Enhancing the Mechanical Properties of Si Particle Reinforced ZA22 Composite by Ti-B Modification

摘要

In situ precipitation of primary Si (Si-P) particles within the microstructure of Si-containing Zn-22Al alloys, also known as ZA22/Si-P composites, can improve their hardness and mechanical strength, provided that the size, morphology, and distribution of Si-P particles are optimized. In this study, Ti-B treatment was employed to modify the microstructure and improve the mechanical properties of ZA22-xSi (x = 4 and 8 wt%) composite. According to the results, Ti-B treatment eliminated the primary alpha-Al dendrites, reduced the volume fraction of remaining alpha-Al phase within the microstructure, reduced the size of Si-P particles, and improved their distribution within the matrix. Moreover, the size of Si-P particles is reduced from 25.2 +/- 9.5 to 30.1 +/- 4.4 mu m in non-modified samples containing 4 and 8 wt% Si to 14.7 +/- 6.3 and 19.6 +/- 5.3 mu m in the samples modified by Ti-B, respectively. Ti-B addition also substantially refined and homogenized the distribution of the other second phases and porosities. The mechanical properties analyses revealed that, at a given Si concentration, the hardness of the alloys modified by Ti-B was relatively less than that of the non-modified ones. Moreover, the tensile strength and fracture strain of modified ZA22-4Si and ZA22-8Si composites are increased by about 15 and 59, and 60 and 82%, respectively.