Effect of Aluminum Content on the Mechanical Properties of Dual Stabilized Ti-Nb Interstitial Free High Strength Steel (IF-HSS)

POSCO TECHNICAL REPORT 2007(VOL. 10 No. 1)

Effect of Aluminum Content on the Mechanical Properties of Dual Stabilized Ti-Nb

Interstitial Free High Strength Steel (IF-HSS)

Heejae Kang and Kwanggeun Chin

1. Introduction

In recent years, interstitial free high strengthsteel(IF-HSS) containing Mn and P andstabilized with either Ti or Ti + Nb have beendeveloped, and due to their moderate-to-goodformability and high tensile strength areextensively used in some automotive panelapplications1-6). However, there are more severeforming applications, for example such as floor,fender or side panels, where similar types of IF-HSS steels might be applied but are not becauseof their slightly inferior formability. Therefore,there is an interest in increasing the formabilityof IF-HSS without decreasing their strength.

It is well-known that in IF steels, carbon andnitrogen in solution are scavenged as precipitatescontaining titanium and/or niobium. Thescavenging effect of Ti and Nb makes both theferrite matrix nearly interstitial free but also leadsto the formation of precipitates such as TiN,NbN, TiS, Ti4C2S4, (TiNb)(C,N), and TiC . Theprecipitation behavior has been claimed to affectthe evolution of the texture and, hence, thedrawability performance in IF steels11-13). Forexample, it has also been suggested that a densedispersion of very fine precipitates in IF steelsleads to a weak intensity of {111} texture14).Therefore, one view of texture optimizationholds that in order to improve the formabilityperformance of IF steels the ferrite matrix shouldbe free of interstitial elements and theprecipitation that takes place should be coarser.In order to accomplish these objectives it is

83

ABSTRACT

The effect of aluminum content during the annealing of interstitial free high strength steel (IF-HSS)containing Mn, P, Ti and Nb was investigated. The resulting mechanical properties were evaluated andrecorded. The results showed that a super formable high strength IF steel with an r-value equal to or higherthan 2.3 can be obtained by Al additions. One of the interesting observations of this investigation was thechange of precipitation behavior with aluminum content. Aluminum has the effect of improving theformability, especially the drawability, of the IF-HSS when more than 0.10wt%Al is added. Texture analysisshowed that the <111>//ND fiber (γ-fiber) was intensified, and <110>//RD (α-fiber) was weakened, with anincrease of aluminum content. These benefits appear to result from the change of precipitation behavior withthe increase of aluminum content. It was confirmed thorough the SANS analysis that the size of theprecipitates in the sample with higher aluminum content was larger and their number was much fewer than inthe sample with lower aluminum content. It appears that the high aluminum in IF-HSS containing Mn, P, Tiand Nb strengthened the scavenging effect of Ti or Nb and thus purifies the iron matrix.

Key words: Ultra Low Carbon Steel; IF-HSS; Aluminum; Drawability; Precipitation

* POSCO, Technical Research Labs, Automotive

Steels Research Group


important to optimize the processing conditions.For example, low slab reheating temperature andhigh coiling temperature are generally applied toincrease the drawability in IF steels; theseprocessing conditions lead to a reduction in theamount of fine precipitates and to the coarseningof precipitates15). The objective of this paper is toexplore the possibility of obtaining coarserprecipitates and higher formability performancein IF-HSS through simple alloying additioneffects.

Aluminum is commercially added to steels inthe range of 0.02~0.07wt% as a de-oxidizerexcept in some special cases such as DP andTRIP steels16-17). It is well- known that there islittle effect of aluminum on the mechanicalproperties of steels when the Al content is in therange of 0.02 to 0.07wt%. However, when the Alcontent is higher such in the case of DP andTRIP steels, the influence of Al on themicrostructure and mechanical properties ofthese steels becomes very important. The role ofAl in DP and TRIP steels has been discussedbecause its influence as a very strong ferritestabilizer18-19) and/or a promoter of austenitecarbon enrichment20-21) and thus the Al has astrong influence on the transformation kinetics.The effect of high aluminum additions to IF steelhas not received much attention despite itsstrong influence on the kinetics of ferriterecrystallization during annealing or the possibleinfluence of high Al additions on theprecipitation behavior in IF steels.

