The document discusses various concepts related to solidification during welding processes: - Grain growth in the weld pool occurs through epitaxial growth from the pre-existing grains in the base metal, avoiding the undercooling needed for nucleation. Grains oriented favorably for growth will overtake others. - Solidification begins at the liquidus temperature. Columns of solid grow perpendicular to the solid-liquid interface for maximum heat extraction into the substrate. In cubic metals, grains with orientations allowing perpendicular growth (e.g. [100] direction in cubic metals) will dominate. - Constitutional supercooling near the weld centerline can lead to equiaxed grain formation. Microsegregation and none

1. A.S.D’Oliveira
SOLIDIFICAÇÃO

2. A.S.D’Oliveira
Qual a temperatura de fusão dos elementos puros?
Qual a temperatura de fusão da liga Pb40wt%Sn?

3. A.S.D’Oliveira
v Solidificação
L
G1
L
S
G2 = G1+ΔG
T
G
T Tf
ΔT
ΔGv
Gsólido
Glíquido
Temperatura de fusão = T de solidificação?
interface

4. A.S.D’Oliveira
v Solidificação
Nucleação homogênea
G2=VSGs
v+ VLGL
V +ASLγSL
Para uma particula esférica:
ΔGr=-4/3πr3 ΔGv + 4 πr2 γSL
Para reduzir energia do sistema:
r* = núcleo crítico:
núcleo < r* redução; núcleo>r* crescimento
TL
T
r
S
m
ΔΔ
−
=
γ2
*
ΔLS = calor latente de solidificação
Tm = temperatura de fusão
γ = energia livre da superfície
ΔT = Tm - T = super-resfraimento
r* = raio critico

5. A.S.D’Oliveira
During Solidification the atomic arrangement changes from a random or
short-range order to a long range order or crystal structure.
Nucleation occurs when a small nucleus begins to form in the liquid, the
nuclei then grows as atoms from the liquid are attached to it.
The crucial point is to understand it as a balance between the free
energy available from the driving force, and the energy consumed in
forming new interface. Once the rate of change of free energy
becomes negative, then an embryo can grow.
Nucleação homogênea
Para reduzir energia do sistema:
r* = núcleo crítico:
núcleo < r* redução; núcleo>r* crescimento

6. A.S.D’Oliveira
v Solidificação
Raio critico r* diminui com o aumento de ΔT
Quanto maior o super-resfriamento menor serão r* e ΔGv*
Efeito do super-resfriamento sobre o raio critico

7. A.S.D’Oliveira
v Solidificação
Taxa de nucleação
Depende do número de aglomerados de átomos com raio r e
da frequência com um átomo se agregam a este aglomerado
É necessário um super-
resfriamento mínimo para
que se inicie a nucleação

8. A.S.D’Oliveira
v Solidificação
Nucleação Heterogênea
Condição necessária para que
a nucleação seja eficiente:
γSI < γIL + γSL
No equilibrio:
γIS = γIL + (γSL cos θ)
0 < θ <90° a condição de molhabilidade é satisfeita, já
para θ > 90° não é.
Ocorrendo molhabilidade, um núcleo com um raio de
curvatura igual ao raio critico em nucleação homogênea pode
ser formado a partir de um número muito menor de átomos do
que seria necessário para a formação de um núcleo livre no
seio do líquido.
super-resfriamento necessário para
a nucleação heterogênea é muito
menor do que o necessário para a
nucleação homogênea.
ΔGhet=VSΔGv+ASLγSL+ASIγSI -ASLγSL

9. A.S.D’Oliveira
v Solidificação
Nucleação homogênea vs nucleação heterogênea
Variação de energia livre para o mesmo r*
Taxa de nucleação

10. A.S.D’Oliveira
Nucleação em trincas – o angulo de contato pode ser bem diferente da consição
anterior; super-resfriamento é muito menor
A trinca tem de ter largura suficiente para permitir o crescimento do sólido
Nucleação na fusão
/m3
with
with
unit
Mould walls not flat
Critical radius
for solid
Nucleation in cracks occur with very little
undercooling

11. A.S.D’Oliveira
v Solidificação
Solidificação:
- nucleação
- crescimento
Temperatura
sólido líquido
Temperatura
sólido líquido
a) b)

