抄録
The age-hardening process of Al2O3 continuous fiber reinforced Al-Si-Cu and Al-Si-Cu-Mg alloys was investigated by using a TEM, DSC, Vickers macro hardness tester and EPMA. A series of composite specimens were solution treated at 773 K for 10h, and subsequently aged at 433 K and 473 K for 10 min to 104 min. The aging characteristics of the composites were compared with those of the unreinforced alloys which were cast and heat treated under identical conditions as the composites. Although the precipitation of composites is accelerated, the over-all age-hardening sequence is similar to that of unreinforced alloys. In the case of Al2O3 / Al-Si-Cu alloy composite, the degree of age-hardening (ΔHV = HV. max-HV. s) is higher than that of unreinforced alloy, because the θ’ phase precipitated preferentially on the dislocations is more uniformly dispersed in the composite with higher density of dislocations. On the contrary, in the Al2O3 / Al-Si-Cu-Mg alloy composite, the λ’ phase homogeneously precipitates in the α matrix independent of dislocations. However, the precipitation amount of λ’ phase is decreased due to the prior formation of MgAl2O4 (spinel) at the interface between the Al2O3 fiber and matrix alloy. Therefore, the precipitation rate is almost unchanged and the degree of agehardening is slightly decreased by the presence of Al2O3 fiber.
