November AMP_Digital

FEATURE A D V A N C E D M A T E R I A L S & P R O C E S S E S | N O V E M B E R / D E C E M B E R 2 0 1 9 6 6 17 Fig. 6 — SEM images of fracture surfaces for test-steel W austenitized at 850°C show that fracture changed from (a) intergranular for an austenitizing time of 1000 s with a peak breaking load of 6920 N to (b) transgranular for an austenitizing time of 2 s with a peak breaking load of 19,921 N [6] . Fig. 7 — Microstructures of an AISI 1045 medium carbon steel show: (a) light optical image of ferrite and pearlite after hot rolling, (b) light optical image of tempered martensite after quenching and tempering, (c) SEM image of large ferrite grains formed during cooling after hot rolling, and (d) SEM image of uniform small carbides formed during induction heating martensite at 200°C/s to 700°C. Uniformly spaced small carbides are required to achieve full austenitization at low austenitizing temperatures during induction hardening. (a) (b) (b) (c) (a) (d) 16