The new alloys enable parts to be used in their ‘as cast’ state, eliminating two costly process steps – heat treatment and straightening – while yielding required mechanical properties.
Environmental and governmental pressures continue to push automakers worldwide to search for new areas of light weighting, and car structural components prove to be the new, fast-growing application for aluminium. This is true for both conventional internal combustion engine (ICE) vehicles, and electric ones. In addition, electric vehicles extensively use aluminium for other components, such as battery housings. The trend, of course, poses the question of optimal material choice for meeting key criteria in cost efficiency, light-weight as well as good mechanical, thermal and crash performance.
Traditionally, high-pressure die casting (HPDC) aluminium components are chosen over extrusions where complex part configuration is required. However, currently available HPDC alloys (both primary and secondary) typically cannot be used in ‘as cast’ state and require lengthy and costly heat treatment. Often, further mechanical straightening is needed to bring the casting to its original geometry after such treatment. The logical solution is to use alloys, which eliminate the process step and still yield sufficient mechanical properties – so called Non-Heat Treat alloys (NHT).
New Alcoa alloys
Alcoa had developed a NHT alloy that has been used by several manufacturers to produce shock towers, doors and other parts, yet it was difficult to cast due to hot cracking tendencies. To address this issue, Alcoa introduced two new, proprietary NHT alloys with improved castability, A152 and A153 (patent pending), at the Dusseldorf Aluminium Fair in October 2018. The new proprietary alloys demonstrate average elongation of nine to 11%, average tensile strength of 265 to 280 MPa and average yield strength of 150 to 170 MPa in the as cast state – comparable to T5 or T6 temper of traditional foundry alloys used for such applications.
“Alcoa has a long history of innovation, developing alloys for the most challenging applications. These new non-heat-treated alloys are products of years of research. We are pleased to introduce them to the market. The alloys are suited for complex thin-wall castings for car body structures for both conventional ICE and electric vehicles and are expected to bring substantial benefits for HPDC foundries, OEMs, and multi-material vehicle integration teams,” says Christine Keener, VP Commercial & Strategy at Alcoa Aluminium.