Influence of Solutionising and Aging Treatments on Mechanical Behavior of Stir-Cast Eutectoid Steel Powder Reinforced Al 7075 Metal Matrix Composites

Abstract

Al 7075 is a good choice as a matrix material to prepare metal matrix composites (MMCs) owing to its better specific tensile strength and toughness. Among different types of the recently introduced composite materials, particles reinforced MMC and in particular aluminium as matrix material have been found to have enormous industrial applications like automotive and aerospace sectors. In the present study, mechanical properties of Al 7075-eutectoid steel powder metal matrix composites is assessed in age-hardened and as-cast conditions. The heat treatment processes are carried out in atmospheric condition. Eutectoid steel (water hardenable tool steel - W1grade) reinforced aluminium 7075 is an attempt to investigate the role of micro-constituent phases on property alterations of metal matrix composites. As an economical and promising route for MMC, liquid stir casting technique is used to reinforce synthesised steel powder in the matrix of Al 7075. Heat treatment is performed as a tool to mould and improve the required mechanical properties as per the requirements. Eutectoid steel powder is selected as the reinforcement material since it is believed to be composed of lamellar pearlite with ferrite and cementite as alternate layers in as-cast condition, serving as micro-hybrid reinforcement to improve hardness and strength. In this work four different proportions of steel powder (2, wt.% 4 wt.% and 6 wt.%) reinforced composites are prepared by a two-stage stir casting process. Age-hardening treatment is given to the samples and analysed critically and compared with alloy matrix for different properties such as tensile strength, hardness and toughness. Results have shown significant improvement in the ultimate tensile strength and hardness of the composites after aging treatment. The 4 wt.% steel powder reinforced composite has shown better results compared to other composites.

Optimization and prediction of the hardness behaviour of LM4 + Si3N4 composites using RSM and ANN: A comparative study

“…When SSHT and MSHT (without artificial aging) were performed on as-cast specimens, the hardness values decreased (table 3). This is because after solutionizing, a homogeneous solid solution is generated, which is transformed into supersaturated solid solution once quenched and this phase is soft and unstable, so, it exhibits lower hardness values than as-cast specimens [23]. MSHT + artificially aged specimens displayed better hardness than as-cast and SSHT + artificially aged specimens because of the presence of more number of precipitates formed, the results of which are in line with the other studies [24], [25].…”

Effects of Solutionizing and Aging Alteration on Tensile Behavior of Stir Cast LM4-Si3N4 Composites

“…It is a soft phase with good formability; however, it is volatile at room temperature. As a result, solutionized specimens exhibit lower hardness than as-cast specimens in both situations (SSHT and MSHT) [29]. These unstable phases strive to become stable secondary solute-rich phases along and inside grain boundaries [30], [31].…”

Influence of Superheating Melt Treatment on Microstructure of Gd-Modified Al-15wt.% Mg2Si In-Situ Composite

“…In fact, the formation and Mg2Si particles distribution in the matrix of the composites affect the hardness of the fabricated materials [19]. The hardness of the composites was enhanced when the particles are distributed homogeneously in the matrix, as harder ceramic particles can resist the stress [20,21]. As depicted in Figure 7, higher superheat temperature contributed to better particles distribution, which affected the hardness of the composites.…”