Rob Torrens

Processing, Microstructure and High Strain Rate Behaviour of Ti-6Al-4V Alloy Produced from a Blended Mixture Using Powder Compact Extrusion

Powder compact extrusion (PCE) is an innovative way of processing titanium and titanium alloys to produce good-quality material with a wide range of compositions, microstructures and mechanical properties. This paper explores PCE processing of Ti-6Al-4V alloy prepared from a blended powder mixture, containing elemental hydride-dehydride (HDH) titanium powder and master alloy (60Al-40V) powder. The warm pressed compacts of blended powders were sintered using a vacuum sintering furnace prior to β extrusion. The resulting material was used to measure the performance under high strain rate and tri-axial stress state using Charpy v-notch testing. A comparison was made of the microstructure after vacuum sintering and hot extrusion in addition to oxygen measurements to determine the degree of oxygen pickup during each processing stage. A comprehensive study of fracture surfaces in selected samples was carried out using optical microscopy and scanning electron microscopy. Based on the results, it is clear that certain samples picked up varying amounts of interstitial impurities during processing and as a consequence a significant number of micro-cracks were observed in lamellar type microstructures. The oxygen content of all as-extruded samples was between 0.34-0.44 wt.% with resultant impact toughness in the range of 10-14 J. The best impact toughness attained for the lowest oxygen as-extruded rods was 20% lower than the literature values for wrought material. In terms of fracture behaviour, ductile dimples, cleavage facets and cracks passing through lamellar structures were observed in all samples. However, the quantity of these fracture features varied significantly in each sample.

Additive manufacturing of Ti-6Al-4V with added boron: Microstructure and hardness modification

Titanium alloy composites with titanium boride (TiB) discontinuous reinforcement have shown improved performance in terms of strength, stiffness, and hardness. Producing this composite through selective laser melting (SLM) can combine the advantages of freeform design with the ability to produce TiB reinforcement in-situ. In this study, SLM was used to consolidate a pre-alloyed Ti-6Al-4V (Ti64) and amorphous boron (B) powder mixture with the intent of producing 1.5wt% TiB reinforcement in a Ti64 matrix. The processing parameters of laser power and scanning speed were investigated for their effect on the density, microstructures, and hardness of the composite material. The results showed that the boron and Ti64 composite could achieve a density greater than 99.4%. Furthermore, it was found that processing parameters changed the microstructural features of the material. The higher the energy density employed the more homogenous the distribution of boron modified material. Macro features were also observed with laser paths being clearly evident in the subsurface microstructure. Micro-hardness testing and density measurement also showed a corresponding increase with increasing energy density. Maximum hardness of 392.4HV was achieved in the composite compared to 354.2HV in SLM fabricated Ti64.

Processing, Microstructures and Properties of a Ti-6Al-4V Extrusion Produced by an Industrial Scale Setup

In this paper, a Ti-6Al-4V rectangular bar was successfully produced from a 5kg blended powder mixture using an industrial scale extrusion facility. The elemental hydride-dehydride (HDH) titanium and 60Al-40V master alloy mixture was warm pressed and vacuum sintered prior to β extrusion in air. The as-processed material was characterised for compositional homogeneity, oxygen pickup, microstructure, tensile properties and fracture behavior. Variation in microstructure and properties along the length of the extruded bar were also studied. It was found that oxygen pickup mainly occurred during vacuum sintering of the green billet and consequently the as-extruded material had an oxygen content of 0.55 wt.%. The processed material had a typical lamellar morphology with some evidence of micro-cracks at high magnification. A significant deviation in prior β grain and α colony sizes was observed along the length of the bar, due to variations in extrusion temperature and cooling rate. Both grains and colonies became finer as the location changed from the tip of the extruded bar to the back end. The as-processed material had ultimate tensile strength in the range of 1068-1268 MPa and elongation to fracture of 1.2-4.5%, mainly due to the high oxygen content and non-optimised microstructure. Fractographic analysis was consistent with the variation in mechanical performances obtained.

Comparing the Cases: What Do They Tell Us About Software Literacy?

This chapter reports the comparative analysis of the two case studies on media studies software (see Chap. 3) and engineering software (see Chap. 4). Common themes emerged across the cases such as students’ tendency to draw from informal learning strategies to supplement formal learning approaches, the diversity of student background and software abilities, and students’ general assumption that a tier 2 software proficiency level (see Chap. 1) would be adequate entry into a professional pathway. However, the cases differed in terms of the nature of the nuanced learning goals and aspirations of each discipline which impacted on the way course curricular, teaching, learning and assessment strategies were structured. These findings have implications for teaching and learning where software plays a central role in understanding and accomplishing disciplinary ideas and practices in tertiary and workplace contexts.

