Rapid construction of multicomponent TRIP stainless steel by powder feeding laser deposition for comprehensive properties

Materials & Design 184 (2019) 108171

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Rapid construction of multicomponent TRIP stainless steel by powder feeding laser deposition for comprehensive properties Kuan Zhang a, b, Wei Li a, b, *, Yuantao Xu a, b, Binggang Liu a, b, Yu Li a, b, Danying Liu c, Xifan Ding c, **, Xuejun Jin a, b, * a b c

Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240, PR China School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China School of Design, Shanghai Jiao Tong University, Shanghai 200240, PR China

h i g h l i g h t s

g r a p h i c a l a b s t r a c t


The 13Cr-xNi-(10-x)Mn-3Al steel with continuous graded composition was produced by laser metal deposition method.
An optimized composition range for the steel was determined efficiently by screening microscopic properties on one specimen. This study provide a guide for exploring the relationship between chemical composition, microstructure, and mechanical properties.

a r t i c l e i n f o

a b s t r a c t

Article history: Received 12 May 2019 Received in revised form 15 August 2019 Accepted 30 August 2019 Available online 31 August 2019

This study developed a powder feeding laser metal deposition (LMD) method that can be used to achieve a layer-by-layer fabrication of component grade material for efficiently screening the properties of different chemical compositions and determining the optimized composition range for TRIP stainless steel. The 13Cr-xNi-(10-x)Mn-3Al steel with continuous graded composition was produced by the LMD method. An optimized composition range for TRIP stainless steel was determined by testing the properties including hardness, austenite content and surface potential of positions with different compositions. The suggested Ni content is between 3%e6% and Mn content is between 4%e7%. This study demonstrates the potential of LMD method to accelerate the development of steel economically. © 2019 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Keywords: Component gradient Layer metal deposition Layer by layer

1. Introduction

* Corresponding authors at: Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240, PR China. ** Corresponding author. E-mail addresses: [email protected] (W. Li), [email protected] (X. Ding), jin@ sjtu.edu.cn (X. Jin).

Strength and ductility sometimes are equally important, and it keeps intriguing the interest of researchers to find metal materials with both high strength and high ductility [1e3]. Advanced highstrength steels (AHSS) have been receiving increasing attention, especially in the automotive industry, because of their favorable performance in the manufacturing process, safety attributes, and weight reduction capability [4e6]. Transformation-induced

https://doi.org/10.1016/j.matdes.2019.108171 0264-1275/© 2019 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/ ).

K. Zhang et al. / Materials & Design 184 (2019) 108171

2 Table 1 Chemical composition of the two powders (wt%). Powders Expected chemical composition

1 2 1 2

Actual chemical composition

Cr

Ni

Mn

Al

Fe

13 13 10.29 13.30

10 0 9.99 0

0 10 0 11.01

3 3 2.24 2.31

Bal. Bal. Bal. Bal.

Fig. 1. SEM images of powders: (a) SEM images of Fe-Cr alloy powder; (b) SEM images of Fe-Ni alloy powder; (c) SEM images of the mixed powder 1; (b) SEM images of the mixed powder 2.

Fig. 2. The schematic profile of the LMD process in this study and the robotic arm used in the experiment; (a) The schematic profile of the LMD process; (b) The robotic arm used in the experiment. Table 2 The chemical composition of the substrate (wt%). Substrate

Ni

Si

Mn

S

C

Al

N

O

Fe

9Ni steel

9.00

0.17

0.53

0.003

0.036

0.041

0.005

0.0027

Bal.

