Martensite Decomposition and Ultrafine Grain Formation during Small Punch Creep Testing of Additively Manufactured Ti64

Abstract

The creep behaviour of as-built additive-manufactured Ti-6Al-4V alloy was studied through small punch creep test (SPCT) experiments at 450 and 500 °C. The couple stress/minimum strain rate deduced from these tests made it possible to draw a Norton plot showing good agreement with tensile test creep results. The microstructure characterisation within the SPCT specimen evidenced the effect of local strain on microstructure evolution. After interrupted creep at 450 °C, in most deformed areas, the as-built martensite structure was fully decomposed to the α + β equilibrium phases, giving rise to a submicron equiaxed grain structure.

Research on the Cold Rolling Process, Microstructure and Properties of 305 Austenitic Stainless Steel Thin Strips

“…The relationship between grain size and annealing time under isothermal annealing conditions can be expressed by the following Beck’s formula [ 25 ] for grain growth kinetics: D − D 0 = kt n where D is the grain size after annealing, D 0 is the grain size before annealing, k is the rate parameter of grain growth, n is the kinetic index of grain growth; t is the annealing time. It is obvious from the formula that the grain size increases with the extension of the annealing time.…”

“…The relationship between grain size and annealing time under isothermal annealing conditions can be expressed by the following Beck's formula [25] for grain growth kinetics:…”