Figure 8a. Weibull Plots for Plastic Elongation for Chill #1 Condition.
Figure 8b. Weibull Plots for Plastic Elongation for Chill #2 Condition.
cc/100 grams Al (see table 2b). For Chill #2 the distribution plots seen in Figures 6b and 7b for plastic elonga- tion and UTS respectively are narrow and have near complete
International Journal of Metalcasting/Winter 10
Figure 6a and 6b show the distribution plots of the plastic elongation data for the two chills used, while Figure 7a and 7b show the distribution plots of the UTS data. Figure 6a and 7a reveal the broad distribution of the tensile test results in samples containing elevated levels of porosity due to elevated hydrogen concentrations. There appears to be better overlap of distribution for iterations 2 and 3, where the test sample po- sition was adjusted, but hydrogen concentrations were at 0.10 to 0.11 H2
overlap, which is presumably due to the more refined micro- structure and the low dissolved hydrogen concentrations.
Figure 8a and 8b show the Weibull plots for plastic elonga- tion for the two chills used, while Figure 9a and 9b show the Weibull plots for the UTS results. The plastic elongation reliability modulus seen in Figure 8a increased from 2.65 to 3.26 with the lowering of the dissolved hydrogen levels (≥ 0.15 cc H2
/100 grams Al), and then with changing the orientation of the tensile test bar the modulus increased to 6.49. Elevated hydrogen concentrations will result in more
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