论文部分内容阅读
利用消失模铸造振动凝固技术,得到Al-Si7-Mg合金的近等轴晶组织。在此基础上研究了580℃不同时间保温半固态等温热处理(SSIT)组织中α-Al晶体的形貌与尺寸变化。结果表明:合金580℃保温1h,得到α晶粒的等积圆直径在50~150μm的分布比例达85%,α晶粒圆度均值1.41。通过凝固动力学和热力学分析,得出半固态热处理过程中,低熔点的三元共晶和二元共晶相首先熔化,并随着溶质元素扩散速度的增加,液相不断增多,α晶体形状大小不断改变;当液相率达到平衡之后,α晶粒在界面张力的作用下,不断圆整球化,合并长大。半固态热处理α枝晶演变形式明显不同于等轴晶演变过程。
Void-casting vibration solidification technology was used to obtain Al-Si7-Mg alloy near-equiaxial grain structure. On this basis, the morphologies and size changes of α-Al crystals in semi-solid isothermal heat treatment (SSIT) at 580 ℃ for different time were studied. The results show that when the alloy is incubated at 580 ℃ for 1 h, the distribution of the equivalent circle diameter of α grains in the range of 50-150 μm is 85%, and the average circularity α grain size is 1.41. Through the solidification kinetics and thermodynamic analysis, it is concluded that the low melting point ternary eutectic and binary eutectic phase are firstly melted during the semi-solid heat treatment, and the liquid phase increases with the increase of the solute diffusion speed. The α crystal shape The size of the continuous change; when the liquid phase rate reaches equilibrium, α grain under the action of the interfacial tension, constantly rounded, merger and grow. Semi-solid heat treatment α dendrite evolution is obviously different from the evolution of equiaxed.