Study On Al-Mn Alloy Prepared By The Mixed Solid-liquid Casting

A novel preparation technology, termed as Mixed Solid-liquid Casting, was adopted to produce Al-Mn allays, which couldn't be prepared by the conventional casting routes. Alloy powders with the same composition as the melt or with good wettability are added into the overheated melt and then intensively stirred, followed by casting or other hot processings. Thus, a material with well-balanced properties is obtained.The thesis involves six respects as follows. The alloy powders and the master alloy of the Al-Mn system were prepared, and its mixed Solid-liquid casting process was studied; On the basis of systematic experiments, the optimal process parameters and the room temperature mechanical properties and wear resistance of the as-prepared Al-Mn alloys were tested. Finnally, the thixoformability of the Al-Mn alloys was primaryly explored.The as-prepered Al-Mn alloy powders were added into the master alloy melt in the appociate proportion, and then the melt was intensively stirred so as to obtain the semi-solid slurry with homogeneous microstnictures. The as-obtained slurry was squeeze cast into bars for micro-structure examination and mechanical property tests. The transter temperature of the slurry was 800℃ and the transfer time was controlled less then 10 seconds.The alloy powders were partially melt during stirring due to the overheating of the melt. The as-prepared Al-Mn alloys were combined a good metallurgical bond between the powder and the melt with the rapidly solidified microstructure of powders. In addition, plastic processing at the semisolid temperature range contributed to the further dispersion of the powder agglomerates.The experimental results show that the primary manganese phase and the microstractures of the alloy matrix can be extremely refined by the added powders. The extrusion resistance force of the semi-solid state is much lower than that of the full-solid samples. With increasing the alloy powers and reducing the particle size of the powder , the mechanical properties of as-prepared Al-Mn alloy samples are improved. The as-prepared Al-Mn alloys bars were of characteristic hovncgeneous microstructures and fine grains with the spherical or rose-shaped morphology. The optimum mechanicalproperties after hot extrusion were σ_b= 130MPa, σ₀.2=80MPa, 5=1%, which were preferable to those of conventional casting and semi-solid casting. Thus, the high manganese alloy, which is difficult to be used, had the possibilities of application.The mean friction coefficient of the as-prepared Al-Mn alloy is 0.46, notably superior to the ingot casting samples and the stirrly casting samples without adding powders. It should be pointed out that the grain abrasion is the dominate mechanism at 200-300 ℃ , while wear gluey over 300℃, resistance increases with the increase of powder quantity. Moreover, the wear resistance of the the Al-Mn alloys increases with the additional powers increasing.The mixed solid-liquid casting is a simple processing that can be utilized to prepare articles with complex structures and large dimensions at lower costs. It has a industrial application perspective.