Effect Of Process Conditions On Composition Uniformity And Precipitation Behavior Of Aluminum Alloy

Aluminum alloys are widely used with high strength、hardness、handling ease、 corrosion resistance and toughness in aerospace field. However, there are element segregation between grain and grain during the solidification. Inhomogeneity of composition and microstructure will affect the properties of alloys.Temperature field in the process of solidification of aluminum alloy was changed by insert precast alloy rod in liquid metal in this paper. The characteristics and change of microstructure of cast ingot pre-and post temperature change were deeply analysis. The reason for the change of microstructure was discussed. The content of precipitated phase in different parts of cast ingot pre-and post temperature change was calculated. The reason for the change also be discussed. The characteristics and change of microstructure of cast ingot pre-and post temperature change after heat treatment were deeply analysis. The result show that:Before the temperature change:ingot microstructure of Al-5%Cu alloy consisted of three part:fine grain region、columnar grain region and equiaxed grain region. After the temperature change:ingot microstructure of Al-5%Cu alloy consisted of four part:fine grain region、columnar grain region、columnar grain and equiaxed grain mixed region、 equiaxed grain region. Before the temperature change:ingot microstructure of Al-2Li-2Cu alloy consisted of three part:star-shaped dendrite grain region、columnar grain region and equiaxed grain region. After the temperature change:ingot microstructure of Al-2Li-2Cu alloy consisted of four part:free dendrite region columnar grain region、columnar grain and equiaxed grain mixed region、standard equiaxed grain region.Pre-and post temperature change, the change of phase content of the precipitates has three characteristics:①Before the change of temperature, precipitations are more and uneven distribute. After the change of temperature, precipitations content are reduce and evenly distribute.②Before the change of temperature, precipitations content on the bottom of ingot is higher than top and edge to center section showing the V distribution. After the change of temperature, precipitations content of ingot is highest on the bottom, lowest in the top and edge to center section showing the W distribution. Pre and post temperature change, precipitation species are the same, but precipitations content trend of ingot slow down.The primary phase of cast ingot pre-and post temperature change is mostly dissolved. And the primary phase of cast ingot after temperature field change is dissolved more quickly than before. Different part of cast ingot needs different times in solution treatment.Different zone of the same part of cast ingot also need different time in solution treatment. After solution treatment, inhomogeneity of composition and microstructure will be improved. Because of the solution treatment, the age treatment will be different.