Effect of trace elements on the pinhole fatigue-resistance of gasoline Al-Si piston alloy

Journal Pre-proofs Effect of trace elements on the pinhole fatigue-resistance of gasoline Al-Si piston alloy Tang Wei-chen, Piao Zhong-yu, Zhang Jian, Liu Shi-ying, Deng Li-jun PII: DOI: Reference:

S1350-6307(19)30952-5 https://doi.org/10.1016/j.engfailanal.2019.104340 EFA 104340

To appear in:

Engineering Failure Analysis

Received Date: Revised Date: Accepted Date:

3 July 2019 22 November 2019 22 November 2019

Please cite this article as: Wei-chen, T., Zhong-yu, P., Jian, Z., Shi-ying, L., Li-jun, D., Effect of trace elements on the pinhole fatigue-resistance of gasoline Al-Si piston alloy, Engineering Failure Analysis (2019), doi: https:// doi.org/10.1016/j.engfailanal.2019.104340

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

© 2019 Published by Elsevier Ltd.

Effect of trace elements on the pinhole fatigue-resistance of gasoline Al-Si piston alloy Tang Wei-chena, Piao Zhong-yua,, Zhang Jianb,, Liu Shi-yingc, Deng Li-junb （a. Key Laboratory of Special Purpose Equipment and Advanced Processing Technology (Zhejiang University of Technology), Ministry of Education, Hangzhou 310014, China; b. College of Electromechanical Engineering, Binzhou University, Binzhou 256600, China; c. School of Transportation and Vehicle Engineering, Shandong University of Technology, Zibo 255000, China） Abstract: Trace elements, i.e., Cu, Ni, Zr and V are added into Al-Si piston alloy to optimize the phase structure. Micro-structures and fatigue performances are discussed. The stress state of pinhole inner-surface is investigated by finite element method (FEM). The comparative tests of original piston alloy and modified piston alloy are conducted on a specialized piston fatigue setup under the same condition as a real engine, and then the fracture analyses are addressed to discuss the relevant mechanisms. Results show the content and size of primary Si particles are restrained after the addition of trace elements. The ultimate tensile strength (UTS) and high cycle (HC) fatigue strength of modified piston alloys under high temperature are increased obviously. The increase of



Corresponding author, Zhejiang University of Technology, Hangzhou 310014, China. E-mail address: [email protected]  Corresponding author, Binzhou University, Binzhou 256600 China. E-mail address: [email protected]

intermetallics and decrease of primary Si are the main reasons. Keyword: trace elements; piston alloy; pinhole; fatigue fracture 1 Introduction Pistons as the key parts of automobile engine always suffer extra-high thermal and mechanical load. Under the effects of thermal and mechanical stresses, the failure processes of pistons or the parts of pistons need to be focused specially, such as pinhole [1-4]. Pinholes usually works under complicated conditions. Heat, deformation and contact all can result in the failure of pinholes. Fatigue fracture is the main failure mode of pinhole [5, 6]. The fatigue cracks often initiate on upper part of pinhole inner-surface where contact the pin directly [7-9]. There are many reasons for the fatigue failure of pinhole, such as the insufficient lubrication, large fitting clearance between pin and pinhole, pinhole deformation and low surface quality [10-13]. The improvement of the material performance is recognized as one of the main approaches to resist fatigue failure of pinhole. Al-Si based alloys are the common materials for fabricating automobile pistons. Other elements are usually added to Al-Si basis to increase the performance [14, 15]. There are many reports about this topic. Yang et al [16] investigated the effects of different existing forms of Si, Cu, Ni and Mg on the microhardness of Al-Si piston alloy. Results show the precipitated Si has the advantage in improving the microhardness of alloy comparing to the solid-solved Si. Moreover, the hardening efficiency of the intermetallic precipitation of Cu, Mg and Ni on improving microhardness is also less than that of the nanoscale precipitated Si under the same mass fraction. Qian et al [17]

