Shrinkage of titanium alloy during cooling and solidification

After the liquid titanium is poured into the holding form, the volume and linear size of the liquid titanium are reduced from liquid to solidification until room temperature, that is, volume shrinkage and linear shrinkage occur.

The solidification and shrinkage process of titanium and titanium alloy castings is closely related to the quality of the casting subsequently obtained, and various defects often appear in the casting (such as shrinkage, porosity, porosity, hot cracking, cold cracking, stress and deformation, etc.) are related to this process. The whole process of solidification shrinkage of titanium and titanium alloy castings is actually volume shrinkage. In order to use easily in engineering, liquid shrinkage and solidification shrinkage are expressed as volume shrinkage, and the solid shrinkage after solidification is directly related to the shape structure and dimensional accuracy of the formed castings, and the contraction at this stage is more than the line shrinkage.

In the solidification process of titanium and titanium alloy castings, if the liquid shrinkage and solidification shrinkage are not compensated, there will be concentrated holes or dispersed holes in the final solidification place of the casting. Concentrated holes are called shrinkage holes; Scattered holes are called shrinkage. Whether there is shrinkage hole or shrinkage porosity in the final casting is closely related to the type of alloying element added. Concentrated shrinkage holes tend to be formed in alloy castings with narrow crystallization temperature interval between alloying elements and titanium. All alloy castings containing alloying elements that can make the crystallization temperature interval of titanium wider tend to form dendritic or spongy shrinkage. The size of shrinkage hole and shrinkage volume in titanium alloy castings is affected by the addition of alloying elements.

In titanium alloy castings, whether the formation of shrinkage or shrinkage, gas plays a great role. When liquid titanium cools, solidifies and shrinks, holes appear when the final solidified place is not compensated, and these holes are vacuum. When the liquid titanium solidifies, the gas will spread out and fill up here. Therefore, the holes in titanium and titanium alloy castings are often called shrinkage holes, and the holes are silver-white, which is one of the characteristics of titanium alloy castings.