K. Zhang et al. / Materials & Design 184 (2019) 108171

plasticity (TRIP) steel has a good combination of strength and ductility, which is ascribed to the multiphase microstructures containing certain amount of austenite that can transform to martensite during deformation [7e9]. Dong et al. [10] reported that the product of strength and elongation linearly increases with increase in the austenite volume fraction in TRIP and Twinning-induced plasticity (TWIP) steel: when the austenite volume fraction is greater than 20%, the product of the strength and elongation exceeds 30 GPa%. The corrosion resistance of the material can be improved to meet the requirements of the corrosion environment by adding certain amounts of Cr and Ni. Moreover, while designing advanced high strength and toughness steel, austenite plays a significant role in balancing of strength and ductility [11]. Ni is a common austenite stabilizer [12], whose concentration significantly affects the mechanical properties of steel. Furthermore, Ni is also reported to be beneficial to the pitting corrosion resistance of stainless steels [11,13]. Yi et al. [14] added different contents of Ni to low carbon 13Cr martensitic stainless steel and determined the optimal Ni content interval to achieve good mechanical properties. Similarly, Mn is also an austenite stabilizing element that can be used because of its lower cost. Moreover, the behavior of Mn is very similar to that of Ni as an alloying element in steel [15e17]. Furthermore, addition of lightweight elements such as Al helps to form a duplex structure of ferrite and austenite at high temperatures, and promotes a variety of precipitations and intermetallic phases including k-carbides, NiAl (b0 -phase), Ni3Al, and Ni2AlMn [18,19]. LMD is a laser additive manufacturing (LAM) method that is capable of producing functional dense parts with required shape, which is obtained from a computer aided model (CAD) using metal powder [18,20]. As the computer design, the laser beam melts the metal powder in a melted pool layer by layer [20,21]. The produced deposition material sometimes could achieve even better properties compared to the traditionally processed materials [18,22]. The LMD method could simultaneously deposit more than one type of metal powder, using more than one nozzle by adjusting the powder de€rn Ocylok livery rates in each layer [23]. It was demonstrated by So et al. [24] that graded layers of smooth composition transition with no cracks and low porosity. LMD has been proved to be suitable for a variety of metal systems such as 316SS, nickel base super alloys, and titanium alloys [25e27]. It was also useful for study the functionally graded coatings in complicated systems, e.g., Ti6Al4V/TiC functionally graded sample with excellent wear resistance [23,28e30]. A. Ramakrishnan et al. [31] fabricated a functionally graded metal

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matrix composite successfully and found that as-deposited samples revealed unique microstructures in each layer. Moreover, it was proved that graded metal glass specimens produced by LMD can screen the composition interval of different alloys with glass forming ability [32,33]. Philipp Kürnsteiner et al. [18] used LMD to build Fe-19Ni-xAl maraging and reported the Al concentration range required to achieve superior properties. It showed markedly efficiency and high accuracy corresponding to the traditional methods. In this study, we present a methodology to build composition gradient TRIP stainless steel using LMD method to identify the optimal composition range required for superior mechanical properties. We prepared component gradient samples of 13Cr-xNi(10-x)Mn-3Al to identify the composition range for better properties. High throughput properties measurements, such as composition, hardness, XRD, and surface potential were examined for determining the appropriate component ranges to obtain TRIP stainless steel with enhanced mechanical properties. 2. Materials and experimental methods 2.1. Additive manufacturing for sample preparation An LMD system including a KUKA robotic arm, Samkoon double barrel powder feeder, and Laserline LDF 4000 was employed to produce samples from metal powders. The metal powders were fed using the double barrel powder feeder where the powder particles are conveyed by argon gasdthe powder feeding system could simultaneously achieve feeding through its two independent barrels. Two powder streams were simultaneously entered into the nozzle and then melted using a laser beam in the melting pool with the protection of argon gas. We used a semiconductor laser with a fiber core diameter of 600 mm and a beam diameter of 3 mm. The maximum output of the laser system is 4000 W. Two kinds of metal powders were prepared, and the chemical composition is shown in Table 1. The actual chemical composition is the same as the ideal composition basically. The powders used for this purpose were prepared from commercially pure metal powder and alloy powders including Fe-Cr alloy powder (50e100 mm), FeNi alloy powder (75e100 mm), pure Al powder (50e100 mm) and pure Mn powder (25e100 mm). These powders except Mn powder were produced by atomization. The Mn powder was produced by mechanical method. The SEM images of powders are shown in

Table 3 Powder delivery rate of the two barrels and expected composition of each layer. Layer

Powder 1 delivery rate (mg/min)

