Cast Intermetallic Alloys and Composites Based on Them by Combined Centrifugal Casting—SHS Process
This work aims to establish a scientific and engineering background in the production of cast multicomponent alloys and metalmartix composite (MMCs) via Self-Propagating High Temperature Synthesis (SHS, combustion synthesis) which is a novel process technique regarding fast and low-cost production ability. We carried out the search for reactive systems and process parameters that would ensure preparation of cast multicomponent materials in a single process. The principles and methods of the SHS thermite-type reaction processes have been investigated under high-gravity values applying loads up to 1000 g with special centrifuge set-up. In this way we expected to improve the yield of target product, remove gaseous byproducts, diminish the grain size in the product, and make product composition more uniform. The obtained results can be expected to make a theoretical background for industrial-scale manufacturing of heat-resistant intermetallic alloys, master alloys, catalysts, MMCs etc.
Structure and properties of NiAl-Cr(Co,Hf) alloys prepared by centrifugal SHS casting. Part 1 – Room temperature investigations
Abstract The structure and mechanical behavior of NiAl-based intermetallic alloys alloyed with Hf, Cr and Co at their total content (Cr+Co)=18 at% were studied. The alloys were prepared by centrifugal SHS casting from oxide raw materials. The mechanism of precipitation hardening is shown to take place at the Cr/Co ratios >0.5, leading to the formation of chromium-based inclusions and nanosized precipitates in the NiAl dendrite body. The resulting alloys have a three-level hierarchical structure with oxygen, nitrogen, and carbon impurity contents of 0.129, 0.0045, and 0.04 wt%, respectively, and the ultimate compressive strength at room temperature equal to 2300 MPa.
Semiautomated quantification of the fibrous tissue response to complex three-dimensional filamentous scaffolds using digital image analysis.
Fibrosis represents a relevant response to the implantation of biomaterials, which occurs not only at the tissue-material interface (fibrotic encapsulation) but also within the void fraction of complex three-dimensional (3D) biomaterial constructions (fibrotic ingrowth). Usual evaluation of the biocompatibility mostly depicts fibrosis at the interface of the biomaterial using semiquantitative scores. Here, the relations between encapsulation and infiltrating fibrotic growth are poorly represented. Virtual pathology and digital image analysis provide new strategies to assess fibrosis in a more differentiated way. In this study, we adopted a method previously used to quantify fibrosis in visceral organs to the quantification of fibrosis to 3D biomaterials. In a proof-of-concept study, we transferred the "Collagen Proportionate Area" (CPA) analysis from hepatology to the field of biomaterials. As one task of an experimental animal study, we used CPA analysis to quantify the fibrotic ingrowth into a filamentous scaffold after subcutaneous implantation. We were able to demonstrate that the application of the CPA analysis is well suited as an additional fibrosis evaluation strategy for new biomaterial constructions. The CPA method can contribute to a better understanding of the fibrotic interactions between 3D scaffolds and the host tissue responses.