# Selective Laser-Melted Alloy 625: Optimization of Stress-Relieving and Aging Treatments
## 1 Introduction
Table 2 provides a summary of the data reported in Table 1 with the range and the average values for each condition. According to these data, the as-built selective laser-melted alloy 625 shows outstanding mechanical properties compared to those of the conventional wrought  
Figure 1: Experimental time–temperature–precipitation (TTP) curves for the delta phase of the SLMed 60 alloy 625 compared to those of the wrought (WR) alloy. Adapted from [10; 17; 18]. and centrifugally cast alloys. Moreover, in the as-built condition, the mechanical strength is reduced by both soft- (1038 \({}^{\circ}\)C) and solution-annealing (1150 \({}^{\circ}\)C) treatments because of grain coarsening after recrystallization and the progressive removal of the original dendritic structure. However, because of the excellent fineness of the as-built microstructure, the mechanical strength upon annealing treatments remains higher than that observed in both the conventional wrought and centrifugally cast alloys. These excellent properties make selective laser melting a promising manufacturing process from the point of view of static mechanical strength. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Condition** & **Hardness** & **YS [MPa]** & **UTS [MPa]** & **A\%** & **Reference** \\ \hline As-built (SLM) & — & 567–783 & 836–1041 & 10–57 & [19] \\ \hline As-built (SLM) & — & 350–400 & 840–910 & 56–62 & [20] \\ \hline As-built (SLM) & 285 HBW & 618–783 & 891–1041 & 33–41 & [21,22] \\ \hline As-built (SLM) & — & 770 & 1039 & 40 & [23] \\ \hline As-built (SLM) & — & 709–859 & 1103–1242 & 27–30 & [24] \\ \hline As-built (SLM) & 342 HV0.5 & 566 & 1087 & 29 & [25] \\ \hline As-built (SLM) & 304 HV0.3 & — & — & — & [26] \\ \hline As-built (SLM) & 332 HV0.5 & 676–767 & 964–1055 & 34–42 & [27] \\ \hline As-built (SLM) & 273–303 HV2 & 630 & 827 & — & [28] \\ \hline As-built (SLM) + 1038 \({}^{\circ}\)C & — & 523–577 & 841–854 & — & [19] \\ \hline As-built (SLM) + 1038 \({}^{\circ}\)C & 253 HV0.5 & 598–633 & 955–1020 & 39–43 & [27] \\ \hline As-built (SLM) + 1150 \({}^{\circ}\)C & — & 379 & 851 & 55 & [22] \\ \hline As-built (SLM) + 1150 \({}^{\circ}\)C & 190 HBW & 396 & 883 & 55 & [21] \\ \hline As-built (SLM) + 1150 \({}^{\circ}\)C & 190 HBW & — & — & — & [29] \\ \hline Wrought (solubilized) & — & 413 & 914 & 70 & [30] \\ \hline Wrought (solubilized) & — & 350 & 809 & 76 & [23] \\ \hline Wrought (solubilized) & 169–275 HV30 & 317–460 & 751–910 & 47–70 & [11,31] \\ \hline Centrifugally cast & 80–90 IRB 151–188 HV & 290–310 & 580–595 & 46–57 & [28,32] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Literature data about the mechanical properties of the selective laser-melted alloy 625 compared to those of the conventional wrought and centrifugally cast alloys. A% is the percentage of elongation. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Condition** & & **YS [MPa]** & **UTS [MPa]** & **YS/UTS [-]** & **A\%** \\ \hline \multirow{2}{*}{As-built (SLM)} & Range & 350–859 & 827–1242 & 0.43–0.76 & 10–62 \\ \cline{2-6}  & Average & 653 & 990 & 0.66 & 38 \\ \hline \multirow{2}{*}{As-built (SLM) + 1038 \({}^{\circ}\)C} & Range & 523–633 & 841–1020 & 0.62–0.68 & 39–43 \\ \cline{2-6}  & Average & 583 & 918 & 0.64 & 41 \\ \hline \multirow{2}{*}{As-built (SLM) + 1150 \({}^{\circ}\)C} & Range & 379–396 & 851–883 & 0.45–0.45 & 55–55 \\ \cline{2-6}  & Average & 388 & 867 & 0.45 & 55 \\ \hline \multirow{2}{*}{Wrought (solubilized)} & Range & 317–460 & 751–914 & 0.43–0.47 & 47–76 \\ \cline{2-6}  & Average & 384 & 851 & 0.45 & 68 \\ \hline \multirow{2}{*}{Centrifugally cast} & Range & 290–310 & 580–595 & 0.50–0.52 & 46–57 \\ \cline{2-6}  & Average & 300 & 588 & 0.51 & 53 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary of the data reported in Table 1 with range and average values for each condition. The additive manufacturing technique permits a high customization level and design freedom in terms of shape and thicknesses.