| Magnesium alloy with light weight, high strength and high stiffness has good thermal conductivity, good electromagnetic shielding, damping properties and can be recovered using characteristics, which Satisfy the automotive industry that meet the weight loss, energy saving, environmental protection and communications Electronics highly integrated device miniaturization and light requirements. Therefore, regarding the development of magnesium alloy and its forming process will be applied in industry and theoretical research.This article selects the magnesium alloy that aluminum-containing 15%. In this paper, the alloy's preparation, refining, semi-solid slurry preparation and thixotropic forming process and die-casting heat treatment were researched to carry out a systematic study.Experiments using Al-5Ti-0.25C intermetallic alloy study the refinement of as-cast magnesium alloy and effect on the properties of alloy, the results proved that Al-5Ti-0.25C played the great role of grain refinement. when refine content was 0.5% and temperature was 730℃, the average grain size of the alloy would reduced from 387μm before adding refinement to 65 u m and tensile strength increased by refinement from 109MPa to 208MPa. It was the reason that Al-5Ti-0.25C alloy at the high temperature can be formed phase TiC, Al4C3 phase, their lattice structure were the same as a-Mg with 5% lattice mismatch, interface with a total of Georgian relations the can be used as alloy solidification process at the non-homogeneous nucleation core. While it showed that refinement did not change rock-candy structure by analysing tensile fracture before and after the alloy.Compared with refining structure of the Mg-15A1 alloy after semi-solid treatment, so it can win the best semi-solid forming solid fraction range from 40% to 60% according to the phase diagram that determined the isothermal temperature of 500℃,520℃,540℃. The results showed that can get excellent semi-solid structure in the above temperature heat 50 minutes, the average grain size of refined semi-solid alloy compared without refining was reduced from 163μm to 60μm. We received suitable semi-solid billet for thixotropic forming and carried out casting experiments to study different solid fraction of the billects at different speeds of injection molding parts and properties through isothermal treatment. Research showed that the best range of solid fraction (40%-60%), the more solid fraction was low, the better performance was excellent. When alloy injection speed was 3m/s and solid fraction was 40%, tensile strength of this process under die casting reached the highest 215Mpa. When alloy the semi-solid slurry solid phase is high, because flow was reduced without forming and gas in the liquid metal discharge rate decreased, which would increase the number of shrinkage, therefore, When the liquid is high, the alloy's mobility increased, but because of the liquid alloy has a higher rate, making the process of alloy solidification contraction becomes more apparent that may result in more shrinkage.
|
PDF Full Text Request