OBSERVATION OF MICROFRACTURE PROCESS OF TIAL-BASED ALLOY

Interaction of microfracture and lamellar microstructure has been stud ied using acoustic emission method and ?EM observation. Ti-34Al-1Mn, - 3Mn(wt%) alloy was prepared by arc-melting in Ar atmosphere. During th e fracture toughness test microfracture behavior was monitored by acou stic emission method Tests were stopped before the unstable fracture t o facilitate a detailed study of the microfracture process. ?hen the s pecimens were sectioned at the plane in the thickness direction and ex amined using optical microscope, ?EM foils were prepared by mechanical grinding to 0.1mm thickness, ultrasonic culling, dimpling and finally ion milling. Then the cracks formed in the foils were observed AE beh avior was found to vary with the orientation relationship between crac k propagation and lamellar interfaces. Crack propagation behaviors par allel and across the lamellar interfaces were observed by TEM. A close -up view of the crack across the lamellar interfaces showed that the c rack went approximately straight in the lamellae, but was deflected by lamellar interfaces. In the ligaments region remarkable plasticity wa s found.