Joining of aluminum-based particulate-reinforced metal matrix composites.

摘要

In this study, 25 Vol% SiCp/6061 Al metal matrix composite (MMC) materials were joined by the transient liquid phase diffusion bonding process using a Gleeble 1500 system. In order to understand the effects of the bonding thermo-mechanical cycle on the mechanical and metallurgical properties of the base material, thermal and thermo-mechanical simulation studies were performed with a regular heat treatment furnace and the Gleeble 1500 system. Thermal simulation conditions included temperatures ranging from 500 to 590{dollar}spcirc{dollar}C and times from 5 to 9 minutes. Thermo-mechanical simulation conditions ranged temperatures from 540 to 580{dollar}spcirc{dollar}C, times from 5 to 60 minutes and pressures from 350 to 900 psi, with resulting deformation at the interface from 1.8 to 11.9%. Degradation in base material mechanical properties (microhardness and strength evaluation) with time, temperature and loading was observed. The simulated bond structures were characterized with optical and scanning-electron microscopy (SEM) and bonding temperatures and times were selected.; TLP bonds in MMC were obtained with a 0.001{dollar}sp{lcub}primeprime{rcub}{dollar} silver interlayer at temperatures ranging from 570 to 580{dollar}spcirc{dollar}C and times from 5 to 30 minutes. Joints characterized with optical microscopy and SEM revealed the occurrence of voids at the interface. Electron microprobe analysis (EPMA) confirmed the silver gradients near the interface. Evaluation of a bond with a 0.005{dollar}sp{lcub}primeprime{rcub}{dollar} interlayer by optical micrography and EPMA identified the chemistry of lamellar solidification products. The tensile strength of the joint bonded at 579{dollar}spcirc{dollar}C for 20 minutes, at 12.9 ksi, yielded a joint efficiency of 29.86% based on the properties of the thermo-mechanically simulated and heat treated sample (575{dollar}spcirc{dollar}C, 30 minutes). SEM fractographs indicated the occurrence of partially dimpled fracture with limited microscopic ductility and particulate fracture. Finally, the process parameters responsible for an improvement in the mechanical properties were identified.