We to be 20% lower than Fe-Si alloys. I)

We reported to
Fe-P based alloys are considered as one of the promising materials which could
replace Si-steel on the basis of two factors: i) the cost
of Fe-P based alloys are expected to be 20% lower than Fe-Si alloys. I)
Phosphorous addition enhances the soft magnetic properties of pure Fe.Elemental
Fe with Fe-P and Fe-Si master alloys were taken in suitable weight ratios and
induction melted to obtain Fe-0.4wt.% P-0.85wt.%Si alloy.Fe-P
based alloys can be produced conventionally by wrought alloy process or by
powder Metallurgical route. The optical micrographs of Fe-P-Si alloys aged at 500 °C with different
aging time. Fe-P-Si rolled sheets were solution zed at 1000 ºC with 1 h soaking
time followed by water quenching to forms the supersaturated solid solution of
P in ?-Fe matrix.The mechanical properties of the Fe-P-Si aged samples were
increasing with aging time up to the peak aged then decrease for the over aged
samples.TEM reveals the presence of two phases: Fe3P phase in
?-Fe matrix phase. The sizes of the precipitates were increasing from ~ 1.2 nm
to ~ 2.2 nm with aging time

 

Introduction:

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Due
to growing energy crises coupled with environmental issues like pollution, the
rising use of electric and hybrid electric vehicles is transforming the future.
The main components of an EV (Electric vehicles) are battery, motor and
controller. In the case of magnetic materials for EV motors, soft as well as
hard magnets of high performance materials are required. In the case of soft
magnetic materials, it should possess high saturation magnetic flux density
(Bs) with low core losses, high permeability, and better mechanical properties.
On the other hand, the hard magnets with high energy product (BH) max,
relatively high remanence magnetization (B r), and high coercivity (H c) are
required for motor application.

.
The compression properties of the novel alloys measured at room and elevated
temperatures. The Ti-45Al-5Fe-5Nb alloy showed higher room temperature
ductility and similar strength at room and elevated temperatures.It has improved
workability at elevated temperatures as compared to ?-solidifying ?(TiAl)
alloys of last generation (TNM
alloys).1Sintered ferrous material is elaborate used in many engineering
application  and its deformation
characters are typical for most of sintered powder materials. Theinfluential
factors were such as deformation strengthening, instantaneous and initial
relative densities etc.2

Properties
are highly influenced by the iron to silicon ratio and the best properties had
obtained with both a ratio close to one and low concentrations of iron and
silicon. Present experimental results show that it is possible to multiply by
two or three the present limit of 0·1 wt-%Fe in these alloys at natural aging
(T4) and still obtain the minimum of 7% elongation required by the automotive
industry.

One
benefit of working Cu saturated microstructure can estimate the true
temperature of the solution heat treatment by conducting a post-analysis of Cu
content in the dendrites. This should be helpful to reduce the variability in
properties and to improve the temperature distribution in heat treating
furnaces. 3

The
mechanical properties of the alloys had reduced as the contents of iron and
silicon in the alloys increased. However, the decrement of tensile strengths
and ductility was quite small.Therefore, higher contents of iron and silicon
could be used in the Al-5Mg-0.8Mn alloy (AA5083 alloy). When the materials are cast
under near-rapid cooling, such that continuous strip casting process 4

Heat
treatments for all high-Cr White cast iron alloys are essential to change their
microstructure and therefore, to improve their wear resistance to suitable the
individual application requirements. Changing in chemical composition and heat
treatment carried out to this alloy related to microstructural characteristics
and mechanical properties of high Cr white cast iron alloys are presented.5

The
optical and SEM micro-graphs can be inferred the aluminum alloy leads to grain
refinement and grain structure modification. The wear properties of AA7175
alloy improved by the addition of TiB2 and higher than that of the unreinforced
aluminum alloy. The wear resistance increased with decreasing particle size of
TIB2 particulates. 6

 

