Laser Powder Bed Fusion – Materials Issues and Optimized Processing Parameters for Tool steels, AlSiMg‐ and CuCrZr‐Alloys

Abstract

Laser Powder Bed Fusion (L-PBF) is the main technology for additive manufacturing of metallic components and is primarily used for rapid prototyping and tooling in cases with very complex geometry or lightweight design and small quantities. There are manifold influencing parameters, which need to be optimized in order to build components with suitable properties. The paper deals with three distinct application fields, like the development of new tool steel grades for injection molds, light weight design using aluminum alloys with optimized post-weld heat treatment as well as production of copper alloys without porosity. The most sensitive process parameters are displayed and the multilayered components are characterized using light and high-resolution microscopy as well as mechanical testing.

CuCrZr processed by laser powder bed fusion—Processability and influence of heat treatment on electrical conductivity, microstructure and mechanical properties

“…Here, the highest hardness (125 HV1) is reached upon aging at a temperature of 450°C for 120 min. This is again in line with Buchmayr et al 27 and Wallis et al 35 reporting hardness values of 112 HV1 and 126 HV1, respectively, for the same SA + A heat treatment strategy (data recompiled in Figure 4). Afterward, the hardness drops down due to overaging.…”

“…The experimentally determined hardness values of the specimens as a result of heat treatment are given in Figure 4. The as‐built condition possesses an average hardness of 80 HV1, which was similarly shown in several studies reporting on LB‐PBF CuCrZr 27,35,40 . This value is in the range of SA conventional conditions 58 .…”

“…Thus, the partially recrystallized microstructure showing traces of initial scan tracks remains unchanged upon DA heat treatment as also revealed in the study of Wallis et al 35 In contrast, significant changes in microstructure evolution upon SA + A can be seen in case of the MC condition as shown in Figure 5D. As a result of SA, a homogeneous, fully recrystallized microstructure being characterized by vanished scan tracks and large grains (including recrystallization twins) develops as numerously shown in literature 27,35 …”

“…The hardness of the as-built condition drops down to 60 HV1 when it is exposed to a solution annealing. This effect, also observed by Buchmayr et al 27 and Wallis et al, 35 can be attributed to the higher dislocation density and fine-grained structure in the as-built condition as has been shown for several materials as a consequence of rapid cooling and intrinsic heat treatment, respectively. 31 Microstructure evolution imposed by the SA treatment will be further discussed in the next section.…”

CuCrZr alloy produced by laser powder bed fusion: Microstructure, nanoscale strengthening mechanisms, electrical and mechanical properties

“…This obtained value is high compared to that of the CuCrZr (SA+WQ) from literature (65-77 HV1 [30]), which is also a microstructural state free from nano-precipitates. Hardness was found to be similar for L-PBF SA+AH and wrought SA+AH CuCrZr tested here and compared to similar CuCrZr SA+AH from the literature [8][9]12,20]. This is probably due to the recrystallization occurring during the SA heat treatment.…”