Dimensional Control in Cu-Ni Containing Ferrous PM Alloys
Bruce Lindsley and Thomas Murphy
Hoeganaes Corporation
Cinnaminson, NJ 08077, USA
ABSTRACT
Dimensional precision is a critical parameter in net shape processing of ferrous PM components.
Elemental additives, such as copper and nickel, modify the dimensional change in sintered parts.
Typically, Cu causes growth and Ni causes shrinkage. Interactions between Cu, Ni and C
complicate these simple trends leading to more complex behavior. With the use of prealloyed Mo
base materials, these alloy systems can be used for sinter-hardening applications. This paper
investigates the dimensional and microstructural changes of Cu-Ni containing PM alloys during
the sintering process.
INTRODUCTION
Dimensional precision is a key attribute in the manufacture of ferrous PM parts, especially in net
shape components. As the PM industry competes for larger sized components, the consistency of
dimensional change becomes increasingly more important. If absolute tolerances of these larger
parts do not change, the dimensional tolerance as a percentage of part diameter must be reduced.
Understanding the dimensional change and corresponding sources of variability of PM alloys is
critical to control part size and compliance.
The dimensional change of sintered compacts is influenced by several factors, including particle
size, density, composition, sintering time and temperature, cooling rate and microstructure. Die
fill and compaction related issues affect the green density distribution in a part, and may lead to
distortion problems. In the sintering furnace, increased sintering temperature and time generally
result in shrinkage while the cooling rate will affect the microstructure. Martensite formation
causes growth, while retained austenite has the opposite effect. Post sintering thermal treatments
will affect both of these structures and also have an effect on dimensions. In addition to these
variables, the powder composition plays an important role on microstructure, dimensional change
and mechanical properties. The most widely used additives to PM iron are graphite, copper and
nickel. Separately, copper and graphite additions cause growth in the sintered compact, while
nickel additions cause shrinkage.
Dilatometric studies have shown that in Fe-Cu alloys, growth is observed at 1083 °C, which is the
melting point of copper. The amount of growth is a direct function of Cu content up to levels of
10 wt% [1-3]. Detailed dilatometry work has also shown that generally, upon heating, graphite
quickly goes into solution in iron after the alpha to gamma transformation [1, 3-5]. During this
solutioning, the sample exhibits considerable growth that is a function of the graphite content.
When both copper and carbon are added to a base alloy, there is an interesting interaction
between the two alloying elements. The carbon inhibits both Cu bulk diffusion into the iron and
copper diffusion along grain boundaries. It has been shown that carbon content changes the
wetting angle and dihedral angle of liquid copper with iron; increased carbon increases both
angles [1,3]. This has an important ramification on copper diffusion in the compact, as at higher
carbon levels, liquid Cu has decreased flow along particle surfaces and especially into grain
boundaries, thereby reducing Cu diffusion. The amount of growth observed in a dilatometer at
1083 °C is significantly reduced in high carbon alloys. Therefore, growth and dimensional
change in a high carbon, high copper mix can be less than if either additive were made alone. It
has been shown that for a series of base alloys, the effect of Cu on dimensional change is reduced
to almost zero at high (1.0 wt%) levels of graphite [6]. In Figure 1, the effect of graphite and
copper content on the dimensional change of iron is presented. The large growth associated with
the addition of 2 wt% Cu at 0.6 wt% graphite becomes minimal at 1 wt% graphite.
Figure 1. Effect of Cu and graphite on dimensional change of PM iron (from [6]).
Nickel additions to PM compacts typically promote shrinkage of the part. The size and
distribution of Ni will play a role, but the behavior is well documented for standard Ni grades
with particle sizes near 8 µm. Alloys such as FLN2-4405 and FLN4-4405 often have negative
dimensional changes relative to die size, and these changes become more negative with
increasing sintering temperature and time. When copper and nickel are added to the same mix,
there is an interaction between the two during sintering [7,8]. The Ni-Cu phase diagram shows
that there is complete solid solubility between the two elements at temperatures above 355 °C.
