Study On Melting Process Of Al-50wt.%Si Alloy

Ultra-high Si Al-50wt.%Si alloy has the advantages of low density, lowcoefficient of thermal expansion good thermal conductivity etc excellent physicalcharacteristics and mechanical properties, so it is widely used in electronicpackaging industries. But large-scale Si results in the existing of needle-like eutecticsilicon and coarse block primary silicon, which dissevers the bonding of the matrixand aggravates the mechanical properties of the alloy. Silicon and coarse plateletprimary silicon, which dissevers the bonding of the matrix and aggravates themechanical properties of the alloy. So alloy melting method must be optimized tocontrol morphology and size of si phase for sake of meeting the needs of electronicpackaging material. Including melt overheating treatment, the content of modifier,cooling rate, heat treatment, which have been studied in order to investigate theireffects to fine structure and improve performances of alloy.Moreover, themechanism of modification was analyzed preliminarily.Melt overheating treatment which have been studied in order to investigatetheir effects to fine structure and improve performances of Al-50wt.%Si alloy withthe primary Si grain size decreasing from300μm to60μm through normalexperiment measure and OM.Effects of phosphorus modification on the base of melt overheating treatmentwhich have been studied in order to investigate their effects to fine structure andimprove Performances of Al-50wt.%Si alloy The microstructure and properties ofUltra-highAl-50wt.%Si alloys with different content of P were studied. The resultsshow that the content of P varying from0wt.%to0.9wt.%has effect on alloy,examination of the microstructure of the alloy by SEM techniques shows that themodification of Al-4.5wt.%P can obviously modify the primary silicon and eutecticsilicon phases The optimal content is adding0.5wt.%P, and the average Size ofprimary si particle is Al-4.5wt.%P modifier can modify both the eutectic si andprimary si of the alloy at the same time. The mechanical properties of alloy aregreatly improved by p modification and the room temperature tensile properties rosefrom29.36MPa to112.74MPa, compared with P modification the tensile strengths ofmodified50wt.%Al–Si alloys become much higher than that of the unmodified one.Therefore it can be concluded that better refinement effect can be obtained bythe p modification method the morphologies of primary si change from plate-likeshape to fine blocky shape, and the size of primary si ranges approximately from 40μm to50μm examination of the thermal expansion property at26℃shows that theCTE of the alloy with0.5wt.%P level is9.2×10^-6/℃, lower than that of unmodifiedalloy.The alloy with p content of0.5wt.%is as shown in research on heat treatmenttechnology of ultra-high si Al-50wt.%si alloy prepared by Al-4.5wt.%Pmodification. The solution and artificial aging treatment of ultra-high si Al-50wt.%si alloy was optimized.The effects of solution, artificial aging temperature and timeon the organizational structure were studied. The optimal heat treatment technologywas determined. The results show that the influence of solution temperature,solution treatment time.On the structure and properties of ultra-high si Al-50wt.%Si alloy is increasing.The best heat treatment process parameters is solution at535℃for8h and artificialaging at175℃for12h, properties of alloy are greatly improved by heat treatmentThe alloy was subjected to tensile testing after T6heat treatment, and the roomtemperature tensile properties rose from112.74MPa to121.65MPa, elongationreached l.26%. Fracture morphology appears from typical brittle to plastic.