12. A.S.D’Oliveira
v Solidificação
Crescimento do sólido depende da interface:
Rugosa (metais) – transição L/S é gradual em várias camadas atômicas;
controlada pelo escoamento de calor (metais puros) ou difusão de soluto (ligas);
átomos chegam no cucleo em qualquer localização – crescimento continuo
Lisa (não metais) – atomicamente plana e compacta;
Nucleação na
superfície
Crescimento em espiral
Crescimento lateral
Influência do super-resfriamento
da interface S/L na taxa de
crescimento para diferentes
interfaces

13. A.S.D’Oliveira
v Solidificação
Crescimento – influência do escoamento de calor
Crescimento planar
Crescimento não planar

14. A.S.D’Oliveira
Crescimento dendritico
Crescimento não planar
v Solidificação

15. A.S.D’Oliveira
Crescimento em ligas metálicas - Equilibrio
v Solidificação
Para a liga Pb30wt%Sn qual a composição das fases nas temperaturas
220C
200C
190C

16. A.S.D’Oliveira
v Solidificação
Crescimento em ligas metálicas fora do equilibrio
Sem difusão no sólido e mistura perfeita no liquido (queda gradual de T do
liq)
Desenvolvimento de dendritas
Segregação do soluto

17. A.S.D’Oliveira
v Solidificação
Solidificação de ligas:
v Sem difusão no sólido e difusão no liquido
Ao atingir a T2 a taxa de crescimento é
constante; o aumento da concentração
de soluto na frente de solidificação
estabiliza

18. A.S.D’Oliveira
Desenvolvimento de dendritas
Segregação do soluto no
desenvolvimento de dendrítas
Dendritas de um sistema Ni-Al
José Eduard/oUnicamp
v Solidificação

19. A.S.D’Oliveira
v Solidificação
Crescimento celular - Frente
de solidificação não planar

20. A.S.D’Oliveira
v Solidificação
Efeito do super-resfriamento
constitucional na morfologia de
solidificação.

21. A.S.D’Oliveira
v Solidificação
Formação de uma estrutura dendritica
Relação com a estrutura de grão
Resistência mecânica é proporcional ao espaçamento entre
braços secundários das dendritas

22. A.S.D’Oliveira
v Solidificação
Formação de grãos em um metal fundido

23. A.S.D’Oliveira
v Solidificação
Crescimento dendritico em um sistema eutético Al-Ni
Com autorização de José
Eduardo/Unicamp

24. A.S.D’Oliveira
v Solidificação
Microestrutura de solidificação no equilibrio e resfriadas
fora do equilibrio?

25. A.S.D’Oliveira
v Solidificação
Liga hipo-eutética

26. A.S.D’Oliveira
v Solidificação
Liga peritética

27. A.S.D’Oliveira
v Solidificação

28. A.S.D’Oliveira
v Solidificação
Solidificação eutética L -> α + β
Eutético divorciado – volume de uma das fases é muito pequeno
Eutético lamelar

29. A.S.D’Oliveira
v Solidificação
Solidificação de lingotes
Zona
equiaxial
Zona
colunar
Zona
coquilhada
Direção de crescimento em metais cúbicos <100>

30. A.S.D’Oliveira
v Solidificação
Solidificação em soldagemSolidificação em soldagem/vazamento continuo
Taxa de aporte de calor (depende do processo de soldagem e da
dimensão da solda; ou do volume e temperatura do fundido, q
Velocidade do arco; velocidade de retirada do tarugo, v
Condutividade térmica do metal sendo soldado ou fundido, Ks
Espessura da placa sendo soldada ou fundida, t

31. A.S.D’Oliveira
Solidificação em soldagem
v Solidificação
Os parâmetros Ks, v, t e q irão determinar a
morfologia da solidificação
Condutividade
Velocidade
espessura

