AA6061 Matrix Research Articles

Prevention of Stick-slip Tearing of a Duralcan AA6061–matrix Composite During Extrusion

Prevention of Stick-slip Tearing of a Duralcan AA6061–matrix Composite During Extrusion

Investigation of the precipitation kinetics in an A16061/TiB 2 metal matrix composite

The aging kinetics of AA6061 (Al−Mg−Si−Cu) based metal matrix composites (MMCs) containing TiB 2-particles were investigated using hardness measurements, texture determination and electron microscopy. The samples were produced by an in-situ process. Two industrially manufactured in-situ composites with an AA6061 matrix and TiB 2-particles (3.4 vol.%, 6.8 vol.% TiB 2) were studied at two different aging temperatures (160°C, 250°C) and compared to a similarly processed non-reinforced AA6061 alloy. An increasing volume fraction of TiB 2 correlated with changes in the aging response of the composites. Samples subjected to three aging times were selected for microstructure analysis in the TEM (10 min, 200 min, 1365 min, aging temperature 250°C). Special emphasis was laid on the investigation of the growth kinetics of metastable needle shaped matrix precipitates, which cause the increase in hardness. The TEM examinations of the MMCs substantiated that precipitate growth was accelerated in the presence of TiB 2 particles as compared to the unreinforced AA6061. These differences in kinetics were related to microstructural changes induced by the presence of the ceramic TiB 2 particles.

Thermal cycling processes in metal-matrix composites

Aluminium-matrix composites have attracted considerable academic and industrial attention in recent years, where modulus increases of 100% and strength increases of 60% over conventional metal alloys have been reported. Further, the emphasis on the use of recyclable and environmentally-friendly materials has lent support to the aluminium industries vis-à-vis other materials. The high specific strength and modulus makes this class of materials highly desirable for the aerospace and transport industries. Aluminium-matrix composites are, however, inherently brittle, thus making superplastic forming an alternate and attractive option. In this work, a study of the behaviour of AA6061 reinforced with alumina particles produced by casting and extrusion, under the action of strain control and thermal cycling conditions, is presented. Comparisons are made with unreinforced AA6061 matrix, and also with the same composite re-extruded to obtain finer grain sizes. Elongations obtained via thermal cycling are compared with those from room temperature and isothermal testing. The work also looks at the differences in cycling at different frequencies, range and rate, for the AA6061 matrix composites.

AA6061 composite reinforced with potassium titanate whisker

Recent works reported the reduction in strength of the AA6061 matrix composite fabricated by powder metallurgy by T6 treatment. Thus, reactions between whisker and aluminium matrix seems to restrict the application of the aluminium matrix composites with potassium titanate whisker. The aim of the present work was to examine whether or not any reaction occurs at the whisker/matrix interface caused by high-pressure infiltration or by T6 heat treatment. This was carried out using carried out using transmission electron microscopy (TEM)