We reported toFe-P based alloys are considered as one of the promising materials which couldreplace Si-steel on the basis of two factors: i) the costof 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.ElementalFe with Fe-P and Fe-Si master alloys were taken in suitable weight ratios andinduction melted to obtain Fe-0.4wt.% P-0.
85wt.%Si alloy.Fe-Pbased alloys can be produced conventionally by wrought alloy process or bypowder Metallurgical route.
The optical micrographs of Fe-P-Si alloys aged at 500 °C with differentaging time. Fe-P-Si rolled sheets were solution zed at 1000 ºC with 1 h soakingtime followed by water quenching to forms the supersaturated solid solution ofP in ?-Fe matrix.The mechanical properties of the Fe-P-Si aged samples wereincreasing with aging time up to the peak aged then decrease for the over agedsamples.TEM reveals the presence of two phases: Fe3P phase in?-Fe matrix phase. The sizes of the precipitates were increasing from ~ 1.2 nmto ~ 2.2 nm with aging time Introduction:Dueto growing energy crises coupled with environmental issues like pollution, therising use of electric and hybrid electric vehicles is transforming the future.
The main components of an EV (Electric vehicles) are battery, motor andcontroller. In the case of magnetic materials for EV motors, soft as well ashard magnets of high performance materials are required. In the case of softmagnetic 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) arerequired for motor application.
.The compression properties of the novel alloys measured at room and elevatedtemperatures. The Ti-45Al-5Fe-5Nb alloy showed higher room temperatureductility and similar strength at room and elevated temperatures.It has improvedworkability at elevated temperatures as compared to ?-solidifying ?(TiAl)alloys of last generation (TNMalloys).1Sintered ferrous material is elaborate used in many engineeringapplication and its deformationcharacters are typical for most of sintered powder materials. Theinfluentialfactors were such as deformation strengthening, instantaneous and initialrelative densities etc.2Propertiesare highly influenced by the iron to silicon ratio and the best properties hadobtained with both a ratio close to one and low concentrations of iron andsilicon. Present experimental results show that it is possible to multiply bytwo 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 automotiveindustry.
Onebenefit of working Cu saturated microstructure can estimate the truetemperature of the solution heat treatment by conducting a post-analysis of Cucontent in the dendrites. This should be helpful to reduce the variability inproperties and to improve the temperature distribution in heat treatingfurnaces. 3Themechanical properties of the alloys had reduced as the contents of iron andsilicon in the alloys increased. However, the decrement of tensile strengthsand ductility was quite small.Therefore, higher contents of iron and siliconcould be used in the Al-5Mg-0.8Mn alloy (AA5083 alloy). When the materials are castunder near-rapid cooling, such that continuous strip casting process 4Heattreatments for all high-Cr White cast iron alloys are essential to change theirmicrostructure and therefore, to improve their wear resistance to suitable theindividual application requirements. Changing in chemical composition and heattreatment carried out to this alloy related to microstructural characteristicsand mechanical properties of high Cr white cast iron alloys are presented.
5Theoptical and SEM micro-graphs can be inferred the aluminum alloy leads to grainrefinement and grain structure modification. The wear properties of AA7175alloy improved by the addition of TiB2 and higher than that of the unreinforcedaluminum alloy. The wear resistance increased with decreasing particle size ofTIB2 particulates. 6 It said that the addition of phosphorus in the pure ironincreased the tensile strength; however, it decreased the ductility. The grainrefining effects and increase in tensile strength due to additions of P werefound to be very significant. However, with increase in annealing time at anytemperature, the mechanical properties changes occur 7.Under quasi-staticloading, the heat treated samples were increase in strength and ductility, forall the alloy compositions.
The addition of cobalt improves the tensile strength8Microstructural studies revealed that the preparedsamples were free from Fe3P phase precipitation and the average grain sizeincreased with increasing the phosphorous content giving rise to the decreaseof hysteresis losses.9 Corrosion resistance has inversely proportional to porosity10.Thesintered density increases with increasing phosphorus content and Fe-3P alloysattaining near full density11 (Fe-P)-Si based alloy with relatively highinduction ,low coercivity ,high resistivity and low core loss comparable to thecommercially available Si-steel12Fe-P based alloys are considered as one of the promisingmaterials 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 thanFe-Si alloys. I) Phosphorous addition enhances the soft magnetic properties ofpure Fe.The Fe-P based alloys can be produced conventionally by wrought alloyprocess or by powder Metallurgical route.
In powder metallurgical route, due tothe lower solubility of P in Fe (5wt% in ?-Fe) P segregates at the grainboundaries resulting in brittleness. Alternatively powder metallurgical route,through liquid phase sintering (LPS) can also be incorporated but involvescomplex compaction techniques. The present work was carried out by wroughtalloy process of low Si, Fe-P based alloy, which has attractive AC and DCmagnetic properties.EXPERIMENTAL DETAILSElemental Fe with Fe-P and Fe-Simaster alloys were taken in suitable weight ratios and induction melted toobtain Fe-0.4wt.% P-0.85wt.%Si alloy.