It said that the addition of phosphorus in the pure iron
increased the tensile strength; however, it decreased the ductility. The grain
refining effects and increase in tensile strength due to additions of P were
found to be very significant. However, with increase in annealing time at any
temperature, the mechanical properties changes occur 7.Under quasi-static
loading, the heat treated samples were increase in strength and ductility, for
all the alloy compositions. The addition of cobalt improves the tensile strength
8

Microstructural studies revealed that the prepared
samples were free from Fe3P phase precipitation and the average grain size
increased with increasing the phosphorous content giving rise to the decrease
of hysteresis losses.9 Corrosion resistance has  inversely proportional to porosity10.The
sintered density increases with increasing phosphorus content and Fe-3P alloys
attaining near full density11 (Fe-P)-Si based alloy with relatively high
induction ,low coercivity ,high resistivity and low core loss comparable to the
commercially available Si-steel12

Fe-P based alloys are considered as one of the promising
materials which could replace Si-steel on the basis of two factors: i) the cost of Fe-P based alloys are expected to be 20% lower than
Fe-Si alloys. I) Phosphorous addition enhances the soft magnetic properties of
pure Fe.The Fe-P based alloys can be produced conventionally by wrought alloy
process or by powder Metallurgical route. In powder metallurgical route, due to
the lower solubility of P in Fe (5wt% in ?-Fe) P segregates at the grain
boundaries resulting in brittleness. Alternatively powder metallurgical route,
through liquid phase sintering (LPS) can also be incorporated but involves
complex compaction techniques. The present work was carried out by wrought
alloy process of low Si, Fe-P based alloy, which has attractive AC and DC
magnetic properties.

EXPERIMENTAL DETAILS

Elemental Fe with Fe-P and Fe-Si
master alloys were taken in suitable weight ratios and induction melted to
obtain Fe-0.4wt.% P-0.85wt.%Si alloy. The melt was cast into a mould to obtain
a 65 mm diameter and 400 mm long ingot, and the alloys were undergone a
radiography test to separate the pipe and sound portions. The composition of
the alloy was confirmed using the inductively coupled plasma-optical emission
spectroscopy technique (M/s Baird Co. DV-4) and LECO C-S (Model CS 600).

The melted ingots were forged in open
die forging to get a required shape and size for the rolling operation. Thin
sheets typically ~0.5 mm thick was obtained followed by hot-rolling at 900 °C. The rolled sheet was solution zed at 1000 °C and subjected to an ageing at 500 °C from 10 min to 10 hours and then quenched by
water.

The finer details of the
microstructure and the phase analysis of the precipitates were studied using a
Transmission Electron Microscope (TEM) (FEI Tecnai G2) operated at 200 keV.
Micro-hardness of the samples was measured by using knoop – micro hardness tester
with a load of 1 kg.

Average hardness of each specimen was
determined by indenting the sample six times. The average values so obtained
were used to plot the age hardening curve. The tensile tests of the samples
were carried out by micro tensile testing machine (Walter-Bai Testing
Industriestrasse, Switzerland) at room temperature. The Tensile specimens were
prepared by ASTM E8 standard with the sample thickness 0.5 mm. The resistivity
of the samples was measured by the standard four-probe potentiometric technique

 

 

 

 

Keithley
2182A nanovoltmeter and Keithley 6221 current source, USA) with an applied DC
current of 100 ?A.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Radiography test:

This test
provides to detect discontinuous alloys and fabricated inner structures. Mold
irregularities removed on the both alloys (inside and outside).radiographic
testing image showed the irregularities or any other discontinuity.

2.1Microstructure:

A very small scale structure of materials is
called microstructure. Structure should prepare above 25× magnification of
microscope.The microstructure of a material have influenced  physical properties such as strength,
toughness, ductility, hardness, corrosion resistance, high/low temperature
behavior or wear resistance  .The optical micrographs of Fe-P-Si alloys
aged at 500 °C with different aging time. Fe-P-Si rolled sheets were solution
zed at 1000 ºC with 1 h soaking time followed by water quenching to forms the
supersaturated solid solution of P in ?-Fe matrix. After Solution zing the
samples were aged at 500 ºC with different aging time.  The materials grain size was measured by the
different aging time.

