(江蘇大學(xué) 材料科學(xué)與工程學(xué)院，鎮(zhèn)江 212013)
摘 要: 研究了添加Si對(duì)Zn-38Al-2.5Cu合金顯微組織、力學(xué)性能及熱疲勞性能的影響。結(jié)果表明:Si的添加使鋅鋁合金產(chǎn)生成分過(guò)冷。當(dāng)Si添加量為0.55%時(shí)，合金組織細(xì)化顯著，力學(xué)性能最優(yōu)。繼續(xù)添加Si，Si相聚集長(zhǎng)大，晶粒粗化，合金力學(xué)性能下降。由于塑性變形形成的凹坑及氧化是熱疲勞裂紋萌生的主要原因。在裂紋擴(kuò)展前期，裂紋附近形成的疏松多孔的氧化區(qū)加快裂紋生長(zhǎng)，符合Paris公式，裂紋主要沿晶界擴(kuò)展。裂紋擴(kuò)展后期，二次裂紋的快速生長(zhǎng)吸收了主裂紋生長(zhǎng)所需的部分能量，裂紋進(jìn)入緩慢增長(zhǎng)階段，裂紋變?yōu)檠鼐Ш痛┚Щ旌系臄U(kuò)展特征。
關(guān)鍵字: Zn-38Al-2.5Cu合金；Si添加；力學(xué)性能；熱疲勞；裂紋生長(zhǎng)；氧化
（School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, China）
Abstract:The influence of Si addition on microstructure, mechanical properties and thermal fatigue behavior of Zn-38Al-2.5Cu alloys was investigated. The results show that constitutional supercooling of ZA38 alloys is formed because of the Si addition. Zn-38Al-2.5Cu-0.55Si alloy shows the dramatically refined microstructure and the best mechanical properties. When the Si addition exceeds 0.55%, α dendrites develop and Si phases become larger and aggregate along the dendrites boundaries, decreasing the mechanical properties. Oxides and pits formed by the plastic deformation are the main factors of cracks initiation. During the early stage of crack propagation, the cracks grow at a high speed well described by Paris law because of the porous and loose oxide, and mainly propagate along the dendrites boundaries. During the slow-growth stage, secondary cracks share the energy of crack growth, delaying the propagation of cracks, and the cracks propagate and fracture by the mixture of intergranular and transgranular modes.
Key words: Zn-38Al-2.5Cu alloy; Si addition; mechanical properties; thermal fatigue; crack growth; oxidation