investigated the effects of different amount of trace Mn addition on the elevated temperature tensile strength and microstructure of a low-iron Al-Si piston alloy. Results show an appropriate mass of Mn addition is positive to strengthen the piston alloy. Whereas, too many Mn addition will result in the negative effect. Han et al [18] reported the effects of Nd content on the microstructure and mechanical properties of gravity cast Al-12Si-4Cu-2Ni-0.8Mg alloys. Image analysis method is introduced to quantitatively reveal the evolution of phase and texture under different Nd contents, and then the influence of Nd content on fatigue performance of piston alloy is also investigated. Results show the appropriate Nd content can increase the ultimate tensile strength (UTS) obviously. Generally, the appropriate additions of other elements are helpful for optimizing fatigue-resistance of piston alloy. In the present paper, the influence of addition of trace elements, i.e., Cu, Ni, Zr and V, on the fatigue-resistance of Al-Si piston alloy is investigated. Two types of pistons with different contents of trace elements were fabricated, respectively. Subsequently, the comparative investigation of performances of two types of pistons were conducted on specialized setup under the same condition as real engines. The failure analysis was completed based on micro-observations and image analysis method. The finite element method (FEM) was used to discuss the relevant mechanism. 2 Experimental methods 2.1 Piston materials and characterization Two types of piston alloy were used to fabricate gasoline pistons in the present paper. They both belong hypereutectic Al-Si alloys, the excellent performance of

hypereutectic alloy is suitable for using as piston material. The piston alloys before and after the additions of trace elements are defined as original piston alloy and modified piston alloy, respectively. The detailed compositions of two piston alloys are listed in Table 1. In the modified piston alloy, the contents of Cu and Ni are enhanced to increase the fatigue-resistance, especially, under high-temperature condition. Simultaneously, Zr and V are also added as new elements to increase grain refinement and homogenization. Accordingly, the contents of Si and Fe are reduced. The purpose of reducing Si content is to restrain the content of primary Si in piston alloy. Simultaneously, rice iron phases are recognized negative to fatigue-resistance. Universal fatigue testing machine is employed to test UTS and high cycle (HC) fatigue strength of two types of piston alloys, respectively. Scanning electron microscope (SEM) is employed to characterize the phase and texture of two piston alloys. Additionally, the image analysis method is employed to distinguish the grain sizes and phase morphologies within two piston alloys. For each image analysis, ten random SEM images are used to ensure the accuracy. Table 1 The detailed compositions of two types of piston alloys (wt.%) Elements

Si

Cu

Ni

Mg

Mn

Ti

Fe

Original piston alloy Modified piston alloy

14.818.0 10.013.0

1.92.9 3.03.8

0.30.8 2.02.7

0.51.0 0.51.0

≤ 0.2 ≤ 0.2

≤ 0.2 ≤ 0.2

≤ 0.8 ≤ 0.5

Zr

V

Al

-

-

Balance

≤ 0.2

≤ 0.2

Balance

2.2 Test setup A specialized test setup developed by INSTRON is introduced to conduct single item test of piston, i.e., fatigue test. This setup can simulate the same working condition as

the real engine. Fig.1 shows the photo of test setup and schematic diagram of control process. The setup is consisted of dynamical system, compute-control system and mechanical system. The high-press hydraulic oil is supported by a hydraulic pump station. A specialized computer-control system is used to control this high-press value. In the present test, the loads are applied on piston through the sinusoidal waveform. The piston is fixed on the bracket by a piston pin. The piston and the sealing piston ring divide the loading cavity into two independent cavities. In the test, the upper and lower loading oil cavities are applied sinusoidal load at the same loading frequency with 180° phase difference, respectively. Because the pinhole fatigue is mainly affected by the high-pressure resulted from gasoline explosion, 120% of the actual maximum burst pressure is used as the peak pressure to accelerate fatigue processes of pinholes. The tests of two types of pistons are stopped after 107 reciprocating cycle times of pistons. Subsequently, the pistons are detected and characterized. The detailed operating parameters during the abovementioned tests are listed in Table 2. After the characterizations, these pistons are reassembled on setup and tested until piston fractures. Finally, the fracture analyses are conducted to compare the fatigue-resistances of two types of pistons.

