浇注温度对固-液轧制A356/2024板材复合界面的影响

Effects of Pouring Temperature on Composite Interface of A356/2024 Sheet by Solid-liquid Rolling

采用固-液轧制法制备A356/2024铝合金层状复合材料,使用SEM和EDS对复合层界面组织及元素分布进行检测,并对复合界面处显微硬度进行测试和XRD物相检测,分析其界面结合强度。结果表明,随着浇注温度提高,板材复合界面处裂纹、气孔等缺陷逐渐消失,A356和2024铝合金溶质元素之间发生了互扩散,界面呈冶金结合并出现过渡区。在浇注温度较低时,界面处元素富集形成Al_2CuMg、CuAl_2金属间化合物等硬脆相。A356到2024铝合金界面处硬度(HV)从61.5突变为123.9,从而在界面处引起脆性;在较高浇注温度下,界面处元素均匀向两侧扩散,不易形成元素堆积,从A356到2024铝合金,硬度(HV)从63.3逐渐上升到104.5,界面结合牢固。

The A356/2024 sheet was fabricated by solid-liquid rolling.The solidification structure and element distribution near the interface of A356/2024 sheet were detected systematically by SEM and EDS.The bonding strength of the interface was evaluated by hardness and XRD.The results reveal that the cracks,pores and other defects at the interface of A356/2024 sheet are disappeared gradually with the increase of pouring temperature of the liquid metal.The interdiffusion of alloy elements in A356 aluminum alloy and 2024 aluminum alloy occurs and there exists an about 110μm wide diffusion layer near the interface,indicating metallurgical bonding.The elements at the interface are enriched to form hard brittle phases such as Al2 CuMg and CuAl2 intermetallic compounds at the lower pouring temperature.The hardness near the interface of A356/2024 sheet is changed from 61.5 HV to 123.9 HV sharply.Therefore,it is easy to cause brittle fracture at the interface and reduce the bonding strength.The elements at interface are diffused uniformly on the both sides at the higher pouring temperature,which is not easy to form the accumulation of elements.The hardness of the compound sheet is increased from 63.3 HV to104.5 HV at one side of the A356 aluminum alloy along the vertical direction of the interface to 2024 aluminum alloy,showing agradient change trend with the firm interface bonding.