1 2 3 4 5 6 7 8 9 10 11

Powder 2 delivery rate (mg/min)

2.5 2.5 2.5 7.5 7.5 12.5 12.5 17.5 17.5 22.5 22.5

22.5 22.5 22.5 17.5 17.5 12.5 12.5 7.5 7.5 2.5 2.5

Expected composition of each layer (wt%) Ni

Mn

Cr

Al

Fe

1 1 1 3 3 5 5 7 7 9 9

9 9 9 7 7 5 5 3 3 1 1

13 13 13 13 13 13 13 13 13 13 13

3 3 3 3 3 3 3 3 3 3 3

Bal. Bal. Bal. Bal. Bal. Bal. Bal. Bal. Bal. Bal. Bal.

Table 4 The tried process parameters. Try parameters Try 1 Try 2 Try 3

Laser power

Laser moving speed

Total powder delivery rate

1600 W 2000 W 2400 W

700 mm/min 700 mm/min 700 mm/min

25 mg/min 25 mg/min 25 mg/min

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K. Zhang et al. / Materials & Design 184 (2019) 108171

Fig. 1 (a) and (b). Then the two prepared powders were mixed in a ball mill mixer separately at a speed of 200 rpm and in argon atmosphere for 2 h to produce a uniform mixture. The SEM images of fixed powders are shown in Fig. 1 (c) and (d). It could be found that the ball milling just mixed the powders and powders dispersed well by the SEM images. We kept the sum of powders delivery rate of two barrels consistent in each layer so the total amount of feed powder is same in each layer. The powders delivery rate of the single barrel was varied in different layers for the building of component gradient steel. Fig. 2 shows the schematic profile of the LMD process of this study and the robotic arm used in the experiment. In this study, a total of 11 layers were deposited on a 9Ni steel substrate. The chemical composition of the substrate is shown in Table 2. The powder delivery rate of the two barrels and the expected composition of each layer is shown in Table 3. The laser power was 2400 W and its speed is 700 mm/min, which was constant in each layer. The parameters were chosen because we tried several different parameters and chose the best one by the surface topography. The

principle of selection is that there is less splash during laser deposition and the surface of the deposited sample is smooth and full. The tried parameters are shown in Table 4. The powder delivery rate in the first three layers was maintained at the same to reduce the influence of the substrate. After confirming that the sample has a component gradient, the sample was subjected to heat treatment: it was first heated to 900  C for 1 h followed by quenching, and then again heated to 500  C for 2 h followed by quenching. The sample was heated to 500  C for 2 h followed by quenching because a variety of precipitations such as NiAl (b0 -phase) and Ni3Al will form at this temperature for precipitation hardening. 2.2. Analytical methods The samples were prepared by abrasive paper grinding using #2000 grit sandpaper followed by polishing. For obtaining the scanning electron microscope (SEM) image, the sample was etched using a corrosive liquid (5 g CuCl2, 40 mL hydrochloric acid, 25 mL ethyl alcohol, and 30 mL distilled water) for 20 s. Compositional

Fig. 3. Trend of elemental distribution and the corresponding cross-section of the sample showing two SEM images in different locations: (a) Elemental distribution of all elements other than Fe along the build direction from the bottom to top of the sample (the detected position is represented by the red solid line in Fig. 3 (b)); (b) Overview of the cross-section of the sample; (c) SEM images of different locations corresponding with the frame color. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

K. Zhang et al. / Materials & Design 184 (2019) 108171

measurements were obtained by energy-dispersive X-ray spectroscopy (EDS) using VEGA 3 XMU SEM (TESCAN Chech) before and after the heat treatment to observe the effect of the heat treatment on the component gradient. The SEM images were also obtained using this equipment. The composition of powders in Table 2 was measured by an Inductively Coupled Plasma Optical (Thermo America). A hardness test was performed using an automatic digital microhardness tester. The hardness was measured at intervals of 350 mm, and a total of 29 locations were measured. X-ray diffraction (XRD) was carried out using BRUKER D8 Advance X-ray Diffractometer (BRUKER Germany), which could measure multiple points continuously. The radiation source is Cu Ka ray. The voltage, current, and increments were set to 40 kV, 35 mA, and 350 mm, respectively; and a total of 29 locations were measured. The scanning Kelvin probe force microscopy (SKPFM) measurement was performed in an atomic force microscopy (AFM) that can measure the morphology and surface potential. The experiment was carried out in air at room temperature. A Pt-Cr tip was used for the SKPFM measurement. When measuring the surface potential, the tip was lifted up to 100 nm from the sample surface and the scan frequency rate is 1 Hz. Furthermore, electron backscatter diffraction (EBSD) was performed using AZtec Nordlys Max3 (Carl Zeiss Germany) to distinguish the phases.

