Slip systems of lamellar α and damage tolerance properties in Ti-5321 alloys formed by laser cladding

Abstract

Ti-5321 alloy formed by laser cladding has good mechanical properties. By subsequent heat treatment of the alloy, not only can rich microstructures be obtained, but its strength, toughness, or damage tolerance performance can also be improved. Four typical microstructures, including basket-weave structure, large layer structure, ultrafine needle-like structure, and rod-like structure were constructed through different heat treatments. Basket-weave structure is composed of slender lamellar α, which has the best plasticity and toughness. Due to the large orientation difference between adjacent lamellar α and the susceptibility to multiple slip during crack propagation, this will greatly increase the crack propagation resistance and the curvature of the crack propagation path, which is beneficial for improving the damage tolerance performance of the alloy. Large layer structure is composed of large layer α and ultrafine needle-like α, with the highest strength. The orientation difference between adjacent large layer α is extremely small and prone to {10–11} pyramidal slip. The crack propagation resistance is reduced, which in turn damages the damage tolerance performance of the alloy. Ultrafine needle-like structure is entirely composed of ultrafine needle-like α, with high strength and extremely low plasticity and toughness. The orientation difference between adjacent needle-like α is single, making it prone to pyramidal slip and first-order pyramidal slip. The strength of rod-like structure matches well with its plasticity and toughness. There are multiple slip systems in rod-like structure and there is significant difference in orientation between adjacent α. Large orientation differences will have certain hindering effect on crack deflection.

Keywords

• Laser cladding
• Damage tolerance performance
• Ti-5321 alloy
• Slip systems