Papers by Keyword: SUS316

Abstract: The martensitic transformations (MT) in austenite stainless steel (SUS316) were observed by using a sensitive Flux-Gate (FG) sensor just after the magnetizations by the permanent magnet in the terrestrial field. MT in the small deformation range less than 5% elongation, was visualized by the 2-dimensional profile at each position together with the profile of the thickness deformations with an accuracy of several microns. We found the local MT enhancements up to 400[nT] at the positions along the changes of the thickness. In this experiment, the observations of MT were able to avoid the effects of the external fields or of the ac fields which was generated by the gating function in the FG sensor.

Abstract: An SUS316L and a Ti-6Al-4V alloy powders are treated by Mechanical Milling (MM) process, which is one of SPD processes, and then sintered by Hot Roll Sintering (HRS) process. The HRS process consolidates powder by hot rolling of an evacuated metal pipe filled with the powder at elevated temperatures. Those MM powders have a heavy deformed microstructure at the surface region and have a work hardened microstructure in the core region of the powder. In the surface region, a nano grain structure forms after the MM treatment in both materials. In case of the SUS316L powder, such a nano grain structure consists of an equiaxed nano ferrite (􀁄) grains which has transformed from nano austenite (􀁊) grains. Volume fraction of the 􀁄 phase decreases with distance from the surface of powder. During HRS the (􀁄 + 􀁊) nano-duplex structure changes to (sigma (􀁖) + 􀁊) nano-duplex structure by transformation of the 􀁄 to the 􀁖 phase. Thus, the SUS316L HRS material consists of a hybrid structure. That is, a (􀁖 + 􀁊) nano-duplex structure at the powder shell region, and a work hardened 􀁊 structure in the powder core region. In case of the Ti-6Al-4V MM powder, though no remarkable transformation occurs, a heavy deformed shell and work hardened core hybrid structure is also produced in the powder. By HRS the Ti-6Al-4V MM powder demonstrates a hybrid structure consists of an equiaxed nano grain structure and a coarse martensite structure. These two HRS materials indicate superior mechanical properties. Mechanical properties are improved by the HRS process. The proof stress and tensile strength in the SUS316L HRS material are x3.8 and x2.1 of the SUS316L conventional material, respectively. In the Ti-6Al-4V HRS material, they are x1.7 and x1.5 compared to the Ti-6Al-4V conventional material.