Solution and ageing heat treatments of ZK60 magnesium alloys with rare earth additions produced by semi-solid casting

• Autor(a) principal: Silva,Erenilton Pereira da
• Data de Publicação: 2014
• Outros Autores: Batista,Larissa Fernandes, Callegari,Bruna, Buzolin,Ricardo Henrique, Warchomicka,Fernando, Requena,Guillermo Carlos, Brito,Pedro Paiva, Pinto,Haroldo Cavalcanti
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Materials research (São Carlos. Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392014000600020
• topic: ZK60; rare earth; age hardening; heat treatment; thixocasting

Rare earth elements reportedly improve high temperature strength and creep resistance of Mg alloys. In the present work, ZK60 Mg alloys containing different amounts (0.5, 1.5 and 2.5 wt.%) of rare earth additions were prepared by thixocasting and submitted to solution and ageing heat treatments (T4, T5 and T6). The as-cast and heat treated microstructures were investigated by scanning electron microscopy and hardness was evaluated as a function of heat treatment parameters. In the as-cast state, the alloys are formed by globular α-Mg grains reinforced by a network of composite Mg-Zn-RE precipitates with either smooth or lamellar/acicular morphologies. Solution of the smooth precipitates took place in alloys containing 0.5 and 1.5wt.%RE for T4-500 ºC but no precipitates were dissolved with T4-380 ºC. The optimum temperature for T5 and T6 was identified as 175 ºC, while T6-500 ºC led to the highest hardness, followed by T5 and T6-380 ºC, respectively.