32. A.S.D’Oliveira
v Solidificação em soldagem
Diluição: alteração da composição
química
Microestrutura/propriedades depende de:
Solidificação: parâmetros de solidificação G e R
Os parâmetros de solidificação são determinados
pelos parâmetros de soldagem
Tx de crescimento (R) depende da velocidade de
avanço da fonte de calor e do formato da poça de
fusão
Tx de resfriamento (ε) e gradiente de T(G) diminuem
com o aumento do aporte de calor
ε= G.R
Fundamentals of Weld Solidification
John N. DuPont, Lehigh University
MICROSTRUCTURAL EVOLUTION dur-
ing solidification of the fusion zone represents
one of the most important considerations for
controlling the properties of welds. A wide
range of microstructural features can form in
the fusion zone, depending on the alloy compo-
sition, welding parameters, and resultant solidi-
fication conditions. The primary objective of
this article is to review and apply fundamental
solidification concepts for understanding micro-
structural evolution in fusion welds.
Microstructural Features in Fusion
Welds
Figures 1 through 3 schematically demon-
strate the important microstructural features
that must be considered during solidification
in fusion welds (Ref 1, 2). On a macroscopic
scale, fusion welds can adopt a range of grain
morphologies similar to castings (Fig. 1), in
which columnar and equiaxed grains can poten-
tially form during solidification. The final grain
structure depends primarily on alloy composi-
tion and the heat-source travel speed. Although
some of the concepts applicable to grain struc-
ture formation in castings apply to welds, there
are also some unique differences. While the
columnar and equiaxed zones can form in
cooled below its liquidus temperature due to
compositional gradients in the liquid. The
extent of constitutional supercooling in the
weld is determined by the alloy composition,
welding parameters, and resultant solidification
parameters. Lastly, the distribution of alloying
elements and relative phase fractions within
the substructure (Fig. 3) are also important
microstructural features that strongly affect
weld-metal properties. The particular example
shown in Fig. 3 represents a case in which
extensive residual microsegregation of alloying
elements exists across a cellular substructure
after nonequilibrium solidification. This micro-
segregation, in turn, produces a relatively high
fraction of intercellular eutectic and associated
secondary phase. The microsegregation behav-
ior and concomitant amount of secondary phase
that forms can each be understood with solute
redistribution concepts. Lastly, dendrite tip
undercooling can become important at
high solidification rates associated with high-
energy-density welding processes. Tip under-
cooling can lead to significant changes in the
primary solidification mode, distribution of sol-
ute within the solid, and final phase fraction
balance. Rapid solidification concepts are
needed to understand these phenomena. All
of these fundamental solidification concepts
(nucleation, competitive grain growth, constitu- Fig. 1 Types of grain morphologies that can form in
ASM Handbook, Volume 6A, Welding Fundamentals and Processes
T. Lienert, T. Siewert, S. Babu, and V. Acoff, editors
Copyright # 2011 ASM InternationalW
All rights reserved
www.asminternational.org

33. A.S.D’Oliveira
v Solidificação em soldagem
Nucleação -> Crescimento epitaxial
Metal de base apresenta uma coerência cristalográfica quase
que perfeita; não existe barreira para a nucleação
Grain Structure of Fusion Welds
As described previously, the weld-metal
grains will grow epitaxially from the preexist-
ing base-metal grains. However, not all of these
grains will be favorably oriented for continued
growth. Two primary factors control the
continued competitive growth of weld-metal
grains:
This is shown schematically in Fig. 10 (Ref
6). Grains at the fusion line may initially be ori-
ented in a favorable direction for growth, but
their direction may become unfavorable as the
curved solid/liquid interface changes its posi-
tion. These grains may then eventually be
overgrown by other grains that exhibit more
favorable orientation for growth as the solid/liq-
uid interface sweeps through the weld. An
example of this is shown on a weld in nearly
pure (99.96%) aluminum in Fig. 11(a) (Ref 7).
Fig. 9 Example of epitaxial growth from the fusion line
in an electron beam weld of alloy C103.
Original magnification: 400Â. Source: Ref 5
Fig. 10 Schemat
growth
near the fusion line.
orientated grains at a
Fig. 8 Comparison of free-energy changes associated
with homogeneous nucleation, heterogeneous
nucleation, and fusion welding
Grãos na poça de fusão crescem diretamente sobre grãos pre-
existentes no metal-base orientados favoravelmente