The goal of this work was to investigate theeffect of aluminum additions on the mechanicalproperties of a dual stabilized Ti-Nb interstitialfree high strength steel (IF-HSS). The majorobjective was to explore the feasibility todevelop an IF-HSS with excellent combinations

of strength and high formability performance.This paper will present and discuss the results ofthis investigation.

2. Experimental Procedure

A series of ultra-low carbon steels withvarious amounts of Al were vacuum melted andcast into approximately 20kg slab ingots in aninduction heating furnace. The chemicalcomposition of these laboratory steels is given inTable 1.

After melting, the laboratory heats werethermomechanical processed (TMP) in a pilothot rolling mill. The as-cast samples were rolledinto a final 3.2mm thickness hot band. The finishrolling temperature of 910˚C was followed byholding at 600˚C for 5 hours and then furnace-cooled to simulate coiling. After pickling, thehot bands were cold rolled 77.5%, and thenannealed in an infrared-ray heating furnace. Theannealing cycle consisted of heating thespecimens to 830˚C at a constant heating rate of7˚C/s and held at temperature for 30s and thencooled to RT. To investigate the recrystallizationbehavior of ferrite, the cold rolled specimens

84

Fig. 1 Schematic illustration of experimental procedures.

Table 1 Chemical composition of steels used (in wt.%).

Name

M1

M2

M3

C

0.0016

0.0020

0.0019

Mn

0.82

0.84

0.80

P

0.080

0.081

0.080

S

0.005

0.006

0.004

Sol.Al

0.043

0.130

0.190

Ti

0.019

0.025

0.021

Nb

0.005

0.006

0.005

B

0.005

0.007

0.005

N

0.0019

0.0024

0.0020

Fe

balance

Effect of Aluminum Content on the Mechanical Properties of Dual Stabilized Ti-Nb Interstitial Free High Strength Steel (IF-HSS)

using the same heating rate conditions wereannealed in the temperature range 620~820˚Cand then water quenched to RT. The TMP andannealing conditions employed in this work areschematically illustrated in Fig. 1.

The fully processed specimens were preparedfor microstructural analysis using standardmetallographic techniques. The microstructurewas observed by optical microscopy and thehardness of the final microstructure was evaluatedby micro-Vickers hardness measurements.

Extraction carbon replica methods were used todetermine the size, shape and distribution ofprecipitates and the precipitates were examined withthe aid of a Philips CM20 transmission electronmicroscopy (TEM) operated at 200kV. Along withTEM observations, the chemical compositions ofprecipitates were analyzed by EDS.

In addition to TEM analysis, SANS (SmallAngle Neutron Scattering) measurements, usinga neutron beam with a wavelength of 0.508 nm,were carried out in the HANARO reactor at theKorea Atomic Energy Research Institute, Korea.The sample-to-detector distance was 4.61m andthe wavelength spread (∆λ/λ) was about 12%.The measured Q-range was 0.01~1.0 nm-1,corresponding to a particle size of approximately6~60 nm. Two-dimensional scattering patternscollected by the two-dimensionally arrayeddetectors with an active area of 64.5cm×64.5cmwere radially averaged to produce a one-dimensional intensity profile.

The standard mechanical properties andformability values were determined using ASTMA370 specimens having a gauge length of50mm. The formability or Lankford value wasmeasured using the standard method, mean r-value (= (r0°∆+2r45°∆+r90°∆)/4).

