China Foundry

, Volume 16, Issue 1, pp 53–62 | Cite as

Effects of trace Cr on as-cast microstructure and microstructural evolution of semi-solid isothermal heat treatment ZC61 magnesium alloy

  • Xiao-feng HuangEmail author
  • Ya-jie Ma
  • Qiao-qiao Zhang
  • Lang-lang Wei
  • Jian-qiao Yang
Research & Development


The content and kind of trace elements in magnesium alloys have important effects on their ascast and semi-solid microstructures. In this research work, effects of trace Cr on as-cast and semi-solid microstructures of ZC61 magnesium alloy were investigated by metal mold casting and semi-solid isothermal heat treatment. The results show that the addition of Cr can refine the α-Mg phase without generating a new phase, noticeably change the eutectic phase, and decrease the average size of solid particles at the same isothermal heat treatment conditions. Non-dendritic microstructures of all alloys are constituted of α1-Mg phases, α2-Mg phases and eutectic phases after water quenching. With isothermal temperature increased or holding time prolonged, the eutectic microstructure (α-Mg+MgZn2+CuMgZn) at the grain boundaries in as-cast alloy is melted preferentially and then turned into semi-solid non-dendritic microstructure by processes of initial coarsening, microstructure separation, spheroidizing and final coarsening. Especially when the ZC61-0.1Cr alloy was treated at 585 °C for 30 min, the ideal non-dendritic microstructure can be obtained, and the corresponding solid particle size and shape factor were 37.5 μm and 1.33, respectively. The coarsening process of solid α-Mg phase at higher temperature or longer time, which is affected by both combining growth and Ostwald ripening mechanism, is refrained when Cr is added to the ZC61 alloy.

Key words

ZC61 magnesium alloy Cr content semi-solid isothermal heat treatment non-dendritic microstructure microstructural evolution 

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Copyright information

© Foundry Journal Agency and Springer Nature Singapore Pte Ltd. 2019

Authors and Affiliations

  • Xiao-feng Huang
    • 1
    Email author
  • Ya-jie Ma
    • 1
  • Qiao-qiao Zhang
    • 1
  • Lang-lang Wei
    • 1
  • Jian-qiao Yang
    • 1
  1. 1.State Key Laboratory of Advanced Processing and Recycling of Nonferrous MetalsLanzhou University of TechnologyLanzhouChina

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