Effect Of Tensile Stress Field On The Aging Behavior Of Al-0.1at%Sc Alloy

As a special field, stress field has the advantage that traditional ways don’t have. It can change the morphology, distribution and volume fraction of precipitation. By means of TEM, HTEM, electrical conductivity measurement and HV hardness measurement, the effect of tensile stress field on the aging behavior of Al-0.1at%Sc alloy was studied. The effect of tensile stress field on the thermodynamics and kinetics of nucleation was studied with the help of first principle method combined with classic nucleation theory. Main conclusions were presented as followed:1. Tensile stress field accelerats the hardening rate and increased hardness value during aging process. Tensile stress field increases the volume fraction and decreases the distance of precipitation. Tensile stress filed increases the electric conductivity of alloy in the aging time from0to120min. The calculated values of electrical field by modified Matthiessen’s formula are agree with experiment data。2. Tensile strain filed changes the diffusion behavior of Al and Sc atom in the matrix. Under the strain, the diffusion activation energy along the direction perpendicular to the strain decreases, and the diffusion activation energy along the direction lie at an angle of45degrees with the tensile strain increases.3. Tensile strain field increases the vibrational entropy of all the system. The solubility enthalpy does not change much with the increasing of strain field. However, the solubility entropy decreases obviously with the increasing of strain field, leading to an increasing of solubility free energy. The resulted solvus boundary curve shifts up on the phase diagram under the strain, suggesting a reduced solubility limit and hence an increased maximum possible precipitation volume of Al3Sc in Al.4. The Sc activity in Al increases with the increasing of temperature. In all the range of our calculations, strain field increases the Sc activity in Al. The interfacial energy of Al3Sc and Al decreases with the increasing of temperature. In all the range of our calculations, strain field decreases the interfacial energy. Compared with the strain vertical to the interface, a parallel strain makes the interfacial energy decreases more.5. Tensile strain field increased the driving force of nucleation. Under the temperature of600K, driving force under the stain of0.1%,0.5%and1%increased by15%,28%and37%respectively. Tensile strain field decreased the critical nucleation radius, and increased the nucleation rate by decreasing the nucleation work and the diffusion activation energy.