THE EFFECT OF HOLD-MELT TIME OF MICRO-REGIME PRECIPITATION SIZE AND HARDNESS IN Al-Cu ALLOY

This study aims to control the characterization and mechanical properties of smelting Al-Cu Alloy through Hold-Melt Time. This research uses aluminum scrap and copper wire scrap to produce quality as-cast ingots, clean the environment, and increase waste utilization. Copper melting point of 1083 °C is immersed in molten aluminum at a temperature of 900 °C for 10–30 minutes causing copper to dissolve in aluminum due to smelting events based on diffusion phenomena. Parameters of temperature and immersion time of copper in molten aluminum in this study are expressed by hold-melt time. In the copper aluminum alloy trade, commonly called Duralumin, it is commonly used for impact loads and is heat-treatable. Resistance to cryogenic temperatures, in the future Duralumin has the potential to replace stainless steel. This study used an electric resistance furnace with the specifications for smelting aluminum 3 kg, electric power 2.5–3.0 kW, electric voltage 220 Volts, maximum temperature 1000 °C. It had been conducted an experiment where copper had been melted under its melting point in duralumin ingot casting. In this study, copper pieces were soaked in liquid aluminum with temperature of 900 °C. After 10–30 minutes of holding melt, the soaked copper became Al-Cu alloys and was called molten Duralumin. After the molten duralumin had been cleaned from dross, it was poured into ingot casting. From specific weight test, more soaking time of the copper in liquid aluminum caused specific weight of ingot duralumin increase from 47.08 % to 57.56 % and its hardness increase from 93 to 113 BHN. This study contributes on melting energy saving and improves the characteristic and hardness of ingot aluminum type 2xxx.