PSI - Issue 68

V. Milani et al. / Procedia Structural Integrity 68 (2025) 1181–1187 V. Milani, G. Angella, G. Timelli/ Structural Integrity Procedia 00 (2025) 000–000

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Table 2. Weibull moduli, β , scale parameters, η , and coefficients of determination R 2 for the elongation to fracture obtained from the two parameter Weibull analysis. Data refer to AlSi9Cu3(Fe) alloy treated at different fluxing conditions and two melt-processing temperatures: (a) 720 and (b) 760 °C. Processing Temperature (°C) Fluxing Condition β η (%) R 2

Flux A Flux B No Flux Flux A Flux B No Flux

9.22 6.48 5.14 9.59 6.63 4.83

2.23 2.43 2.30 3.06 3.12 3.32

0.95 0.86 0.96 0.89 0.93 0.96

720

760

At 720 °C, the molten alloy preliminary treated with the flux show higher β values if compared to the untreated (No-flux) condition, with Flux A providing the greatest improvement, indicating lower dispersion of El%. The same effect of fluxing condition was observed at the higher processing temperature of 760 °C, with Flux A providing the higher Weibull modulus and the untreated condition leading to the lowest value of β. The two-parameter Weibull analysis highlighted the importance of controlling the processing temperature and of using fluxes to achieve higher β values, which correspond to lower scattering and greater reliability in terms of alloy’s ductility. The R 2 values suggest that the 2-parameter Weibull distribution fits the data well in most cases; however, there is potential for further refinement. To address this, the application of the three-parameter Weibull distribution was also studied. According to Tiryakioğlu and Campbell (Tiryakioğlu & Campbell, 2010), the threshold parameter λ should not be assumed to be zero, because a proper interpretation of Weibull plots can provide valuable information on the defect distributions in the castings. Figure 2 shows the three-parameter Weibull probability plots, where the threshold parameters λ are positive, indicating the absence of a second defect distribution (Tiryakioğlu & Campbell, 2010). This is further supported by the individual value plots, which show no gaps between the strain values, independently of the processing temperature and fluxing condition (see Figure 1). In general, gaps among the values would suggest two distinct distributions of casting defects (Eisaabadi et al., 2013).

Fig.2 Three-parameter Weibull plots of the elongation to fracture. Data refer to AlSi9Cu3(Fe) alloy treated at different fluxing conditions and two melt-processing temperatures: (a) 720 and (b) 760 °C.

Eisaabadi et al. (2013), when investigating the effect of melt quality and filtering on the Weibull distributions of tensile properties of AlSi7Mg alloy castings, found that stirring of the melt caused significant damage, partially mitigated by a filter, which resulted in mixed Weibull distribution of tensile strength and elongation. However, the present work does not show a mixed Weibull distribution, indicating that the filling system did not introduce