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3. Results and discussion Fig. 3 (a) shows the trend of elemental distribution for all elements along the build direction from the bottom to top of the sample. A line scan mode was chosen and totally 100 points were measured in the line. The detected position is represented by the red solid line in Fig. 3 (b). The result shows that the sample has a component gradient with varying Ni and Mn contents along the build direction and constant Fe, Cr and Al contents basically. In the first few layers, Mn content is greater than Ni content. During the first few layers of deposition, the Ni in the substrate would diffuse to deposition layers so the trend of Ni and Mn concentrations have a plate at the beginning. Fig. 3 (b) shows a cross-sectional view of the sample after polishing and no obvious pores or cracks are observed in the sample. The black arrows in Fig. 3 (a) and (b) indicate the build direction. The SEM images after heat treatment are shown in Fig. 3 (c) and the tested regions are shown by the yellow and green square frames in Fig. 3 (b). The images show that the solidification produced by the LMD process is a typical dendritic microstructure as shown in Fig. 3 (c). Fig. 4 shows the properties of the as-built sample. Hardness measurement position is shown by the black solid line from bottom to top in Fig. 3 (b) and the hardness values are shown in Fig. 4 (a). A total of 29 points were measured

Fig. 4. The hardness message and the SEM images of the as-built sample: (a) The change in hardness from bottom to top (hardness measurement position is shown by the black solid line from bottom to top in Fig. 3 (b)); (b) SEM images of different locations corresponding with the frame color in Fig. 3 (b).

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K. Zhang et al. / Materials & Design 184 (2019) 108171

Fig. 5. Trend of elemental mass fraction and hardness after heat treatment; (a) The hardness points and the corresponding property detection areas; (b) Trend of Ni and Mn mass fraction after heat treatment, which reveals that there is still a component gradient; (c) Hardness distribution map matching with the component (the black dots are data points).

with the interval of 350 mm. It could be seen that all hardness values are less than 460 HV. The SEM images before heat treatment are shown in Fig. 4 (b) and it could be seen that as-built sample also has dendritic microstructure. Fig. 5 (a) shows the hardness indents using as position marks with the interval of 350 mm. All tests including EDS, XRD, and SKPFM were performed in the regions marked by black square frames next to the hardness points. The hardness point is marked in the red square frame and a total of 29 points were measured. Fig. 5 (b) shows

the mass fractions of Mn and Ni of each of the 29 points. The EDS point scan mode was chosen to analyze the composition of each position. It is observed that the basic component gradient is maintained after the heat treatment. The hardness messages of the 29 points are shown in Fig. 5 (c), and the property is matched with the components. Hardness measurement position is also shown by the black solid line from bottom to top in Fig. 3 (b). It is observed that the hardness values range between 300 HV and 600 HV, and most values are higher than 500 HV which means the hardness of the sample is

K. Zhang et al. / Materials & Design 184 (2019) 108171

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Fig. 6. XRD data of each location and the austenite contents calculated from the XRD; (a) XRD data of 29 points shown in one chart; (b) Austenite contents distribution map matching with the component (the black dots are data points).

