Abstract
Influence of the abnormal structure, such as scattered chill structure or cold shut, in JIS AC4CH (Al-7.3%Si-03.%Mg) aluminum alloy squeeze castings on the reliability of mechanical properties was investigated. The shot time lag (STL) and the heat transfer coefficient between molten alloy and shot sleeve were changed as the process parameters to control the formation of the abnormal structure. Both the tensile strength and its reliability were remarkably improved by using the powder lubricant or by decreasing the STL Regarding the fracture elongation, the average elongation was improved due to the reduction of abnormal structure on the fracture surface. However, the reliability of the fracture elongation was sufficiently improved by neither STL nor the type of lubricants. It is found that the reduction of abnormal structure is effective to improve the strength and fracture elongation of squeeze castings.