3. Results

3. 1 Mechanical properties and microstructuresof annealed sheets

The typical Interstitial free high strength steel

(IF-HSS) alloyed with Mn, P, Ti and Nb hasalready been developed by the authors22) , andhas been successfully applied for automobilepanels with complex shapes due to its gooddrawability. However, certain panel applicationsdemand still higher formability and uniformproperties. In this section, the mechanicalproperties of the fully processed experimentalsteels with various aluminum contents arepresented in Fig. 2. This fig. shows the effect ofaluminum content on the tensile strength,elongation and Lankford value of the annealedsteel sheets. The tensile results presented in Fig.2(a) show that the tensile strength decreased

85

Fig. 2 Effect of aluminum content on the mechanical

properties of the IF-HSS containing Mn, P, Ti and

Nb : (a) Tensile strength (MPa), (b) Elongation(%)

and (c) Mean r-value.


slightly with increasing the aluminum contentwhile Figs 2(b) and 2(c) exhibit the ductility andformability of the same steels. The results fromthese figures clearly show that the elongationand formability parameter, i.e. mean r-value, washigher in the steels with higher aluminumcontent.

There is a lack of evidence regarding theeffect of Al additions on the overall mechanicalproperties of the steels. In general, it is believedthat Al additions have a small effect on thestandard mechanical properties of steels.However, the results of this work have shownthat Al additions seem to contribute to animprovement in the formability of dualstabilized Ti+Nb IF-HSS while maintaining hightensile strength values.

The resulting ferrite microstructure of thesteels after annealing is presented in Fig. 3. Theresults from this figure show that the averageferrite grain size of the steel with 0.043wt%Al(M1) was about 18•Ïm while the steel with0.19wt%Al (M3) exhibited an average ferritegrain size of about 22µm. The difference in theaverage ferrite grain size between steels M1 andM3 seems to explain the slightly lower strengthobserved in the steels with higher Al contents. Inaddition, the results from Fig. 3 also seem toindicate that the steels with higher Al contenttend to have faster ferrite recrystallizationkinetics than steels with lower Al content.Similar results have been observed by otherinvestigators23). This observation leads to thequestion of what is the effect of high Al contentin solid solution on the recrystallization behavior

of ferrite during annealing. One possibleexplanation might be related to the precipitationbehavior observed in the steels. The average sizeof the precipitates in the high Al content steelswas coarser than in those with lower Al content.Another explanation might be related to theeffect of Al on the self-diffusion of Fe24,25).

3. 2 Crystallographic texture of annealedsteels

Fig. 4 shows the intensity of the {110},{100}, and {111} components of therecrystallization textures at the mid-plane of theannealed steels with various Al contents. Theintensity of {111} was always much higher thanthose of {110}, {100} textures, which is anormal characteristic of IF steel. However, it isalso evident that the intensity ratio of the steelswith higher Al content (0.13wt% and 0.19wt%)is much higher when compared to the steels withlower Al content (0.043wt%). This means thatthe <111>//ND fiber(γ-fiber) was intensified, andthe <110>//RD(α-fiber) was weakened with theincrease of aluminum content. The result couldalso be confirmed by (100) pole figure data forthe annealed sheet M1 (0.043%Al) and the M3(0.19%Al), as shown in Fig. 5, which wasdetermined by EBSD at the mid-plane of thesteels. It can be seen in Fig. 5 that steel M3 has a

86

Fig. 3 Optical micrographs observed in the annealed

sheets after recrystallization at 830˚C : (a) M1

sample with 0.043%Al, (b) M3 sample with 0.19%Al.Fig. 4 Effect of aluminum content on recrystallization

textures at the mid-plane of the annealed sheets.


stronger γ-fiber than the other steels. The higherintensity of the {111} crystallographic texture insteel M3 is in good agreement with theformability results presented in Fig. 2(c),compared to the other steels.

3. 3 Recrystallization of cold rolled sheets

A simple indication of the annealing behaviorof cold rolled materials is the change in hardness.The variation in hardness, (Hv), after the heattreatment is shown in Fig. 6. The hardness of thecold rolled M1 sample remains unchanged up to680°C and begins to decrease above 710°C,while in the cold rolled M3 sample softeningoccurs at 680°C. This means that the cold rolledM3 sample with high aluminum content wasundergoing softening earlier than the M1 sample.

