Microstructure and mechanical properties of lightweight TiC-steel composite prepared by liquid pressing infiltration process

Journal Pre-proof Microstructure and mechanical properties of lightweight TiC-steel composite prepared by liquid pressing infiltration process

Yeong-Hwan Lee, Namkyu Kim, Sang-Bok Lee, Yangdo Kim, Seungchan Cho, Sang-Kwan Lee, Ilguk Jo PII:

S1044-5803(19)32663-4

DOI:

https://doi.org/10.1016/j.matchar.2020.110202

Reference:

MTL 110202

To appear in:

Materials Characterization

Received date:

30 September 2019

Revised date:

12 February 2020

Accepted date:

12 February 2020

Please cite this article as: Y.-H. Lee, N. Kim, S.-B. Lee, et al., Microstructure and mechanical properties of lightweight TiC-steel composite prepared by liquid pressing infiltration process, Materials Characterization (2018), https://doi.org/10.1016/ j.matchar.2020.110202

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© 2018 Published by Elsevier.

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Microstructure and Mechanical Properties of Lightweight TiC-steel Composite Prepared by Liquid Pressing Infiltration Process

Yeong-Hwan Lee

a,c

, Namkyu Kim b, Sang-Bok Lee a, Yangdo Kim c, Seungchan Cho a,*,

Sang-Kwan Lee a,* Ilguk Jo d,*

a

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Composites Research Division, Korea Institute of Materials Science (KIMS), Changwon

Industrial Technology Support & Safety Division, Korea Institute of Materials Science

(KIMS), Changwon 51508, Republic of Korea c

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b

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51508, Republic of Korea

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School of Materials Science and Engineering, Pusan National University, Busan 46241,

d

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Republic of Korea

Advanced Materials Engineering, Dong-Eui University, Busan 47340, Republic of Korea

*

Abstract

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[email protected] (I. Jo),

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Corresponding authors: [email protected] (S. -K. Lee), [email protected] (S. Cho),

A TiC reinforced steel composite was fabricated by a liquid pressing infiltration (LPI) process. The TiC reinforced steel composites with density less than 6.0g/cm3 were fabricated with a high volume fraction of TiC reinforcement. The results showed that the core-rim structure in the composite was formed by partial dissolution of the reinforcement during the LPI process. The effect of dissolution of TiC particles on the microstructure and mechanical properties of the composites was investigated. Enhanced mechanical properties are attributed to the effective load transfer from the matrix to the TiC because of the strong interfacial bonding. This interfacial stability results from chemical bonding from the partial dissolution

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and the precipitation of the TiC during the process. In order to establish the correlation between the core-rim structure and properties of the composite, the hardness (H) and Young's modulus (E) were examined by nano-indentation.

Keywords: Lightweight; TiC-steel composite; Liquid pressing infiltration; Microstructure;

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Mechanical property; Partial dissolution;

1. Introduction

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The development of advanced lightweight steels with excellent mechanical properties is

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an important goal for industrial applications, such as automotive components, tools, and other

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wear-resistant components. Research on lightweight steels that use aluminum as the alloying element has been performed with the goal of reducing overall weight. However, there are

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limits on the ways in which the alloying Al can reduce the weight of steel [1, 2]. One

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promising way to achieve weight reduction in steel is to introduce lightweight ceramics into the steel matrix to create a composite, which can combine superior mechanical properties, in addition to high corrosion and wear resistance with a low density [3-5]. Among the reinforcement materials, titanium carbide (TiC) has received increasing attention in recent years due to its good thermal stability and superior mechanical properties, such as hardness, modulus, and wear resistance [6]. High volume fraction TiC reinforced steel composites fabricated by the conventional powder metallurgy (PM) method have been intensively studied. Z. Wang et al. [7] reported the microstructure and mechanical properties of TiC (> 60 vol. %) reinforced 35CrMo steel composite via vacuum sintering process which has a hardness of 65 HRC. B. Almangour et al. [8] produced TiC-316L composites using selective laser melting (SLM) process, where the TiC particle size, process parameter of the

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SLM were analyzed. However, particle clustering and defect formation at the interfaces due to the poor wettability between the TiC and the steel matrix are the main drawbacks of the PM process [9, 10]. To overcome these disadvantages, liquid pressing infiltration (LPI) has been developed to infiltrate molten metal into a ceramic preform with a separated heating system using hydrostatic pressure, which leads to a uniform dispersion of reinforcements inside the steel matrix [11, 12].

