(1. 沈陽航空航天大學(xué) 機(jī)電工程學(xué)院，沈陽 110136；
2. 沈陽航空航天大學(xué) 航空制造工藝數(shù)字化國防重點(diǎn)學(xué)科實(shí)驗(yàn)室，沈陽 110136)
摘 要: 針對典型高速列車車體用6N01鋁合金，對十字角接接頭的顯微組織和疲勞性能進(jìn)行研究。結(jié)果表明：十字角接接頭的焊縫組織為等軸狀鑄態(tài)組織；在熱影響區(qū)，與淬火區(qū)晶粒尺寸相比，過時效區(qū)晶粒尺寸增大，同時析出大量Mg2Si相。顯微硬度試驗(yàn)結(jié)果表明，十字角接接頭的焊縫顯微硬度最低，平均值為94.2 HV；熱影響區(qū)的顯微硬度平均值為111.6 HV，但在距離熱影響區(qū)中心0.25 mm左右的區(qū)域，顯微硬度下降至108.5 HV，形成軟化區(qū)。室溫環(huán)境下，獲得應(yīng)力比為0.5和-1的疲勞S-N曲線，與母材相比，十字角接接頭的室溫疲勞強(qiáng)度分別降低了75.1%和64.4%。應(yīng)力集中程度較高的焊趾導(dǎo)致疲勞裂紋易于萌生，同時接頭處強(qiáng)化相聚集長大，導(dǎo)致焊縫強(qiáng)度降低，合金疲勞極限降低。
關(guān)鍵字: 6N01鋁合金；十字角接接頭；顯微結(jié)構(gòu)；疲勞性能
（1. School of Mechatronics Engineering, Shenyang Aerospace University, Shenyang 110136, China;
2. Key Laboratory of Fundamental Science for National Defense of Aeronautical Digital Manufacturing Process, Shenyang Aerospace University, Shenyang 110136, China）
Abstract:Aiming at a typical 6N01 aluminum alloy used in high-speed train bodies, the microstructure and fatigue performance of the cross angle joints were studied. The results show that the weld zone consists of equiaxed grains which is a typical as-cast structure. In the heat-affected zone, the size of equiaxed grains in the over-aged zone is bigger than that of the quenched zone due to the welding heat. Meanwhile, a large amount of Mg2Si particals can be found inside the heat-affected zone. The lowest microhardness position locates inside the weld zone , with an average value of 94.2 HV. The average microhardness of the heat-affected zone is 111.6 HV, but the value decreases to 108.5 HV in the area about 0.25 mm away from the center of the heat affected zone, forming a softened zone. At room temperature, fatigue S-N curves are obtained. The analysis shows that the fatigue strength of the cross angle joint decreases by 75.1% and 64.4%, respectively, with stress ratios of 0.5 and -1 compared with the base metal. The weld toes with high stress concentration cause fatigue cracks to easily initiate, and at the same time, the aggregating and growing up of the strengthening phase at the joint results in the strength and fatigue limit decrement of the 6N01 aluminum alloy weld.
Key words: 6N01 aluminum alloy; cross angle joint; microstructure; fatigue performance
