Microstructure And Properties Of Hot-rolled Sheet With High Strength And High Heat Of TC4 Titanium Alloy Plastic

TC4titanium alloy (Ti-6A1-4V) is a kind of two phase alloys ((α+β) with the most widely used and most mature and excellent comprehensive performance, it possess high strength, high plasticity, good corrosion resistance, which was much attention at home and abroad. Titanium alloy performance has close relationship with the microstructure at room temperature.In this paper, The effects of hot-rolled and heat treatment process on the microstructure and properties (mechanical properties and penetration properties) of the TC4titanium alloy plate were investigated by means of optical c microscope (OM), scanning electron microscopy (SEM), X-ray diffraction analysis(XRD) microscopic hardness meter and tensile test. Author analyzes the characteristics of TC4titanium alloy microstructure changed during hot-rolled process, and discussed the influence of the solution heat treatment temperature, the cooling rate, the aging temperature and the aging time on the microstructure and the mechanical properties in the process of solid solution aging heat treatment, and studied the material deformation and damage by the means of penetration holes around. The results show that:After a hot-rolled inβ-phase region, the microstructure of TC4was typical of hot-worked structure, the obvious flow line in the longitudinal direction, and the microstructure has occurred in the hexagonal structure martensite α’and the rhombic martensite α". After rolling of the second stage, the temperature closer to the phase transition point, the microstructure is more uneven, the composition segregation is more serious and easy to form β plaques, while the alloy possess higher strength, plasticity has changed a little.After a hot-rolled inβ-phase region, solid solution treatment on the upper of two-phase zone, quench and aging heat treatment have been used. In two phase solid solution treatment, regardless of the water-cooling or air-cooling, the most part of the deformation and stretch a phase turn into equiaxed, and banded structure (β patch) disappear, microstructure homogenization. The product of tensile strength gradually increased and plasticity decreased with solution temperature increased. Compared with air cooling, water quenching has higher tensile strength and yield strength and lower plasticity. Tensile strength and yield strength of the alloy first increased and then decreased with the isothermal holding temperature in the range of500～600℃; With the increase of aging time (2h～8h), tensile strength and yield strength of the alloy first decreased and then increased. To obtain better matching strength and plasticity, the heat treatment is recommended for the style as follow:950℃,30min, WQ+550℃,2h,AC.To large size of titanium alloy sheet after950℃,30min, WQ+550℃,2h, AC heat treatment, the microstructure is relatively uniform, banded structure has been basically eliminated, the transverse and longitudinal mechanical properties are basically the same. T1titanium alloy plate transverse tensile strength is1207MPa, while maintaining high elongation rate (12.2%); T2titanium alloy plate transverse tensile strength is1218MPa, and also has high elongation (11.5%). After a hot-rolled inβ-phase region and heat treatment on the style of950℃,30min, WQ+550℃,2h, AC, the large size of TC4titanium alloy plates has reached the armor plates (targets) requirements on the mechanical performance.Penetration experiments have been carried on the large size of TC4targets after heat treatment. The ductile hole failures and back-surface shearing tear when the conical projectiles penetrated targets. The side wall crack is given priority to radial cracks, maintained about45°with the rolling direction. The crack formation guarding is mainly microvoid accumulation fracture mechanism, and formed the main crack along penetration direction. Material is soften because of the deformation acutely at the edge of the crater, and the hardness is increases with the increase of the distance from the crater and to the normal value at last. Hardness of this change is mainly due to the thermal softening results in target material.