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During the composite manufacturing process, high temperature environment cause the

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formation of the core-rim structure by dissolution and reprecipitation of the TiC particle [13, 14]. T. Lin et al [15] produced the TiC-steel composites with 36 wt.% TiC with core-rim

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structure and the hardness and transverse rupture strength of the composite were studied. J.

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Pörnbacher et al. [16] adopted hot isostatic pressing process to fabricate TiC reinforced steel

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MMC and investigated the effect of powder milling process on the formation of core-rim structure. Jin [17] found the formation mechanism of core-rim structure in TiC-steel which

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prepared by melt infiltration is competition of interfacial energy minimization and coherency

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strain energy during the process. Core-rim structures in TiC reinforced steel composites are known to be an important microstructural feature influencing the mechanical properties of the composite. However, most studies were focused on the mechanical properties of the composites or microstructural analysis, so the evaluation on the relationship between the core-rim structure and the mechanical properties of the composites are rare. So it is necessary to characterize the core-rim structure of TiC reinforced steel composite to understand excellent properties of the composites. In this research, the LPI process under applied pressure was used to produce lightweight TiC reinforced steel composites with improved mechanical properties. The strengthening mechanisms of the high volume fraction composites fabricated under an isothermal temperature condition were investigated from a microstructural perspective, including the

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interfacial stability results from core-rim structure which produced by partial dissolution and reprecipitation of the TiC reinforcement.

2. Materials and methods

2.1. Composite fabrication

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The chemical composition of the matrix steel (JIS SKD11) was Fe-1.4C-11.1Cr-

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0.80Mo-0.23V in wt.% (equivalent to AISI D2). As the reinforcement, 99.5% purity TiC (Changsha Langfeng Metal Materials Co., Ltd) with particle size of 1~10 µm was used and

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the TiC preform was made by uniaxial pressing using a cylindrical mold with a height of

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25mm and a diameter of 55mm (80 MPa). This preform with a green density of 61 ± 1% was

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subsequently sintered at 1400 oC for 2 h under an argon atmosphere. In accordance with the LPI process, the TiC preform was located in the crucible (60mm×60mm×6mm) beneath the

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steel alloy ingots, followed by degassing and vacuuming. The preform and the ingots were

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isothermally heated to 1600 oC by vacuum induction melting, and then were pressurized with argon pressure of 0.5 MPa for 5min followed by pouring.

2.2. Microstructural characterization The microstructures of the TiC powder, preform, and the composites were observed by a scanning electron microscope (SEM, LEO-1450). The volume fraction of the composite was measured from five SEM images using the ImageJ analysis program. Crystalline phases in the matrix alloy and the composite were characterized by using an X-ray diffractometer (XRD, D MAX-2500, Rigaku). Each sample was scanned by XRD using Cu-Kα (λ=0.154 nm) radiation at a scanning rate of 1°/ min over an angular range of 30–90°.

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The interfacial morphology and the elements were characterized using transmission electron microscopy (TEM, JEM200). The element distribution of the matrix alloy and the composite was investigated using electron probe micro-analysis (EPMA, JXA- 8530F, JEOL). A field emission scanning electron microscope (FESEM, Tescan MIRA 1) with an electron backscatter diffraction (EBSD) detector was used for the grain size analysis.

