(1. 上海交通大學(xué) 材料科學(xué)與工程學(xué)院，輕合金精密成型國家工程研究中心，上海 200240；
2. 上海納特汽車標準件有限公司，上海 201111)
摘 要: 研究了微量Sr變質(zhì)對Al-7Si-0.35Mg-0.1Ti合金微觀組織和力學(xué)性能的影響，再以某汽車用壓鑄零部件為研究對象，通過數(shù)值模擬技術(shù)對0.06%Sr變質(zhì)Al-7Si-0.35Mg-0.1Ti合金壓鑄工藝中的澆注溫度和壓射速度進行模擬計算，并進行實驗驗證。模擬結(jié)果表明：當澆注溫度為680 ℃時，合金二次枝晶臂間距更小；隨著壓射速度的提高(1 m/s、2 m/s、4 m/s)，雖卷氣現(xiàn)象更明顯，卷氣部位和數(shù)量更多，但氣孔尺寸相對較小。壓鑄驗證實驗結(jié)果顯示：隨著壓射速度從1 m/s提高到4 m/s，初生α(Al)相由胞狀樹枝晶部分轉(zhuǎn)變?yōu)榍驙罹Щ蚪驙罹В揖ЯＦ骄叽缰饾u減小；鑄件中卷氣由大尺寸的氣孔轉(zhuǎn)變?yōu)樾〕叽绲目s孔疏松，與數(shù)值模擬結(jié)果基本一致。同時，鑄件的抗拉強度和伸長率分別提升23.7%和188.5%，且合金斷裂機制也由1 m/s時的大尺寸氣孔起決定作用的脆性斷裂轉(zhuǎn)變?yōu)? m/s時共晶Si相起決定作用的脆性斷裂和韌性斷裂的混合斷裂模式。
關(guān)鍵字: Al-7Si-0.35Mg-0.1Ti合金；壓鑄；數(shù)值模擬；澆注溫度；壓射速度
（1. National Engineering Research Center of Light Alloy Net Forming, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;
2. Shanghai NATE Automobile Fastener Co., Ltd., Shanghai 201111, China）
Abstract:The effects of micro Sr modification on the microstructure and mechanical properties of Al-7Si-0.35Mg-0.1Ti alloy were firstly studied. Then, the pouring temperature and injection speed of 0.06% Sr modified Al-7Si-0.35Mg-0.1Ti alloy in the die casting process were calculated by numerical simulation technology, and the experimental verification was carried out. The simulation results show that when the pouring temperature is 680 ℃, the secondary dendrite arm spacing is smaller; with the increase of injection speed (1 m/s, 2 m/s, 4 m/s), although the air entrainment is more obvious, the position and quantity of air entrainment are more, but the pore size is relatively small. The results of die casting verification experiment show that, with the increase of injection speed from 1 m/s to 4 m/s, the primary α(Al) phase changes from cellular dendrite to globular or near globular, and the average grain size decreases gradually; the volume gas in the casting changes from large-size pores to small-size shrinkage porosity, which is basically consistent with the numerical simulation results. At the same time, the ultimate tensile strength and elongation of the die casting alloys increase by 23.7% and 188.5%, respectively. And the fracture mechanism of the tested alloys changes from the brittle fracture determined by large pores at 1 m/s to mixed fracture mode of brittle fracture and ductile fracture determined by eutectic Si phase at 4 m/s.
Key words: Al-7Si-0.35Mg-0.1Ti alloy; die casting; numerical simulation; pouring temperature; injection speed
