摘要
The type-1aluminized（Al-10mass% Si）coating on hot stamped steel is used in commercial applications.The effect of temperature on microstructure and formability of the Al-10mass% Si coating was investigated.Hot-dip aluminized 22MnB5 steel was heated at 870,900,930,and 1 050 ℃ for 5 min.After heat treatment at different temperatures,the microstructure of Al-10mass% Si was characterized by field-emission scanning electron microscopy and energy-dispersive spectroscopy.The results show that when the Al-10mass% Si coating was heated at 870℃for 5min,three types of intermetallic phases were formed：two ternary Fe-Si-Al phases（Fe2SiAl7＋Fe2Si2Al5and Fe2SiAl2＋Fe2Si2Al5）and one binary Fe-Al phase（FeAl3）.The phases in the coating became Fe2SiAl2＋Fe2Si2Al5and FeAl3,the binary Fe-Al phase near the interface became Fe2Al5 and the Si-rich layers were decreased with the increase of heating temperature.When the heat treatment was 1 050℃for 5min,the Si-rich layer disappeared,the coating consisted of FeAl and Fe3 Al,and the Kirkendall voids were formed.When the heating temperature was increased through 870,900,and 930℃,the coating hardness was reduced and cracks were formed in the coating after hot stamping.The formability of the coating with temperature change was confirmed by a hot stamping test.When heated at 1 050 ℃,the coating was formable but continuous Kirkendall voids were observed.
The type-1aluminized（Al-10mass% Si）coating on hot stamped steel is used in commercial applications.The effect of temperature on microstructure and formability of the Al-10mass% Si coating was investigated.Hot-dip aluminized 22MnB5 steel was heated at 870,900,930,and 1 050 ℃ for 5 min.After heat treatment at different temperatures,the microstructure of Al-10mass% Si was characterized by field-emission scanning electron microscopy and energy-dispersive spectroscopy.The results show that when the Al-10mass% Si coating was heated at 870℃for 5min,three types of intermetallic phases were formed：two ternary Fe-Si-Al phases（Fe2SiAl7＋Fe2Si2Al5and Fe2SiAl2＋Fe2Si2Al5）and one binary Fe-Al phase（FeAl3）.The phases in the coating became Fe2SiAl2＋Fe2Si2Al5and FeAl3,the binary Fe-Al phase near the interface became Fe2Al5 and the Si-rich layers were decreased with the increase of heating temperature.When the heat treatment was 1 050℃for 5min,the Si-rich layer disappeared,the coating consisted of FeAl and Fe3 Al,and the Kirkendall voids were formed.When the heating temperature was increased through 870,900,and 930℃,the coating hardness was reduced and cracks were formed in the coating after hot stamping.The formability of the coating with temperature change was confirmed by a hot stamping test.When heated at 1 050 ℃,the coating was formable but continuous Kirkendall voids were observed.
