Mg-Si摩尔比及Zr的添加对Al-Mg-Si合金性能的影响及其机理

Effect of Mg-Si molar ratio and Zr addition on properties of Al-Mg-Si alloy and its mechanism

本文研究了Mg-Si摩尔比及Zr的添加对Al-Mg-Si合金力学、导电性能与耐热性能及其影响机理。发现合金中Mg-Si摩尔比低于2时,有利于β″相形核并得到细小弥散的β″相,提高合金力学性能;过剩Si因溶解度低对导电率的不利影响小。随着合金中Mg-Si摩尔比增大并超过2.5,β″相形核率降低并形成较粗的β″相,同时出现富Mg粗大相,力学性能变差;时效后过剩Mg仍固溶于基体,增加晶格畸变程度,降低了导电率。添加Zr元素使合金的导电率下降,抗拉强度升高。Zr溶质原子降低了合金中Mg、Si原子的扩散速率。在含0.13%Zr和0.18%Zr的铝基体中Mg、Si原子扩散系数分别为无Zr铝基体中Mg、Si原子扩散系数的0.92与0.75。因而含Al-Mg-Si-Zr合金中较低的Mg、Si原子扩散系数延长了β″相形核孕育期,阻碍了β″相长大,使β″相更细小弥散;β″相向β′相转变速度变慢,合金的力学性能与耐热性能增强。

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 ofβ″phase and obtains fine and dispersedβ″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 ofβ″phase decreases,the particles ofβ″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 ofβ″phase,and hinder the growth of theβ″phase particles,which results in fine dispersed particlesβ″phase;the phase transformation speed fromβphase toβ′phase becomes slow;the mechanical properties and heat resistance of the alloy are enhanced.