Aluminium Micro-Alloying with increased tensile strength

Cast aluminium alloys are widely used in light-weighting structures in the automotive and aerospace industry because of their high strength-to-weight ratios, anti-corrosion and good castability. However, the mechanical properties of commercially cast aluminium alloys are not as high as wrought aluminium alloys and other lightweight materials, such as titanium-based alloys.

There is a need to improve existing alloys, developed several decades ago, as the mechanical property requirements have greatly increased since then. For industrial applications, particularly in automobile and aerospace, an increase in yield strength of 20% at room and high temperature (250°C) versus existing alloys, whilst maintaining ductility, would be a significant improvement.

Mechanical properties can be improved to some degree through microstructure refinement of both grains and secondary phases by chemical and physical methods. Another method of improving aluminium alloy strength is to add alloying elements to form nano-sized strengthening phases - precipitation strengthening. However there are limitations to how far this can be used due to the resultant reduction in ductility, measured as elongation. There is a need to increase tensile strength without sacrificing ductility.

In addition, existing cast aluminium alloys are relatively sensitive to the wall thickness of the castings. For example, for the commercial A356 alloy, the elongation can be reduced from 8% to 2% as the thickness of the castings is increased from 5 mm to 40 mm. There is a need to reduce such sensitivity to casting wall thickness.

In order to obtain the desired benefits, existing commercial alloys are treated by adding chemical elements at a low level of up to 0.5% on top of that already in the existing commercial alloy. The elements that can be used are nickel, silver, niobium, molybdenum, cerium, lanthanum, yttrium, and scandium. They result in the formation of at least one type of sub-micron or nano-sized solid particles uniformly distributed in the solidified castings. The solid phases are formed as prior phases or as eutectic phases during solidification. They are controlled to exhibit a granular morphology with specified particle sizes and distribution which are too small to be detected (see attached TEM micrograph).

See attached data sheet for alloy compositions and technical data.

Technnology benefits:

• Tensile strength increased by 20% at room temperature and high temperature (250°C) versus existing aluminium alloys;
• ductility maintained at a same level as for existing aluminium alloys;
• finer precipitates than that of the current commercial aluminium alloys so that particles are not detectable.
• use in Automotive and Aerospace applications; potential for replacing wrought aluminium alloys and titanium alloys

Intellectual property status

Patent already applied for

Patent application number : WO2018/142141

Where : Worldwide

Current development status

Experimental technologies

Desired business relationship

Patent licensing

Technology development

New technology applications