A356低壓鑄造鋁合金輪圈之疲勞失效分析

Analysis of Fatigue Failure in Low Pressure Casting A356 Aluminum Wheels

陳貞光(J. K. Chen) ； 盧柏佑(P. Y. Lu) ； 林文翔(W. H. Lin)

《鑄造工程學刊》 43卷1期 (2017/03) Pp. 1-6

摘要

本研究分析低壓鑄造鋁輪圈經由彎曲力矩耐久試驗後之失效原因。分析結果顯示，疲勞裂紋存在區域有組織不均勻之現象(共晶Al-Si相較周圍組織多)，主要判斷此部位造型設計與冷卻系統設計不良，導致此區域形成熱點成為最後凝固區，使得該區域有共晶Al-Si相的堆積，並有粗化共晶矽存在。其二，在共晶Al-Si相中可觀察到板針狀的鐵基金屬間化合物，主要為β-Al_5FeSi和π-Al_8FeMg_3Si_6相，其針狀型態使材料產生應力集中效應，進而影響材料的機械性質。其三，局部區域有微縮孔存在，使得疲勞裂紋容易經由這些缺陷位置延伸，導致輪圈發生疲勞破壞。因此如何降低組織不均、微縮孔以及鐵基金屬間化合物的形成，是改善此鑄件疲勞性能的重要關鍵。

關鍵字

鋁合金輪圈 ； 彎曲疲勞試驗 ； 疲勞失效

並列摘要

This study analyzes the fatigue failure of the low pressure casting aluminum wheels via bending test. The fatigue cracks were observed in the non-uniform area where mainly Al-Si eutectic phase was formed. The design of the parts and the cooling system can be improved to reduce the formation of the hot spots. The coarsened Al-Si eutectic phases was formed due to the prolonged solidification in these areas. Secondly, the needle or plate shapes of iron-containing intermetallic compounds, β-Al_5FeSi and π-Al_8FeMg_3Si_6 phases were observed in the microstructure. These needle-shaped compounds led to stress concentration effect, thereby reducing the elongation. Furthermore, micro-porosity was coalesced in the propagation of fatigue cracks, causing rim failure in fatigue tests. The reduction of non-uniform structures, micro-porosity, and iron-containing intermetallic compounds are the keys to improve the fatigue performance of the low pressure casting aluminum wheels.

並列關鍵字

Aluminum wheels ； Bending test ； Fatigue failure