摘要
Semi-solid processing of A380 aluminum alloy was performed by gas induced semi-solid(GISS)process.The effects of argon inert gas flow rate,starting temperature and duration of gas purging as key GISS parameters and also modification with Sr on the structural refinements,hardness and impact strength of GISS alloys were investigated.Microstructural evolution shows that there is an important effect of the pouring temperature and Sr addition on the morphology and size of primaryα(A1)in the alloy to change from coarse dendritic to fine globular structure.The best sample which has fine grains of 51.18μm in average size and a high level of globularity of 0.89 is achieved from a GISS processing of Sr modified alloy in which the gas purging started at 610℃.The impact strength of the GISS optimized samples((4.67±0.18)J/cm^(2))shows an increase of about 40%with respect to the as-cast sample due to the globular structure and fibrous Si morphology.Moreover,the hardness of the optimized GISS sample((89.34±2.85)HB)increases to(93.84±3.14)HB by modification with the Sr and GISS process.The fracture surface of Sr modified alloy is also dominated by complex topography showing typical ductile fracture features.
采用气体诱导半固态(GISS)加工工艺制备A380铝合金,研究氩气惰性气体流量、起始温度和气体吹扫时间等GISS关键参数以及Sr改性对合金的组织细化、硬度和冲击强度的影响。显微组织演化表明,浇铸时间和Sr添加对合金中初生α(Al)的形貌和尺寸有较大影响,使其由粗大的枝晶状组织转变为细小的球形组织。对Sr改性合金进行GISS加工,当气体注入的起始温度为610℃时,获得具有平均晶粒尺寸为51.18μm、高球形度(0.89)细晶组织的最优样品。与铸态样品相比,GISS加工获得的最优样品由于球形组织和Si的纤维状形貌,其冲击强度((4.67±0.18)J/cm^(2))提高约40%;而且,Sr改性和GISS加工使合金的硬度从(89.34±2.85)HB提高到(93.84±3.14)HB。Sr改性合金的断裂面以复杂形貌为主,具有典型的韧性断裂特征。