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2.3. Characterization of mechanical properties

The density of the steel alloy and the composite was measured by the Archimedes

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method. The Vickers micro-hardness values reported are the average of 10 measurements for

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each sample. Plate-type tensile specimens with a gage length of 5mm, a width of 2mm, and a

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thickness of 2 mm were prepared, and were tested at room temperature at a strain rate of 3.4×10-4 s-1. The compressive behaviors of both the matrix and the composite specimens

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(Φ3mm x 6mm) were studied under strain rates of 5×10-4 s-1. The presented strength data are

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the average of three measurements.

Nano-indentation was performed using a Nanoindenter XP (MTS) to measure the hardness (HIT) and elastic modulus (EIT) of the composite with a Berkovich indenter, using the continuous stiffness measurement (CSM) technique. To obtain reliable data, a total of 300 indentations were made on the composite specimen at room temperature and the penetration depth limit was 300 nm. The hardness and Young's modulus values were obtained at a depth of 300 nm. Each value of hardness and modulus was taken and averaged statistically.

3. Results and Discussion

3.1 Microstructure

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Fig. 1 shows SEM micrographs of raw and sintered TiC powder and TiC-SKD11 composite produced by the LPI process. As can be seen from Fig. 1(a), the starting TiC particles had an irregular shape with a size of 1~10 µm. The formation of necks was perceived in the preform after sintering at 1400℃ (Fig. 1(b)); however, no change in the TiC morphology was recognized. From this weak bonded-preform, a form suitable for composite

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fabrication was identified. The microstructure of the TiC reinforced steel composites is

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presented in Figs. 1(c) and (d). The TiC was homogeneously distributed in the matrix at an area fraction of about 60% (± 2%), which is the same as the green density of the preform. It

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was noted from Figs. 1(c) and (d) that the boundaries of the TiC particles were smooth and

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spherical as compared with the starting powder, as shown in Fig. 1(d), which indicates that

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partial dissolution and the precipitation of TiC occurred during the LPI process. It is reported that the TiC particles are partially dissolved in the matrix with a temperature over 1600° in

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the TiC-SKD11 composite system, and that they are re-precipitated during the solidification

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process [18]. The interfaces between the matrix and the reinforcement were clean with no defects such as pores, cracks, or de-bonding. Additionally, the infiltration of the steel melt was achieved even below the 100nm inter-particle distances, which indicates good wettability of the TiC through the steel melt in the LPI process.

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Fig. 1. Microstructure of (a) raw TiC powders, (b) sintered TiC preform, and (c,d) TiC-

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SKD11 composites fabricated by the LPI process.

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TEM analysis was applied to better understand the details of the interface of the composite. As Figs. 2(a) and (b) show, the interfaces between the TiC particle and the matrix were well-bonded to one another. Fig. 2(c) shows the selected area diffraction pattern (SADP) of TiC, which reveals that the TiC is single crystal with a face-centered cubic (FCC) structure. The diffraction pattern reflects the (020) and (200) planes in the [001] zone axis of the TiC reinforcement. The unidentified phases with a few hundred nanometer scale are identified between the reinforcements marked by a yellow arrow. In order to analyze the phases, EDS mappings of Fe, Ti, Cr, and C elements were obtained, and they revealed that the phases are chrome-rich carbide (Fig. 2(e)). Generally the SKD11 alloy includes chromium carbide in the matrix [19]. According to the Cr mapping in Fig. 2(e), it can be found that the Cr-rich carbide

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phases are bridging the TiC particles, as indicated by a yellow rectangle. Furthermore, there is also a Cr-rich carbide phase attached to the surface of the TiC reinforcement (yellow circle). XRD and EPMA analyses was carried out on the matrix alloy and the composite to identify

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the carbide and the presence of elements.

Fig. 2. (a,b) TEM bright-field image of the composites; (c) SADP of TiC particle; (d) STEM annular dark-field image of the composite; and (e) EDS mapping of the composite.

