C.A. León

Wettability and spreading kinetics of Al and Mg on TiC

The wetting of TiC by liquid aluminum and magnesium under static argon between 800 and 1000 C is studied using the sessile drop technique. Extensive interfacial reaction occurs between Al and TiC, leading to the formation of aluminum carbide; conversely no reaction occurs for Mg/TiC. 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.

Small punch testing for assessing the tensile strength of gradient Al/Ni-SiC composites

Abstract The versatility of the shear punch test (SPT) was considered as an alternative for assessing the tensile properties of Al/Ni–SiC gradient composites fabricated by infiltration of liquid aluminum into coated ceramics. Tensile strength values of the order of 220 to 250 MPa were obtained. The nature of the shear-fractured surfaces was irregular for the composite specimens, with shear failure over most of the surfaces but with some tensile failure at the margins. The substantial accumulation of NiAl 3 in the upper section specimen resulted in a higher strength and brittleness of the matrix compared to the low nickel content matrix sections.

Wettability of TiC by commercial aluminum alloys

The effect of alloying elements on the wettability of TiC by commercial aluminum alloys (1010, 2024, 6061 and 7075) was investigated at 900°C using a sessile drop technique. Wetting increased in the order 6061 < 7075 < 2024 < 1010 for both, static argon or vacuum atmospheres. Alloys 1010 and 2024 wet TiC under both atmospheres, leading to contact angles in the order of 60° and less, while 7075 only wets under vacuum, with the poorest wettability being exhibited by 6061. Evaporation of Zn and Mg under vacuum conditions contributed to the rupture of the oxide film covering the aluminum drop and thereby improving wetting and spreading. Continuous and isolate Al4C3 was detected in all the cases. CuAl2 precipitation at the interface slightly decreased Al4C3 formation and increased the adhesion of 2024 to TiC.

Properties of AlN-Based Magnesium-Matrix Composites Produced by Pressureless Infiltration

A novel ceramic-metal composite with continuous interconnected ceramic and metal phases has been fabricated from sintered porous particulate AlN preforms infiltrated with magnesium. The 48 vol. % AlN composites are fabricated by pressureless infiltration in argon in the temperature range of 870 °C to 960 °C. An increase in the infiltration rate is observed as the temperature increases. Results on the mechanical characterization of the composites indicate an elastic modulus of 90 to 110 GPa and hardness of 70 to 80 HRB. The tensile strength calculated by the shear punch test method ranges from 260 to 390 MPa. As a general rule, it is observed that the lower the infiltration temperature, the higher the tensile strength. The linear coefficient of thermal expansion of the infiltrated composites in the temperature range of 215 to 315 °C is 7.65 x 10-6 °C-1. This value is lower than those found for similar Al/AlN composites reported in the literature.

Spreading Mechanism of Molten Al-Alloys on TiC Substrates

The contact angle data drawn from sessile drop tests of commercial aluminum alloys (1010, 2024, 6061 and 7075) on TiC substrates (at 900 °C, under vacuum and argon atmospheres) was plotted on a logarithmic time scale. Several aspects were taken into account to describe the spreading mechanism in four kinetic stages in systems that exhibited wetting (1010, 2024 in both environments and 7075 under vacuum). It was found that commercial multi-element alloys do not improve wetting of Al on TiC and that alloying elements and the atmosphere exert a significant role on the wetting behavior in the early stages. A physical model describing spreading in the early stages is presented. The influence of alloying elements and the type of atmosphere on the deoxidation of the drops are discussed.