Introduction: Software and Other Literacies

This chapter outlines the role and significance of software in contemporary society. Drawing from the new field of Software Studies, it sets outs key concepts relevant to the study of software, including affordances, agency, human-machine assemblages, and performance to explain the ways users co-create with software. It proposes the notion of software literacy as a framework to help readers unpack the ways the affordances of software can (re)shape the ways we think and act. These ideas are then grounded in an examination of an educational research project into the ways in which students become more literate about the nature and implications of software which they encounter as part of their tertiary studies.

A Genealogy of Software Applications

This chapter outlines a broad genealogy of two areas within software culture: Digital Non-Linear Editing (DNLE) and Computer-Aided Design (CAD) software. Emerging from distinct institutional environments, their respective historical developments and the implications these have generated within their professional domains provide a broader context for the software at the centre of this educational research project (see Chaps. 3 and 4). Each of these histories demonstrate how decisive the institutional and industrial contexts of their creation were in inscribing the affordances, interfaces and conceptual frameworks coded into these software.

The Learning, Use and Critical Understanding of Software in Media Studies

This chapter (as with the next, Chap. 4) reports on the findings from a two-year funded empirical study (2013–2014) exploring how tertiary students in media studies and engineering develop the understandings and skills needed to use software as forms of software literacy. Two case studies were developed. The case studied experiences of media studies students’ software literacy development is the focus of this chapter. Two cohorts of media studies undergraduate students were tracked, at different stages of study and using mixed methods, in their learning of discipline-specific software, Final Cut Pro, and the Adobe Creative Suite. The findings illustrate the ways student software literacy develop in a specific tertiary context. The findings will be revisited in Chap. 5 and discussed to include implications for the wider field of software teaching and learning.

The Learning, Use and Critical Understanding of Software in Engineering

This chapter (as with Chap. 3) details the findings from a two-year funded empirical study aimed at understanding tertiary students’ development of the understandings and skills needed to use software as forms of software literacy. Two case studies were developed. A case study of engineering students’ software literacy development is the focus of this chapter. Two cohorts of students were tracked using mixed methods to explore their learning and understanding of discipline-specific software (here the Computer-Aided Design (CAD) software SolidWorks). An additional group of advanced final year CAD students were also interviewed to ascertain if there were particular nuances in their software learning experience. The findings of this case study provide insight into engineering students’ software literacy development in a specific tertiary context. A discussion of the findings including implications for what the findings might mean in relation to the wider field of software teaching and learning is addressed in Chap. 5.

Software Literacy: Education and Beyond

Software literacy is an essential part of learning and living in the 21st century; something which, we argue, transcends the use of any particular tool and any particular educational, social and cultural context. Software literacy is an increasingly central part of the palette of understandings and skills that comprise the broadening umbrella of digital literacy. It is therefore essential that citizens have a critical understanding of software to make more informed choices about their use, can transfer this critical understanding to software they have yet to encounter, and understand that all software has nuanced affordances and limitations. In tertiary settings this is needed to ensure equitable and critical learning with and through software. This chapter summarises our key insights from our own research into these issues and offers recommendations for future research in the field.

Mechanical Properties of Ti-6Al-4V Rods Produced by Powder Compact Extrusion

This paper describes the mechanical properties of Ti-6Al-4V alloy produced by consolidation of a blended powder mixture of elemental hydride-dehydride (HDH) titanium powder and master alloy (60Al-40V) powder. The warm pressed compacts of blended powders were sintered using a vacuum sintering furnace prior to the extrusion process. Impact toughness and micro-hardness were measured using as extruded Ti-6Al-4V alloy rod with an extrusion ratio 9:1. In addition, tensile testing was performed on extruded rod with an extrusion ratio 25:1. Detailed work was performed using optical microscopy and scanning electron microscopy to explore the microstructure and fracture surfaces of the tested material. The tensile properties of as extruded Ti-6Al-4V rod were found to be comparable with corresponding literature values of wrought material. However, impact toughness was found to be lower than published data. Some possible reasons contributing to the measured mechanical properties of the Ti-6Al-4V rods in this study are discussed.