Preparation method of high-strength and high-toughness A356.2 metal matrix composites for hub

A preparation method of a A356.2 metal matrix composite for a hub, comprising the following steps:

• step (1) charging an aluminum ingot into a resistance furnace after a temperature of the resistance furnace is increased to 420° C.;
• step (2) completely melting the aluminum alloy ingot, increasing the temperature to 720-740° C., adding an Al-20Si master alloy, and holding the temperature of a resulting melt at 720-740° C.;
• step (3) adding a magnesium ingot into a liquid surface of the melt, performing an electromagnetic stirring until the melt is homogenized, and adding 2-4 kg/ton of chlorine salt and fluorine salt refining agents under an argon atmosphere for refining at a refining temperature of 720-740° C.;
• step (4) adding an aluminum-graphene-hafnium diboride master alloy after statically holding the temperature for 5 min, and performing a slag-off treatment and a furnace discharging, wherein a content of graphene is 1-5% of a content of aluminum in the aluminum-graphene-hafnium diboride master alloy, a content of hafnium diboride is 0.3-1% of the content of aluminum in the aluminum-graphene-hafnium diboride master alloy, and a preparation method of the aluminum-graphene-hafnium diboride master alloy in the step (4) is:
• adding an aluminum-10% hafnium master alloy into an aluminum melt of 740-760° C., then adding an aluminum-5% boron master alloy and an aluminum-10% graphene master alloy, and continuously casting and continuously rolling to produce an aluminum-graphene-hafnium diboride master alloy wire with a diameter of 9.5 mm;
• step (5) performing a pressure casting at a temperature of 690-720° C.;
• step (6) performing a solution and aging heat treatment process;
• step (7) performing a shot blasting, a mechanical finishing, an alkaline cleaning, an acid cleaning, a surface anodic oxidation, and a finished product packaging,
• wherein the A356.2 metal matrix composite for the hub is composed of the following alloy in mass percentage:
• 6.5-7.5% of Si, 0.30-0.45% of Mg, 0.04-0.08% of Cu, 0.03-0.15% of graphene, 0.01-0.05% of HfB2, not more than 0.1% of Ti, not more than 0.1% of Fe, not more than 0.05% of Mn, and the balance of Al.