The Research On Continuity Test Of Hypereutectic Al-Si Alloy

Hypereutectic Al-Si Alloy, a new generation of structural materials of developing, haslots of advantages, such as light weight, high thermal conductivity and low coefficient ofexpansion. Therefore, the research on its linking have great significance. The characteristicand applications of hypereutectic Al-Si Alloy were summarized in this research,and themain problems in its welding were analyzed. Some methods and updated research results,which is used in welding hypereutectic Al-Si Alloy, were pointed out.In this paper, The research on hypereutectic Al-Si Alloy by connectivity was infurnance, the soldering of hypereutectic Al-Si Alloy with the brazing fillers of Cu、Zn andBAl88SiMg and the laser welding with the pulsed laser welding machine were researched.Macroscopic morphology, microstructure, distribution of elements and connectormicrohardness were analyzed by means of metallography, vickers, scanning electronmicroscopy with energy dispersive spectrometer. and we discussed the influence of weldingmethods and different brazing parameters on joints. The major research efforts of thepresent study are follows:The results show that effective metallurgical bondings can be got under properconditions with the fillers of BAl88SiMg, Zinc and pure copper foil in the vacuum furnacebrazing of hypereutectic Al-Si Alloy. Structure of interfacial region grew from base metal tocentre with basal of base metal, and it was similar with base metal, so metallurgycompatibility was well. Along with the increase of brazing temperature and holding time,diffusible area become the wide gradually, and element diffusion behavior worse.Contact reaction brazing (CRB) for hypereutectic Al-Si Alloy with the interlayer of Cuwill create intermetallic compounds in the brazing seam inevitably, which influence themechanical properties of the brazing joints and result in brittle crack.Intergranularpenetration will arise because of low melting point eutectic.A lot of holes arise in the brazing seam because of big mutual solubility between Znand Al and heavy reactions, which will accelerate with rising of the holding time andinterlayer. But the solid solution and eutectic of Zn-Al can strengthen the organization ofseam and improve the mechanical property.The joint of hypereutectic Al-Si Alloy forms well by laser welding with the defects ofstomatal and incomplete fusion in the brazing seam, the structure of the brazing seam is equiaxial crystal, which is the ideal structure.Hardness of brazed joints decrease graduallyfrom diffusible area to interfacial region and to central area.Distribution curves of hardness present a U-shaped with variation in distance of seamcenter. Hardness of joints using Cu from Zn, but was higher than that from BAl88SiMgbecause of burnt Metal.