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

In situ precipitation of primary Si (SiP) particles within the microstructure of Si-containing Zn–22Al alloys, also known as ZA22/SiPcomposites, can improve their hardness and mechanical strength, provided that the size, morphology, and distribution of SiPparticles 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 a-Al dendrites, reduced the volume fraction of remaining a-Al phase within the microstructure, reduced the size of SiPparticles, and improved their distribution within the matrix. Moreover, the size of SiPparticles is reduced from 25.2?±?9.5 to 30.1?±?4.4 µm in non-modified samples containing 4 and 8 wt% Si to 14.7?±?6.3 and 19.6?±?5.3 µm 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.