Abstract
Aluminium alloys are promising candidates for energy-and cost-efficient components in automotive and aerospace industries, due to their excellent strength-to-weight ratio and relatively low cost compared to titanium alloys. As modern cast processing and post-processing, e.g. hot isostatic pressing, result in decreased frequency and size of defects, the weakest link depends on microstructural characteristics, e.g. secondary dendrite arm spacing (SDAS), Si eutectic morphology and α-Al solid solution hardness. Hereby, fatigue investigations of the effect of the microstructure characteristics on the cyclic stress-strain behaviour as well as fatigue mechanisms in the low cycle and high cycle fatigue regime are performed. For this purpose, samples of the aluminium cast alloy EN AC-AlSi7Mg0.3 with different Si eutectic morphology and α-Al solid solution hardness were investigated. To compare the monotonic and cyclic stress-strain curves, quasistatic tensile tests and incremental step tests were performed on two microstructure conditions. The results show that the cyclic loading leads to a hardening of the material compared to monotonic loading. Based on damage parameter Woehler curves, it is possible to predict the damage progression and fatigue life for monotonic and cyclic loading in hypo-eutectic Al-Si-Mg cast alloys by one power law.
Highlights
Aluminium alloys are promising candidates for energyand cost-efficient components in automotive and aerospace industries, due to their excellent strength-to-weight ratio and relatively low cost compared to titanium alloys
As modern cast processing and post-processing, e.g. hot isostatic pressing, result in decreased frequency and size of defects [1,2,3,4,5], the weakest link depends on microstructural characteristics, e.g. secondary dendrite arm spacing (SDAS) [6,7,8], Si eutectic morpho-logy [6, 9,10,11,12] and Al solid solution hardness
3.1 Monotonic stress-strain behaviour To determine the monotonic properties of batches T6/A and T6/B quasistatic tensile tests were performed
Summary
Aluminium alloys are promising candidates for energyand cost-efficient components in automotive and aerospace industries, due to their excellent strength-to-weight ratio and relatively low cost compared to titanium alloys. As modern cast processing and post-processing, e.g. hot isostatic pressing, result in decreased frequency and size of defects (oxides, porosity) [1,2,3,4,5], the weakest link depends on microstructural characteristics, e.g. secondary dendrite arm spacing (SDAS) [6,7,8], Si eutectic morpho-logy [6, 9,10,11,12] and Al solid solution hardness They are relevant to ensure a safe design for safety-relevant components made of aluminium cast alloys. While the impact of porosity and SDAS on S-N curve has already been investigated, the effect of microstructure characteris-tics as Si eutectic morphology and α-Al solid solution hardness on the cyclic stressstrain behaviour as well as fatigue mechanisms in the low (LCF), high (HCF) and very high cycle fatigue (VHCF) regime is not well understood For this purpose, samples of the aluminium cast alloy EN AC-AlSi7Mg0.3 were casted in a steel mold with grain refinement and Sr modification. Micro hardness mappings were carried out on longitudinal cross sections of fractured specimens to determine the effect of cyclic loading related to the specific Si eutectic morphology and the α-Al solid solution hardness
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