Effect of Ti and multidirectional forging on shear mechanical properties of in-situ ZA22-4Si composite

Achieving the desired mechanical properties in in-situ composites is governed by morphological modification, refinement, and even distribution of reinforcement particles which are formed during their solidification. This study was aimed to investigate the effect of Ti addition and multidirectional forging (MDF), as an industrially practical process, on microstructure and shear mechanical properties of cast ZA22-4Si composite. The obtained results showed that chemical modification of composite through 0.2 wt. % Ti addition converted the coarse primary grains to the well-refined equiaxed grains and reduced the size of primary Si particle (SiP), and porosities and improved their distribution within the matrix. The image analysis results also indicated that the average size of grains and SiP particles reduced from 750 and 25 mm to about 135 and 15 mm, respectively. Applying MDF at 100 ° C at the different passes breaks the primary dendrite network, decreased the average size of SiP particles, and promoted their even distribution within the matrix. According to the image analysis results in 2- and 5-pass MDFed composite the average size of SiP particles reached to about 8 and 6 μm, respectively. The shear punch tests also indicated that the combined effect of MDF and Ti addition reduced the strength whilst improved the ductility of as-cast composite where the yield and tensile shear strength of 5-pass MDFed sample reduced from 135 and 164 MPa to about 92 and 130 MPa, respectively, and its normal displacement value improved from 0.52 to about 0.72.