(中南大學 材料科學與工程學院，長沙 410083)
摘 要: 本文研究了Mg-Si摩爾比及Zr的添加對Al-Mg-Si合金力學、導電性能與耐熱性能及其影響機理。發(fā)現(xiàn)合金中Mg-Si摩爾比低于2時，有利于β″相形核并得到細小彌散的β″相，提高合金力學性能；過剩Si因溶解度低對導電率的不利影響小。隨著合金中Mg-Si摩爾比增大并超過2.5，β″相形核率降低并形成較粗的β″相，同時出現(xiàn)富Mg粗大相，力學性能變差；時效后過剩Mg仍固溶于基體，增加晶格畸變程度，降低了導電率。添加Zr元素使合金的導電率下降，抗拉強度升高。Zr溶質原子降低了合金中Mg、Si原子的擴散速率。在含0.13%Zr和0.18%Zr的鋁基體中Mg、Si原子擴散系數(shù)分別為無Zr鋁基體中Mg、Si原子擴散系數(shù)的0.92與0.75。因而含Al-Mg-Si-Zr合金中較低的Mg、Si原子擴散系數(shù)延長了β″相形核孕育期，阻礙了β″相長大，使β″相更細小彌散；β″相向β′相轉變速度變慢，合金的力學性能與耐熱性能增強。
關鍵字: Al-Mg-Si合金；Zr添加；耐熱鋁合金；析出相；擴散
（School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The electrical conductivity, mechanical property and heat resistance of Al-Mg-Si alloy with Zr adding were investigated. It is found that lower Mg-Si molar ratio in the alloy, which is lower than 2, promotes the nucleation of β″ phase and obtains fine and dispersed β″ phase, and improves the mechanical properties of the alloy. The excess Si has little adverse effect on the electrical conductivity of the alloy due to its low solubility in aluminum. As the Mg-Si molar ratio is greater than 2.5, the nucleation rate of β″ phase decreases, the particles of β″ phase are coarsened, Coarse Mg-enriched phase occurs, the mechanical properties of the alloy are deteriorated. Excess Mg is still dissolved in the base metal after aging, which increases lattice distortion level and reduces the electrical conductivity of the alloy. After adding Zr, the electrical conductivity of the alloy decreases and the tensile strength increases. Dissolved Zr atoms reduce the diffusion rate of Mg and Si atoms in the alloy. During aging, the diffusion rates of Mg and Si atoms in alloys with 0.13% Zr and 0.18% Zr are 0.92 time and 0.75 time of that diffusion rate in the alloy without Zr, respectively. Therefore, the lower diffusion rate of Mg and Si element in Al-Mg-Si-Zr alloy prolongs the nucleation incubation period of β″ phase, and hinder the growth of the β″ phase particles, which results in fine dispersed particles β″ phase; the phase transformation speed from β phase to β′ phase becomes slow; the mechanical properties and heat resistance of the alloy are enhanced.
Key words: Al-Mg-Si alloy; Zr addition; heat-resistant aluminum alloy; precipitated phase; diffusion coefficient
