Combined effect of stress and strain on crystallographic orientation of bainite

Experiments have been conducted to see whether specific crystallographic variants of bainite form in polycrystalline steel when transformation occurs from plastically deformed austenite which is otherwise free from externally applied stress. It is demonstrated by studying both overall and microtexture that there is no perceptible variant selection as bainite forms. Indeed, the texture is found to weaken on transformation

Bearing area curve based partitioning for the verification of theoretical supplemental geometry on additively manufactured lattice structures

The geometrical qualification of additively manufactured lattice structures has largely focused on the mea-surement of strut diameter, form variations, and surface texture. However, the exterior surfaces of the lattice structure, defined through theoretical supplemental geometry, are critical surfaces that dictate the contact area of the structure on other components within assemblies. Form variations on these surfaces complicate the measurement process by adding ambiguity into what surfaces of the component belong to the controlled ge-ometry. Previous works have developed novel methods to improve data extraction for the measurement of these surfaces using computer aided design (CAD) data for various lattice structures. This work presents an adaptation of these methods to work with additively manufactured (AM) geometries, specifically designing the methodology to account for the form variations between lattice struts. The presented results show the applicability of these methods to AM lattice structures for the measurement of form defined by a theoretical supplemental surface

Crystallographic Analysis of Martensite in 0.2C-2.0Mn-1.5Si-0.6Cr Steel by EBSD

The crystallography of martensite formed in 0.2C-2.0Mn-1.5Si-0.6Cr steel was studied using the EBSDtechnique. The results showed that the observed orientation relationship was closer to the Nishiyama-Wassermann (N-W) than to the Kurdjumov-Sachs (K-S) orientation relationship (OR). The microstructure ofmartensite consisted of parallel laths forming morphological packet-like structures. Typically, there were threedifferent lath orientations in a morphological packet consisting of three specific N-W OR variants sharing thesame {111} austenite plane. A packet of martensite laths with common {111} austenite plane was termed as acrystallographic packet. Generally, the crystallographic packet size corresponded to the morphological packetsize, but occasionally the morphological packet was found to consist of two or more crystallographic packets.Therefore, the crystallographic packet size appeared to be finer than the morphological packet size. Therelative orientation between the variants in crystallographic packets was found to be near 60°/<110>. Thisappears to explain the strong peak observed near 60° in the grain boundary misorientation distribution.Martensite also contained a high fraction of boundaries with their misorientation in the range 2.5-8°.Typically these boundaries were found to be located inside the martensite laths forming lath-like sub-grains,whose long axes were parallel with the long axis of the martensite laths

Lath Structured Monazite from Haughton Dome, Canada Reveals Shock-Induced Tetragonal High Pressure Polymorph of REEPO4

Shock deformed monazite, mono-clinic rare earth element (REE) phosphate, from the Haughton Dome impact structure, Nunavut, Canada, contain lath-structured lamellae. Microstructural phase heritage indicate the former presence of a previously unreported, shock-produced, tetragonal-structured, high pressure polymorph of REEPO4. This study presents an electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) study of shock deformed monazite from the historic sample DIG-9, a shock stage III, biotite sillimanite gneiss sample from near the central uplift of the Haughton Dome (7522'20"N, 8940'50"W), in which shock features in monazite were first described

Evolution of grain boundary network topology in 316L austenitic stainless steel during powder hot isostatic pressing

The grain boundary network evolution of 316L austenitic steel powder during its densification by hot isostatic pressing (HIPing) was investigated. While the as-received powder contained a network of random high angle grain boundaries, the fully consolidated specimen had a large fraction of annealing twins, indicating that during densification, the microstructure evolves via recrystallization. By interrupting the HIPing process at different points in time, microstructural changes were tracked quantitatively at every stage using twin boundary fractions, distribution of different types of triple junctions, and the parameters associated with twin related domains (TRDs). Results revealed that, with increase in temperature, (i) the fraction of annealing twins increased steadily, but they mostly were not part of the grain boundary network in the fully consolidated specimen and (ii) the average number of grains within a TRD, the length of longest chain, and twinning polysynthetism increased during HIPing and (iii) the powder characteristics and the HIPing parameters have a strong influence on the development of grain boundary network. Based on the results obtained, possible alterations to the HIPing process are discussed, which could potentially allow twin induced grain boundary engineering

Pancreatic cancer intrinsic PI3Kα activity accelerates metastasis and rewires macrophage component.

Pancreatic ductal adenocarcinoma (PDAC) patients frequently suffer from undetected micro-metastatic disease. This clinical situation would greatly benefit from additional investigation. Therefore, we set out to identify key signalling events that drive metastatic evolution from the pancreas. We searched for a gene signature that discriminate localised PDAC from confirmed metastatic PDAC and devised a preclinical protocol using circulating cell-free DNA (cfDNA) as an early biomarker of micro-metastatic disease to validate the identification of key signalling events. An unbiased approach identified, amongst actionable markers of disease progression, the PI3K pathway and a distinctive PI3Kα activation signature as predictive of PDAC aggressiveness and prognosis. Pharmacological or tumour-restricted genetic PI3Kα-selective inhibition prevented macro-metastatic evolution by hindering tumoural cell migratory behaviour independently of genetic alterations. We found that PI3Kα inhibition altered the quantity and the species composition of the produced lipid second messenger PIP3 , with a selective decrease of C36:2 PI-3,4,5-P3 . Tumoural PI3Kα inactivation prevented the accumulation of pro-tumoural CD206-positive macrophages in the tumour-adjacent tissue. Tumour cell-intrinsic PI3Kα promotes pro-metastatic features that could be pharmacologically targeted to delay macro-metastatic evolution