Strength in numbers for 3-D printing | 3/18/2019 | Staff
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Additive manufacturing, also called 3-D printing, is commonly used to build complex three-dimensional objects, layer by layer. A*STAR researchers have shown that the process can also help to make a high-performance alloy even stronger.

Cobalt-chromium-iron-nickel-manganese (CoCrFeNiMn) is known as a high entropy alloy. Discovered in 2004, it is particularly good at withstanding fractures under harsh environmental conditions, such as low temperatures. To make an object from the alloy, researchers typically pour the molten metal into a cast, allow it to cool, and then machine it into the desired shape. However, this can be a time-consuming and costly way of making complex components. In principle, additive manufacturing could skip the machining step to directly fabricate complex components.

Nai - Mui - Ling - Sharon - A*STAR

Nai Mui Ling Sharon of the A*STAR Singapore Institute of Manufacturing Technology (SIMTech), her colleagues, and international collaborators have shown that an additive manufacturing method, called selective laser melting, is well suited to building components from CoCrFeNiMn. The process uses a powerful laser beam to melt tiny powder particles of the alloy, which then fuse to make a solid object. Remarkably, the researchers found that the process actually produces a stronger material than conventional casting methods. "It exhibits an enhanced strength with a relatively good ductility," says Zhu Zhiguang, a research fellow in the SIMTech team that led the study.

The researchers first created a pre-alloyed powder of CoCrFeNiMn, containing particles that were an average of 36 micrometers across. Then they used laser melting to craft the particles into 10-millimeter-wide cubes, or flat bars of 90 millimeters. They also varied the laser's power, and the speed that it scanned over the alloy particles, to understand how different printing conditions affected the alloy's performance.

Analysis - Samples - Number - Features - Material

Analysis of the samples revealed a number of features that determined the material's properties. For example, it contained microscopic melt pools, rather like miniature welds...
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