2.2. Microstructure Characterizations

            Quantify microstructuralcharacterized,
morphological and material property.Morphologicalproperty can be determining
such as volume fraction, inclusion morphology, void and crystal
orientations.  Micrographs commonly used optical
as well as electron microscopy .Material property can be determining of
properties in micron and submicron level.

2.3 Transmission electron microscopy

TEM is
electrons transmitted through a specimen and form an image. The specimen is
often less than 100nm thick in ultrathin section. The images have formed from
the interaction electrons. The image is magnified and focused onto screen.Reveals the presence of secondary Fe3P Nano
precipitates phase in ?-Fe matrix phase. With increase in aging time, the sizes
of the precipitates were increasing as shown in table 1

Aging Time (h)

Average Grain
Size (µm)

Average
Precipitate
Size(nm)
 

No. of
precipitates per unit area
observed by TEM (1018 m-2)

0

156

0.5

125

1.2

0.63

2

126

2.0

0.27

10

132

2.2

0.24

 

Table 1 No. of precipitates per unit
areaobserved by TEM

Table 1. Average Grain Size, Average Precipitate size
and number of Fe3P precipitates per unit area in ?-Fe matrix of Fe-P-Si aged
samples for various aging time

2.4 Knoop hardness test

The Knoop hardness test is a micro hardness test.
Here test were conducted by the standard of ASTM E-384 .The testing purpose for to find mechanicalhardness on
particular brittle materials or thin sheets, where only a small indentation. A pyramidal diamond point
is pressed into the polished surface of the test material with a known (often
100g) load, for a specified dwell time, and the resulting indentation is
measured using a microscope. The
geometry of this indenter is an extended pyramid with the length to width ratio
being 7:1 and respective face angles are 172 degrees for the long edge and 130
degrees for the short edge. The depth of the indentation can be approximated as
1/30 of the long dimension. The Knoop hardness HK or KHN is then given by the
formula:

Where L =Length of
the long axis of the indentation,

Cp=Correction
factor,     P = Load

 

 

 

Fgture2:
Angles of a Knoop hardness test indenter

2.5 MICRO TENSILE TEST

The primary use of the testing machine is to create the
stress-strain diagram. Tensile test determines the strength of the material
subjected to a simple stretching operation. The Tensile specimens were prepared
by ASTM E8 standard with the sample thickness 0.5 mm. The resistivity of the
samples was measured by the standard four-probe potentiometric technique .standard
dimension test samples are pulled slowly (static loading) and at uniform rate
in a testing machine while the strain ( the elongation of the sample) is
defined as: Engineering Strain = e = (change in length)/(original length)

3.
Result and discussion

3.1 MICROSTRUCTURE STUDIES

            Fig. 3.1 shows the optical
micrographs of Fe-P-Si alloys aged at 500 °C with different aging time. Fe-P-Si
rolled sheets were solutionized at 1000 oC with 1 h soaking time
followed by water quenching to forms the supersaturated solid solution of P in
?-Fe matrix. After Solutionzing the samples were aged at 500 ºC with different
aging time. The averaged grain sizes of the samples were measured using
intercept method and inserted in figure 1. It was observed that the
solutionized samples become finer in grain size after aging whereas there was
no significant change in grain size with aging time. Because the aging temperature
of 500 °C was lower than the recrystallization temperature. Hence, the grain
growth was not significant.Optical microstructural
images (with inserted average grain size) of Fe-P-Si alloy in a) the
solutionized condition, b) under aged (0.5 h), c) peak aged (2 h) and d) over
aged (10 h) at 500 ºC

 

 

 

Fig 3.1Microstructure of
aging study

3.2 Transmission Electron
Microscopy Studies

TEM study of solutionized samples shows the single phase
of ?-Fe (P) and no significant Fe3P
precipitates were observed because of the presence of supersaturated solid
solution of P in ?-Fe matrix as shown in figure3. 2(a). While the SAED pattern
from 100 zone axis of ?-Fe(P) matrix phase reflects the diffraction spots
from Fe3P precipitates.
Hence, there were some small volume fraction of fine Fe3P precipitates are present which is highly
difficult due to their fine size and the coherency with the BCC-Fe matrix.   TEM images of Fe-P-Si
unaged sample shows the absence of precipitates; inserted high magnification
image 3.2 b) SAED pattern from 100 zone axis of ?-Fe(P) matrix phase shows
the diffraction spots of Fe3P precipitates.

