铝合金晶界结构控制与钎焊过程晶界渗透行为的研究

Control of Grain Boundary Structure of Aluminum Alloy and Grain Boundary Penetration in Brazing Process

近年来,汽车的轻量化已成趋势。汽车热交换器用钎焊铝箔替代铜箔,不但可以减轻汽车自重,而且还能降低生产成本。但由于铝箔散热器钎焊加工过程中会发生皮材中Si向芯材渗透,使芯材溶蚀以至于影响整个散热器的使用性能。采用金相显微镜、扫描电子显微镜(SEM)、电子背散射衍射(EBSD)分析、织构能谱分析等实验设备和手段研究不同控制轧制工艺及热处理工艺对Al/4343/Al以及4343/3003铝箔组织和钎焊渗透的影响,探索钎焊过程中晶界渗透行为的机理。研究结果显示,纯Al以及3003铝箔再结晶晶粒均随着热处理温度的提高而长大。钎焊后Al/4343/Al发生沿晶界渗透,并且小角度晶界相对于大角度晶界不容易发生渗透,而中间退火及精轧率对晶界渗透行为无显著影响。而4343/3003则主要发生液膜迁移(在钎焊过程中,液体的前端会形成液膜,在液膜前端的固体合金的溶质会重新分布)。钎焊前后Al/4343/Al以及4343/3003铝箔组织的织构取向趋于一致。本文采用SEM,EBSD等多种微观分析方法,深入研究了钎焊工艺对晶界渗透行为的影响,其结果对复合钎焊铝箔材料的退火和轧制等工艺具有指导意义。

In recent years, the lightweight of automobile has become a trend. As one of the major automobile components, heat exchanger was once made of copper. Aluminum alloy has higher thermal con-ductivity compared with copper, as well as lower density and lower cost, which contributes to the lowering of automobile’s weigh and cost. Since the radiator brazing foil process, the Si material of the skin will penetrate to the core material, so that the core material’s corrosion will happen. In this paper, optical microscope, SEM, electron backscatter diffraction (EBSD) analysis, texture energy spectrum analysis of laboratory equipment were used to investigate the influence of varied approaches of controlled rolling process and the different heat treatment on Al/4343/Al. The re-sults indicate that aluminum foil of pure Al and 3003’s grains grows up with ascending annealing temperature. After brazing, Al/4343/Al penetration happened along the grain boundaries. It is shown that small angle grain boundaries are less likely to infiltrate than the high angle grain boundaries, and middle rates of annealing and finishing have no significant effects on the permea-tion performance of grain boundaries. Besides, the 4343/3003 mainly conducts liquid migration. Finally, the texture orientations of aluminum foil around the Al/4343/Al and 4343/3003 line co-incide gradually with those before brazing.