This observation was also confirmed byinvestigating the microstructures of the twosamples annealed at 740°C, as shown in Fig. 7.Fig. 7 shows clearly that recrystallization in theM3 sample progressed faster than in the M1sample.

3. 4 Precipitation in the Hot Band

The results of the identification andcharacterization of precipitates in the IF-HSS areshown in Fig. 8. Various sizes and types ofprecipitates were observed and the chemicalcomposition of precipitates was identified bymeans of EDS analysis. A remarkable differencein the size, distribution and composition ofprecipitates could be observed between twosamples by TEM observations.

The major precipitates observed in the hotband M1 with low aluminum content were: (i)TiN and FeTiP larger than 60nm in size; (ii) TiS,(Ti,Nb)C and Ti4C2S2 ,with a Mn peak in theEDS data, ranged from 10 to 60 nm, and (iii) TiCless than 10 nm. It was also noted that small TiCprecipitates were nearly spherical, while otherprecipitates larger than 10 nm displayed anirregular shape. The compositions and shapes ofthe precipitates detected in the M1 sample aretypical in the IF-HSS containing Mn, P, Ti andNb22). TEM observations of the M3 sample inthe hot band condition revealed that the numberof precipitates was much less than thoseobserved in the hot band of M1 samples. Inaddition, an interesting observation from the

87

Fig. 5 (100) pole fig.s determined at the mid-plane by

EBSD : (a) The annealed sheet M1 (0.043%Al) and

(b) The annealed sheet M3 (0.19%Al).

Fig. 6 Variation in hardness, (Hv), after the heat treatment

in the temperature range of 620~820°C.

Fig. 7 Optical micrographs observed after annealing at

740°C for 30s : (a) M1 sample with 0.043%Al and

(b) M3 sample with 0.19%Al.


EDS analysis of the hot band M3 is that most ofthe precipitates have an Al peak along with thepeaks of other elements such as Ti, Nb, Mn, S,and C. Examples of the EDS data of the hot bandM3 are shown in Fig. 9.

On the other hand, the distribution ofprecipitate size was also determined by SANS aswell as by TEM in this work. The TEMobservations using carbon extraction replicashave the advantage of imaging real precipitatesin steels. However, many precipitates may bemissed or broken during the preparation ofreplicas and the observation is always limited toa very small area, which often leads to less thanaccurate quantification. This problem isovercome by using the high penetration ofneutron beams, e.g., the SANS analysis, whichprovides more accurate statistical data from thebulk samples26,27).

Fig. 10 shows the SANS patterns observed inthe hot band M1 and M3 samples. The SANSpatterns from the M1 and M3 samples displaydifferent scattering intensities. The scatteringintensity of the M3 sample is higher than that ofthe M1 sample in the Q-range between 0.02 and

0.1 , which correspond to a particle diameterof 20 and 60 nm, respectively. The intensity ofthe SANS patterns in the Q-range > 0.2approaches the background level.

4. Discussion

4. 1 Effect of aluminum on the precipitationbehavior of IF-HSS containing Mn, P, Tiand Nb

The statistical data of the size and number ofprecipitates was determined from the TEMmicrostructures using an observed area from thecarbon extraction replicas of 168µ m2(4rectangular units of 6µm×7µm). The size anddistribution of the precipitates was thenquantitatively determined by means of an imageanalysis system.

The results of the image analysis of two hotbands M1 and M3 is presented in Table 2 andFig. 11. The total number, average size and areaof the precipitates in the M1 and M3 samples,are listed in Table 2, respectively. The area ofprecipitates in Table 2 is the area occupied by the

88

Fig. 8 TEM images observed in the hot bands : (a) M1

sample with 0.043%Al and (b) M3 sample with

0.19%Al.

Fig. 10 SANS patterns obtained from the hot bands.

