Showing papers by "Tadashi Maki published in 1982"
TL;DR: In this article, the effect of prior deformation on the processes of tempering and austenitizing of lath martensite was studied by using low carbon steels.
Abstract: The effect of prior deformation on the processes of tempering and austenitizing of lath martensite was studied by using low carbon steels. The recrystallization of as-quenched lath martensite was not observed on tempering while the deformed lath martensite easily recrystallized. The behavior of austenite formation in deformed specimens was different from that in as-quenched specimens because of the recrystallization of deformed lath martensite. The austenitizing behavior (and thus the austenite grain size) in deformed specimens was controlled by the competition of austenite formation with the recrystallization of lath martensite. In the case of as-quenched (non-deformed) lath martensite, the austenite particles were formed preferentially at prior austenite grain boundaries and then formed within the austenite grains mainly along the packet, block, and lath boundaries. On the other hand, in the case of lightly deformed (30 to 50 pct) lath martensite, the recrystallization of the matrix rapidly progressed prior to the formation of austenite, and the austenite particles were formed mainly at the boundaries of fairly fine recrystallized ferrite grains. When the lath martensite was heavily deformed (75 to 84 pct), the austenite formation proceeded almost simultaneously with the recrystallization of lath martensite. In such a situation, very fine austenite grain structure was obtained most effectively.
97 citations
TL;DR: In this paper, the dynamic recrystallization behavior of austenite in an 18-8 stainless steel and an 18 Ni maraging steel was studied mainly by microstructural observations of the specimens which were water-quenched immediately after the tensile deformation to various strains at temperatures ranging from 800 to 1200 °C.
Abstract: The dynamic recrystallization behavior of austenite in an 18-8 stainless steel and an 18 Ni maraging steel was studied mainly by microstructural observations of the specimens which were water-quenched immediately after the tensile deformation to various strains at temperatures ranging from 800 to 1200 °C and at strain rates of 10'3 10-~ s-1, The changes in austenite grain size and hardness at room temperature due to the dynamic recrystallization were also studied. The deformation conditions for the occurrence of dynamic recrystallization in both steels were made clear as a function of deformation temperature
53 citations
TL;DR: The change in the morphology of lath martensite with deformation of austenite (ausforming) has been studied by using an 18% Ni maraging steel.
Abstract: The change in the morphology of lath martensite with deformation of austenite (ausforming) has been studied by using an 18% Ni maraging steel. Specimens in austenitic state were deformed in tension by several strains (true strain E = 0.1 -1.0) at 773 K (which was above Md temperature). In the case of conventionally quenched (not-deformed) specimen, an austenite grain contained several packets and each packet was almost completely partitioned by parallel blocks. However, this morphology of packets and blocks was markedly changed when martensite was formed from deformed (work-hardened) austenite. The packet size was increased with an increase in the amount of deformation. On the other hand, block width was decreased with an increase in the amount of deformation (up to about E = 0.2) and blocks became wavy or finely segmented when austenite was heavily deformed (E = 0.4~1.0). From the observation of the formation process of lath martensite by applying the Greninger-Troiano heat treatment, it was found that laths with the same habit plane (one of four {lllIy habit planes) were preferentially formed in an austenite grain when the specimen was deformed before transformation, although four {lll}y martensite habit planes were almost evenly observed in an austenite grain in a conventionally quenched specimen. Because of such a restriction of the variant of martensite habit plane, the ausformed lath martensite exhibits the characteristic morphology.
16 citations
TL;DR: In this article, the effect of applied total strain range on the critical condition necessary for the onset of a'-martensitic transformation kinetics during the fatigue deformation was studied in AISI type 304 metastable austenitic stainless steel at room temperature.
Abstract: The effect of applied total strain range on the critical condition necessary for the onset of a'-martensitic transformation kinetics during the fatigue deformation was studied in AISI type 304 metastable austenitic stainless steel at room temperature. In the case of fatigue deformation, the a'-martensite formation was observed even in the condition that the saturated stress amplitude of austenite phase is smaller than the critical applied stress for the onset of a'-martensite formation for the monotonic tensile deformation. Furthermore, the amount of (3'-martensite increased with the number of cycles even in the saturated stage of austenite phase in which the stress amplitude of austenite phase is almost constant during the fatigue deformation, The (3'-martensite formation was enhanced as the applied total strain range was increased. Such an enhancement of transformation was closely related with the increase in saturated stress amplitude of austenite phase due to the increase in applied total strain range. It was emphasized that the a'-martensite was preferentially induced in the near-surface layer of the specimen by the increase in local concentrated stress due to the increase in number of piled-up dislocations with the number of cycles even in the saturated stage of austenite phase.
7 citations
TL;DR: In this article, the authors examined the change in martensite morphology with ausaging in Fe-31%Ni-3%Ti and Fe- 31%Ni 3%Ti-10%Co alloys and found that thin plate martensites formed in both solution treated and ausaged specimens.
Abstract: The change in martensite morphology with ausaging in Fe-31%Ni-3%Ti and Fe-31%Ni-3%Ti-10%Co alloys has been examined. By the ausaging, austenite hardness and Ms temperature changed with the precipitation of coherent ordered fcc γ'-Ni3Ti. It was found that in the case of Fe-Ni-Ti-Co alloy the thin plate martensite formed in both solution treated and ausaged specimens, and the formation temperature of thin plate martensite was markedly increased by ausaging, whereas only the lenticular martensite was formed in Fe-Ni-Ti alloy. Present results indicated that the addition of Co to Fe-Ni-Ti alloy and the ausaging were favorable for the formation of thin plate martensite. Thin plate martensite in Fe-Ni-Ti-Co alloy showed a good (but not complete) shape memory effect in both solution treated and ausaged specimens, although the martensite was not typically thermoelastic.
2 citations