34. A.S.D’Oliveira
v Solidificação em soldagem
Crescimento:
Ø Grãos crescem perpendicularmente a
interface S/L sendo a extração de calor é
máxima (calor escoa pelo substrato)
Ø Sólido cresce na direção cristalográfica que for
mais fácil ( metais cubicos [100] – grãos com
[100] orientados perpendicularmente a
interface vão crescer)
atching. An example of this in a fusion weld
ade with the electron beam process is shown
Fig. 9 (Ref 5). Note that there are no fine
quiaxed grains at the fusion line, as often
bserved in the chill zone of castings. Instead,
e weld-metal grains grow directly from the pre-
xisting base-metal grains. As a result, there is no
arrier to formation of the solid. This condition is
ferred to as epitaxial growth, because growth
ccurs directly from the preexisting solid without
e need for nucleation. Therefore, there is no
ndercooling required to initiate solidification
the fusion line, and solidification commences
the liquidus temperature of the alloy. It should
e noted that undercooling can still occur near the
eld centerline due to the process of constitu-
onal supercooling, as explained in more detail
ter. This can lead to the formation of the central
quiaxed zone often observed in fusion welds.
ndercooling can also be required for nucleation
new phases during solidification.
Grain Structure of Fusion Welds
As described previously, the weld-metal
ains will grow epitaxially from the preexist-
g base-metal grains. However, not all of these
ains will be favorably oriented for continued
owth. Two primary factors control the
ontinued competitive growth of weld-metal
ains:
to the solid/liquid interface. The second crite-
rion results from the preferred crystallographic
growth direction, which, for cubic metals, is
along the [100] directions. By combining these
two criteria, it can be seen that grains that have
their easy-growth direction most closely
aligned to the solid/liquid interface normal will
be most favorably oriented to grow, thus
crowding out less-favorably-oriented grains.
This phenomenon accounts for the columnar
grain zone that is often observed in castings,
shown schematically in Fig. 5. In this case,
the grains that nucleated near the mold wall
and have their easy-growth direction aligned
normal to the mold/casting interface outgrow
the less-favorably-oriented grains, leading to
the columnar region.
The situation is slightly more complex in
fusion welding, because the pool shape pro-
duces a curved solid/liquid interface that is con-
stantly in motion as it follows the heat source.
This is shown schematically in Fig. 10 (Ref
6). Grains at the fusion line may initially be ori-
ented in a favorable direction for growth, but
their direction may become unfavorable as the
curved solid/liquid interface changes its posi-
tion. These grains may then eventually be
overgrown by other grains that exhibit more
favorable orientation for growth as the solid/liq-
uid interface sweeps through the weld. An
example of this is shown on a weld in nearly
pure (99.96%) aluminum in Fig. 11(a) (Ref 7).
to the growth rate. Because the growth rate is
highest at the weld centerline, the release rate
of latent heat is also highest at the weld center-
line. However, the temperature gradient is at a
Schematic illustrations of competitive grain
Fonte de calor em movimento – interface S/L curva
e em movimento
Grãos que inicialmente exibem orientação favorável
podem perder esta condição
Crescimento normal as isotermas;
ajuste a velocidade da fonte de calor

