
to
fabricate
Ti6Al4V
and
TiC/Ti6Al4V
composites.
We
then
investigated
the
effect
of
solution
heat
treatment
temperature
aging
time
on
microstructural
mechanical
properties
both
alloy
The
findings
showed
that
with
an
increase
in
temperature,
acicular
martensite
matrix
composites
progressively
transitioned
into
plate-bar
alpha
phase.
Concurrently,
there
a
distinct
irregularity
morphology
beta
columnar
grain
boundaries,
accompanied
by
evenly
enhanced
distributed
With
respect
hardness,
microhardness
initially
displayed
slight
drop
followed
significant
increase,
reaching
peak
430
HV.
contrast,
composite
materials
exhibited
initial
minor
substantial
surge,
maximum
value
607
Post
treatment,
samples
observed
decrease
from
463.2
HV
362.7
had
notable
influence
+
structure,
where
size
martensitic
phase
constrained
This
study
revealed
extension
resulted
increased
strengthening
phase,
subsequently
leading
reduction
composite's
microhardness.
underscored
pivotal
role
defining
Virtual and Physical Prototyping,
Год журнала:
2024,
Номер
19(1)
Опубликована: Июль 12, 2024
The
in-situ
analysis
of
mass
transfer
behaviours
in
a
novel
underwater
wire-laser
directed
energy
deposition
(ULDED)
technique
was
conducted
using
X-ray
high-speed
imaging.
By
creating
stable
local
dry
cavity
within
the
water
environment,
three
distinct
modes
were
identified:
droplet
transfer,
liquid
bridge
and
spreading
modes.
effectively
managed
by
maintaining
mode
to
enhance
formability
metal
deposits.
inherent
heat
treatment
effect
ULDED
provides
unique
opportunity
tailor
microstructures
mechanical
properties
situ
with
establishing
thermal
environment
conducive
preferred
lamellar
α+β
microstructure
instead
acicular
α′
martensite.
With
increasing
input,
diffusion-controlled
transformation
pathway
gave
rise
martensite
decomposition,
underpinned
morphological
characteristics
crystallographic
orientations
constituent
phases.
