High pressure die casting is a well known and cost effective technology for producing cheap and accurate parts in zinc alloys. The advantage of this fine accuracy is, however, often lost due to the bad creep performance of the hexagonal structure of the zinc alloys. Zinc components obtained by high pressure die-casting also suffer from the variation of their mechanical performances with time because of natural ageing effect that induces a redistribution of metastable phases. Concerning creep behaviour of Zamak5 alloy, it was observed that the total strain during primary creep is influenced by ageing times; particularly it decreases continuously down to an asymptotic value for the longest ageing times. The aim of this paper is to assess whether, during creep tests, concurrent artificial ageing may occur that interferes with the creep behaviour of the alloy. For this reason, different artificial ageing times and temperatures were investigated in order to reach steady state microstructure and mechanical properties and subsequently to compare them with the standard parameters used during zinc alloys creep test. The artificial ageing temperatures able to influence creep behaviour were found to be higher than those normally prescribed for mechanical purposes.
Effect of artificial ageing on creep behavior of Zemak5 die-casting alloy
POLA, Annalisa;CORNACCHIA, Giovanna;ROBERTI, Roberto;
2008-01-01
Abstract
High pressure die casting is a well known and cost effective technology for producing cheap and accurate parts in zinc alloys. The advantage of this fine accuracy is, however, often lost due to the bad creep performance of the hexagonal structure of the zinc alloys. Zinc components obtained by high pressure die-casting also suffer from the variation of their mechanical performances with time because of natural ageing effect that induces a redistribution of metastable phases. Concerning creep behaviour of Zamak5 alloy, it was observed that the total strain during primary creep is influenced by ageing times; particularly it decreases continuously down to an asymptotic value for the longest ageing times. The aim of this paper is to assess whether, during creep tests, concurrent artificial ageing may occur that interferes with the creep behaviour of the alloy. For this reason, different artificial ageing times and temperatures were investigated in order to reach steady state microstructure and mechanical properties and subsequently to compare them with the standard parameters used during zinc alloys creep test. The artificial ageing temperatures able to influence creep behaviour were found to be higher than those normally prescribed for mechanical purposes.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
