摘要
用TEM,oM,SEM和Vickers硬度仪测定、表征了铸态、固溶+时效态下不同La含量AZ91合金的显微组织和析出相的形态和尺寸以及硬度变化,研究了不连续β相和Al_(11)La_3相的形貌对合金硬度的影响及其机理,并计算时效过程中Al原子的扩散系数.结果表明,不同La含量AZ91合金在170℃时,La含量为0.16%的合金时效24 h达到的硬度最大,为138 HV;延长时效时间和改变La含量可使不连续脱溶相转变为板条状连续脱溶相,降低Al原子的扩散系数,从而影响不连续β相的数量、大小与分布;晶界处的Al_(11)La_3相的形貌虽不受热处理过程影响,但却制约β相的长大.可见控制La含量和时效时间,可改善不连续(片层)β相的尺寸和数量,有效地提高合金强韧性能.
The changes of microhardness,microstructures and precipitation phase morphologies of as-cast and aged AZ91 alloys with different La were characterized by TEM,OM,SEM and Vickers. The influences of discontinuousβphase and Al_（11）La_3 on AZ91 magnesium alloy were discussed and the diffusion coefficient of Al atom in the aging process was calculated.The results showed that the alloy with 0.16%La aged at 170℃for 24 h has the largest hardness（138 HV）.By extending aging time and adding La element,the discontinuous precipitation phases was transformed into continuous lath-sharped phases and the diffusion coefficient of Al atom was decreased,the volume and distribution ofβphase were changed.During the process of heat treatment,the topography of Al_（11）La_3 in grain boundary was not changed,but the anchoring effect of Al_（11）La_3 restricted the growth ofβphase.By controlling the content of La and parameters of aging treatment,the volume and size ofβphase were changed,in the mean time the strengthening and toughness properties of alloys can been improved effectively.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2012年第5期607-614,共8页
Acta Metallurgica Sinica
基金
国家自然科学基金资助项目50901048~~
关键词
AZ91镁合金
时效处理
La固溶
扩散系数
AZ91 magnesium alloy
aging treatment
La solution
diffusion coefficient