Fig. 9 Examples of the EDS data observed in the hot band

M3:(a) Data with Ti, C and Al of major peaks and (b)

Data with Ti, S, Mn and Al of major peaks.


precipitates out of the area of 168µm2. The totalnumber of precipitates in the M3 sample wasapproximately one third of that in the M1sample, while the area of the precipitates in theM3 sample was a little larger than that in the M1sample. This means that the average size of theprecipitates determined from the M3 sample iscoarser than that in the M1 sample, as shown inTable 2. Fig. 11 also shows the distribution ofprecipitates with their sizes. It appears fromthese observations that the M3 sample containsvery few fine precipitates smaller than 40nm indiameter when compared to M1 sample. Inaddition, coarser precipitates over 80nm in sizewere more common in the M3 sample than in theM1 sample.

Using the determined volume fraction (or thenumber of precipitates perµ m2) in the bulksamples, the SANS patterns in Fig. 10 wereanalyzed with sufficient accuracy by assumingoverlapped log-normal distributions ofprecipitates in the IF-steels. The results arepresented in Fig. 12 by plotting the volumefraction and the number perµm2 of precipitatesin size intervals of 10 nm. It was repeatedlyconfirmed through the SANS analysis that thesize of the precipitates in the M3 sample withhigher aluminum content were coarser than inthe M1 sample.

The results from this work strongly suggestthat the presence of high aluminum in IF-HSSstudied has an effect on the size and distributionof the precipitates formed during TMP. Thiseffect has not been reported in the openliterature, furthermore there is not a clearunderstanding on the mechanism by whichaluminum promotes the precipitates of the IF-HSS to be coarser. It can be suggested that Aladditions changes the precipitation start

89

Fig. 11 Size distribution of precipitates in the hot bands

determined by image analysis of TEM images.

Fig. 12 Analysis of SANS results : (a) Volume fraction of

precipitates and (b) number of precipitates per µm2

Table 2 Results of image analysis for the precipitates observed from the extraction replicas.

SampleNumber of precipitates Area Average size

5~40nm 40~80nm 80~150nm Total of precipitates of precipitates

M1 631 267 14 912 4875 nm2 35.6 nm

M3 114 173 23 310 5128nm2 45.9 nm


temperature, hence precipitation takes place at anearly stage or at higher temperatures than thosedictated by the solubility products. The earlyformation of precipitates would certainly resultsin fewer and coarser precipitates.

4. 2 Effect of aluminum addition on recrystallizationbehavior and drawability of IF-HSS containingMn, P, Ti and Nb

The size and dispersion of the precipitates inan IF steel can interact with recrystallization,texture evolution and, thus, drawability. It isbelieved that a dense dispersion of fineprecipitates does not impair the nucleation ofrecrystallized grains with {111} orientations.However, the growth of these grains is retardedby the pinning force exerted by the particles onthe grain boundary28). In general, the pinningforce is directly proportional to the volumefraction of precipitates but is inversely related tothe average precipitate size. The finerprecipitates tend to retard the grain boundary ifthe volume fractions of precipitates were thesame.

As investigated by TEM and SANSobservation in this work, the IF-HSS with highaluminum content of more than 0.10wt% hascoarser precipitates in size and much fewer innumbers, compared with the steel having lowaluminum content of 0.04wt%. Note that therecrystallization was completed earlier in thecold rolled M3 sample with the high aluminumcontent (refer to Fig. 6) and the grain size of theannealed sheet M3 was larger than the M1 withthe low aluminum content (refer to Fig. 3). It is,therefore, thought that these results mentionedabove could be derived from the difference ofprecipitation behavior in the two steels.

It has been reported that a dense dispersion offine precipitates correlated with a weak intensityof {111} texture and a low Lankfordvalue14,29,30). Following this argument, it can alsobe easily inferred from the TEM and SANSobservations of this study that the annealed steelwith high aluminum content should have a

stronger γ-texture and thus a better mean r-valuebecause of the relative absence of fineprecipitates smaller than 40nm (refer to Fig. 10).In addition, it is well known that a “pure” ironmatrix brought about by gathering interstitialatoms as a spare dispersion of precipitates usingTi or Nb are important requisites to promote{111} recrystallization texture11,31-33). It is alsothought that the high aluminum content in theIF-HSS with Mn, P, Ti and Nb might encouragethe scavenging effect of Ti or Nb and thus makethe iron matrix more pure. As seen in Fig. 9, theAl peak in the EDS data from most precipitatesof the M3 sample is evidence that shows thataluminum helps the formation of theprecipitates.