Given that the two elements can easily alloy together, it is not surprising that an interaction exists
in sintered compacts. It has been shown that the initial Ni distribution in the green compact
affects the final Cu distribution after sintering [8,9]. It was also found that the addition of both
2 wt% Ni and 2 wt% Cu in combination caused more growth than either separate additions of
4 wt% Ni or 4 wt% Cu, whereas if no interaction was present, one would expect the dimensional
change of the 2 wt% Ni plus 2 wt% Cu alloy to lie between that of the 4 wt% Ni alloy and 4 wt%
Cu alloy [7].
The purpose of this paper is to investigate the dimensional response of Ni-Cu-Mo steels and
determine the mechanisms for the dimensional behaviors of each alloying element and
interactions between them. The anomalous dimensional behavior of alloys containing both
admixed Ni and Cu will be studied in detail.
EXPERIMENTAL PROCEDURE
Four commercially available ferrous powders were selected for study, Table I, with the primary
focus of the investigation on the 0.85 wt% Mo base alloy. All weight % will be designated as %
hereafter. To each of the Fe-Mo bases, 5 levels of Cu (0%, 0.5%, 1%, 1.5%, 2%), 2 levels of
graphite (0.6%, 0.9%) and two levels of nickel (0%, 2%) were added for a total of 20 mixes per
base material. An atomized Cu with a d50 of 40µm was primarily used in the study, although
additional tests were run with a copper particle size of 11µm. 0.75% EBS wax was used as the
lubricant for all mixes. Standard transverse rupture strength bars were pressed at 690 MPa
(50 tsi) and sintered in 90% nitrogen / 10% hydrogen at 1120 °C (2050 °F) in a continuous belt
furnace. The cooling rate in the sample measured between 650 °C (1200 °F) and 315 °C (600 °F)
was 0.7 °C/sec (1.3 °F/sec). Time at temperature experiments were performed in a pusher
furnace, also set at 1120 °C with the same atmosphere as the belt furnace. Samples were heated
to nominally 705 °C (1300 °F) for 15 minutes to burn out the lubricant prior to being pushed into
the hot zone. Time at temperature started immediately upon the samples entering the hot zone.
Dimensional change (DC) was determined by the difference between the length of the die and the
sintered length of the bar, divided by the length of the die. Hardness and transverse rupture
strength were also measured for all conditions. All testing was performed in accordance with
MPIF standards [10].
Table I. Nominal composition of base irons tested (in wt%).
Base Iron
MPIF Designation
Mo
Cu
®
FL-4400
0.85
Ancorsteel 85 HP
Ancorsteel 30 HP
0.30
Distaloy 4600A
FD-0200
0.5
1.5
Distaloy 4800A
FD-0400
0.5
1.5
Ni
1.75
4.0
Samples for metallographic examination were cross-sectioned, mounted, ground and polished
using well established practices. Microstructural evaluations were made using both light optical
®
Ancorsteel is a registered trademark of Hoeganaes Corporation
and scanning electron microscopy. In the SEM, backscattered electron imaging was used in
combination with electron dispersive spectroscopy (EDS).
RESULTS
Individual Alloying Element Effects on Dimensional Change
The individual contribution to dimensional change of each alloy element was measured in Fe-NiMo-Cu-C alloys. The effect of Mo and C (graphite) with various copper contents and no nickel is
shown in Figure 2. There is a clear effect of carbon content, as the slope of the dimensional
change vs. copper content curve decreases to roughly zero when graphite is increased from 0.6%
to 0.9% (solid lines to dotted lines). At 0.9% graphite, copper additions tend to have little effect
on growth. This correlates well with previous work by the authors [6]. There appears to be a
small effect of Mo content on dimensional change. The slope of the DC vs. copper content curve
decreases slightly with the increase in Mo content (circles vs. squares). It is unknown at this time
whether this slight change is a result of the different Mo content or an effect of base alloy particle
size distribution. A finer base alloy particle size may cause shrinkage with no Cu present and
more growth with the addition of Cu.
