Of Zl109 Spray Deposition - The Hot Extrusion Process

The ZL109 is the foundry eutectic Al-Si alloy, it' s often used to make pistons. The plasticity of ZL109 is bad, the extension rate is only 0.5% at the room temperature. The main reason lies in that the Si phases in the microstructure are shaped as thick needles or discontinuous strips, which dissevers the matrix seriously. In this article, the Spraying Deposition and Hot Extrusion technologies were used in conventional foundry ZL109, and the needle or strip shaped Si phases were changed to irregular pieces, which eliminated the dissevering effect ultimately, fined the grains at the same time. As a result, the mechanical properties of ZL109 have been greatly enhanced. After spraying deposition and hot-extrusion, the extension rate was enhanced by 14 times, attaining to 7.5%;the tensile strength was enhanced nearly 40% on the average. On the other hand, the basic theories and mathematics models of the spraying deposition were studied deeply and generally. By analyzing the experiment results, the relation among the spraying deposition parameters, miscrostructure and mechanical properties has also been discussed, then the opinion that the solidification shrink is the first mechanism to engender porosities in the deposition body at the condition of low cooling capability and the great liquid phase amount is put forward.