在工具转速800 r/min, 焊接速度100 mm/min的工艺参数下, 对6 mm厚的15%SiC_p/2009Al (体积分数)板材在软态(固溶态)和硬态(自然时效态)下进行搅拌摩擦焊接, 均获得致密无缺陷的接头. 结果表明, 样品原始状态对焊核区的晶粒尺寸、析出相(Al₂Cu)分布和硬度均影响不大. 2种样品的热影响区均存在2个低硬度区. 靠近焊核区的低硬度区在焊接热循环过程中温度较高, 2种样品均发生Al₂Cu相的粗化, 硬度值相同; 但在远离焊核区的低硬度区, 固溶态样品不发生固溶原子团簇回溶, 该区域的硬度略高于自然时效态样品, 并且位置更靠近焊核中心. 2种接头横向拉伸时均断裂在靠近焊核的低硬度区, 强度基本相同, 可达母材强度的83%. 这表明, 固溶软态下进行15%SiC_p/2009Al板材的搅拌摩擦焊接, 可以取得常规时效硬态下焊接的效果, 有助于扩大焊接工艺窗口, 减少焊接工具磨损.

Discontinuously reinforced aluminum matrix composites (AMCs) have been widely applied in structures of aerospace industry. Wide industrial applications of AMCs depend on effective joining methods, which are dependent on the use of a specific material and process. As a new solid-state welding technique, friction stir welding (FSW) has been attempted for joining the AMCs in last few years. However, few attentions have been paid to the effect of initial heat treatment tempers of the AMCs on the FSW joints. In this work, 6 mm thick SiC_p/2009Al composite plates in both soft (solution temper) and hard (natural aging temper) conditions were successfully friction stir welded at a rotation rate of 800 r/min and a welding speed of 100 mm/min (named as Sol-FSW and T4-FSW samples). In the nugget zone (NZ) of both samples, the grain size and the distribution of the coarse Al₂Cu phases were similar. In the heat affected zone, two low hardness zones (LHZs) were observed. LHZ I adjacent to the NZ had the lowest hardness. Both samples had the similar hardness in this zone. For the Sol-FSW sample, LHZ II far away from the NZ had a higher hardness and was closer to the NZ compared to that of the T4-FSW sample. The ultimate tensile strength of both the samples was similar and reached 83% of T4-tempered base metal. Both samples failed in LHZ I adjacent to the NZ due to the lowest hardness in this zone. This indicates that for the SiC_p/2009Al composite under solution temper it is possible to produce similar joints to that under natural aging temper using FSW technique. FSW of the composites under soft condition is beneficial to enlarging the welding process window and reducing the tool wear.