Development and Testing of Chilled Aluminum Alloy-Corundum Particulate Composite for Automotive Applications.

摘要

The present work focuses on the development and evaluation of Micro hardness, high temperature wear, thermal conductivity, and coefficient of thermal expansion of chilled aluminum alloy-corundum particulate composite for automobile piston and cylinder sleeve applications. The alloys selected were LM 13, LM 28, and LM 30 which are the standard alloys used in the automobile sector for the mentioned applications. The reinforcement used was corundum (Al2O3) because of its high wear resistance and less thermal conductivity and CTE properties. By preliminary studies the reinforcement content was fixed at 9 wt percent . The composites were developed using the classical stir casting technique and the samples were selected form three different regions in order to establish the chill effect. Since the application was for automotive, except for micro hardness, the study was conducted at high temperature. For micro hardness, standard Zwick/Roell Indentec Tester was used. In high temperature wear the specimen was continuously heated and the study was conducted on a Pin-on-Disc apparatus. For measuring thermal conductivity an experimental setup was prepared exclusively for the purpose since no standard setup was available. However, the CTE of the MMCs were measured using TMA setup. From the analysis it was found that the micro hardness increased at the chill end with a maximum for LM 30 composite. In the wear test, as expected, the chill end of the specimen exhibited least wear with LM 30 composite exhibiting minimum wear. The thermal conductivity decreased as one moved away from the chill end. Thus, the specimen at the chill end had the maximum K value while those at the far end had the minimum K value. LM 13 composite (at the far end of the chill) had the least value of K while the rest two composites almost had the same K values. The CTE results show that it varies with temperature at a pace that is higher for pure aluminum than for the composites. The morphology of the composite was found to influence the CTE of the composite, since, as the volume fraction and the size of the reinforcements increased in a given specimen the CTE of the specimen decreased due to the ceramic nature of the reinforcement. As seen from the results LM 13 composite had the maximum CTE while LM 28 composite at the chill end had the minimum CTE values.