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3.2. Composition and Elemental Distribution Mapping

The XRD patterns of (a) SKD11 matrix alloy and (b) TiC-SKD11 composites produced by the LPI process are given in Fig. 3. It is found that alpha bcc iron (martensite) is the main phase of the SKD11 matrix (Fig 3a). It is noteworthy that diffraction peaks of M7C3 are detected in both specimens, which is in accord with the results of TEM observation. Very

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low intensity of M23C6 peaks was also detected. M stands for random occupancy of the Fe

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lattice sites with Fe and appropriate fractions of other metal atoms substituting for Fe in the solid solution (M = Fe, Cr, V, Mo). XRD results show that the TiC reinforced SKD11

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composites were successfully fabricated without unwanted reaction phases or impurities.

Fig. 3. XRD patterns for (a) SKD11 matrix, and (b) SKD11–TiC composite.

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For further phase characterization, the distribution of the elements in the matrix alloy and the composite was characterized by EPMA and the results are shown in Fig. 4. Fig. 4(a) shows the SEM morphologies and EPMA analysis results of the SKD11 matrix alloy. According to the element maps shown in Fig. 4(a), carbides of various sizes (white arrows) with high color intensities of Cr, C, V were observed with rather less color intensity of Mo

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element. With combine elemental mapping result and XRD pattern, these phases were

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concluded to be M7C3 or M23C6 type carbides.

A SEM image (Fig. 4b) taken from the TiC-SKD11 composite shows the presence of

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finely dispersed reinforcements. EPMA mapping for the elements such as Fe, Cr, V, and Mo

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was carried out on dispersed phases of the composite to identify the elemental distribution.

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As stated previously, the XRD analysis confirms these phases as the formation of M7C3 or M23C6 precipitates at the SKD11 matrix. The EPMA mapping image clearly shows the

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distribution of C, Cr, Fe, and V in the matrix area, as shown in Fig. 4b. The light green

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colored rim observed from the Fig. 4b inside the TiC reinforcement was identified as a V and Mo rich region. It can be deduced that the TiC particles are partially dissolved during the LPI process, whilst V and Mo from the matrix diffused towards TiC before solidification of the steel melt. A (Ti, Mo, V)C solid solution consequently forms on the edge of the TiC reinforcement. As can be seen from Fig. 4b, it was confirmed that the V and Mo elements diffused to the center of the TiC particles. The dissolution of the reinforcement yields lowenergy interfaces and results in enhancement of the wetting of TiC in the matrix, and hence increases the interfacial bonding strength [20]. This effect will drastically increase the loadbearing capacity, thus improving the mechanical properties of the produced composites. The partial dissolution of TiC is also in agreement with Fig. 1 showing that the morphology of TiC is changed from an angular shape in the starting TiC to a spherical shape in the

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Fig. 4. Elemental mapping with EPMA in the (a) SKD11 matrix alloy, and (b) TiC-SKD11 composite.

3. 3 Mechanical Properties

Table 1 summarizes the physical and the mechanical properties of the matrix and the composite. The density of the composite was 5.77 g/cm3, which is about 25% lighter than that

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of the matrix (7.81 g/cm3). The average Vickers hardness of the composite is about 1432.4 HV, which is 5.8 times higher than that of the SKD11 matrix (245.9 HV). The hardness of the 61 vol.% TiC reinforced steel composite fabricated by powder metallurgy process [7, 21] is about 720 HV and 830 HV, respectively. The hardness of a 70 vol.% TiC reinforced stainless steel produced through the powder technology is about 1035 HV [22]. Therefore, it can be seen that the TiC-SKD11 composite produced by the liquid pressing infiltration process has

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an effective load transfer from soft matrix to hard reinforcement. Compared to the matrix, the

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composite exhibited a higher yield strength (YS), ultimate tensile strength (UTS), and elastic modulus. No necking was observed during the tensile test on the composite specimen, and

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YS (830MPa) seen in the stress-strain plots was close to the UTS value (935MPa), which

