Development of mechanical properties of plastically consolidated RS442 aluminium alloy by heat treatment methods

摘要

Advanced methods for grain refinement in metals and alloys are effective way for improving their mechanical properties. They include plastic consolidation of rapid solidified disintegrated forms (flakes, powders, etc.) which enables manufacturing semi- and final products having much better operational properties comparing with traditional manufacturing methods. Plastic consolidation is acknowledged as particularly interesting method of development of microstructure and mechanical properties of Al-Si alloys. It can be alternative method for plastic working - difficult due to low plasticity of mentioned group of alloys. Characteristic feature of plastically consolidated RS442 alloy is high refinement of phase constituents (matrix grain size < 1 um) which results in even doubled static tensile strength. Alloy in this conditions preserves its high strength also after annealing at the temperature of 450°C. It was assumed that precipitation process of intermetallic phases compensated material softening caused by matrix grains growth. Plastic consolidation of rapidly solidified RS442 alloy flakes was conducted by extrusion method. Produced rods were heat treated - annealing at 450°C for 2h and solution treatment at the temperature of 475°C (1h) with water quenching and following ageing in the temperature range of 50-100°C. SEM microscopic and mechanical properties (tensile and hardness tests) examinations were carried out. It was found that precipitation hardening of plastically consolidated RS442 alloy led to reduction of its yield stress (about 25%) and increase in hardness (about 10%) without essential effect on ultimate tensile strength.