Microstructural influences on the fatigue crack initiation and propagation mechanisms in hypo-eutectic Al-Si cast alloys
Microstructural influences on the fatigue crack initiation and propagation mechanisms in hypo-eutectic Al-Si cast alloys
复制标题
微观结构对亚共晶铝硅铸造合金疲劳裂纹萌生和扩展机制的影响
DOI：
10.1016/j.prostr.2020.01.137
复制
发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Walther
中科院分区：
文献类型：
--
作者：
Tenkamp;Scherbring;Bleicher;Michels;Walther
铸造铝硅合金中存在不同的缺陷和组织不均匀性，如气孔、二次枝晶臂间距（SDAS）的变化和共晶的多次出现。这些问题是众所周知的，但在技术上很难防止行业。为了提高铸造铝合金的轻量化性能，本文研究了两种亚共晶铸造铝合金AlSi 8 Cu 3（砂型铸造）和AlSi7Mg0.3（实验室重力压铸件）在高周疲劳（HCF）和超高周疲劳（VHCF）条件下，非均匀性对裂纹萌生和扩展机制的影响。此外，小面区域的发生和它们在早期和晚期状态的疲劳损伤演化的作用进行了讨论，通过显示结果从修改的北川-高桥分析和异位的计算机断层扫描调查在间歇HCF实验。在早期HCF制度裂纹萌生开始在多个孔。由于这些缺陷的合并，剪切应力控制的裂纹扩展沿着滑移带导致小平面的出现。在VHCF状态下，孔隙度提供了失效循环次数的强烈分散。SDAS的降低显著增加了疲劳强度。然而，在没有孔隙的情况下，疲劳裂纹的萌生和扩展是由小面状滑移面上的剪切应力控制的。此外，这些试样还显示了共晶区对位错运动的阻挡作用。
Al-Si cast alloys are accompanied by different defects and microstructural heterogeneities like porosity, varying secondary dendrite arm spacings (SDAS) and multiple appearances of the eutectic. These issues are well known but technically difficult to prevent for the industry. To improve the light weight performance of cast aluminum alloys the present work deals with influences on crack initiation and propagation mechanisms of such heterogeneities in the high-cycle-fatigue (HCF) and very-high-cycle-fatigue (VHCF) regime for the two hypo-eutectic cast aluminum alloys AlSi8Cu3 (in-series sand castings) and AlSi7Mg0.3 (laboratory gravity die castings). Furthermore, the occurrence of facet-regions and their role in early and late state of fatigue damage evolution is discussed by showing results from modified Kitagawa-Takahashi analysis and ex-situ computed tomography investigation during intermitted HCF experiments. In the early HCF regime crack initiation starts at multiple pores. Due to coalescence of these defects, shear-stress-controlled crack propagation along slip bands leads to the occurrence of facets. In the VHCF regime, porosity provides strong scattering of the number of cycles to failure. A reduction in SDAS increases the fatigue strength significantly. However, in absence of porosity fatigue crack initiation and propagation is controlled by shear stresses on facet-like slip-planes. Additionally, the barrier role against dislocation movement of eutectic regions can be shown by means of these specimens.
登录
查看更多内容
显微组织对亚共晶 Al-Si-Mg 铸造合金循环应力应变行为和疲劳寿命的影响
DOI：
10.1051/matecconf/201816515004
发表时间：
2018
期刊：
影响因子：
--
作者：
Tenkamp;Knorre;Michels;Walther
通讯作者：
Walther
微观结构不均匀性对铝铸件疲劳阈值的意义
DOI：
10.1051/matecconf/201816514005
发表时间：
2018
期刊：
影响因子：
--
作者：
Knorre;Michels
通讯作者：
Michels
“铸造319-T7铝合金疲劳裂纹萌生机理”的探讨
DOI：
--
发表时间：
2009
期刊：
影响因子：
--
作者：
J. Campbell
通讯作者：
J. Campbell
DOI：
10.1007/s00170-017-0192-6
发表时间：
2017-09-01
影响因子：
3.4
作者：
Ben Ahmed, A.;Nasr, A.;Fathallah, R.
通讯作者：
Fathallah, R.