Customised Alloy Blends for In-Situ Al339 Alloy Formation Using Anchorless Selective Laser Melting

Abstract

Abstract:The additive manufacturing process Selective Laser Melting (SLM) can generate large thermal gradients during the processing of metallic powder; this can in turn lead to increased residual stress formation within a component. Metal anchors or support structures are required to be built during the process and forcibly hold SLM components to a substrate plate and minimise geometric distortion/warpage due to the process induced thermal residual stress. The requirement for support structures can limit the geometric freedom of the SLM process and increase post-processing operations. A novel method known as Anchorless Selective Laser Melting (ASLM) maintains processed material within a stress relieved state throughout the duration of a build. As a result, metal components formed using ASLM do not develop signification residual stresses within the process, thus, the conventional support structures or anchors used are not required to prevent geometric distortion. ASLM locally melts two or more compositionally distinct powdered materials that alloy under the action of the laser, forming into various combinations of hypo/hyper eutectic alloys with a new reduced solidification temperature. This new alloy is maintained in a semi-solid or stress reduced state for a prolonged period during the build with the assistance of elevated powder bed pre-heating. In this paper, custom blends of alloys are designed, manufactured and processed using ASLM. The purpose of this work is to create an Al339 alloy from compositionally distinct powder blends. The in-situ alloying of this material and ASLM processing conditions allowed components to be built in a stress-relieved state, enabling the manufacture of overhanging and unsupported features.

Residual stress reduction of LPBF-processed CM247LC samples via multi laser beam strategies

“…Furthermore, with the mixed powder, a stress reduced state throughout the build was created with powder bed preheating. Similarly, according to [6], in situ alloying of Al339 (Al-Si-Cu-Mg-Ni), based on pre-alloyed batch blends AlMg and SiCuNi, does not develop significant residual stresses within the process and allows building parts without anchors or supports when powder bed pre-heating is applied.…”

Review on residual stress in selective laser melting additive manufacturing of alloy parts

“…Ti-5Al-2.5Sn alloy [111], 1 cycle laser re-melting on each solidified layer leads to residual stress increasing, while 2 or more cycles make principal residual stresses decreasing Experiments AlSi10Mg [189] Residual stress can be reduced with multiple re-melting Experiments Factors: Post heat treating is shown in Table 4 so-called metal eutectic systems, the anchorless selective laser melting (ASLM) or semi-solid state processing (SSP) [23,182] could keep the material of immediately processed layer stay semi-solid state through controlling input laser energy and preheating building platform [23,182] and thus suppressing the residual stress in parts.…”

Review of materials used in laser-aided additive manufacturing processes to produce metallic products

“…This condition limited the geometric freedom of the process and made post-processing necessary. The development of residual stresses and the use of anchors were eliminated by using anchorless SLM [117]. These were achieved by maintaining the material in a stress-relieved state for the duration of the build.…”