With the addition of 2% nickel, the behavior of the system changes substantially (Figure 3). The
small effect of different Mo base alloys, be it from Mo content or different base alloy particle
size, is no longer evident. More importantly, the effect of carbon content on dimensional change
has virtually been eliminated. At 0% Cu, the effect of graphite content can be seen, as the
FLN2-4405 type alloys show less growth than the FLN2-4408 type alloys. This is typical of
ferrous PM alloys; an increase in C content increases dimensional change. Above 0.5% Cu,
however, there is no longer any effect of graphite content within the graphite content range tested.
So in an FLNC-440X type material, carbon content has little effect on dimensional change. This
again assumes no accelerated cooling. Increased cooling rates would change the transformation
products, which in turn would affect the dimensional change.
Any dimensional benefit that could be realized by the independence of dimensional change on
carbon content is easily overshadowed by the dependence of dimensional change on copper
content. The dimensional change of FLNC-440X type alloys is a very strong function of copper
content, as the zero Cu alloys have the least growth and the 2% Cu alloys have the most growth
of any compositional conditions studied. This is opposed to the Ni free material, where the
dimensional change of FLC-4408 was relatively independent of Cu content (dotted lines in Figure
2). This strong dependence with Cu content at 0.9% graphite is different than for previous alloys
studied. With the F-0008, FL-4608 and FL-4808 alloys [6], and FL-4408 and 0.3% Mo plus
0.9% graphite alloys in the current study (Figure 2), Cu has limited effect on dimensional change.
These include systems with prealloyed Ni. The obvious difference with FLNC-4408 is the 2%
admixed Ni. The addition of both Ni and Cu increase the local hardenability within the alloys
considerably. It is possible that the increased hardenability could cause an increase in martensite
content, which in turn would increase the dimensional change. Given this possibility, accelerated
cooling was used with the Ni free samples to achieve the same hardness level as the
conventionally cooled nickel containing samples. This was possible in the sintering furnace in all
but the 0% copper specimens. In the Ni-containing and Ni-free samples with 0.9% graphite and
Ni-Free Alloys
0.6
0.5
0.4
0.3
0.2
0.3Mo,
0.8Mo,
0.3Mo,
0.8Mo,
0.1
0.0
0
0.5
1
1.5
Cu Content (%)
0.6Gr
0.6Gr
0.9Gr
0.9Gr
2
2.5
Figure 2. The effect of Mo, C and Cu on dimensional change in Ni free PM steels.
2% Ni Alloys
0.6
0.5
0.4
0.3
0.2
0.3Mo,
0.8Mo,
0.3Mo,
0.8Mo,
0.1
0.0
0
0.5
1
1.5
Cu Content (%)
2
0.6Gr
0.6Gr
0.9Gr
0.9Gr
2.5
Figure 3. The effect of Mo, C and Cu on dimensional change in 2% Ni PM steels
cooled to achieve similar hardnesses and levels of martensite, the dimensional change remained
quite different. The 0% Ni alloys maintained the overall shape of the graph in Figure 2, while the
2% Ni alloys maintained the shape of Figure 3. The transformation products are therefore not the
reason of the different behavior. The question is then why does this behavior occur in alloys with
admixed Ni and Cu.
Nickel-Copper Interaction
The reason for the odd behavior is the Ni-Cu interaction that occurs during sintering. This
interaction can clearly be seen in Figure 4. In this experiment, different amounts of the Cu were
added to a 0.85%Mo-0.9%Gr base with either 0%, 2% or 4% Ni. Again, at 0% Ni, copper has
little effect on dimensional change. Increasing Ni contents promote shrinkage, although as
copper levels increase in these Ni-containing alloys, the dimensional change increases. This is
most apparent with the 2% Ni alloy. Compared with the 0% Ni alloy, the 2% Ni, 1.5% Cu
exhibits a small amount of growth while the 2% Ni, 2% Cu alloy shows significantly higher
growth.
µ
0.6
0.0% Cu
0.5% Cu
1.0% Cu
1.5% Cu
2.0% Cu
0.5
0.4
0.3
0.2
0.1
0.0
-0.1
0
1
2
3
Ni Content (%)
4
5
Figure 4. Dimensional change of FL-4408 with different levels of Cu and Ni.
