SLM adapted to work with soft alloys and materials

08 Mar 2016

Fraunhofer ILT says technique for welding Mg and Cu alloys promises new bio-implants and industrial benefits.

A new materials processing technique processing technique now allows selective laser melting (SLM) to be applied with problematic materials like magnesium or copper alloys, and other crack-prone, hard-to-weld metals.

Use of these materials in SLM significantly extends the range and capabilities of additive manufacturing and rapid prototyping. Several new examples will be presented in a session at the forthcoming International Laser Technology Congress AKL’16 and the accompanying “Laser Technology Live” event at the Fraunhofer ILT in April, 2016.

Selective laser melting with established materials like stainless steel, aluminum or titanium alloys has already come of age in the world of production, says the developer of the new approach, the Fraunhofer ILT. “Those materials and processes have been extensively researched, and the related machinery is available from a number of vendors,” said the launch statement.

“Things only get difficult when developers attempt to work with challenging materials such as magnesium. It is not only 30% lighter than aluminum, but it can also be used to produce resorbable implants, thus making it extremely desirable for use in lightweight construction and medical technology applications."

Experts at Fraunhofer ILT have developed a processing technique that now makes it possible to work with difficult materials using SLM. To combat heavy smoke formation, a new process chamber featuring optimized shielding gas flow was developed in cooperation with ILT spinoff Aconity3D for use with magnesium alloys. In addition, processes for use with copper alloys were optimized, as were special systems with high temperature preheating for use with crack-prone and hard-to-weld metals.

Bioresorbable Mg-based implants

Desirable features of implants, such as tailored designs and complex structures, can be produced at no extra expense using SLM, say the Fraunhofer team: “As a material, magnesium offers the added advantage of being resorbable by the human body. Implants based on solid magnesium materials are already in use, but further benefits are promised for new generation implants with a porous structure.”

The Fraunhofer ILT says that the idea here is that following insertion into the body, new bony material will grow into the implant, while at the same time the metallic material is resorbed by the body. Fraunhofer ILT has developed an SLM process for magnesium alloy implants of this type, in which both the exact shape and pore size of the implant can be determined. The biocompatibility of the implant prototypes has already been demonstrated in vitro.

While Fraunhofer ILT continues to research new materials and processes, SLM equipment for magnesium alloys is already available from Aconity3D.

Industrial benefits

The advantages of magnesium alloys have long been known in the worlds of aerospace and motorsports. These materials are typically 30% lighter than aluminum, but again much more difficult to work. The new SLM processing technique also solves this problem. To explore the concept in detail, the Fraunhofer ILT constructed a motorcycle triple clamp in 1:4 scale, by optimizing the entire topology of the component by computer. The objective was to achieve full structural and weight optimization for comparable lightweight parts.

The developers concluded, “This trial represents one of the world’s first example of complex components made from magnesium alloys. In terms of quality, the parts are equal to other SLM products, yet with respect to strength they are even superior to cast parts. This opens the door to new applications not only in lightweight construction, but also in medical technology, such as custom-made surgical bone replacements for cranio maxillofacial applications.“

SLM live at AKL’16

In addition to magnesium alloys, research is continuing on developing SLM for processing novel materials such as high-temperature alloys for turbomachinery applications or copper alloys. The various processes will be exhibited at the International Laser Technology Congress (AKL ’16) in Aachen, Germany, between April 27-29, 2016. As a part of the exhibition, Fraunhofer ILT will be once again offering around 70 “Laser Technology Live” presentations in addition to talks with subject area experts at its Application Center.

About the Author

Matthew Peach is a contributing editor to optics.org.