Application of the Billet Casting Method to Determine the Onset of Incipient Melting of 319 Al Alloy Engine Blocks
Application of the Billet Casting Method to Determine the Onset of Incipient Melting of 319 Al Alloy Engine Blocks
复制标题
应用小坯铸造法测定319铝合金发动机缸体初熔起始点
DOI：
10.1007/s11665-015-1419-z
复制
发表时间：
2015
影响因子：
2.3
通讯作者：
R. Mackay
中科院分区：
文献类型：
--
作者：
A. Lombardi;C. Ravindran;R. Mackay
汽车应用中Al的使用增加是由于需要提高车辆燃料效率。铝合金发动机缸体满足轻量化的需要。然而，存在与铝和灰铸铁气缸套之间的热机械失配相关联的许多挑战，这导致沿气缸孔沿着的大的拉伸残余应力。这就要求在该区域中改善机械性能，以防止发动机过早失效。在这项研究中，复制小方坯铸件被用来模拟发动机缸体固溶热处理过程，并确定初熔的开始。在热处理过程中的微观组织变化进行了评估，与SEM和EDX，而热分析进行了差示扫描量热法。结果表明，在500 °C下的固溶热处理在溶解第二相颗粒方面是有效的，而在515或530 °C下的固溶引起Al2Cu和Al5Mg8Cu2Si6的初始熔化。初熔导致淬火时形成由Al、Al2Cu和Al5Mg8Cu2Si6组成的超细共晶团簇。此外，DSC分析发现，对于所有坯料，初始熔融在507 °C下开始，尽管局部熔融的量随着微观结构细化而减少，如较小的吸热峰和能量吸收所证明的。这项研究的结果将有助于提高发动机缸体铸件的完整性和工艺效率。
The increased use of Al for automotive applications has resulted from the need to improve vehicle fuel efficiency. Aluminum alloy engine blocks fulfil the need of lightweighting. However, there are many challenges associated with thermo-mechanical mismatch between Al and the gray cast iron cylinder liners, which result in large tensile residual stress along the cylinder bores. This requires improced mechanical properties in this region to prevent premature engine failure. In this study, replicating billet castings were used to simulate the engine block solution heat treatment process and determine the onset of incipient melting. Microstructural changes during heat treatment were assessed with SEM and EDX, while thermal analysis was carried out using differential scanning calorimetry. The results suggest that solution heat treatment at 500 °C was effective in dissolving secondary phase particles, while solutionizing at 515 or 530 °C caused incipient melting of Al2Cu and Al5Mg8Cu2Si6. Incipient melting caused the formation ultra-fine eutectic clusters consisting of Al, Al2Cu, and Al5Mg8Cu2Si6 on quenching. In addition, DSC analysis found that incipient melting initiated at 507 °C for all billets, although the quantity of local melting reduced with microstructural refinement as evidenced by smaller endothermic peaks and energy absorption. The results from this study will assist in improving engine block casting integrity and process efficiency.