A comparative study on the mechanical and tribological characteristics of AA7075/h-BN and AA7075/h-BN/MoS₂ hybrid nano-composites produced using stir-squeeze casting process

Abstract

AA7075 is used in several automobile applications due to its low density and better mechanical properties. However, the friction and wear properties of AA7075 are not up to the mark to extend its application for tribological applications. Hence, this present study focuses on improving the mechanical and wear properties of AA7075 through different reinforcements like h-BN and MoS 2 nanoparticles. Two different composites namely AA7075/h-BN and hybrid AA7075/h-BN/MoS 2 are produced using a stir-squeeze casting process by varying weight percentages of h-BN and MoS 2 particles and their mechanical and tribological characteristics are compared. Physical characterization like morphology, phase structure, density, and porosity values are determined. The reinforcement of MoS 2 and h-BN particles has modified the microstructure in terms of dendrite formation. Hardness is measured and correlated with the tensile strength of the developed composites. Maximum ultimate tensile strength (UTS) of 361.5 MPa is obtained for AA7075/h-BN composite as compared to hybrid AA7075/h-BN/MoS 2 and AA7075. A higher hardness of 164.39 HV is attained for AA7075/1.0h-BN/0.5MoS 2 composite as compared to AA7075/h-BN composites and AA7075. Tribological characterization is studied using the pin-on-disc apparatus at an applied load of 40 N, a sliding distance of 1000 m, and a sliding velocity of 2 m s −1 . Higher delamination and adhesion wear exhibited by AA7075 is controlled with the reinforcements of h-BN and MoS 2 nanoparticles. Comparatively, the hybrid AA7075/h-BN/MoS 2 has shown better tribology behavior than the other composites. Additionally, the various wear mechanisms of AA7075/h-BN and hybrid AA7075/h-BN/MoS 2 composites during the sliding are studied.

Tribological performance evaluation of h-BN nanoparticle reinforced AA 7075 and as-cast AA7075 using Taguchi and genetic algorithm

“…The porosity in cast metals is common and it cannot be eliminated full, however, it could be reduced near to zero by various techniques. Squeeze process is one of the effective methods to reduce the porosity, which is confirmed by the previous researchers [31,43,51]. On account to that the porosity exhibited for AA 7075 and AA 7075/h-BN composites are comparatively lower.…”

“…The inclusion of h-BN nanoparticles marginally improved the hardness of AA 7075 MMCs due to the microstructural changes (Refer to figure 4(c)). In addition, several following factors such as; grain refinement, restriction of dislocations based on the Orowan's strengthening mechanism, effective load transfer from the matrix to reinforcement region and better interfacial bonding between the matrix and reinforcement has contributed the hardness improvement for the AA 7075/h-BN composites [41,42,[51][52][53].…”

Aluminium-Silicon based Metal Matrix Composites for brake rotor applications: a review

“…Ultrasonic vibration breaks nano agglomerations when nanoparticles are used as reinforcements in molten alloys. Finally, the melts are fed into a pre-heated cylindrical die and forced using hydraulic pressure [35][36][37]. Different operating parameters recommended for squeeze-assisted stir casting to manufacture the best quality AMC disc brakes are shown in figure 3.…”

Effect of Calcium Silicate on Mechanical and Frictional Wear Behaviors of AA7075 Hybrid Composites: A Statistical Analysis

“…A selflubricating material like graphite, graphene, molybdenum, etc. is an appropriate choice of solution based on the application [10].…”