In terms of a commercial production of theIF-HSS with a extremely good formability, onevery attractive aspect of the high Al steels is theability to lower the heating and soakingtemperature during in-line annealing whilemaintaining good properties. It has beensuggested in the literature 28) that the annealingtemperature of the super formable, high strengthsteel should be controlled over 850°C to obtainan r-value of 2.3 or more. However, when hightemperatures are used during in-line annealing, itmay result in poor surface quality, propertyuniformity and overall productivity of the line.The coarsening of the precipitates or othereffects such as increased diffusivity andaccelerated annealing promoted by the aluminumadditions greater than 0.10wt% to the IF-HSScontaining Mn, P, Ti and Nb can permit theannealing temperature to be lowered during in-line annealing.

5. Conclusions

The effect of aluminum content on themechanical properties of Ti-Nb containinginterstitial free high strength steel, (IF-HSS), wasinvestigated to develop the super formable highstrength steels with an r-value of 2.3 or more. Theinvestigation was especially focused on the

90


change of precipitation behavior with aluminumcontent. The conclusions obtained are as follows ;1) Aluminum improved the formability of the IF-

HSS containing Mn, P, Ti and Nb when over0.10wt%Al is added, especially increasing thedrawability.

2) Texture analyses showed that the <111>//NDfiber(γ-fiber) was intensified, and<110>//RD(α-fiber) was weakened, with theincrease of aluminum content.

3) Recrystallization was completed earlier in thesteel with the high aluminum content and thegrain size of the annealed sheet was largerthan that of the annealed steel with the lowaluminum content.

4) The results mentioned above are related toeither the change of precipitation behavior orthe increased annealing kinetics associatedwith the increase in aluminum content.

5) It was confirmed thorough the SANS analysisthat the size of the precipitates in the samplewith higher aluminum content was larger andtheir number was much fewer than in thesample with lower aluminum content.

6) It appears that the high aluminum content inIF-HSS containing Mn, P, Ti and Nbimproved the scavenging effect of Ti or Nband thus purified the iron matrix.

6. Acknowledgements

The authors would like to express sincerethanks to Dr. Shin and Dr. Seong of KoreaAtomic Energy Research Institute for analyzingthe precipitates by the SANS.

7. References

(1) A. Okamoto and N. Mizui : Metallurgy ofVacuum-Degassed Steel Products, Editedby R. Pradhan, TMS-AIME, Warrendale,PA, USA, (1990), 161.

(2) T. Matsumoto : Physical Metallurgy of IFSteels, ISIJ, Tokyo, (1994), 269.

(3) T. Matsumoto : CAMP-ISIJ, 10 (1997),1401.

(4) N. Yoshinaga, K. Ushioda and O. Akisue :ISIJ International, 34 (1994), 33.

(5) C. Brun, P. Patou and P. Parniere : TMS-AIME Annual Meeting, Dallas, TX, USA(1982), 173.

(6) N. Mizui and A. Okamoto : CAMP-ISIJ, 3(1990), 1814.

(7) S. Carabajar, J. Merlin, V. Massardier andS. Chabanet : Mater. Sci. Eng., A281(2000), 132.

(8) S. Hinotani, J. Endo, T. Takayama, N.Mizui and Y. Inokuma : ISIJ International,34 (1994), 17.

(9) J. S. Rege, M. Hua, C. I. Garcia and A. J.Deardo : ISIJ International, 40 (2000), 191.

(10) R. Mendoza, J. Huante, M. Alanis, C.Gonzalez-Rivera and J. A. Juarez-Islas :Mater. Sci. Eng,. A276 (2000), 203.

