The High-Temperature Creep Behavior of In-Situ TiB2 Particulate Reinforced Al12Si4Cu2NiMg Composite

Abstract

In the present work, the in-situ TiB 2 /Al12Si4Cu2NiMg (denoted as 'Al-12Si') composites were successful synthesized through the salt-metal reaction route. The influences of weight fraction (0, 4, and 9 wt.%) and heat treatment (T5 and T7) on the tensile creep deformation were studied at ≥623 K under constant load in air. At the investigated temperature and stress condition, TiB 2 particles increased creep deformation resistance, as compared to the unreinforced alloy, while the composites presented similar strength when the weight fraction of reinforcement increased from 4% to 9%. It was found that the steady-state creep rate was lower in the 4 wt.% TiB 2 /Al-12Si composite (T5), as compared with that in the 4 wt.% TiB 2 /Al-12Si composite (T7). The result has been rationalized by using the load-partitioning model and relative to the evolution of the rigid phase. The creep deformation of the 4 wt.% TiB 2 /Al-12Si composite was controlled by the climb of dislocations in the aluminum alloy matrix.2 of 16 sources [22,23]. Requena et al. [14] has showed the considerably lower creep resistance of 22 vol.% Al 2 O 3 /AA6061 composites compared with that of the unreinforced matrix. The role played by particulate reinforcement, especially in nano-scale size, during creep is still not well understood.Furthermore, little attention has been paid to the influence that heat treatment may have on the creep strength of the composite, although the work on the Al12SiCuMgNi alloy [24] has suggested that heat treatment affected the creep resistance of the material directly. Besides, the major creep researches are conducted on the DRAMCs, which are typically fabricated by powder metallurgy (PM). The PM processed DRAMCs have always shown higher creep resistance and more regular experimental data compared to the ingot metallurgy (IM) method [13,25]. However, the IM process is widely used and continuously developed due to its ability to achieve high part volumes and tight part tolerances at lower cost in the industrial application [26]. The study of creep behavior for the IM DRAMCs has been largely neglected by the academia.The present study is aiming to understand the steady state creep behavior and fracture mechanism of in-situ TiB 2 /Al12Si4Cu2NiMg composite produced by the IM strategy. The study consists of two sections. In Section 1, the similarities and differences in the creep behaviors between composites and the alloy as well as the relevant creep mechanisms, such as the role of the particle reinforcement, are identified and discussed. In Section 2, the analysis, based on the concept of load transfer, has been proposed to describe the creep behavior of the composite at different heat-treated states. Materials and Methods MaterialsIn this work, an Al12Si4Cu2NiMg alloy (hereafter denoted as 'Al-12Si alloy') and two Al-12Si alloy matrix composites reinforced with 4 wt.% and 9 wt.% of particulate TiB 2 were used. The nominal chemical composition of the Al-12Si alloy is given in Table 1.

Effect of TaC/Ti/Si3N4 Hard Ceramics on Mechanical and Microstructural Behaviour of AA7075 Processed through Stir Casting Process

“…e origin of the threshold stress could be confederate with the Orowan strengthening of c-Mg 17 Al 12 platelets that dynamically precipitated in the magnesium. Dai et al [13] synthesized in situ TiB 2 / Al 12 Si 4 Cu 2 NiMg (mentioned as "Al-12Si") composite processed by salt metal reaction methodology. e influence of reinforcements in wt% and heat treatment on creep deformation was evaluated at 632 K under steady force in the air.…”

In Situ 3D-µ-Tomography on Particle-Reinforced Light Metal Matrix Composite Materials under Creep Conditions

“…In this field, the materials are exposed to high mechanical and thermal loads leading to creep [4]. Due to their lower thermal expansion and good thermal conductivity, lightweight-MMCs are well-suited for use at creep conditions and particulate reinforced aluminum-and titanium-based MMCs are frequently investigated until today, e.g., by [5][6][7][8][9][10][11][12]. Creep occurs at constant stress below the yield point and at constant elevated temperatures above 0.3-0.4 T H , with T H being the homologous temperature calculated from the applied temperature T divided by the melting temperature T m (T H = T/T m ) [13].…”