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K. Zhang et al. / Materials & Design 184 (2019) 108171

Fig. 7. Two separate XRD data; (a) XRD data of 6th point (Ni content is about 2%); (b) XRD data of 27th point (Ni content is about 9%).

greatly improved after heat treatment. In addition, it is observed that as the mass fraction of Ni decreases, the hardness tends to decrease. The points with less than 500 HV hardness are mainly concentrated in the area where the Ni content is less than 4%. This may be defined as a bound of element concentration range required to achieve better mechanical properties for TRIP stainless steel. The XRD results are shown in Fig. 6 (a), which reveal the change in the diffraction peaks of austenite and ferrite. Fig. 6 (b) shows the austenite contents distribution map matching with the component. The austenite content at each point was calculated from the corresponding XRD data: the points at which the austenite content values are higher are mainly concentrated in the areas with low Ni mass

fraction. The equation for austenite calculation is shown as below:

0 1,20 1 I gj Igj 1Xq 1Xp @ A 4 @ A Vg ¼ ¼1 ¼1 j q p j Rgj Rgj 0 13 Xq Igj 1 A5 þ@ ¼1 j q Rgj

(1)

In this equation, I is the diffraction peak integral intensity. R is the material scattering factor. And q and p are the number of corresponding diffraction peaks of each phase. The diffraction

K. Zhang et al. / Materials & Design 184 (2019) 108171

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Fig. 8. Average surface potential of each location to compare the corrosion resistance ability; (a) Average surface potential distribution map matching with the component (the black dots are data points); (b) Map of the surface potential of 14th point (Ni content is about 4%) and 18th point (Ni content is about 5%) in the region where Ni content is between 3%e6% and Mn content is between 4%e7%.

intensities of (200) g, (220) g, (311) g, (200) a, (211) a and (220) a peaks were measured by XRD to calculate the austenite content. Fig. 7 shows the two separate XRD data: one having both body center cubic and face center cubic phase and the other having only the body center cubic phase. Considering the product of the strength and elongation, a certain amount of austenite is required [10]. As the high hardness points are mainly observed in the areas with high Ni mass fraction while the higher austenite content points are observed in the areas with low Ni mass fraction, a medium Ni concentration may be suitable for obtaining a product of high strength and elongation with superior properties. To compare the corrosion resistance at different positions, the surface potential was tested every two points in the black frame region as shown in Fig. 5 (a). The surface potential indicating the tendency of corrosion is the potential difference at the contact between the sample and the probe of the atomic force microscope [34,35]. Fig. 8 (a) shows that in areas where Ni and Mn have

medium concentrations, the surface potential has a high value compared to the other locations, which corresponds to a higher corrosion resistance. Fig. 8 (b) is the map of the surface potential of the 14th point (Ni content is about 4%) and 18th point (Ni content is about 5%). It is observed that the location of the 18th point has a higher average surface potential than the 14th point, and the potential distribution is relatively uniform. For the discovery of the component interval in which the TRIP stainless steel has better mechanical properties, we identified the positions at which hardness, austenite content, and surface potential values were better and placed them on a binary composition map, as shown in Fig. 9. The divided values are listed in the chart. As mentioned earlier, according to the study by Dong et al., when the austenite volume fraction is greater than 20%, the product of the strength and elongation exceeds 30 GPa%. Therefore, we chose a value higher than 20% for austenite content as the divided value in this study. It is observed that the three different values coincide in

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Fig. 9. Region have better mechanical properties marked by the blue ellipse overall considering the hardness, austenite content and surface potential, plotted on a binary composition map. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 10. Phase distribution at different locations of multicomponent TRIP stainless steel: the red region is the austenite (fcc structure) and the blue region is the martensite (bcc structure). The frame color reveals the texted locations on the sample as shown in Fig. 2 (b). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

