TANTALUM ADDITIONS AS GRAIN REFINER TO ALUMINIUM ALLOYS.

This paper explores the possibility of making beneficial additions of tantalum, as a grain refiner, to the aluminum-copper alloys LM-22 and LM-12, and the aluminum-magnesium alloy LM-10, on a quantitative basis. Chip formation during turning and power consumption during drilling, determined by a calorimetric method, were taken as the criteria for evaluating machinability. Tantalum was found to cause extensive grain refinement even at lower additions in the case of LM-10 and of LM-12, the effect being more pronounced in LM-10. Improvement in machinability was observed in all alloys treated with tantalum in the range from 0. 1 to 0. 15%. Improvement in tensile strength is obtained only in the case of LM-12, with an optimum addition of 0. 15% tantalum.