Effects of the addition of Ti powders on the microstructure and mechanical properties of A356 alloy

• In situ Al3Ti/A356 composites were fabricated in 780 °C by using Ti powders as the additive.
• The morphology and size of α-Al crystals changed a lot by adding Ti powders.
• The mechanical properties of A356 were improved significantly by adding Ti powders.

In the present research, the effects of the addition of Ti powders on the microstructure, especially the morphology and size of α-Al crystals and the mechanical properties of A356 alloy were studied. The experimental process involved that 1.5 wt.% and 3.0 wt.% of Ti powders were added into the molten A356 alloy at 780 °C, respectively. In the meantime, high-intensity ultrasonic vibration was introduced into the melt for 5 min for dispersing particles and degassing melt. The microstructures and mechanical properties of samples after T6 heat treatment were investigated, respectively. The results showed that in situ formed Al3Ti particles containing element Si were blocky in morphology, with the size in the range of 2–7 μm. With the addition of Ti particles, α-Al crystals of A356 transferred from long columnar dendrite to roughly spherical in morphology, and the size of which decreased obviously as well. Comparing with A356 alloy, the hardness, tensile strength and elongation of A356/3.0 wt.%Ti improved by 24.7%, 42.3% and 29.9%, respectively.

Figure. OM images of samples: (a) A356, (b) A356/1.5 wt.%Ti, and (c) A356/3.0 wt.%Ti.Figure optionsDownload as PowerPoint slide