(11) S. Satoh, O. Takashi and K. Tsunoyama :Transactions ISIJ, 26 (1986), 737.

(12) A. R. Jones and N. Hansen : Acta metal,. 29(1981), 589.

(13) P. A. Manohar, M. Ferry and T. Chandra :ISIJ International, 38 (1998), 913.

(14) S.V. Subramanian, M. Prikryl, B. D. Gaulin,D. D. Clifford, S. Benincasa and I.O°Øreilly : ISIJ International, 34 (1994),61.

(15) H.C. Chen, L. Chang, P. Lee and Y. Hwang: IF Steels 2000, ISS, Pittsburgh, PA, USA,(2000), 23.

(16) O. A. Girinia and M. N. Fonstein :Developments in Sheet Products forAutomotive Applications, Organized byJames R. Fekete and Roger Pradhan,Materials Science & Technology 2005,International Conference, Sept. 25-28,2005, Pittsburgh, PA, (ASM, ACerS, AIST,AWS and TMS, 2005), 65.

(17) J. E. Gonzalez, C. I. Garcia, A. J. DeArdoand M. Hua : Developments in SheetProducts for Automotive Applications,Organized by James R. Fekete and RogerPradhan, Materials Science & Technology

91


2005, International Conference, Sept. 25-28, 2005, Pittsburgh, PA, (ASM, ACerS,AIST, AWS and TMS, 2005), 3.

(18) A. Mertens, P. J. Jacques, L. Zhao, S. O.Kruijver, J. Seitsma and F. Delannay :Journal De Physique. IV : France, 112 I,October, (2003), 305.

(19) M. De Meyer, D. Vanderschueren and B. C.De Cooman : ISIJ Inernational, 39 (1999),813.

(20) P. J. Jacques, E. Girault, A. Mertens, B.Verlinden and J. Van Humbeeck : ISIJInernational, 41 (2001), 1068.

(21) E. Girault, A. Mertens, P. J. Jacques, Y.Houbaert, B. Verlinden and J. VanHumbeeck : Scripta Mat., 44 (2001), 885.

(22) S. Han, H. Kang and J. Chung : IF steels2000 Proc. ISS, Pittsburgh, PA, USA,(2000), 157.

(23) G. Enrique : PhD Thesis, University ofPittsburgh, Pittsburgh, PA, USA, (2004).

(24) S. D. Gertsriken and M. P. Pryanishnikov :Ukr. Fiz. Zh., 3 (1958), 255.

(25) S. D. Gertsriken, I. Ya. Dekhtyar, N. P.Plotnikova, L. F. Slastnikova and T. K.Yachenko : Issled, Zharpr. Splav., 3 (1958),68.

(26) C.G. Windsor : J. Appl. Cryst., 21 (1988),582.

(27) Feigin, L. A.; Svergun, D. I.: StructureAnalysis by Small-Angle X-ray andNeutron Scattering, Plenum Press, NewYork (1987).

(28) H.Kubodera and H.Inagaki : Bull. Jpn. Inst.Met., 7 (1968), 383.

(29) S.V. Subramanian, M. Prikryl, B. D. Gaulin,M. Koch and S. Benincasa : Proc. of ASMInt. Conf., ed. by R. Pradhan and I. Gupta,MMMS, (1992), 219.

(30) Okamoto, A.; Mizui, N.: Proc. Metallurgyof Vaccum-Degassed Products. Edited by R.Pradhan, TMS-AIME, Warrendale, PA,USA, (1990), 161.

(31) M. Matsuo, S. Hayami and S. Nagashima :Proc. ICSTIS 2, Suppl. To Trans. ISIJ, 2(1971), 867.

(32) W. B. Hutchinson and K. Ushioda : Scan. J.met., 13 (1984), 269.

(33) O. Hashimoto, S. Satoh and T. Tanaka :Trans, ISIJ, 27 (1987), 746.

92

Documents

Effect of Aluminum Content on the Mechanical Properties of Dual Stabilized Ti-Nb Interstitial Free High Strength Steel (IF-HSS)