Fig.1 Photo and schematic diagram of control process of piston fatigue test setup

Table 2 Main parameters of piston fatigue test Operating parameters

Value/type

Hydraulic oil type Pressure at top of piston Hydraulic oil temperature Frequency Reciprocating cycle times

DTE-25 10.5MPa 55℃ 15Hz 107cycles

2.3 FEM model FEM is an appropriate approach for analyzing the stress state of pinhole during engine working, especially, in the expansion stroke, because the main damages of piston always occur in the expansion stroke [19, 20]. PISTYN as a specialized FEM software to simulate process of piston working is employed to analyze the stress state in the present paper. Because when the piston is working, the temperature around the pinhole is high. Thus, the temperature field of pinhole is one of the most important boundary conditions for the simulation based on PISTYN. To improve the accuracy of temperature field analysis, ANSYS is introduced to analyze the temperature distribution on the pinhole inner-surface at the gasoline explosion point. At the explosion point, the pinholes are suffered the maximum pressure. An axisymmetric model is established to improve the calculating efficiency. Fig.2 shows axisymmetric model after meshing. The material properties and boundary conditions are defined, such as the initial temperature and contact state. During numerical simulation, the detailed parameter about engine is listed in Table 3.

Fig.2 Axisymmetric model after meshing Table 3 Engine parameters

Parameter

Cylinder diameter (mm)

Pin hole diameter (mm)

Stroke (mm)

Power (kW/L)

Peak pressure (MPa)

Compression ratio

Peak power/speed (kW/rpm)

Value

76.5

19

85.9

49.8

8.8

10.2

79/5000

Cylinder gas temperature and gas convection heat transfer coefficient are important boundary conditions for temperature field analysis based on ANSYS. In order to set the exact temperature-dependent boundary conditions, temperature measurements of key points around the pinhole are conducted on real engine test. Templug method is used to conduct the temperature measurements of key points. Fig.3 shows the distribution of 11 key points for temperature measures. Most of these points are around the top surface of piston, where is suffered the highest heat from the gasoline explosion. The temperature measurements of two cylinders assembled the original and modified pistons are conducted to ensure the accuracy of results, respectively. Fig.4 shows the results of temperature measurements of two types of pistons. Subsequently, these results are used to validate the temperature distribution from FEM. When the results of numerical simulation are consistent with the results of temperature measurements, these results of numerical simulation can be furtherly used in PISDYN as boundary conditions. Finally, the value and distribution of pressure and shear stress on the pinhole

inner-surface are calculated by PISDYN.

Fig.3 Distribution of key points for temperature measures

Fig.4 Temperature distributions of two types of pistons 3 Results and discussions 3.1 Micro-structures and fatigue resistance Fig.5 and Fig.6 show the cross-sectional morphologies of original and modified piston alloy, respectively. The additions of trace elements change the micro-structure of piston alloy. Especially, the content and size of primary Si (indicated by red arrows) is reduced after the addition of Cu, Ni, Zr and V. Simultaneously, the distribution of intermetallic (gray phases in SEM image) is more uniform in modified piston alloy. The contents and sizes of primary Si and intermetallic are analyzed by abovementioned image analysis method. Fig.7 shows the addition of trace elements indeed reduces the

content of primary Si and obviously increases the content of intermetallic. Fig.8 shows the results of phase sizes of primary Si and intermetallic. After the addition of trace elements, the sizes of primary Si are reduced. Conversely, the sizes of intermetallic are increased. The additions of Zr and V are the main reasons. The primary Si particles are usually recognized as the origins of fatigue cracks. The comparative investigations of UTS and HC fatigue strengths of two types of pistons are conducted under different ambient temperatures. Triplicate experiments are conducted to clarify the reproducibility of experimental results. The detailed experimental results are listed in Table 4, the results show the reproducibility is ideal. Fig.9 shows UTS and HC fatigue strengths of two types of piston alloys. The curves show UTS and HC fatigue strength tend to decrease as a function of the a “pseudo over-aging” between 150℃ and 180℃. Generally, under the lower temperature condition (below 250℃), the modified piston alloy don’t exhibit obvious advantage. Whereas, as the increase of working temperature (more than 250℃), both UTS and HC fatigue strength of modified piston alloy are obviously higher than original piston alloy. The real temperatures during engine working are always around or above 250℃ as shown in Fig.4. Theoretically, the modified piston alloy has better performance in resisting fatigue fracture of pinhole.

