Thermomechanical Fatigue Behavior of Spray-Deposited SiCp/Al-Si Composite Applied in the High-Speed Railway Brake Disc

Wei Li,Lu Zuo,Cong Li,Dongliang Xu,Jianjun He,Yanjie Ren,Zhuoyin Peng,Sheng-De Zhang,Jian Chen,Huitao Chen

doi:10.1155/2020/6150794

Abstract

The thermomechanical fatigue (TMF) behaviors of spray-deposited SiCp-reinforced Al-Si alloy were investigated in terms of the size of Si particles and the Si content. Thermomechanical fatigue experiments were conducted in the temperature range of 150-400°C. The cyclic response behavior indicated that the continuous cyclic softening was exhibited for all materials, and the increase in SiC particles size and Si content aggravated the softening degree, which was attributed to dislocation generation due to differential thermal contraction at the Al matrix/Si phase interface or Al matrix/SiC particle interface. Meanwhile, the TMF life and stress amplitude of SiCp/Al-7Si composites were greater than those of Al-7Si alloy, and increased with the increasing SiC particle size, which was associated with “load sharing” of the direct strengthening mechanism. The stress amplitude of 4.5μmSiCp/Al-Si composite increased as the Si content increased; however, the influence of Si content on the TMF life was not so significant. The TMF failure mechanism revealed that the crack mainly initiated at the agglomeration of small-particulate SiC and the breakage of large-particulate SiC, and the broken primary Si and the exfoliated eutectic Si accelerated the crack propagation.

Highlights

The depletion of natural resources and environmental pollution are major challenges facing humanity today
The thermomechanical fatigue behaviors of spray-deposited SiCp/Al-Si composites were investigated in terms of the size of SiC particles and the Si content in the temperature range of 150-400°C
(2) There exists a continuous cyclic softening in Al-7Si alloy and SiCp/Al-Si composite. Both the increase in SiC particle size and Si content can aggravate the softening degree obviously, which is correlated with the dislocation generation in differential thermal contraction at the Al matrix/Si phase and Al matrix/SiC particles

Summary

Introduction

The depletion of natural resources and environmental pollution are major challenges facing humanity today. New energy vehicles are using clean energy to save resources and protect the environment [1]. The light-weight, wear resistance, and thermomechanical fatigue properties of composites for automotive brake discs are very important [2,3,4]. The traditional metal brake discs are easy to crack and cannot ensure the safety of the vehicles due to the high temperature produced by friction between wheel and rail with high driving speed (≥400 km/h). Some new composites like carbon/carbon fiber-reinforced carbon matrix composites have excellent high-temperature wear resistance, but oxidation and high manufacturing cost restrict their widespread application. SiCp/Al-Si composite, owing to advantages such as high-specific strength, excellent thermal conductivity, and low expansion coefficient, is considered as an ideal metal matrix composite (MMC) for brake disc [5,6,7,8]. In the process of actual braking, the residual stress caused by the mismatch in thermal-expansion coefficient (CTE) between SiC particle and Al-Si alloy while the composites are subjected to mechanical load leads to thermomechanical fatigue (TMF) collaboratively

Results

Discussion

Conclusion