بررسي اثر شدت سرد شدن و گاز هيدروژن بر فاصله بين دندريتي و خواص مكانيكي كامپوزيت پايه آلومينيوم A356-9%wttib2

Effect of Cooling Rate and H2 Gas on the Inter-Dendritic Distance and Mechanical Properties of A356- 9%wtTiB2 Composite

In this paper, effect of cooling rate on dendrite arm space, porosities density and mechanical properties of A356 -9%wtTiB2 composite has been investigated during degassing with H2. For this purpose a wedge sample was designed, and then the A356 ~9%wtTiB2 composite was cast under two degassing conditions: i. 100%Ar, ii. Ar-5%H2. Before pouring, some thermocouples were placed into the wedge. Then thermal history of the wedge was saved in a computer using a data acquisition system which connected to the thermocouples. Then hardness and stiffness tests were conducted on the wedge. Finally, microstructures of the composites were investigated and relations between mechanical properties and cooling rate of composites were extracted. In the case of Ar — 5°/oH2> results show effect of the micro-porosities on the mechanical properties will be omitted when the cooling rate controlled between 2-2.5 0 C/ sec