35. A.S.D’Oliveira
v Solidificação em soldagem
O aspecto geométrico da poça de fusão determina a forma da interface S/
L e depende dos parâmetros de soldagem
minimum at the weld centerline, so it is difficult
to transport the latent heat away from the pool
to permit solidification. This causes elongation
of the pool near the weld centerline and leads
to the teardrop shape. In this case, the direction
of grain growth does not change (because the
solid/liquid interface is no longer curved), and
the grains grow straight toward the weld center-
line until grains growing from each side of the
weld intersect. This process typically leads to
a centerline grain boundary, as shown in
Fig. 11(b) (Ref 7).
Axial grains that grow along the direction of
heat-source travel can also occasionally be
observed in fusion welds. The various types of
grain morphologies are summarized in Fig. 12
(Ref 6). Examples of grain structures produced
with elliptical and teardrop-shaped weld pools
were shown in Fig. 11. Figures 12(c) and (d) rep-
resent conditions in which an axial grain grows
along the direction of the heat-source travel.
These grains form in the region where the solid/
liquid interface is generally perpendicular to the
direction of heat-source travel, so that it becomes
favorable for one or more grains to grow in this
direction. The width of this zone can depend on
the pool shape. The region of the interface that
is perpendicular to the heat-source direction is
relatively small in an elongated weld pool, so
the width of axial grains will also be small. By
comparison, this perpendicular region is rela-
tively larger for an elliptical pool, so the axial
grain region can also be larger.
The large columnar grains and the potential
presence of centerline grain boundaries are gen-
erally undesirable from a weldability and
mechanical property point of view. Centerline
grain boundaries can often lead to solidification
cracking associated with solidification shrinkage
and low-melting-point films that become concen-
trated at the centerline. Fine, equiaxed grains are
desired over coarse columnar grains for improve-
ments in both cracking resistance and mechanical
properties (at low temperature). One effective
means for minimizing or eliminating the coarse
columnar grains is through manipulation of the
pool shape. Figure 13 shows an example of a
weld in which the arc was oscillated at a fre-
quency of 1 Hz in a direction normal to the
heat-source travel (Ref8). In this case, the contin-
uously changing direction of the solid/liquid
interface makes it difficult for the columnar
grains to extend over large distances, thus
providing a degree of grain refinement. Grain
size reduction can also be achieved through the
use of inoculants. This process takes advantage
of heterogeneous nucleation (discussed previ-
ously) and liquid undercooling that occur due to
constitutional supercooling. This topic is
morphologies within the grains that can be cel-
lular, columnar dendritic, or equiaxed dendritic.
Cellular and columnar dendritic morphologies
develop due to breakdown of the initially planar
solid/liquid interface that forms at the fusion
line, while equiaxed dendrites form by nucle-
ation of solid in undercooled liquid, typically
near the weld centerline. Formation of these
features can be understood with the concept of
constitutional supercooling. The basics of this
topic are described first, followed by applica-
tion of the theory to understanding the substruc-
ture formation in fusion welds.
Constitutional Supercooling
As shown by the phase diagram in Fig. 14(a),
formation of a solid leads to rejection of solute
into the liquid. The extent of solute enrichment
in the liquid progresses as solidification pro-
ceeds and the liquid composition follows the
liquidus line. The solute rejected by the solid
at the solid/liquid interface must be transported
away from the interface by diffusion and/or
convection in the liquid. If the solid/liquid
interface growth rate is relatively high (which
leads to a high rate of solute rejection) and/or
the transport of solute into the liquid by diffu-
sion or convection is low, then a solute bound-
ary layer can develop in the liquid near the
solid/liquid interface. Because solute enrich-
ment leads to a reduction in the liquidus tem-
perature (for an element that partitions to the
liquid), it follows that the presence of a solute
Fig. 13 Grain structure in a fusion weld of alloy 2014
made with transverse arc oscillation. Source:
Ref 8
Fig. 11 Examples of (a) competitive grain growth and
(b) a centerline grain boundary forming on a
weld in 99.96 % Al. The weld in (a) was made at a
welding speed of 250 mm/min (10 in./min). The weld in
(b) was made at a welding speed of 1000 mm/min (40
in./min). Source: Ref 7
100 / Fundamentals of Fusion Welding
minimum at the weld centerline, so it is difficult
to transport the latent heat away from the pool
to permit solidification. This causes elongation
of the pool near the weld centerline and leads
to the teardrop shape. In this case, the direction
of grain growth does not change (because the
solid/liquid interface is no longer curved), and
the grains grow straight toward the weld center-
line until grains growing from each side of the
weld intersect. This process typically leads to
a centerline grain boundary, as shown in
Fig. 11(b) (Ref 7).
Axial grains that grow along the direction of
heat-source travel can also occasionally be
observed in fusion welds. The various types of
grain morphologies are summarized in Fig. 12
(Ref 6). Examples of grain structures produced
with elliptical and teardrop-shaped weld pools
were shown in Fig. 11. Figures 12(c) and (d) rep-
resent conditions in which an axial grain grows
along the direction of the heat-source travel.
These grains form in the region where the solid/
liquid interface is generally perpendicular to the
direction of heat-source travel, so that it becomes
favorable for one or more grains to grow in this
direction. The width of this zone can depend on
the pool shape. The region of the interface that
is perpendicular to the heat-source direction is
relatively small in an elongated weld pool, so
the width of axial grains will also be small. By
comparison, this perpendicular region is rela-
tively larger for an elliptical pool, so the axial
grain region can also be larger.
The large columnar grains and the potential
presence of centerline grain boundaries are gen-
erally undesirable from a weldability and
mechanical property point of view. Centerline
grain boundaries can often lead to solidification
cracking associated with solidification shrinkage
and low-melting-point films that become concen-
trated at the centerline. Fine, equiaxed grains are
desired over coarse columnar grains for improve-
ments in both cracking resistance and mechanical
properties (at low temperature). One effective
means for minimizing or eliminating the coarse
columnar grains is through manipulation of the
pool shape. Figure 13 shows an example of a
weld in which the arc was oscillated at a fre-
quency of 1 Hz in a direction normal to the
heat-source travel (Ref8). In this case, the contin-
uously changing direction of the solid/liquid
interface makes it difficult for the columnar
grains to extend over large distances, thus
providing a degree of grain refinement. Grain
size reduction can also be achieved through the
morphologies within the grains that can be cel-
lular, columnar dendritic, or equiaxed dendritic.
Cellular and columnar dendritic morphologies
develop due to breakdown of the initially planar
solid/liquid interface that forms at the fusion
line, while equiaxed dendrites form by nucle-
ation of solid in undercooled liquid, typically
near the weld centerline. Formation of these
features can be understood with the concept of
constitutional supercooling. The basics of this
topic are described first, followed by applica-
tion of the theory to understanding the substruc-
ture formation in fusion welds.
Constitutional Supercooling
As shown by the phase diagram in Fig. 14(a),
formation of a solid leads to rejection of solute
into the liquid. The extent of solute enrichment
in the liquid progresses as solidification pro-
ceeds and the liquid composition follows the
liquidus line. The solute rejected by the solid
at the solid/liquid interface must be transported
away from the interface by diffusion and/or
convection in the liquid. If the solid/liquid
interface growth rate is relatively high (which
leads to a high rate of solute rejection) and/or
the transport of solute into the liquid by diffu-
sion or convection is low, then a solute bound-
ary layer can develop in the liquid near the
solid/liquid interface. Because solute enrich-
ment leads to a reduction in the liquidus tem-
perature (for an element that partitions to the
liquid), it follows that the presence of a solute
Fig. 13 Grain structure in a fusion weld of alloy 2014
made with transverse arc oscillation. Source:
Ref 8
Fig. 11 Examples of (a) competitive grain growth and
(b) a centerline grain boundary forming on a
weld in 99.96 % Al. The weld in (a) was made at a
welding speed of 250 mm/min (10 in./min). The weld in
(b) was made at a welding speed of 1000 mm/min (40
in./min). Source: Ref 7
100 / Fundamentals of Fusion Welding
250mm/min
1000mm/min
Liberação de calor latente de solidificação é proporcional a tx de crescimento
(R) que é máxima no centro do cordão;
mas o gradiente térmico (G) é minimo on centro do cordão o que dificulta a
transferencia de calor – provoca o alongamento da poça – interface S/L reta
Contorno no meio do cordão é indesejável

