Evaluation of the partitioned mechanical properties and the hall-petch relationship of cast aluminum alloy cylinder head

Kangjie Yan,Zhengxing Zuo,Dingyun Hu,Jinxiang Liu,Weiqing Huang,Chengzhang Zhao,Peirong Ren,J Zhu

doi:10.1051/matecconf/202235501003

Abstract

In view of the non-uniform distribution of mechanical properties of cast aluminum alloy cylinder head, the mechanical properties evaluation and microstructure heterogeneity of cylinder head were studied. The results showed that the head plate position of the cylinder head has the best mechanical properties and microstructure characterization, followed by the floor plate and the thick partition plate. The mechanical properties of the floor plate position attenuate with increasing temperature. From 23°C to 300°C, the tensile strength and yield strength decrease in the same range, but the break elongation changes most obviously. The mechanical properties and microstructure characterization of cylinder head in-situ sampling satisfy the Hall-Petch relationship. If the required ultimate tensile strength is not less than 255MPa, the upper threshold of the grain size, by considering the error limit of the Hall-Petch relationship, is 603.4μm, and the upper threshold of secondary dendrite arm spacing is 69.1μm. Meanwhile, established the relationship between hardness and yield strength, the average error of the nonlinear model is 4.35%. The prediction accuracy of the nonlinear model is sufficient to meet the actual needs of the engineering.

Highlights

Due to the advantages of high explosion pressure, high power output and high combustion efficiency, diesel engine occupies an absolute share in the heavy-duty civilian and military vehicle market
Because of the large wall thickness step, local structure size mutation and high curvature of the surface in the key parts of the cylinder head, the solidification rate of liquid phase is different at different positions, accompanied by local eddy current phenomenon, which leads to obvious differences in secondary dendrite arm spacing (SDAS), grain size and eutectic silicon morphology at different positions
Compared with the head plate position, the tensile strength of the thick partition plate position is reduced by 15.3%, the yield strength is reduced by 4.2%, and the break elongation is reduced by 67.5%; the tensile strength of the floor plate is reduced by 10.4%, the yield strength is reduced by 1.2%, and the break elongation is reduced by 59.5%

Summary

Introduction

Due to the advantages of high explosion pressure, high power output and high combustion efficiency, diesel engine occupies an absolute share in the heavy-duty civilian and military vehicle market. The state strictly limits the emissions of environmental pollutants, requiring heavy-duty diesel vehicles to reduce nitrogen oxide and particulate emissions by more than 60%, In order to meet increasingly stringent emission regulations, it is necessary to continue to improve the combustion efficiency and power density of diesel engines, which undoubtedly worsens its operating conditions. Due to the advantages of good casting performance, low density, high strength, and corrosion resistance, aluminum-silicon alloy has become a lightweight material for casting that is widely used in automotive, aviation, shipbuilding and other industrial fields. Highly-intensified diesel engines widely use aluminum alloy as the material of the body and cylinder head to achieve the purpose of lightweight[1]. The inhomogeneity of mechanical properties caused by microstructure heterogeneity becomes an important factor restricting the further improvement of cylinder head performance and the overall strength evaluation and reliability problems of cylinder heads under non-uniform mechanical properties need to be resolved urgently. The thermal instability of the material greatly limits the further improvement of the structural product performance[2, 3]

Objectives

Results

Conclusion