Influence Of ALTI Agent On Microstructures And Mechanical Property Of Al-Mg₂Si Composite

Because Al-Mg₂Si composite has many advantages, such as low density, low cost, high modulus ratio, simple preparation process, it is suitable for lightweight component, such as the cylinder sleeve of automobile's engine. But primary Al-Mg₂Si phase is coarse and gerippt in Al matrix, these characteristics seriously impact the property of composite. To improve primary Al-Mg₂Si phase's feature and size and composite's mechanical property becomes the main problems.The research of the topic is on the influence of microstructure and mechanical properties when AlTi agent is added in Al-Mg₂Si composite. Through adding three kinds of AlTi agents,to observe the refining effectiveness of Mg₂Si phase in Al-Mg₂Si composite,and to compare the improvement of Al-Mg₂Si composite's mechanical properties, finaly to analyse refining mechanics.The three kinds of agents include AlTiC, AlTiP and AlTiZr grain refiner. The dosis of grain refiner added into Al-Mg₂Si composite is lower than 1% of Al-Mg₂Si composite′s weight. The Al-Mg₂Si composite used in experiment is Al-30% Mg₂Si or Al-40% Mg₂Si composite.Through adding AlTi agent, Mg₂Si phase is smaller in size and rounder in edge. Through mechanical properties test, the hardness and tensile strengh are found to improve.To further, the influence of Al-Mg₂Si composite′s microstructure and mechanical properties is studied through changing the dosis of agents. The dosis of agents is 0.2%,0.4%,0.6%,0.8% or 1%. The study shows that refining effectiveness of Mg₂Si phase in Al-Mg₂Si composite and mechanical properties of Al-Mg₂Si composite are not improvedwith the inceasing dosis of AlTi agent. When the dosis of AlTi agent is more than certain level, the refining effectiveness of Mg₂Si phase falls down, the pattern and size become coarse and the mechanical properties of Al-Mg₂Si composite fall down. Therefore, in certain range, the refining effectiveness and mechanical properties are better. Through related detection and comparing experiment, the refining mechanics of AlTiC, AlTiP and AlTiZr grain refiner are further analysed in macroscopic and microscopic view.