Machining is one of the major contributors to the high cost of titanium-based components. This is as a result of severe tool wear and high volume of waste generated from the workpiece. Research efforts seeking to reduce the cost of titanium alloys have explored the possibility of either eliminating machining as a processing step or optimising parameters for machining titanium alloys. Since the former is still at the infant stage, this article provides a review on the common machining techniques that were used for processing titanium-based components. These techniques are classified into two major categories based on the type of contact between the titanium workpiece and the tool. The two categories were dubbed conventional and non-conventional machining techniques. Most of the parameters that are associated with these techniques and their corresponding machinability indicators were presented. The common machinability indicators that are covered in this review include surface roughness, cutting forces, tool wear rate, chip formation and material removal rate. However, surface roughness, tool wear rate and metal removal rate were emphasised. The critical or optimum combination of parameters for achieving improved machinability was also highlighted. Some recommendations on future research directions are made.

Research has been the tool for recycling existing scientific ideas to promote improved concepts for the development of new materials. All technological innovations have links with the ancient philosophies that are being adapted progressively. Given this, composite material development remains one of the most excellent methods to influence the environment to meet human needs. Various studies have shown that polymer-based composites have emerged as the leading group of composites that are fast displacing all other materials in several applications due to their inherent properties. Polymer-based composites can be entirely synthetic, completely natural, or a mixture of synthetic and natural-based. However, a recent desire for eco-friendly materials has shifted attention from complete synthetic-based materials to natural fibers, whether in a partial or total replacement. Thus, this review provides an overview of research trends from synthetic to natural based polymer composites. The article also highlights the different intrinsic classifications of composites, their development, areas of applications, and their projection into the future in line with considerations for environment and applications.

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An overview of welding methods and process parameters and its effects on mechanical behaviour and structural integrity of magnesium and its alloys are discussed. These alloys are less dense and beneficial structural alloys for improved energy efficiency, eco-friendliness and driver of circular economic model for sustainable design and innovative ecosystem. While the application of Mg-alloys is projected to increase, understanding the mechanical behaviour and structural integrity of welded joints are critical. Thus, fusion and solid-state welding processes of these alloys are discussed with emphasis on mechanical characterization. Laser welding is the most effective fusion welding technique for most Mg alloys whereas, the predominant solid-state method is friction stir welding. The importance of process variables such as heat inputs, welding velocity (speed) and post weld treatments on the microstructural evolution, on mechanical and physical properties of the distinct zones of the weld joints are described. The weldment is the most susceptible to failure due to phase transformation, defects such as microporosity and relatively coarse grain sizes after solidification. The implication of the design of quality weld joints of Mg alloys are explored with areas for future research directions briefly discussed.

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