Study On Molding Orthopaedics Of AZ91D Magnesium Alloy Ultra-thin Laptop Shell

In recent years,the die-cast laptop shell made of magnesium alloy has been widely used for its light weight,high strength,good electromagnetic shielding and heat dissipation.But in the pursuit of low cost and lightweight,many engineers rarely consider the difficulty of casting when designing the structure of magnesium alloy ultrathin laptop shell.As a result,the complex structure,large difference in wall thickness and high precision of products has brought great challenges to the development and production of die-casting technology.Therefore,orthopaedic technology is needed to overcome the defects and improve the quality of ultra-thin and die-cast products.Flatness-substandard AZ91D magnesium alloy ultrathin laptop shell is the research object in this study.And the orthopaedic technology was adopted.The main research content includes: The numerical simulation of the die casting process;The design of orthopaedic mold;The molding orthopaedic experiment of parts;The evolution of microstructure and mechanical properties in the process of molding.In this experiment,Pro Cast software was used to simulate the die-casting process of AZ91D magnesium alloy ultrathin laptop shell,and the influence of various parts of that on the flatness and filling process was analyzed on the basis of temperature field and stress field.After that,the die was designed and improved by means of "local discretization" for the position of waterproofing table and cooling hole,so as to carry out the test of molding.In the molding orthopedic experiments,the effects of mold temperature,workpiece heat-preservation temperature and pressure-maintaining time on the flatness of AZ91D magnesium alloy ultrathin laptop shell were studied.The best technology obtained from the experiments: Firstly,put the workpiece which need to be rectified into a constant temperature furnace at 200℃ for 10 min,and then quickly transferred it to a mold heated to 280℃ for molding orthopaedics,and the pressure was kept for 50s;Finally,the workpiece was removed and cooled in air to room temperature.By analyzing the microstructure and mechanical properties of AZ91D magnesium alloy ultra-thin laptop case,it was found that its grains were small,mostly equiaxed or rose-shaped.Under the optimal molding technology,molding experiments were carried out.The yield strength and tensile strength of the workpiece reached 159.72 MPa and 266.22 MPa respectively,both of which were 17.33% higher than the original.The reduction of die pressing temperature and the prolonging of pressure holding time promoted the precipitation of Mg17Al12 phase in AZ91D alloy and promoted the transformation of Mg17Al12 phase from discontinuous network to continuous network,which was conducive to the improvement of mechanical Properties.