Hot formability of 6000 series aluminum alloys

It has recently been clarified in a previous paper that 6XXX aluminum alloys of medium grain size exhibit a characteristic hot ductility behavior above 773 K, in which the elongation to fracture is minimum in medium strain rate range while it maintains high levels between 200% and 340% both in low and high strain rate. In this paper is discussed the relationship between such ductility behavior and rate controlling mechanisms of deformation and fracture at 803 K. The results are summarized as follows: (1) In spite of the fact that both strain rate sensitivity and ductility are high, hot working at low strain rate is not appropriate if not, for example, superimposing back-pressure because cavitation occurs remarkably at the grain boundaries. (2) Hot working at high strain rate is recommended, not only because productivity is high but also because, in spite of m-values as low as 0.2, the elongation up to 200% is obtained without remarkable cavitation.