K. Zhang et al. / Materials & Design 184 (2019) 108171

the region where the Ni content is between 3%e6% and Mn content is between 4%e7%. This can be considered as the range for Ni and Mn content required to achieve superior mechanical properties for the TRIP stainless steel. Yi et al., using a traditional bulk steel sample preparation, observed that the most suitable range for Ni content is 3.5%e6%, which has a component system similar to that used in this study [14]. EBSD is a suitable method to distinguish the phases. To confirm the austenite content trend calculated from the XRD, EBSD was performed at three different positions, as shown in Fig. 10. The frame color shows the tested positions in Fig. 3 (b). The white phase is the zero resolution zones. It is observed that in the middle location, the austenite content is much higher than that in the top and bottom locations. From the bottom through the middle to the top, the austenite content calculated from the figures is 3.39%, 25.1%, and 4.24%, respectively. This result is similar to that obtained by XRD. In this study, component gradient steel 13Cr-xNi-(10-x)Mn-3Al was built by the LMD method. Using the hardness point as a reference to achieve a consistent composition and performance and examining the hardness, austenite content, and surface potential, a better component interval was obtained. The identified optimal ranges for the Ni and Mn contents were 3%e6% and 4%e7%, respectively. This study, in an attempt to improve the efficiency of steel development, demonstrated the effectiveness of the LMD method to develop component gradient steel for accelerating the steel development. Furthermore, the findings of this study provide a guide for exploring the relationship between chemical composition, microstructure, and mechanical properties in order to design economic steels with a high product of strength and elongation. 4. Conclusions 1. The 13Cr-xNi-(10-x)Mn-3Al TRIP effect stainless steel with continuous graded composition was successfully built using LMD method with appropriate laser and tool path parameters. There were no obvious pores or cracks found on the surface of the cross-section. With this method, a significant chemistry variation was built into one small specimen. Microregional properties measurements, such as EDS, hardness, XRD, and SKPFM were examined for determining the appropriate component ranges to obtain TRIP stainless steel with enhanced mechanical properties. 2. The produced component gradient TRIP effect stainless steel in the range of Ni 3%e6% and Mn 4%e7% have the combination properties of high product of strength and elongation and good corrosion resistance assessed by hardness, austenite content and surface potential. The results are in good agreement with the data from traditional experiments. In the optimistic composition range, the hardness is higher than 500 HV and the austenite volume fraction is more than 20%.

Credit author statement Kuan Zhang, Wei Li, Yuantao Xu, Yu Li and Xuejun Jin developed the concept. Kuan Zhang, Yuantao Xu and Binggang Liu synthesized the samples and conducted the experiments. Kuan Zhang, Wei Li and Yuantao Xu analysed the data and co-wrote the paper. Danying Liu and Xifan Ding beautified the charts. All the authors discussed the whole paper. Acknowledgments The authors are thankful to the financial support of the National

