Investigation of the age hardening behaviour of 6063 aluminium alloys refined with Ti, RE and B

Abstract: The purpose of this study is to obtain a better understanding on the effect of ageing on the hardness of 6063 aluminium alloys refined with Ti, cerium-rich mixtures of rare earth (RE) and B with the aids of SEM, EDS, TEM, DSC, etc. The following conclusions have been obtained: the 6063 alloy with the joint additions of Ti, B and RE (10 w(Ti)/w(B) mass ratio) has the finest grain, compared to alloys with Ti or Ti and RE additions. Artificial ageing must be performed more than 7d after extrusion. The 6063 alloys refined with Ti, Ti+RE or Ti+RE+B all have better ageing behaviour. It takes shorter ageing time to obtain a hardness near peak ageing hardness and there is no obvious decrease of ageing hardness of the alloys until ageing for 6h at 200°C. The addition of RE forms Al–Si–Mg–RE intermetallic constituents, resulting in lower strength of alloys than that with Ti addition. [Copyright &y& Elsevier]