36. A.S.D’Oliveira
v Solidificação em soldagem
Desenvolvimento de sub-estruturas – diferente morfologias dentro de um
grão
Celular/colunar dendritico/equiaxial dendritico
Interrupção da interface plana Nucleação de sólido no liq
super-resfriado
Relações que determinam as caracteristicas da estrutura/propriedades
G/R -> tipo de estrutura
G.R -> refino da estrutura
Propriedades dependem do espaçamento entre braços das dendritas que
é proporcional a tx de resfriamento; determina pelo aporte de calor

37. A.S.D’Oliveira
Valores de G e R mudam contantemente em direções opostas em torno da
interface S/L
Linha de fusão:
- alto gradiente térmico (G) e baixa taxa de crescimento (R) pode
ter uma estrutura planar
Centro do cordão:
- baixo gradiente térmico (G) e alta taxa de crescimento (R)
Crescimento mais rápido no centro e mais lento nas bordas
v Solidificação em soldagem
Relação entre taxa de crescimento e velocidade de soldagem (v)
R=v.cosΘ
R≈0, linha de fusão
R≈v ,linha central

38. A.S.D’Oliveira
38
Fig. 15 Schematic illustrations showing (a) stability of a pla
temperature gradient and (b) breakdown of a plana
temperature gradient
G/R – super-
resfriamento
v Solidificação em soldagem
Desenvolvimento da estrutura na poça de fusão
G/R muito alto na linha de fusão e vai diminuindo até a linha central
Sequencia de solidificação
Estrutura planar
Celular
Colunar dendritica
Equiaxial dendritica
(Alto super-resfriamento
constitucional)
Linha de fusão
Centro do cordão

39. A.S.D’Oliveira
Considere as aletas de turbinas abaixo. Assumindo que todas foram
produzidas com a mesma liga de Ni, descreva como se desenvolvem as 3
estruturas de solidificação
v Solidificação

40. A.S.D’Oliveira
2.4mm
substrato
Vergara, V.M., Tese de doutorado 2007
v Solidificação em soldagem
Descrever solidificação do
revestimento

41. A.S.D’Oliveira
v Solidificação
Ni12wt%Al
Ni30wt%Al
Explique o desenvolvimento das estruturas de solidificação considerando
que o desenvolvimento do composto intermetálico é exotérmico