Table 4 Experimental results of UTS and HC fatigue strengths Temperature ／℃ 25 50 100 150 200 250 300 350

UTS-Original

UTS-Modified

HC-Original

HC-Modified

／MPa

／MPa

／MPa

／MPa

260 254 245 241 183 127 81 57

256 250 243 238 180 124 79 55

264 258 247 244 186 130 83 59

250 242 238 232 181 127 84 66

247 240 235 230 180 125 83 64

253 244 241 234 182 129 85 68

115 113 110 98 82 59 43 34

113 110 108 96 81 58 42 33

117 116 112 100 83 60 44 35

97 97 95 90 77 67 50 43

96 95 92 86 75 65 49 41

98 99 98 94 79 69 51 45

Fig.5 Cross-sectional morphology of original piston alloy, (a) low magnification, (b) high magnification

Fig.6 Cross-sectional morphology of modified piston alloy, (a) low magnification, (b) high magnification

Fig.7 Contents of primary Si and intermetallic in two types of piston alloys

Fig.8 Sizes of primary Si and intermetallic in two types of piston alloys

Fig.9 Comparisons of UTS and HC fatigue strength of two types of piston alloys

3.2 Analysis of pressure state on pinhole The analysis and simulation of temperature field is the premise of simulation of pressure state on pinhole. Fig.10 shows the analysis result of temperature field on pinhole at the explosion point based on ANSYS. Although there are some differences in material compositions of two pistons, there are no obvious differences on temperature distribution. Generally, the top half is subjected to higher temperature for close to the explosion point, then the temperature gradually decreased along the radial. These results of temperature fields are inputted into PISDYN to analyze the pressure state on pinhole as boundary conditions.

Fig.10 Temperature fields on pinhole inner-surfaces, (a) original piston alloy, (b) modified piston alloy Fig.11 shows the pressure states on pinholes fabricated by different piston alloys. Fig.11(a) shows the angular distribution of pinhole for good comprehension of simulation results. Fig.11(b) and (c) show the pressure distribution on two pinhole inner-surfaces, respectively. Because the line-types of pinhole inner-surface are symmetrical, the pressure distributions are also symmetrical. To improve calculating efficiency, only pressure states of half of pinhole inner-surface are analyzed as shown

in Fig.11(b) and (c). The tendencies of contact pressure distributions of two types of piston alloys are similar. From axial direction, the maximum pressure always appears near the pinhole face. From circumference direction, the maximum pressure always appears at 270° position. Fig.12 shows the shear stress states on pinholes. Fig.12(a) also shows the angular distribution of pinholes. Fig.12(b) and (c) show the shear stress distribution on two pinholes, respectively. The distributions of maximum shear stresses are similar with pressures on two pinholes. Obviously, contact pressure and shear stress are both reduced after the additions of trace elements. The coefficients of thermal expansion and heat conduction are changed after modification. Thus, the pinhole of modified piston alloy has stronger anti-deformation ability. The roundness comparation is also conducted by roundness meter as shown in Fig.13. Both the two types of pinholes are elongated after 107 reciprocating cycles owing to the higher pressure and shear stress near pinhole face as shown in Fig.11 and Fig.12. Obviously, the pinhole of original piston alloy exhibits more severe deformation than modified piston alloy. That reveals the anti-deformation ability of piston alloy is indeed improved after the addition of trace elements. On another hand, there deformations are positive to resist the fracture in pinhole edges. Because plastic deformation can absorb and accommodate dislocations and slips, there will not fractures in pinhole edges. Whereas, there are no enough spaces to absorb material flow under pressure and shear stress in the pinhole inner-surface. Thus, the probabilities of fractures are comparatively higher.

Fig.11 Pressure distribution on pinhole, (a) angular distribution of pinhole, (b) original piston alloy, (c) modified piston alloy

Fig.12 Shear stress distribution on pinhole, (a) angular distribution of pinhole, (b) original piston alloy, (c) modified piston alloy

Fig.13 Roundness measurements of pinholes, (a) original piston alloy, (b) modified piston alloy 3.3 Fracture analysis The pinhole inner-surfaces of two types of piston alloys are detected by penetrating flaw detecting technique, then the surface morphologies were observed by SEM. Fig.14 shows the surface damages on two pinholes after 107 reciprocating cycles. The cracks are indicated by arrows. Obviously, there are more cracks on pinhole fabricated by the

original piston alloy. Additionally, the cracks on both two types of pinholes mostly locate near the pinhole faces. These phenomena are consistent with the results of stress state from numerical simulation based on PISDYN. Although the maximum pressure and shear stress locate in pinhole edges, the regions near pinhole face are also subjected to higher stresses, as shown in Fig.11 and Fig.12. Thus, the contact pressure and shear stress are the main drivers of these cracks.

