UBC Theses and Dissertations
Grain refinement of B319 alloy using spark plasma sintered Al-Ti-C grain refiners Mok, Justin Alfred
The B319 aluminum alloy is a candidate material for automotive applications, where engineers and materials designers are seeking to improve vehicle efficiency through vehicle weight reduction. Although the alloy has many desirable properties, such as it’s excellent castability and moderate strength to weight ratio, continued efforts on further enhancement of the alloy’s strength via the grain refinement approach have been reported. However, in addition to the fundamental challenges related to solidification phenomena, there also remain several challenges related to the efficient dispersion of inoculating particles in the liquid alloy during casting, as well as its casting characteristics (e.g., fluidity) as a result of the grain refinement. Further, a method for fabricating effective and homogenous grain refining master alloys remains a challenge. This research focused on examining the grain refining ability of various grain refiners produced via the spark plasma sintering (SPS) powder metallurgy route. Analysis of solidification events was used to track phase evolution and its effect on the final grain size and also on the alloy’s fluidity. The mechanical properties of the as-cast material were measured via tensile tests according to ASTM B557M standard. The results indicate that SPS enabled production of a homogenous grain refining master alloys for metal casting. Two grain refiners (Aluminum-Titanium Carbide [Al-TiC] and Aluminum-Titanium-Carbon Black [Al-TiCB]) were produced at high and low concentrations and added to the molten B319. The high concentration formulations for both Al-TiC and Al-TiCB had the greatest effect on the properties of the B319 aluminum alloy, as a result of achieving a reduction in the average grain size of 31% and 25%, respectively. Concurrently, these grain refiners increased the ultimate tensile strength by 6% and 8%, respectively. The flow length of the B319 was reduced by 15%, 31%, 29%, and 32% after addition of Al-1TiC, Al-5TiC, Al-1TiCB and Al-5TiCB, respectively, thus suggesting the need for further work in optimizing the casting parameters to achieve optimal casting fillability.
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