Influence of Hot Isostatic Pressing Temperature on the Microstructure and Properties of AlSi7Cu2Mg Alloys

The roles of hot isostatic pressing (HIP) temperatures (490 °C/100 MPa/2 h, 510 °C/100 MPa/2 h, 530 C/100 MPa/2 h) in the microstructure and properties of AlSi7Cu2Mg alloy step castings with three types wall thicknesses were studied. The experimental results show that HIP at 490 C could effectively eliminate the internal closed porosity of the castings with a wall thickness of ≼40 mm, but for heavy castings (70 mm), even HIP at 530 C, a few loose defects remained inside the castings. Two types of incipient eutectics containing Al5Mg8Si6Cu2 and Al2Cu were observed in the samples that HIP at 530 C, which was responsible for the decrease of the tensile strength of the castings within the medium wall thickness (40 mm) compared with that HIP at 490 C. HIP could greatly reduce the difference of the tensile strength values of castings with wall thicknesses 17 mm and 70 mm from 117.93 MPa (without HIP) to 25.7 MPa (with HIP at 530 C).