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suggests that the composites failed after yielding. It should be noted that no distinct yielding

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would take place in the high volume fraction composites because of their brittleness [23]. Additionally, if the composite is not produced well, the tensile strength in high volume

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fraction ceramic reinforced metal matrix composites is decreased due to the weak interfacial

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bonding and defects [24]. In this research, however, the UTS of the high volume fraction TiC reinforced composite was 935 MPa, which is higher than that of the SKD11 matrix (743 MPa). The increase in the strength from the TiC addition could be attributed to good interfacial bonding and fewer defects, as compared to the composite prepared by conventional processes. As expected, the modulus of the composite (369 GPa) was highly increased, relative to the steel matrix (205 GPa). Above all, the compressive yield strength (CYS) of the composite (3.32 GPa) was 7.4 times higher than the corresponding values of the steel matrix (0.45 GPa).

Table 1. Summary of the physical and the mechanical properties of the matrix and the TiCSKD11 composite.

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Density

Hardness

YS

UTS

Modulus

CYS

(g/cm3)

(HV)

(MPa)

(MPa)

(GPa)

(GPa)

Steel

7.81

245.9

340

743

205

0.45

TiC- SKD11

5.77

1432.4

830

935

369

3.32

Fig. 5 indicates that particle cracking is the main mode of failure under the tensile and the

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compressive load. As shown in Fig. 5(a), there is a primary crack path (marked as P) and

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several secondary crack paths (marked as S) through the TiC particles that are perpendicular

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to the tensile loading axis. The fracture in the composite under the tensile load might be initiated by the nucleation and formation of micro-pores within the TiC reinforcement.

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Further increase in the stresses can cause the micro-pores to coalesce into a primary micro-

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crack. In this stage, strong interfacial bonding increases the resistance to the crack propagation before the plastic deformation of the steel matrix. These primary cracks then

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extend to the matrix through secondary crack formation, and the final fracture occurs through

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the primary crack path. The crack propagation, even at a small TiC size (which can be observed from the detailed microstructure of the secondary crack path and is shown in Fig. 5(b)), indicates effective load transfer at the interface. This is attributed to good interfacial bonding, such that it is able to perfectly transfer the load from the matrix to the TiC particles. Also, it is known that the fracture path is likely to develop from the residual porosity and particle/matrix de-bonding in the composite [25]. However, because of a strong interfacial bonding, no defects or de-cohesion at the interface is observed in the fracture specimen (Figs. 5(a) and (b)). As compared to the tensile test specimen, compressive test specimen showed roughly 45 degrees shear failure to the direction of compressive axis. The fractography of the compression test specimen (Fig. 5(d)) showed a micro-dimple pattern, by the ductile matrix fracture with the brittle reinforcement fracture. The matrix dimple was not observed on the

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other side of the reinforcement, which reveals the constraints in plastic flow of the composite

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matrix in the presence of discontinuous TiC reinforcement.

Fig. 5. Fracture morphologies of the (a,b) side view of the tensile test specimen; (c) tensile fracture surface; and (d) compressive fracture surface.

As shown in Fig. 6, the morphology of an indent on the sample surface is captured using FESEM. No interfacial debonding, TiC particle cracking or radial crack propagating from the indent corner is found for any indent area on the specimen. Triangular pyramid craters were formed during penetration of the indentation tip in different phases. The size of the residual nano-indentation impression corresponds to the indentation displacements during the loading process [26]. For this reason, the distance between the center and the vertex of the equilateral triangle indentation mark was measured to compare the displacement of each region. The

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indent position was divided into five regions: TiC core, TiC core-rim interfaces, TiC rim, SKD11/TiC interface, and SKD11 matrix area. The average length of three distance between the center of the indent and three vertexes of each area was 814.32, 889.53, 992.65, 1402.04, and 1507.92 nm, respectively. The displacement gradually increased from the center of the TiC particle towards the SKD11 matrix. This indicates that the hard ceramic particle was less deformed compared with the soft matrix. The lower hardness values are mostly associated

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with indents that are placed in the matrix alloy and have the largest distances from the indent

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center to the vertex among indent positions.