The microstructure of samples sintered for typical times at temperature can not clearly reveal the
cause of this interaction. The copper and nickel have diffused with the iron and identification of
individual constituents is impossible. Certainly, previous work has been done using EDS in an
SEM to analyze the Ni and Cu contents and a tendency was found for the Ni and Cu to be
concentrated in the same locations [7]. To understand what happens during sintering, samples
were sintered for different times in a pusher furnace. The sample composition was 0.8%Mo,
0.9% graphite, 1.5% copper and either 0 or 2% Ni. The dimensional change of these alloys for
different times in the hot zone is shown below in Figure 5. The dimensional change of the
samples sintered for zero minutes (lubricant burn out only) was 0.35% for both alloys. The two
minute samples continued to grow for both compositions. At times greater than 2 minutes, the
Ni-free material shrank with time, with the dimensional change leveling off at times greater than
20 minutes. The 2% Ni sample exhibited growth in the first ten minutes followed by continual
shrinkage as sintering continued. The Ni-Cu interaction appears to play an important role in the
early minutes of sintering. Therefore, samples within the first ten minutes of sintering were
investigated metallographically to determine if the mechanism could be identified.
Figure 5. Effect of Ni content and sintering time on dimensional change.
Figures 6 and 7 show the effect of time in the sintering furnace on the as-polished microstructures
of the Ni-free FLC2-4408 and the Ni containing FLNC-4408, respectively. The as-polished
microstructures revealed that the copper did not melt in the samples sintered for 2 minutes,
indicating that the samples had not yet reached 1083 °C. The growth up to this time can be
associated with carbon diffusion into the iron. Even though the copper has not melted at 2
minutes, the presence of nickel can be seen in Figure 7a. The copper particle in the lower left of
the figure had no nickel adjacent to it and maintained the same color as the copper in Figure 6a.
The copper particle in the upper right, however, resided next to nickel and alloying of the nickel
and copper in the solid state is apparent from the color change. Alloying can occur at relatively
low temperatures and short times in this system.
In the 5 minute samples, the copper melted and moved throughout the pore network, leaving
behind large, characteristic pores. The typical expansion observed in a dilatometer as the copper
melts [1,3] was not found in the current study, which is likely an effect of the high carbon
content. In the nickel free FLC2-4408 (Figure 6), the copper is well distributed throughout the
sample and is found in the particle boundaries, filling in the long, thin pores. This is consistent
with earlier work [11]. The rapid contraction seen in Figure 5 at times ≤ 10 minutes coincides
with the presence of liquid copper in the boundaries. The location of the liquid copper may
enable rapid sintering until the liquid copper is exhausted via copper diffusion into iron at the
sintering temperature. Lesser amounts of free copper were observed in the 10 minute sample and
very little was found at 20 minutes.
The copper also melted within 5 minutes at temperature in the Ni containing FLNC-4408, but the
location of the liquid copper is clearly different in this sample (Figure 7). The amount of Cu in
the long, thin base iron particle-particle boundaries is greatly reduced and instead, the copper is
clustered around the small, admixed nickel particles. The change in color of the copper rich alloy
surrounding the Ni particles is now more evident as the unique orange color of copper fades with
further Ni alloying. This is clearly different than the Ni free sample, where the amount of free
copper decreased with time, but the appearance (color) of copper remained the same. The
equilibrium concentration of Fe in liquid Cu is quite low (about 4%) and has little effect on the
melting point, and therefore the copper remains as liquid until it diffuses into the solid iron. In
the Ni containing material, Cu and Ni have complete solubility, resulting in a Ni-Cu composition
gradient.
(a)
(b)
(c)
(d)
Figure 6. As-polished microstructures of FLC2-4408 sintered for (a) 2 minutes, (b) and (c) 5
minutes and (d) 10 minutes. Note the higher magnification in (c) and (d).
(a)
(b)
(c)
(d)
Figure 7. As-polished microstructures of FLNC-4408 sintered for (a) 2 minutes, (b) and (c) 5
minutes and (d) 10 minutes. Note the higher magnification in (c) and (d).
In a side experiment, copper and nickel powders were mixed together and placed in the pusher
furnace at 1120 °C. The compositions varied in Ni content from 0% to 10% in 2.5% increments.
