Sintering and mechanical properties of prealloyed 6061 Al powder with and without common lubricants and sintering aids

Abstract

Physical and mechanical properties for prealloyed 6061 Al powder processed with and without additions of solid and/or liquid lubricants and sintering aids (Pb, Sn, Ag) are presented. For comparison, both vacuum and nitrogen sintering were carried out on as received (gas atomised) and degassed powder compacts pressed at 340 and 510 MPa. Vacuum degassing of the prealloyed powder provided better compressibility and thus higher green densities than those for the as received powder. Highest sintered densities of y98-99% of theoretical were obtained for the prealloyed (and degassed) Al compacts by sintering under pure nitrogen with an addition of 0 . 6 wt-% paraffin wax as solid lubricant or 1 . 33 vol.-% liquid paraffin, or with a 0 . 12 wt-%Pb addition as sintering aid and no lubricant. It was found that additions of solid lubricants such as lithium stearate and acrawax to both the premixed (elemental) and prealloyed powders provided reasonable green densities of y94 . 5-95 . 5% TD, but had deleterious effect on sintered densities and microstructures, particularly under vacuum sintering. Other lubricants such as zinc stearate, stearic acid and liquid paraffin provided similar green densities, but higher sintered densities and less porous microstructures, particularly by sintering under pure nitrogen. The prealloyed compacts sintered under pure nitrogen consistently provided much higher sintered densities than elementally premixed compacts sintered under pure nitrogen or vacuum. It is therefore concluded that both lubricant type and sintering atmosphere will have a major effect on the sintered properties of the 6061 Al powder. Sintering under pure nitrogen resulted in higher sintered densities as compared with vacuum sintering for this grade of Al alloy. Tensile properties of the degassed and vacuum sintered (and T6 tempered) prealloyed powder compacts were higher than those of the equivalent alloy prepared by elemental mixing and comparable with those of the commercial (wrought) 6061 Al alloys.

Densification, microstructure and properties of supersolidus liquid phase sintered 6711Al-SiC metal matrix composites

“…This mode of sintering characteristic to prealloyed powder system is referred to as supersolidus liquid phase sintering (SLPS) [27][28]. Though there is literature on supersolidus liquid phase sintering (SLPS) of 6061 Al alloy, SLPS to Al alloy based composites have been still lacking [29][30][31][32]. Recently Asgharzadeh et al [19] has studied the SLPS of 6061Al-SiC composites in comparison with unreinforced alloy.…”

Supersolidus liquid phase sintering of Al6061/SiC metal matrix composites

“…To improve the densification, liquid phase sintering (LPS) can be useful. It has been shown [10][11][12][13][14][15][16][17] that similar to the unreinforced powders, the presence of a liquid phase improves the densification of composite compacts, although the sintering rate is less pronounced. During the past decade, the application of liquid phase sintering in fabrication of high performance Al alloys has been shown repeatedly, for example Ref.…”

Microstructures and properties of high-fraction Sip–6061Al composites fabricated by pressureless sintering

“…As shown in Figure 3, the 30 wt-% Sip/6061Al composites sintered at 660-700°C are rather dense without large pores remaining in the composites, indicating their much higher sintering capability. Actually, the sintering densification of the 6061Al alloy can be achieved at 620°C [14,15]. However, the sintering temperature of the high-fraction Sip/6061Al composites is reasonably higher than that of the 6061Al alloy, and increases with increases in the Si fraction.…”