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Fig. 6. (a) Schematics and detailed microstructure of impression after nano-indentation on (b) TiC core; (c) TiC core-rim interface; (d) TiC rim; (e) TiC/SKD11matrix interface; and (f) matrix alloy.

Representative load-displacement curves of five regions during nano-indentation on the composite specimen are shown in Fig. 7. Compared to other phases, a higher indentation

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load is needed to reach an indentation depth of 300 nm at the center of TiC reinforcement, which means that the TiC particle possesses a relatively higher hardness. For a given depth of 300 nm, the applied load for the TiC phase was 44.6 mN, which is higher than that of the matrix (15.1 mN). The load-displacement curves of the TiC core-rim interface and the TiC rim phase show similar trends. Furthermore, it is noted that the maximum indentation loads for the core-rim interface (49.2 mN) are higher than at the TiC/SKD11 interface (32.1 mN),

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indicating the area near the matrix alloy has a lower average hardness. In the load-

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displacement curve, large elastic recovery is observed by a reduction in displacement at an analysis point close to the center of a TiC particle. For an elastic-plastic contact, the

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unloading curve is different from the loading curve and the area between them represents the

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energy lost as not only heat but also deforming energy of crystals during the plastic

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deformation. As shown in the inset of Fig. 7, the elastic recovery of indentation, he, can be calculated from the following equation [27]:

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he = hmax - hf

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where hmax is the maximum penetration depth and hf is the residual penetration depth. The elastic recovery of the TiC core, the TiC core-rim interface, the TiC rim, TiC/SKD11 interface, and the SKD11 matrix regions was about 45.9, 44.7, 46.3, 41.8, and 27.2% of the maximum penetration depth, respectively. The elastic recovery of the TiC/SKD11 interface was not substantially less than that of the TiC particle. The high elastic recovery for the reinforcement and matrix appears to be mainly due to the strong interfacial bonding. The elastic recovery of the SKD11 matrix (27.2%) was lower than at the other positions.

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for nano-indentation test).

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Fig. 7. Representative load-displacement graph (inset graph: typical load-displacement curve

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A summary of hardness (H) and elastic modulus (E) from the nano-indentation tests is shown in Fig. 8. The H and the E of the composite had different values depending on the location where the indentation was applied. The H and the E values of the TiC core and corerim interfaces are similar but decrease gradually close to the matrix area. The TiC core and the TiC core-rim interface exhibit a hardness of 443.5 GPa and 448.3 GPa, and a modulus of 29.7 GPa and 29.3 GPa, respectively. The nano-hardness measured from the TiC rim and TiC-SKD11 interface was 415.7 GPa and 368.5 GPa, respectively, and their elastic modulus was 25.3 GPa and 13.9 GPa, respectively. The SKD11 matrix has hardness and a modulus of about 327.1 GPa and 7.3 GPa, which are the lowest among all five regions. The hardness at the TiC core zone is about 443.5 GPa, which is about 35% higher compared to the hardness of the matrix (327.1 GPa). According to the literatures [28, 29], an H/E ratio also determines

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the elastic recovery of a material upon deformation. The calculated H/E value increased as the indent position moved towards the TiC particle. The TiC core has the H/E ratio of 0.067, which is much higher compared to the matrix alloy (0.022). This indicates the incorporation

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of a high volume fraction of TiC particle increases the resistance to mechanical damage.

Fig. 8. Summary of average nano-hardness (H) and elastic modulus (E) as a function of indentation position of composite.

