According to Velo3D’s process engineering technologist, Suraj Rao, many industries are replacing aluminium–magnesium-silicon alloys, like F357 and AlSi10Mg, with Aheadd CP1 for a number of compelling reasons.

With weight-reduction being a priority, many manufacturers have recently turned to the lightweight aluminium-silicon-magnesium based alloys, like F357 and AlSi10Mg, when 3D printing parts for everything from race cars to rockets.

Depending on the application, it’s true that more-expensive titanium alloys can have a better strength-to-weight ratio than aluminium ones, and copper alloys can provide better heat-transfer coefficients. Magnesium alloys may support lower densities and higher galvanic potential. But when looking to optimise the cost, performance and manufacturability of additively manufactured (AM) parts, aluminium alloys can deliver all three goals very efficiently.

Aluminium–magnesium alloys were adapted for AM by tweaking existing materials that have been used in conventional casting for years. And we’ve seen a wide range of successful 3D-printed parts in these alloys performing well across multiple industries.

However, just in the last year or so, a new aluminium alloy - Aheadd CP1 - has leapt over aluminium-silicon-magnesium alloys in adoption by many AM users. CP1 is an aluminium-zirconium-iron alloy that was specifically designed for metal laser powder bed fusion (LPBF) printers by leading global aluminium products and solutions provider, Constellium. The development of CP1 has been greeted with noticeable enthusiasm: here at Velo3D, we’ve seen many manufacturers that have been printing aluminium with one of our AM systems switch to CP1. What’s the attraction? A number of interesting answers.

Created from scratch

Because CP1 was created from scratch, tailored, and engineered with the specific rigors of the AM process in mind, it avoids some of the challenges manufacturers have had to overcome when using other aluminium alloys.

While aluminium is the common denominator, CP1 contains zirconium and iron, whereas F357, AlSi10Mg, and similar alloys contain silicon and magnesium. Due to the high solidus temperature and the absence of magnesium (which makes it better for brazing), and lack of silicon (which can cause porosity when welding), CP1 is evolving as the alloy of choice for applications that need to be brazed or welded with conventional materials.

Another benefit of CP1: After printing parts with F357, manufacturers must thermally treat them using three separate steps that involve solution treatment, quenching and aging. While other aluminium-silicon-magnesium alloys, including AlSi10Mg, are easier to heat treat, their other material properties, including strength, corrosion resistance, and ability to anodise do not fit the needs of many applications. CP1 parts, on the other hand, need only a single, four-hour, lower temperature-treatment process that provides significant time and cost savings and avoids the thermal distortion that can occur when treating at higher temperatures. In addition to the inherent corrosion resistance properties, CP1 exhibits stable microstructure up to 300°C, enabling finished parts to better maintain their properties in valuable high-temperature applications such as heat exchangers.

Because CP1 material is isotropic, Constellium has demonstrated that parts made from it have the same mechanical characteristics regardless of how their geometries are oriented on the build plate. This simplifies setup time and frees the AM engineer to optimise for other desired properties such as surface roughness or performance.

An important side-benefit of the composition of CP1 is that its one-step heat treatment precipitates the zirconium and iron phases, leading to an almost-pure aluminium matrix that provides high electrical and thermal conductivity. Tests are showing conductivity-performance metrics that are equal or surpass some of those for more-expensive, non-aluminium alloys. (The thermal conductivity of CP1 when heat treated is 187W/mK; F357 standard value is about 150W/mK, and standard AM titanium alloy Ti6Al4V is around 6.7W/mK.)

No wonder CP1 has already been qualified for use in several different AM systems. Powder-production scalability and overall lower cost of ingredients add to the savings equation.

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