Forming Process And Performance Research Of Laser Additive Manufacturing Al-12Si Alloy

Aluminum alloy has been found various applications in automotive, aerospace, mechanical and electronic fields due to its high specific strength, low thermal expansion coefficient, enhanced wear and corrosion resistance. Manufacturing complex aluminum alloy parts with traditional casting fabrication method will lead high production cost, long production cycle, low material utilization and especially unable to forming complex inner cavity aluminum alloy structure components. Laser additive manufacturing technology is an advanced manufacturing technology based on dispersion-accumulation principle, combining with the rapid prototyping technology and laser cladding technology. It can rapid manufacture the complex aluminum alloy parts. Laser additive manufacturing aluminum alloy will produce poor forming quality, balling, slag, crack and porosity defects due to aluminum alloy have low density, poor liquidity, strong oxidizing, high reflectivity and conductivity etc. In order to understand the key problem of laser additive manufacturing aluminum alloy, in this paper, the effect of substrate and process parameters on the structure and properties of laser additive manufacturing Al-12Si alloy was analyzed. The effect of process parameters and solution treatment on the microstructure, phase distribution and vibration damping performance of laser additive manufacturing Al-12Si alloy was discussed.By studying the morphology, microstructure and properties of laser additive manufacturing Al-12Si alloy on Al-12Si alloy, Ti6Al4 V alloy, pure Ni substrate respectively, The comprehensive performance is best for laser additive manufacturing Al-12Si alloy on pure Ni substrate. By researching the process parameters of laser additive manufacturing Al-12Si alloy, we finally obtained the optimum process parameters range. The laser power is 600 W to 800 W, the laser scan speed is 10 mm/s to 16 mm/s, the powder feed rate is 2.1 g/min to 3.2 g/min. At the same time, we have studied the effect on microstructure, properties of laser additive manufacturing alloy with different laser scanning paths. Laser deposition Al-12Si alloy with an identical laser scan direction was proved to be the best laser scan path. The microstructure of laser additive manufacturing Al-12Si alloy was observed by optical microscope and scanning electron microscopy. The columnar dendrites transfer to equiaxed dendrites on the top of layer. The microstructure is composed by circular or fibrous Si particles and the cellular structure of primary Al, most of Si particles surround in the bound ary of primary Al, Al-Si solid solution is formed by part of Si particles solid solution to the Al matrix.The mechanical properties of laser additive manufact uring Al-12Si alloy was explored. The strength and ductility of laser additive manufacturing Al-12Si alloy are all superior to those produced by cast method. The tensile strength and elongation increased 15.6% and 6.25% respectively compare with cast Al-12Si alloy. At some time, the effect of solution treatment on microstructure, phase distribution and vibration damping performance of laser additive manufacturing Al-12Si alloy were explored. After solution treatment at 500 ℃ with different holding time, the Si particles gradually precipitate from Al-Si solid solution and grow up. And the Si particles uniformly distribute in the Al matrix with the holding time increasing. This leads strength decreasing, ductility and vibration damping performance improving.In this thesis, the substrate and parameters of laser additive manufacturing Al-12Si alloy was studied. And high performance laser add itive manufacturing Al-12Si alloy components was obtained. The effect of substrate, process parameters and solution treatment on properties of laser additive manufacturing Al-12Si alloy parts were investigated.