Microstructure, Texture and Mechanical Property of TA32 Titanium Alloy Thick Plate

TA32 alloy is a new near alpha titanium alloy designed by optimizing the alloy elements ratio based on a series of elements Ti-Al-Sn-Zr-Mo-Si-Nb-Ta which has less beta-stabilizing elements. This alloy has an excellent match of heat resistance and heat stability at 550 degrees C, and good short-term mechanical properties at 600 similar to 650 degrees C. TA32 titanium alloy thick plate can be applied to the key components in high temperature service of the hypersonic vehide. Due to the low deformation degree of thick plate during rolling process, the heterogeneity of microstructure, texture and mechanical properties of the thick plate increases. In order to provide theoretical basis and experimental basis for the subsequent optimization of mechanical properties of TA32 titanium alloy thick plate, the microstructure, texture and mechanical properties of this alloy with a thickness of 60 mm are investigated in this work. Results show that the microstructure of the as-received material is mainly composed of lamellar alpha grains with few retained thin beta layers, and the microstructure difference is not obvious from the surface to the center along the thickness direction of the plate no matter of the RD (rolling direction)-ND (normal direction) plane or the TD (transverse direction)-ND plane. Moreover, the rolling streamline can be obviously observed on the two planes. The morphology of alpha grains of the alloys presents either straight or wavy depending on their orientations with respect to the principal rolling directions. XRD results show that the as-received material has a typical T-type texture with c-axis of alpha phase approximately parallel to TD. At the same time, the <10<(1)over bar>0> poles are parallel to RD while <10<(1)over bar>1> poles present random distribution. As the c-axis gradually deviates from the TD of the surface to the center along the thickness direction of the plate, the Schmidt factors gradually increase, which is one of the main reasons for the gradual decrease of tensile strength; and the decrease of fraction of intragranular substructure from the surface to the center along the thickness direction is another important factor. The tensile properties have no obvious difference along the TD and RD at the same thickness position of the as-received material, but slightly worse along the ND. In addition, the influences of microstructure and texture on tensile properties are further clarified by adding two sets of heat treatment experiments (920 degrees C, 30 min, AC+600 degrees C, 5 h, AC; 950 degrees C, 30 min, AC+600 degrees C, 5 h, AC). The results show that the texture is the main factor affecting the tensile strength of TA32 titanium alloy plate at different positions under the condition of no obvious difference in microstructure. After double annealing, microstructure difference is the main factor affecting tensile strength.