PSI - Issue 57

Martin Matušů et al. / Procedia Structural Integrity 57 (2024) 327 – 334 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction This study describes the experimental evaluation of tensile and fatigue properties of AlSi10Mg specimens produced additively within one L-PBF build cycle. The manufactured specimens were processed by four different heat treatments (HT). Additionally, temperature response during cyclic loading was measured to analyze the effect of HT on heat dissipation during dynamic loading [1]. The effect of HT conditions on the static parameters of the specimens was previously demonstrated to be significant [2]. It has been observed that using HT, the fatigue life performance of specimens can be improved [3; 4]. This finding is consistent with papers by Li et al. [2] and by Zhang et al. [3], where the effect of four different HT conditions on service life was analyzed. Although only one of the four HT conditions used in [3] was similar to our HT setups, the results support our approach of investigating the effect of multiple HT conditions. Baek et. al [4] evaluated the case of HT based on age-hardening only, without higher imposed temperatures, with interesting results. These papers discussed the effect of HT on specimens with removed AM-built surface layer, while the paper presented here deals with as-built surface quality. Aboulkhair et al. [5] demonstrated the effect of surface machining and of HT on fatigue properties. All three teams discussed in [3], [4] and [5] the T6 condition as one of the HT. It is interesting to note, that these three studies do not agree in the potential beneficial or negative effect of this treatment, which is likely intrinsically related to the differences in the AM processes used by each team. The application of T6 heat treatment is not evaluated in this paper. HTs were chosen based on the decomposition temperature of the silicon mesh, with two pairs located beneath it and one pair positioned above it. Thanks to leaving one series of specimens without any heat treatment, we observed that the additional HT improves the fatigue properties of specimens in all cases. This study provides a deeper understanding of the effect of HT on the fatigue properties of AlSi10Mg specimens produced by additive manufacturing. Additionally, by measuring the temperature response during cyclic loading, we can characterize the heat dissipation behavior of the specimens under different HT conditions. The observed heat dissipation during cyclic loading can be utilized as an additional fatigue parameter to estimate the expected numbers of cycles until failure [6], or to estimate the fatigue limit [7; 8]. Such information can be useful for optimizing the HT process to improve the overall performance of the specimens in practical applications.

Nomenclature Θ

Stabilized temperature increase

Thermoelastic effect

S t

Time constant for thermal exchange between the specimen and its surroundings

τ

Thermal dissipation Initial temperature rate Closing temperature rate.

d 1 R o R γ

Number of cycles

N

Number of cycles till failure Theoretical fatigue limit Young modulus of elasticity Yield strength at 0.2% of strain Ultimate tensile strength

N f

σ FL

E

R p0,2

R m

R a , R z Roughness parameters (arithmetic average and maximum peak to valley height, respectively) ρ Density c Material specific heat