Fig.14 Surface cracks on pinholes, (a) original piston alloy, (b) modified piston alloy After the observations of pinhole surfaces, two pinholes were reassembled on test setup to run until the piston thoroughly fractured. Then the fracture morphologies of two types of pistons were observed, respectively. Fig.15 shows the fracture morphology of pinhole fabricated by original piston alloy. The fracture surface exhibits the characteristic of brittle fracture (indicated by arrows). The primary Si particles with large sizes are the origins of these brittle fractures. Additionally, the higher content of primary Si in original piston alloy also increases the brittleness of the whole piston. Thus, the original piston locally exhibits brittle fractures. Fig.16 shows XRD spectrums of original and modified piston alloys. The higher contents of Cu and Ni generate many intermetallics in modified piston alloy, such as FeNiAl9 and Al7Cu4Ni. Fig.17(a) shows

the fracture morphology of pinhole fabricated by modified piston alloy. The fracture surface exhibits the characteristic of ductile fracture. There are many dimples on the fracture surface, indicated by arrows in Fig.17(b). The lower content of primary Si is a main reason of the increase of toughness of piston. Fig.17(c) and (d) show intermetallics in modified piston alloy, these intermetallics have excellent deformation capacities and obviously improve the fatigue-resistance of piston. Generally, the piston alloy is optimized in terms of resisting fatigue fracture after the addition of trace elements. Limitation of primary Si and increase of intermetallics both are the main reasons.

Fig.15 Fracture morphology of pinhole fabricated by original piston alloy, (a) low magnification, (b) high magnification

Fig.16 XRD spectrums of original and modified piston alloys

Fig.17 Surface morphology and phase of pinhole fabricated by modified piston alloy, (a) Fracture morphology, (b) high magnification, (c) FeNiAl9 intermetallic, (d) Al7Cu4Ni intermetallic 4 Conclusions (1) Cu, Ni, Zr and V are added in the traditional piston alloy to modify the fatigue performance. The content of primary Si is decreased and the content of intermetallic is increased after the addition of trace elements. UTS and HC fatigue strength of modified piston alloy are obviously improved, especially, when the ambient temperature is above 250℃. (2) The maximum pressure and shear stress on pinhole inner-surface during piston working are investigated by FEM. The pinhole edges are suffered maximum pressure and shear stress. Simultaneously, the regions near the pinhole face are also subjected to higher pressure and shear stress. (3) Fracture analysis revealed that primary Si particles are the potential origins of fatigue cracks. Whereas, intermetallic can increase the toughness of piston and restrain the fatigue fracture. That is reason for the fatigue-resistance of piston alloy became better after the addition of trace elements.