3.4 Grain size distribution

Detailed information of the grain size distribution in the matrix and the composite was obtained by EBSD (Fig. 9). The average grain size of 11.6 μm (equivalent diameter) was calculated from the matrix and can be compared to an average grain size of 5.4 μm in the

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composite (Fig. 9). The improved YS stemming from grain refinement (∆𝜎𝐺𝑅 ) could be estimated from the Hall-Petch relationship as follows [30]: ∆𝜎𝐺𝑅 = 𝑘(𝑑 −0.5 − 𝑑0−0.5 ) where k is a constant (1.0 MN·m-3/2 for low-carbon steel [31, 32]), and d and d0 are the average grain size of the composite and the matrix, respectively. The ∆𝜎𝐺𝑅 predicted from the equation is about 130 MPa, which was smaller than the YS improvement (490 MPa)

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measured experimentally. This result shows that the grain refinement might contribute to

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strengthening of the composite, and that other strengthening mechanisms are also combined.

Fig. 9. EBSD maps and grain size distribution of (a) the steel matrix and (b) the TiC- SKD11 composite.

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From the experimental data, we have deduced the following findings, which may all contribute to the strengthening mechanism of TiC-SKD11 composites: (a) Effective load transfer from the matrix to the reinforcement takes place because of the strong interfacial bonding by the partial dissolution of TiC during the LPI process. (b) Fewer defects and a uniform distribution of TiC prevent premature fracture of the composite under an applied load.

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(c) Grain refinement of the matrix occurs due to the incorporation of reinforcements.

These strengthening mechanism factors, whether independently or concurrently, are

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considered to be responsible for enhancing the mechanical properties of TiC–SKD11

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Conclusion

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composites.

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The strengthening mechanism of a high volume fraction TiC reinforced steel composite

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fabricated by the LPI process has been investigated through the extensive characterization of microstructure and mechanical properties of the composite. The composite with a density of 5.77g/cm3 exhibited superior mechanical properties, as compared with the matrix. The increases in the mechanical properties is attributed to the incorporation of the hard ceramic reinforcement and effective load transfer from the matrix to the reinforcement. Interfacial stability and strong bonding between the reinforcement and the matrix could be obtained from the enhanced wettability from the partial dissolution and reprecipitation of the TiC reinforcement during the LPI process. In conclusion, core-rim structure formation of TiC by V and Mo diffusion and grain refinement of the matrix contributed to enhanced mechanical properties of TiC-SKD11 composites fabricated by the LPI process.

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Declaration of competing interest None

Acknowledgments

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This work was financially supported by the Fundamental Research Program (PNK7020) of the Korea Institute of Materials Science (KIMS). This work was also

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supported by the Korea Basic Science Institute(KBSI) National Research Facilities & Equipment Center(NFEC) grant funded by the Korea government(Ministry of Education)

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Data availability

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(No.2019R1A6C1010045)

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The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.

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[3] H. Springer, R. Aparicio Fernandez, M.J. Duarte, A. Kostka, D. Raabe, Microstructure refinement for high modulus in-situ metal matrix composite steels via controlled

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solidification of the system Fe–TiB2, Acta Mater. 96 (2015) 47–56.

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[4] I. Sulima, S. Boczkal, L. Jaworska, SEM and TEM characterization of microstructure of

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stainless steel composites reinforced with TiB2, Mater. Charact. 118 (2016) 560–569. [5] D. Abolhasania, S. M. H. Seyedkashi, T.W. Hwang, Y.H. Moon, Selective laser melting of

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Declaration of interests

☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

☐The authors declare the following financial interests/personal relationships which may

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be considered as potential competing interests:

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Ref: MATERIALSCHAR_2019_2572

Pressing Infiltration Process

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Journal: Materials Characterization

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Title: Microstructure and Mechanical Properties of Lightweight TiC-steel Composite Prepared by Liquid

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Highlights  The strengthening mechanisms of the TiC/steel composites fabricated under an isothermal temperature condition is clarified.  The core-rim structure was formed by partial dissolution of the TiC reinforcement.

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 Effective load transfer from the matrix to the reinforcement takes place because of the strong interfacial bonding from the partial dissolution of TiC.

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