Achieving ultra-high strength and ductility in Mg–9Al–1Zn–0.5Mn alloy via selective laser melting

Additive manufacturing of magnesium and its alloys: process-formability-microstructure-performance relationship and underlying mechanism

“…It should also be noted that the Hall-Petch coefficients k H utilized in different papers are different, making it difficult to compare the computation results among different investigations. For instance, Chang et al utilized k H = 164 MPa•µm 1/2 to evaluate the grain boundary strengthening effect and indicated that the contribution of grain boundary strengthening in LPBF-processed Mg-9Al-1Zn-0.5Mn alloy could reach 38.1% of the overall yield strength [150], which is smaller than the results shown by Deng et al If the utilized k H value was increased to 280 MPa•µm 1/2 (which is the same as the k H value used by Deng et al), the contribution proportion of grain boundary strengthening would be increased to 65.2%, which is consistent with the investigation by Deng et al The similar comparison is also found in the WAAM-processed Mg alloys. Li et al [151] and Cao et al [148] used k H = 158 MPa•µm 1/2 and 250 MPa•µm 1/2 , respectively, to evaluate the grain boundary strengthening effects in the WAAM-processed Mg alloys.…”

“…Solid solution strengthening is also an important strengthening mechanism in AM-process Mg alloys. For instance, Chang et al indicated the solid solution strengthening contributed 52.9 MPa to yield strength of LPBF-processed Mg-9Al-1Zn-0.5Mn alloy with the proportion of 17.7% [150]. Theoretically speaking, the solid solution strengthening effect has little to do with the forming process, which means the AMprocessed microstructure should exhibit similar solid solution strengthening effect to the as-cast microstructure as for a certain Mg alloy.…”

“…Li et al indicated that the dislocation strengthening could only contribute 3.2-8.6 MPa to the overall yield strength (the proportion was 5%-8%) [151]. However, Chang et al found that the dislocation strengthening contribution in the LPBF-processed Mg alloy could reach 55.9 MPa, occupying 18.7% of the overall yield strength [150]. This observation is ascribed to the heat accumulation and cooling rate during AM process.…”

“…However, the current literature in this field is very limited, making it difficult to conduct an in-depth discussion. For instance, Chang et al [150] and Li et al [151] discussed the Orowan strengthening effect caused by large nanoparticles in LPBF-and WAAMprocessed Mg alloys, respectively. However, the variation of precipitate strengthening effect (Orowan mechanism to cutting mechanism) with nanoparticle size is still unclear.…”

Influence of Aging Treatment Regimes on Microstructure and Mechanical Properties of Selective Laser Melted 17-4 PH Steel

“…Thus, the SLM-produced metallic components are commonly featured as equivalent or better mechanical properties [5]. To date, the SLM technique has been applied to the manufacturing of various kinds of metallic and composite materials, such as Ti alloys [6], Ni-based superalloys [7], Al-based alloys [8,9], Mg-based alloys [10,11], and Fe-based alloys [12]. Among all the steels, 17-4 PH (precipitation hardened) steel possesses an outstanding combination of high strength, excellent corrosion resistance, and favorable toughness [13][14][15].…”