The mixtures with ≤ 5% Ni melted and formed a button, while the 7.5% and 10% Ni alloys did
not fully melt. The compositions that melted at 1120 °C match nicely with the Cu-Ni phase
diagram, which predicts alloys less than approximately 7% Ni will be fully molten at 1120 °C,
and those higher than this value will be partially solid until the solidus composition of nominally
15% Ni is reached, at which point the alloy is fully solid. It is also interesting to note that the
copper quickly loses its characteristic color as the nickel content is increased. Roughly half of the
color fades with a 5% Ni add and with 10% Ni, only a hint of Cu color remains. This whitening
effect is evident in the US nickel coin, which is 25% Ni and 75% Cu, and in “Nickel Silver”
alloys, one of which is 12% Ni and 88% Cu (NS-12). No evidence of copper, based on color, is
apparent in either the coin or the NS-12 alloy. The addition of 5% iron into the copper-nickel
mixes had no measurable effect on the melting temperature, but interestingly, iron negates the
whitening effect of nickel on copper. Therefore, more nickel is required to whiten the copper
when iron is present. Understanding the color change is useful in interpreting the as polished
microstructures of Ni-Cu containing samples sintered for short times.
As sintering proceeds and the copper continues to alloy with the nickel in FLNC-4408, it reaches
a composition that is solid at 1120 °C. Again, according to the phase diagram and the experiment
above, this composition is between 7% and 15% Ni, assuming no effects of Fe or C. This is also
in the compositional range where copper loses most of its orange color. These two events appear
to correspond with the 10 minute sintering sample. As can be seen in Figure 7, the copper-nickeliron alloy is barely visible in the as-polished microstructure. The change in dimensional behavior
at ten minutes suggests that the effect of the copper-nickel interaction is minimal after 10
minutes. It is postulated that the liquid Cu - solid Ni interaction is responsible for the growth
between 2 and 10 minutes and that once the copper alloy solidifies, the compact begins to behave
in a typical manner.
Electron backscattered imaging (BEI) was used in the SEM to reveal the compositional
differences in the as-polished microstructures of the 5 minute sintered samples. In addition, EDS
was used to semi-quantitatively measure the composition of the various regions. Figure 8 shows
the difference between the Ni-free and Ni-containing samples. The copper-rich areas are white
due to its higher atomic number, with the gray level of nickel between that of copper and iron. In
the Ni free sample, the copper was found along particle / grain boundaries. The copper was
relatively pure and little copper diffusion into the iron was evident. In the FLNC-4408, the
majority of copper was found in the vicinity of the Ni additive and these copper rich regions
contain significant amounts of both Ni and Fe after only 5 minutes total time in the hot zone. A
range of compositions was found in these bright areas. At the low alloying end, areas contained
6% Ni and 10% Fe, while at the higher end, the copper rich regions contain upwards of 10% Ni
and 14% Fe. It is expected that the copper rich regions containing 6% Ni were liquid at 1120 °C,
while the 10% Ni alloys may have been a mix of liquid and solid. Analysis of the Ni-rich regions
revealed that the prior Ni particles contain an average of 10% Cu and 33% Fe. Significant
diffusion occurs in these systems during the initial stages of sintering. One possibility for the
difference in dimensional behavior between the two alloys is that copper locally infiltrates and
fills pores in the Ni-free material, whereas in the Ni-containing alloys, the copper moves
preferentially to the Ni-rich regions and causes local swelling via diffusion with Ni and Fe in
those areas, resulting in growth of the overall compact.
Diffusion of the copper and nickel can also be seen along the rims of the iron particles. In Figure
8b, there is a light gray band on the edges of the iron particles. This gray level contrast is due to
the presence of copper and nickel in the base iron. The composition of these regions is nominally
5% Ni and 3% Cu. It is interesting to note that no such alloy rim in apparent in the nickel free
alloy. This alloy rim on the iron particles is another difference between the two samples and may
contribute to the different dimensional response. Copper does not diffuse quickly into high
carbon iron, but the presence of nickel in these areas may change this behavior. Just as the
increase in carbon changed the dimensional response in Figure 2 by modifying the copper
behavior, the addition of nickel into the high carbon system may cause the copper to behave more
like it does in a lower carbon, nickel free alloy.
