(1. 廣西大學(xué) 資源環(huán)境與材料學(xué)院，南寧 530004；
2. 廣西大學(xué) 廣西有色金屬及特色材料加工重點(diǎn)實(shí)驗(yàn)室，南寧 530004；
3. 東莞理工學(xué)院 機(jī)械工程學(xué)院，東莞 523000)
摘 要: 利用光學(xué)顯微鏡、掃描電鏡/能譜、X衍射分析儀及力學(xué)性能測試等手段，研究不同添加量的Zr(0.15%, 0.3%, 0.45%, 0.6%)加入Al-20Si合金后對微觀組織和力學(xué)性能的影響。結(jié)果表明：Al-20Si合金中添加微量Zr能使合金中初生硅形態(tài)從粗多邊形和星形細(xì)化為細(xì)小多面體形狀，并逐漸球化；共晶硅形態(tài)從粗大片狀、針狀結(jié)構(gòu)變?yōu)殡x散顆粒細(xì)纖維結(jié)構(gòu)。當(dāng)Al-20Si合金中的Zr添加量為0.3%時(shí)，其細(xì)化變質(zhì)效果最明顯，初生硅平均長徑比由1.71降至1.26，共晶硅平均長度由20.6 μm降至8.7 μm。此時(shí)，合金的拉伸強(qiáng)度和伸長率分別由初始的89.4 MPa和0.67%增至132.1 MPa和1.2%，分別提高了47.8%和79.1%。從XRD和EDS分析結(jié)果可知，Al-20Si合金中加入Zr元素形成了Al4Si5Zr3合金相。由斷口分析可知，添加Zr形成的Al4Si5Zr3相使合金顆粒彌散并形成了釘扎強(qiáng)化，從而使其力學(xué)性能得到顯著提升。
關(guān)鍵字: Al-20Si合金；微量Zr；第二相；細(xì)化變質(zhì)；力學(xué)性能
（1. School of Resources, Environment and Materials, Guangxi University, Nanning 530004, China；
2. Guangxi Key Laboratory of Processing for Non-ferrous Metal and Featured Materials, Guangxi University, Nanning 530004, China；
3. School of Mechanical Engineering, Dongguan University of Technology, Dongguan 523000, China）
Abstract:In this research, the effects of different zircon additions(0.15%, 0.3%, 0.45%, 0.6%, mass fraction) on the microstructure and mechanic properties of Al-20Si alloy were investigated using OM, SEM/EDS and XRD, and their strength and hardness were measured. The results show that the phenomenon of microstructure modifications are occurred when the zircon is added at trace amount. The coarse polyhedral and star like primary silicon are refined and modified to small polyhedral shape as well as be spherized. When the zircon addition of Al-20Si alloy is 0.3%, the effect of refine and modification is the most obvious. The length-diameter ratio of primary silicon is decreased from 1.71 to 1.26. The coarse silicon with flack/needle shape is changed to fine fiber shape dispersed on the matrix. The length of eutectic silicon decreases from 20.6 μm to 8.7 μm. From the XRD patterns, the Al4Si5Zr3 phase is formed owing to the zircon addition of Al-20Si alloy. The ultimate tensile strength increases from 89.4 MPa to 132.1 MPa, by 47.8%, and the elongation increases from 0.67% to 1.2%, by 79.1%. From the fracture surface, the promotions of mechanical properties are due to the dispersion and pinning reinforcement caused by the addition of trace zircon.
Key words: Al-20Si alloy; trace zirconium; secondary phase; refine and modification; mechanical properties