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Key Research and Development Program of China (No. 2017YFB0703003), National Natural Science Foundation of China (U1564203, Nos. 51571141 and 51201105), and the Interdisciplinary Program of Shanghai Jiao Tong University (No. YG2014MS23). The authors gratefully acknowledge the support provided by the Tescan China. References [1] R. Chen, G. Qin, H. Zheng, et al., Composition design of high entropy alloys using the valence electron concentration to balance strength and ductility, Acta Mater. 144 (2018) 129e137. [2] Y.M. Wang, T. Voisin, J.T. McKeown, et al., Additively manufactured hierarchical stainless steels with high strength and ductility, Nat. Mater. 17 (2018) 63. [3] B. Schuh, R. Pippan, A. Hohenwarter, Tailoring bimodal grain size structures in nanocrystalline compositionally complex alloys to improve ductility, Mater. Sci. Eng. 748 (2019) 379e385. [4] W.W. Sun, Y.X. Wu, S.C. Yang, et al., Advanced high strength steel (AHSS) development through chemical patterning of austenite, Scr. Mater. 146 (2018) 60e63. [5] M. Bhargava, S. Chakrabarty, V.K. Barnwal, et al., Effect of microstructure evolution during plastic deformation on the formability of transformation induced plasticity and quenched & partitioned AHSS, Mater. Des. 152 (2018) 65e77. [6] X. Wang, C. Yang, B. Rolfe, Numerical simulations on warm forming of stainless steel with TRIP-effect, AIP Conf. Proc. 1252 (2010) 595e601. [7] Q. Ran, Y. Xu, J. Li, et al., Effect of heat treatment on transformation-induced plasticity of economical Cr19 duplex stainless steel, Mater. Des. 56 (2014) 959e965. €tter, Properties and application of TRIP-steel in [8] E. Doege, S. Kulp, C. Sunderko sheet metal forming, Steel Res. 73 (2002) 303e308. €ssel, L. Krüger, G. Frommeyer, et al., High strength FeeMne(Al, Si) TRIP/ [9] O. Gra TWIP steels developmentdpropertiesdapplication, Int. J. Plast. 16 (2000) 1391e1409. [10] H. Dong, X. Sun, W. Cao, et al., On the performance improvement of steels through M 3 structure control, Adv. Steels (2011) 35e57. [11] C. Man, C. Dong, D. Kong, et al., Beneficial effect of reversed austenite on the intergranular corrosion resistance of martensitic stainless steel, Corros. Sci. 151 (2019) 108e121. [12] X.P. Ma, L.J. Wang, C.M. Liu, et al., Microstructure and properties of 13Cr5Ni1Mo0.025Nb0.09V0.06N super martensitic stainless steel, Mater. Sci. Eng. A 539 (2012) 271e279. [13] X. Lei, Y. Feng, J. Zhang, et al., Impact of reversed austenite on the pitting corrosion behavior of super 13Cr martensitic stainless steel, Electrochim. Acta 191 (2016) 640e650. [14] Bangwang Yi, Xuejun Qian, Wenyun Lang, et al., The influence of the Nicontent on properties of 13Cr-series low carbon martensitic stainless steel, Met. Funct. Mater. (1997) 75e78. [15] F. Qian, J. Sharp, W.M. Rainforth, Microstructural evolution of Mn-based maraging steels and their influences on mechanical properties, Mater. Sci. Eng. A 674 (2016) 286e298. [16] K.H. Kwon, I.C. Yi, Y. Ha, et al., Origin of intergranular fracture in martensitic 8Mn steel at cryogenic temperatures, Scr. Mater. 69 (2013) 420e423. [17] C. Herrera, D. Ponge, D. Raabe, Design of a novel Mn-based 1 GPa duplex stainless TRIP steel with 60% ductility by a reduction of austenite stability, Acta Mater. 59 (2011) 4653e4664. [18] P. Kürnsteiner, M.B. Wilms, A. Weisheit, et al., Massive nanoprecipitation in an Fe-19Ni-xAl maraging steel triggered by the intrinsic heat treatment during laser metal deposition, Acta Mater. 129 (2017) 52e60. [19] E.V. Pereloma, A. Shekhter, M.K. Miller, et al., Ageing behaviour of an Fee20Nie1.8 Mne1.6 Tie0.59 Al (wt%) maraging alloy: clustering, precipitation and hardening, Acta Mater. 52 (2004) 5589e5602. [20] K.I. Schwendner, R. Banerjee, P.C. Collins, et al., Direct laser deposition of alloys from elemental powder blends, Scr. Mater. 45 (2001) 1123e1129. [21] B. Graf, A. Gumenyuk, M. Rethmeier, Laser metal deposition as repair technology for stainless steel and titanium alloys, Phys. Procedia 39 (2012) 376e381. [22] G.K. Lewis, E. Schlienger, Practical considerations and capabilities for laser assisted direct metal deposition, Mater. Des. 21 (2000) 417e423. [23] R.M. Mahamood, E.T. Akinlabi, Laser metal deposition of functionally graded Ti6Al4V/TiC, Mater. Des. 84 (2015) 402e410. [24] S. Ocylok, A. Weisheit, I. Kelbassa, Functionally graded multi-layers by laser cladding for increased wear and corrosion protection, Phys. Procedia 5 (2010) 359e367. [25] Z. Sun, X. Tan, S.B. Tor, et al., Selective laser melting of stainless steel 316L with low porosity and high build rates, Mater. Des. 104 (2016) 197e204. [26] J. Li, H.M. Wang, Microstructure and mechanical properties of rapid directionally solidified Ni-base superalloy Rene’41 by laser melting deposition manufacturing, Mater. Sci. Eng. A 527 (2010) 4823e4829. [27] C.M. Liu, X.J. Tian, H.B. Tang, et al., Microstructural characterization of laser melting deposited Tie5Al-5Moe5Ve1Cre1Fe near b titanium alloy, J. Alloys

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