文章信息/Info

Title:

Formation mechanisms and prediction of solidification defects in aluminum alloy castings

作者:

劉永勤; 介萬奇

西北工業大學凝固技術國家重點實驗室

Author(s):

Liu Yongqin;  Jie Wanqi

State Key Laboratory of Solidification, Northwestern Polytechnical University

關鍵詞:

鋁合金; 鑄造缺陷; 孔洞; 熱裂; 模型

DOI:

10.7502/j.issn.1674-3962.2014.06.06

文獻標志碼:

A

摘要:

孔洞與熱裂是鑄件在凝固過程中最常遇到的典型缺陷。兩者均形成于合金凝固末期，與液相補縮不足相關，但又有各自的形成機理。鋁合金熔體對氫氣有很大的溶解度，凝固過程中又因為溶解度的劇降而析出。孔洞是液相中過飽和的氣體壓力與凝固收縮引起的壓力降共同作用的結果。熱裂則是在凝固末期由于鑄件收縮受阻而產生的應力以及液相補縮不足而導致，其不僅與合金性質、鑄造條件有關，并且受鑄件形狀的影響。文章基于近年來的理論研究成果，總結了關于孔洞與熱裂的形成機理以及幾種目前所應用的經典預測模型，并對這幾種模型的理論基礎以及所考慮的關鍵參數進行了分析與討論，在此基礎上提出了未來新模型的研究方向和亟需解決的關鍵問題。

Abstract:

Porosity and hot tearing are representative defects in solidification of shape castings. They are all related to lacking of feeding at the final stage of solidification but have different forming mechanisms. The hydrogen has high solubility in melt of aluminum alloy but will be released during solidification. The supersaturation pressure of the gas and pressure drop induced by solidification shrinkage all contributed to the formation of porosity. Hot tearing usually occurred due to blocking of shrinkage and lacking of feeding, and is related to alloys properties, casting technology in the shaping of castings. Based on the fundamental researches of solidification, formation mechanisms and several classical prediction criterions of these two types of solidification defects were generalized. Analyses and discussion were done for the formation criterion and key parameters. Finally the research directions of new criterion and the problems to be resolved immediately were given.