PSI - Issue 34

T. Silva et al. / Procedia Structural Integrity 34 (2021) 45–50

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Author name / Structural Integrity Procedia 00 (2019) 000–000

Fig. 3. Relative sample length in function of instantaneous temperature for the CMed (a) and AMed (b) maraging steel, for a constant heating rate of 1 ◦ C / min; slope of the dilatometric curves of both CMed (c) and AMed (d) maraging steel during heating stage; specific heat capacity ( c p ) and thermal conductivity ( λ ) for both AMed and CMed 18Ni300 maraging steel.

commonly di ff ering microstructure of AMed vs. CMed steel (Bajaj et al., 2020). The existence of a more significant amount of retained austenite (6-11%) in the microstructure of as-built AMed maraging steel (comparatively to the CMed) means that less martensite is transformed into austenite, which in turn explains the smaller material contrac tion of the AMed maraging steel. Moreover, Bajaj et al. (2020) indicate that due to the high cooling rates very little or no precipitates are found in the microstructure of the AMed material, which supports its smaller precipitation-related contraction. In sum, the thermal expansion coe ffi cient of the tested materials, up to phase change occurrence, is quite similar but the subsequent phase changes reveal key di ff erences in the materials microstructure. The results for specific heat capacity ( c p ) and thermal conductivity ( λ ) are shown in figure 3e for both metallurgical conditions. Monotonic trends (quasi-linear) can be observed up to the occurrence of phase changes (approximately 500 ◦ C), which hinder further calculation of reliable c p and λ values. The CMed maraging steel presents slightly higher thermal conductivity and specific heat capacity for the whole tested temperature range.

3.2. Mechanical testing

Figure 4 describes the numerical and experimental results used for the development of the required input data towards numerical simulation. With the goal of determining a simple plastic law that is sensitive to the state-of stress, the Swift-Voce model was inversely calibrated based on the double notched experimental results, having the compression and tensile curves as upper and lower boundaries (refer to the curve labelled as hybrid tensile approach