The melt was cast into a mould to obtaina 65 mm diameter and 400 mm long ingot, and the alloys were undergone aradiography test to separate the pipe and sound portions. The composition ofthe alloy was confirmed using the inductively coupled plasma-optical emissionspectroscopy technique (M/s Baird Co. DV-4) and LECO C-S (Model CS 600). The melted ingots were forged in opendie forging to get a required shape and size for the rolling operation. Thinsheets 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 bywater. The finer details of themicrostructure and the phase analysis of the precipitates were studied using aTransmission Electron Microscope (TEM) (FEI Tecnai G2) operated at 200 keV.Micro-hardness of the samples was measured by using knoop – micro hardness testerwith a load of 1 kg. Average hardness of each specimen wasdetermined by indenting the sample six times. The average values so obtainedwere used to plot the age hardening curve. The tensile tests of the sampleswere carried out by micro tensile testing machine (Walter-Bai TestingIndustriestrasse, Switzerland) at room temperature. The Tensile specimens wereprepared by ASTM E8 standard with the sample thickness 0.
5 mm. The resistivityof the samples was measured by the standard four-probe potentiometric technique Keithley2182A nanovoltmeter and Keithley 6221 current source, USA) with an applied DCcurrent of 100 ?A. Radiography test:This testprovides to detect discontinuous alloys and fabricated inner structures. Moldirregularities removed on the both alloys (inside and outside).radiographictesting image showed the irregularities or any other discontinuity.2.
1Microstructure:A very small scale structure of materials iscalled microstructure. Structure should prepare above 25× magnification ofmicroscope.The microstructure of a material have influenced physical properties such as strength,toughness, ductility, hardness, corrosion resistance, high/low temperaturebehavior or wear resistance .The optical micrographs of Fe-P-Si alloysaged at 500 °C with different aging time. Fe-P-Si rolled sheets were solutionzed at 1000 ºC with 1 h soaking time followed by water quenching to forms thesupersaturated solid solution of P in ?-Fe matrix. After Solution zing thesamples were aged at 500 ºC with different aging time. The materials grain size was measured by thedifferent aging time.
2.2. Microstructure Characterizations Quantify microstructuralcharacterized,morphological and material property.Morphologicalproperty can be determiningsuch as volume fraction, inclusion morphology, void and crystalorientations. Micrographs commonly used opticalas well as electron microscopy .
Material property can be determining ofproperties in micron and submicron level.2.3 Transmission electron microscopyTEM iselectrons transmitted through a specimen and form an image. The specimen isoften less than 100nm thick in ultrathin section. The images have formed fromthe interaction electrons. The image is magnified and focused onto screen.Reveals the presence of secondary Fe3P Nanoprecipitates phase in ?-Fe matrix phase.
With increase in aging time, the sizesof 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 unitareaobserved by TEMTable 1. Average Grain Size, Average Precipitate sizeand number of Fe3P precipitates per unit area in ?-Fe matrix of Fe-P-Si agedsamples for various aging time2.4 Knoop hardness testThe 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 onparticular brittle materials or thin sheets, where only a small indentation.
A pyramidal diamond pointis pressed into the polished surface of the test material with a known (often100g) load, for a specified dwell time, and the resulting indentation ismeasured using a microscope. Thegeometry of this indenter is an extended pyramid with the length to width ratiobeing 7:1 and respective face angles are 172 degrees for the long edge and 130degrees for the short edge. The depth of the indentation can be approximated as1/30 of the long dimension. The Knoop hardness HK or KHN is then given by theformula:Where L =Length ofthe long axis of the indentation,Cp=Correctionfactor, P = Load Fgture2:Angles of a Knoop hardness test indenter2.5 MICRO TENSILE TESTThe primary use of the testing machine is to create thestress-strain diagram. Tensile test determines the strength of the materialsubjected to a simple stretching operation.
The Tensile specimens were preparedby ASTM E8 standard with the sample thickness 0.5 mm. The resistivity of thesamples was measured by the standard four-probe potentiometric technique .standarddimension test samples are pulled slowly (static loading) and at uniform ratein a testing machine while the strain ( the elongation of the sample) isdefined as: Engineering Strain = e = (change in length)/(original length) 3.
Result and discussion 3.1 MICROSTRUCTURE STUDIES Fig. 3.1 shows the opticalmicrographs of Fe-P-Si alloys aged at 500 °C with different aging time.