(a)
(b)
Figure 8. Backscattered electron images of (a) FLC-4408 and (b) FLNC-4408 sintered for 5
minutes. Cu rich regions are white.
Effect of Copper Particle Size
The role of copper distribution in the green compact can play a large role on the dimensional
stability of a sintered part. Assuming a well mixed sample with no segregation, the copper
distribution can be changed by modifying the initial copper size. The reduction of particle size
can be beneficial with respect to dimensional change [8]. In Ni-free alloys, there is little effect of
copper particle size on dimensions. Figure 9 shows the effect on an 0.85% Mo base alloy with 2
carbon levels. At 0.6% graphite, little effect is seen, while at 0.9% graphite, increased growth is
found at high copper contents with the finer copper. The finer copper is not beneficial in this
alloy as liquid copper can freely migrate throughout the pore network; hence initial copper
distribution has little effect. The large pores are eliminated with the finer copper, but no benefit
to hardness or transverse rupture strength was found. In Ni free materials, the added cost for finer
Cu additives is generally not warranted.
0.6
0.5
0.4
0.3
0.2
40um Cu,
11um Cu,
40um Cu,
11um Cu,
0.1
0.0
0
0.5
1
1.5
Cu Content (%)
2
0.6Gr
0.6Gr
0.9Gr
0.9Gr
2.5
Figure 9. Effect of Cu particle size (d50) on dimensional change of FLC2-440X alloys.
In the nickel containing alloys, the initial copper particle size and distribution is important for
improved dimensional change. Figure 10 shows the effect of Cu size on the dimensional change
of FLNC-4408. The overall growth is decreased and the slope of the Cu-DC line is reduced,
indicating better dimensional control with small variations in Cu content. This reduction in
dimensional variation is also demonstrated in Figure 11. The data in Figure 4 was reproduced
using a fine Cu additive and both are shown in the figure. The fine Cu shifts the lines toward the
0% Cu, FLNX-4408 curve. In fact, 0.5% 11 µm Cu has nearly identical dimensional change as
0% Cu and 0.1% 11µm Cu is similar to 0% Cu across the range of nickel contents tested.
Overall, the spread in dimensional change is greatly reduced.
Two diffusion alloy data points, FD-0208 and FD-0408, have been included in the 11 µm Cu
graph. Both of these alloys contain 1.5% Cu and interestingly, fall right on the 1.5% 11µm Cu
(FLNC-4408) line. Note that the dimensional change of the diffusion alloys do not match up with
the 40 µm 1.5% Cu line. The 0.5% molybdenum is diffusion alloyed in the FD alloys, whereas
the 0.85% Mo is prealloyed in the FLNC-4408 type materials. Little effect of Mo content was
found in Fe-Mo-Ni-Cu alloys (Figures 2 and 3), so the Mo difference between the FL and FD
alloys is expected to be small. Given that Mo content has little effect, the use of fine Cu in
FLNC-4408 type systems can make these systems behave similarly to diffusion alloys with
respect to dimensional change. A good distribution of the fine Cu in the green state is required to
take advantage of this effect and a bonding process would be advantageous in this system by
fixing the additives to the base iron and preventing segregation.
2% Nickel Alloys
0.6
40um Cu
0.5
11um Cu
0.4
0.3
0.2
0.1
0.0
0
0.5
1
1.5
Cu Content (%)
2
2.5
Figure 10. Effect of copper particle size and copper content on dimensional change of
FLNC-4408.
Figure 11. The effect of copper size on dimensional change of 0.85% Mo + 0.9% graphite alloys
with admixed Cu and Ni. Distaloy FD-0208* and FD-0408 were also tested.
* Additional Ni was added to FD-0208 to produce a 2% Ni alloy.
CONCLUSIONS
Dimensional precision is a critical parameter in net shape processing of ferrous PM components.
Additive compositions, amounts and size play a critical role on the dimensional change. The
sinter-hardening grade FLNC-4408 utilizes both admixed nickel and copper and a strong
interaction between these additives has been found that affects the dimensional behavior in this
system. The following conclusions have been drawn from this study.