 

Fig3.2TEM Images

Further, the TEM investigation of Fe-P-Si aged samples as observed
from figure 3.2 reveals the presence of secondary Fe3P Nano
precipitates phase in ?-Fe matrix phase. With increase in aging time, the sizes
of the precipitates were increasing as shown in table 1. In figure 3.2 b, the
inserted SAED patterns of the Fe-P-Si aged samples along the zone axis of 001
shows the diffraction spots corresponding to Fe3P phase.
These precipitates also inhibit the grain growth with aging time. This is also
a reason of no significant grain growth with aging time.

3.3 TEM Images of aging study

TEM images of
Fe-P-Si aged samples showing Fe3P nano precipitates dispersed in Fe matrix
phase. The inset shows the SAED pattern from 100 zone axis of ?-Fe matrix
with diffraction spots corresponding to Fe3P phase

Figure 3.3 TEM Images of aging study                                                 
                                                                                                                                                

3.4 Mechanical Properties

The micro hardness of Fe-P-Si alloy
with respect to ageing time at 500 oC is
shown in Fig3.4 . The hardness increases upon ageing, reaches a peak value at 2
h and decreasing further, where 10 h is considered as over ageing. The change
in the hardness with aging time can be explained by precipitation hardening
mechanism.

The increased in the strength of an
aged samples is due to the interaction of the moving dislocations with
dispersed precipitates. Initially when the precipitates size was very small,
the dislocation cuts through the precipitates zone and strengthen the material.
As the aging time increase, the size of the precipitates increase and the
interparticle distance decreases.

When the precipitates size is high,
the dislocation unable to cut through the precipitate, it then bows to bypass.
As the distance between the precipitates during over aging increases, the strength
of the alloy decreases.

Fig 3.4Stress Strain diagram

         Fig 3.5 shows the stress-strain curve
of the Fe-P-Si aged samples with varying aging time. P is known to increases
the strength of parent iron by strengthening the ferrite matrix. It also has
precipitation (Fe3P) hardening effect. From figure 3.5 it is
observed that the tensile strength of the aged samples increased with aging
time due to precipitates hardening mechanism as explained above. While there is
not significant effect on the

Variation of Knoop micro hardness of Fe-P-Si aged
samples at 500 oC with different aging time and the optical image of
the indentation on the specimen were inserted ductility of the Fe-P-Si aged
samples with aging time.

Fig 3.5 Hardness diagram                                                                           
               

CONCLUSION

          In this works effect of aging studies
on the mechanical properties of Fe-P-Si alloys have been studied by doing the
aging treatment on the solutionized rolled sheets at a temperature of 500 °C
(lower than the recrystallization temperature) with varying aging time. From
the results of the proposed work, we observed the following concluded remarks:

1.      
There is no significant grain
growth of the aged samples with varying aging time. This can be due to low
kinetic energy for grain growth because of the lower aging temperature (below
recrystallization temperature) and due to inhibits the grain growth by
secondary Fe3P nano-precipitates phase dispersed in ?-Fe matrix phase.

2.      
TEM reveals the presence of two
phase: Fe3P phase in ?-Fe matrix phase. The sizes of the precipitates were
increasing from ~ 1.2 nm to ~ 2.2 nm with aging time.

 

3.      
The mechanical properties of
the Fe-P-Si aged samples were increasing with aging time up to the peak aged
then decrease for the over aged samples. The enhancement in the strength of the
Fe-P-Si alloys with aging can be explained by precipitates hardening mechanism.

4.      
The enhancement in the
resistivity of the Fe-P-Si aged samples is due the presence of fine Fe3P
nano precipitates which acts as a scattering center for the flow of the
electron.

5.      
Fe-P-Si aged samples can be
potential materials as a stator in a motor for the automotive applications due
to its high mechanical and electrical properties.