Fe-P-Sirolled sheets were solutionized at 1000 oC with 1 h soaking timefollowed by water quenching to forms the supersaturated solid solution of P in?-Fe matrix. After Solutionzing the samples were aged at 500 ºC with differentaging time. The averaged grain sizes of the samples were measured usingintercept method and inserted in figure 1. It was observed that thesolutionized samples become finer in grain size after aging whereas there wasno significant change in grain size with aging time. Because the aging temperatureof 500 °C was lower than the recrystallization temperature. Hence, the graingrowth was not significant.
Optical microstructuralimages (with inserted average grain size) of Fe-P-Si alloy in a) thesolutionized condition, b) under aged (0.5 h), c) peak aged (2 h) and d) overaged (10 h) at 500 ºC Fig 3.1Microstructure ofaging study3.2 Transmission ElectronMicroscopy StudiesTEM study of solutionized samples shows the single phaseof ?-Fe (P) and no significant Fe3Pprecipitates were observed because of the presence of supersaturated solidsolution of P in ?-Fe matrix as shown in figure3.
2(a). While the SAED patternfrom 100 zone axis of ?-Fe(P) matrix phase reflects the diffraction spotsfrom Fe3P precipitates.Hence, there were some small volume fraction of fine Fe3P precipitates are present which is highlydifficult due to their fine size and the coherency with the BCC-Fe matrix. TEM images of Fe-P-Siunaged sample shows the absence of precipitates; inserted high magnificationimage 3.2 b) SAED pattern from 100 zone axis of ?-Fe(P) matrix phase showsthe diffraction spots of Fe3P precipitates. Fig3.2TEM ImagesFurther, the TEM investigation of Fe-P-Si aged samples as observedfrom figure 3.
2 reveals the presence of secondary Fe3P Nanoprecipitates phase in ?-Fe matrix phase. With increase in aging time, the sizesof the precipitates were increasing as shown in table 1. In figure 3.2 b, theinserted SAED patterns of the Fe-P-Si aged samples along the zone axis of 001shows the diffraction spots corresponding to Fe3P phase.
These precipitates also inhibit the grain growth with aging time. This is alsoa reason of no significant grain growth with aging time.3.
3 TEM Images of aging studyTEM images ofFe-P-Si aged samples showing Fe3P nano precipitates dispersed in Fe matrixphase. The inset shows the SAED pattern from 100 zone axis of ?-Fe matrixwith diffraction spots corresponding to Fe3P phaseFigure 3.3 TEM Images of aging study 3.4 Mechanical PropertiesThe micro hardness of Fe-P-Si alloywith respect to ageing time at 500 oC isshown in Fig3.4 . The hardness increases upon ageing, reaches a peak value at 2h and decreasing further, where 10 h is considered as over ageing.
The changein the hardness with aging time can be explained by precipitation hardeningmechanism. The increased in the strength of anaged samples is due to the interaction of the moving dislocations withdispersed 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 theinterparticle 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 strengthof the alloy decreases.Fig 3.4Stress Strain diagram Fig 3.
5 shows the stress-strain curveof the Fe-P-Si aged samples with varying aging time. P is known to increasesthe strength of parent iron by strengthening the ferrite matrix. It also hasprecipitation (Fe3P) hardening effect. From figure 3.5 it isobserved that the tensile strength of the aged samples increased with agingtime due to precipitates hardening mechanism as explained above. While there isnot significant effect on theVariation of Knoop micro hardness of Fe-P-Si agedsamples at 500 oC with different aging time and the optical image ofthe indentation on the specimen were inserted ductility of the Fe-P-Si agedsamples with aging time.Fig 3.5 Hardness diagram CONCLUSION In this works effect of aging studieson the mechanical properties of Fe-P-Si alloys have been studied by doing theaging treatment on the solutionized rolled sheets at a temperature of 500 °C(lower than the recrystallization temperature) with varying aging time.
Fromthe results of the proposed work, we observed the following concluded remarks:1. There is no significant graingrowth of the aged samples with varying aging time. This can be due to lowkinetic energy for grain growth because of the lower aging temperature (belowrecrystallization temperature) and due to inhibits the grain growth bysecondary Fe3P nano-precipitates phase dispersed in ?-Fe matrix phase.2.
TEM reveals the presence of twophase: Fe3P phase in ?-Fe matrix phase. The sizes of the precipitates wereincreasing from ~ 1.2 nm to ~ 2.2 nm with aging time.
3. The mechanical properties ofthe Fe-P-Si aged samples were increasing with aging time up to the peak agedthen decrease for the over aged samples. The enhancement in the strength of theFe-P-Si alloys with aging can be explained by precipitates hardening mechanism.4. The enhancement in theresistivity of the Fe-P-Si aged samples is due the presence of fine Fe3Pnano precipitates which acts as a scattering center for the flow of theelectron.
5. Fe-P-Si aged samples can bepotential materials as a stator in a motor for the automotive applications dueto its high mechanical and electrical properties.