激光熔化沉积4045铝合金显微组织及显微硬度
发布时间：2018-10-18 19:49
【摘要】：采用激光熔化沉积技术制备了4045铝合金薄壁试样,研究了沉积试样热处理前后的显微组织演化,并测试其显微硬度。结果表明,沉积试样显微组织具有定向快速凝固特征,由Al枝晶和Al-Si共晶组成,其一次枝晶间距约22.3μm,二次枝晶间距约7.5μm,体积分数约42.7%,沉积试样顶部出现柱状树枝晶向等轴树枝晶转变。当前沉积层从底部到顶部冷却速度的降低导致Si相从珊瑚形貌向片状形貌转变,足够高的重熔率能保证后续沉积层重熔掉当前沉积层顶部片状Si相,以获得变质效果良好的珊瑚形貌Si相,热影响作用使紧邻熔合线过热区的珊瑚形貌Si相发生粗大等轴粒状化,导致其显微硬度低于层内区。珊瑚形貌Si相在540℃等温热处理保温20 min即可完成粒状化,并且随着保温时间延长,Si相发生粗化长大,显微硬度下降。
[Abstract]:4045 aluminum alloy thin wall specimens were prepared by laser melting deposition technique. The microstructure evolution and microhardness of 4045 aluminum alloy samples before and after heat treatment were studied. The results show that the microstructure of the deposited samples has the characteristics of directional rapid solidification and consists of Al dendrite and Al-Si eutectic. The primary dendritic spacing is about 22.3 渭 m, the secondary dendritic spacing is about 7.5 渭 m, the volume fraction is about 42.7, and the columnar dendritic to equiaxed dendritic transition appears at the top of the deposited sample. The decrease of cooling rate from the bottom to the top of the current sedimentary layer leads to the transition of the Si phase from the morphology of the coral to the morphology of the sheet. The high remelting rate can ensure that the subsequent deposit layer remelts the Si phase at the top of the current deposit. In order to obtain the Si phase with good metamorphic effect, the Si phase near the superheated zone of the fusion line is coarse and equiaxed, resulting in the microhardness of which is lower than that of the inner layer. The morphology of coral Si phase can be grained after isothermal heat treatment at 540 鈩，
本文编号：2280189
[Abstract]:4045 aluminum alloy thin wall specimens were prepared by laser melting deposition technique. The microstructure evolution and microhardness of 4045 aluminum alloy samples before and after heat treatment were studied. The results show that the microstructure of the deposited samples has the characteristics of directional rapid solidification and consists of Al dendrite and Al-Si eutectic. The primary dendritic spacing is about 22.3 渭 m, the secondary dendritic spacing is about 7.5 渭 m, the volume fraction is about 42.7, and the columnar dendritic to equiaxed dendritic transition appears at the top of the deposited sample. The decrease of cooling rate from the bottom to the top of the current sedimentary layer leads to the transition of the Si phase from the morphology of the coral to the morphology of the sheet. The high remelting rate can ensure that the subsequent deposit layer remelts the Si phase at the top of the current deposit. In order to obtain the Si phase with good metamorphic effect, the Si phase near the superheated zone of the fusion line is coarse and equiaxed, resulting in the microhardness of which is lower than that of the inner layer. The morphology of coral Si phase can be grained after isothermal heat treatment at 540 鈩，
本文编号：2280189
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