Acknowledgements This project is supported by National Natural Science Foundation of China (Grant No. 51675483, 51705028, 51305397), Natural Science Foundation of Shandong Province (Grant No. ZR2016EEB36), Fundamental Research Funds for the Provincial Universities of Zhejiang (RF-A2019008), Foundation (61409230606). Reference [1] F. Szmytka, M. Salem, F. Rézaï-Aria, A. Oudin, Thermal fatigue analysis of automotive Diesel piston: Experimental procedure and numerical protocol, International Journal of Fatigue 73(Supplement C) (2015) 48-57. [2] L. Witek, Failure and thermo-mechanical stress analysis of the exhaust valve of diesel engine, Eng. Fail. Anal. 66(Supplement C) (2016) 154-165. [3] P. Obert, T. Müller, H.-J. Füßer, D. Bartel, The influence of oil supply and cylinder liner temperature on friction, wear and scuffing behavior of piston ring cylinder liner contacts – A new model test, Tribology International 94(Supplement C) (2016) 306314. [4] Z.Y. Piao, Z.Y. Zhou, J. Xu, H.D. Wang, Use of X-ray Computed Tomography to Investigate Rolling Contact Cracks in Plasma Sprayed Fe-Cr-B-Si Coating, Tribology Letters 67(1) (2019) 8. [5] W. Qin, J. Li, Y. Liu, J. Kang, L. Zhu, D. Shu, P. Peng, D. She, D. Meng, Y. Li, Effects of grain size on tensile property and fracture morphology of 316L stainless steel, Materials Letters 254 (2019) 116-119. [6] D.Z. Meng, G. Yan, W. Yue, F. Lin, C.B.A. Wang, Thermal damage mechanisms of Si-coated diamond powder based polycrystalline diamond, J. Eur. Ceram. Soc. 38(13) (2018) 4338-4345. [7] T.O. Mbuya, P.A.S. Reed, Micromechanisms of short fatigue crack growth in an Al–Si piston alloy, Materials Science and Engineering: A 612(Supplement C) (2014) 302-309. [8] Y. Wang, L.M. Wu, S. Liu, M. Li, Y. Cui, Fretting fatigue optimization of piston skirt top surface of marine diesel engine, Proc. Inst. Mech. Eng. Part C-J. Eng. Mech. Eng. Sci. 233(4) (2019) 1453-1469. [9] Z.Y. Piao, B.S. Xu, H.D. Wang, X.X. Yu, Rolling Contact Fatigue Behavior of Thermal-Sprayed Coating: A Review, Critical Reviews in Solid State and Materials Sciences. [10] G. Han, W. Zhang, G. Zhang, Z. Feng, Y. Wang, High-temperature mechanical properties and fracture mechanisms of Al–Si piston alloy reinforced with in situ TiB2 particles, Materials Science and Engineering: A 633(Supplement C) (2015) 161-168. [11] A.R.A. Al-Samarai, Haftirman, K.R. Ahmad, Y. Al-Douri, Effect of Roughness of Hypo-and Hyper-Eutectic Al-Si Piston Alloy on Wear Characteristics under

Lubrication, Procedia Engineering 53(Supplement C) (2013) 616-623. [12] Y. Li, Y. Yang, Y. Wu, Z. Wei, X. Liu, Supportive strengthening role of Cr-rich phase on Al–Si multicomponent piston alloy at elevated temperature, Materials Science and Engineering: A 528(13) (2011) 4427-4430. [13] B. Zabala, A. Igartua, X. Fernández, C. Priestner, H. Ofner, O. Knaus, M. Abramczuk, P. Tribotte, F. Girot, E. Roman, R. Nevshupa, Friction and wear of a piston ring/cylinder liner at the top dead centre: Experimental study and modelling, Tribology International 106(Supplement C) (2017) 23-33. [14] W.R. Osorio, C.A. Siqueira, C.A. Santos, A. Garcia, The Correlation between Electrochemical Corrosion Resistance and Mechanical Strength of As-Cast Al-Cu and Al-Si Alloys, International Journal Of Electrochemical Science 6(12) (2011) 62756289. [15] M. Wang, J.C. Pang, H.Q. Liu, S.X. Li, Z.F. Zhang, Influence of microstructures on the tensile and low-cycle fatigue damage behaviors of cast Al12Si4Cu3NiMg alloy, Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process. 759 (2019) 797-803. [16] Y. Yang, Y. Li, W. Wu, D. Zhao, X. Liu, Effect of existing form of alloying elements on the microhardness of Al–Si–Cu–Ni–Mg piston alloy, Materials Science and Engineering: A 528(18) (2011) 5723-5728. [17] Z. Qian, X. Liu, D. Zhao, G. Zhang, Effects of trace Mn addition on the elevated temperature tensile strength and microstructure of a low-iron Al–Si piston alloy, Materials Letters 62(14) (2008) 2146-2149. [18] L. Han, Y. Sui, Q. Wang, K. Wang, Y. Jiang, Effects of Nd on microstructure and mechanical properties of cast Al-Si-Cu-Ni-Mg piston alloys, J. Alloy. Compd. 695(Supplement C) (2017) 1566-1572. [19] J. Zhang, Z. Piao, S. Liu, Influence of Skirt Profile Structure of Gasoline Engine Piston on the Friction and Wear Characteristics Under Standard Conditions, Journal of Tribology 140(2) (2017) 021703-021703-11. [20] J. Zhang, H. Li, Influence of manganese phosphating on wear resistance of steel piston material under boundary lubrication condition, Surface and Coatings Technology 304(Supplement C) (2016) 530-536.



Trace elements were added to Al-Si piston alloy to improve fatigue-resistance.



FEM was used to investigate the stress state during piston working.



Additions of trace elements restrained the primary Si and increased intermetallic.

 