•
•
•
•
•
The addition of nickel to FLC-440X alloys greatly reduces the effect of carbon on the
dimensional change; nevertheless, the dimensional change is strongly dependent on
copper content.
The addition of both copper and nickel into an FL-4408 alloy can produce growths larger
than the addition of either additive alone.
The nickel-copper interaction was observed during the measurement of dimensional
change with time. A nickel free FLC2-4408 shrank after the copper melted, whereas the
nickel containing FLNC-4408 continued to grow after melting until the copper liquid resolidified.
Upon melting, the copper moves to different locations dependent upon Ni content. In Nifree materials, copper moves to pores at particle boundaries and may enhance sintering.
In Ni-containing mixes, the majority of copper moves to the nickel-rich regions and alloys
with the nickel. This different copper reaction is responsible for the change in
dimensional behavior.
The use of fine copper was found to improve the dimensional response in FLNC-4408.
Less growth was found with the finer copper. The dimensional change of FLNC-4408
type alloys made with fine copper was very similar to that of diffusion alloys FD-0208
and FD-0408.
ACKNOWLEDGEMENTS
The authors would like to thank Ron Fitzpatrick for his assistance in collecting the data found
within this paper.
REFERENCES
1. N. Dautzenberg and H. J. Dorweiler, “Dimensional behavior of copper-carbon sintered steels”,
Powder Metallurgy International, Vol. 17, No. 6, 1985, p. 279.
2. Y. Trudel and R. Angers, “Properties of iron copper alloys made from elemental or prealloyed
powders”, Int. Journal of Powder Metallurgy & Powder Technology, Vol. 11, No. 1, 1975, p. 5.
3. R. L. Lawcock and T. J. Davies, “Effect of carbon on dimensional and microstructural
characteristics of Fe-Cu compacts during sintering”, Powder Metallurgy, Vol. 33, No. 2, 1990, p.
147.
4. F. Chagnon and M. Gagne, “Dimensional control of sinter hardened P/M components”,
Advances in Powder Metallurgy & Particulate Materials, compiled by W. G. Eisen and S.
Kassam, Metal Powder Industries Federation, Princeton, NJ, 2001, part 5, p. 5-31.
5. F. J. Semel, “Processes determining the dimensional change of P/M steels”, Advances in
Powder Metallurgy & Particulate Materials, compiled by W. G. Eisen and S. Kassam, Metal
Powder Industries Federation, Princeton, NJ, 2001, part 5, p. 5-113.
6. B. Lindsley, G. Fillari and T. Murphy, “Effect of composition and cooling rate on physical
properties and microstructure of prealloyed P/M steels”, Advances in Powder Metallurgy &
Particulate Materials, compiled by C. Ruas and T. A. Tomlin, Metal Powder Industries
Federation, Princeton, NJ, 2005, part 10, p. 10-353.
7. T. Singh, T. F. Stephenson and S. T. Campbell, “Nickel-copper interactions in P/M steels”,
Advances in Powder Metallurgy & Particulate Materials, compiled by W. B. James and R. A.
Chernenkoff, Metal Powder Industries Federation, Princeton, NJ, 2004, part 7, p. 7-93.
8. T. Singh and T. F. Stephenson, “Ni-Cu-Mo interactions in sinter-hardening steels”, Euro
PM2005, EPMA, vol. 1, p. 261
9. L. Azzi, T. Stephenson, S. St-Laurent and S. Pelletier, “Effect of nickel type on properties of
binder-treated mixes”, Advances in Powder Metallurgy & Particulate Materials, compiled by C.
Ruas and T. A. Tomlin, Metal Powder Industries Federation, Princeton, NJ, 2005, part 10, p. 101.
10. “Standard Test Methods for Metal Powders and Powder Metallurgy Products”, Metal Powder
Industries Federation, Princeton, NJ, 2006.
11. T. F. Murphy, “Quantifying the degree of sinter in ferrous P/M materials”, Euro PM2004,
Ed. by H. Danninger and R. Ratzi, EPMA, 2004, vol. 3, p. 219.