Manufacturing processes such as casting, rolling, forging, extrusion, material removal processes, etc. are some of the common techniques used today in manufacturing industries. However, these processes must be carried out with utmost precision and precaution. Even the slightest negligence can give rise to anomalies which can be classified as defects or discontinuities depending upon their repairability. Non-Destructive Testing or NDT is amode of testing which has been adopted by industries for decades to test mass manufactured products for anomalies. This paper discusses various NDT methods, such as Visual Testing, Magnetic Particle Inspection, Penetrant Testing, Ultrasonic Testing, Radiographic Testing, Acoustic Emission and Eddy Current Testing. The paper also discusses how technical advancements have broadened the scope of NDT even in industries that may not be manufacturing oriented, indicating that NDT is not limited to detection of anomalies. Even though these developments have made NDT more favourable, this paper highlights the fact that these techniques are mostly manual and heavily dependent upon inspectors’ knowledge and experience, leaving room for errors. This paper also discusses the key challenges and future scope in the field of NDT.

In the present research work, AA7075 composite reinforced with silicon carbide particles has been fabricated using Friction stir processing (FSP). The silicon carbide particles having a size of 40 μm were placed in grooves of length 160 mm, width 2 mm, depth 3.5 mm, that were generated on the AA7075 plate. The square pin tool is utilized for fabricating the composite at two different rotational speed i.e. 700 and 1000 rpm. Effect of processing, particle addition and tool rotational speed is analyzed on mechanical and wear properties of the material. On friction stir processing the microhardness value and elongation of the material increased. Reinforcement addition contributed to decrease in ductility and tensile strength while on the contrary microhardness and wear resistance of the material improved. Tool rotational speed showed a direct relation with the tested mechanical and wear properties. Adhesive wear was the prominent wear mechanism and Fe layer formation was observed on the worn surface, contributing to increased wear resistance. These fabricated composites can find vast application in industries like automotive, defence and aerospace.

In the present research, work is carried out for the parametric effects like tool rotation speed, tool profile and reinforcement in friction stir processing (FSP) of AA7075 on the microhardness and microstructural properties. The experiment design was carried out using Taguchi L ₉ orthogonal array with three factors at three levels. Three different tool pin profiles viz. circular, triangular and square were used to experiment. The AA7075 matrix material was reinforced with SiC, RHA, and B ₄ C. The tool rotational speed was chosen as 700, 1000 and 1300 rpm. Using the Taguchi method, the optimum level of each of these parameters was obtained. It was found that rotational speed is the most influential parameter followed by the type of reinforcement and tool profile respectively. The average microhardness of AA7075/B ₄ C composite was found to be increased by 1.5–1.6 times of the base indicating that B ₄ C is better compared to SiC and RHA in improving the microhardness value of the composites.

Mechanical and wear properties of AA7075-T6 reinforced with SiC and Aloevera ash, fabricated using Friction stir processing (FSP) are investigated in this study. Due to less density, easy availability, and cost-effectiveness, aloevera ash is considered as one of the reinforcements. FSP is done using a square tool pin profile, at different tool rotational speeds. To study wear behaviour, pin on disc test is carried out on High Temperature Rotary Tribometer at 20N, 30N and 40N applied load. Wear increases on increasing the applied load and at 20N load Al+SiC/Aloevera ash composite, processed at 600 tool rpm gave the best results due to the formation of oxide tribolayer. At 30N and 40N applied load Al+SiC composite, processed at 900 tool rpm showed the least wear because of proper scattering of ceramic particles due to high tool rotational speed. Coefficient of friction increases on increasing the applied load and all fabricated composite samples showed a lesser coefficient of friction than the base metal. Microhardness, ductility and Ultimate tensile strength increases on the addition of reinforcement and had a direct relation with tool rpm. Wear morphology was analysed using Scanning Electron Microscope (SEM). Energy Dispersive Spectroscopy (EDS) analysis after wear shows the presence of C, Fe, O, Mg, Zn, Si, Al elements and confirms the formation of an oxide layer which is responsible for decreasing wear loss.

In comparison to the traditional reinforced composites, Friction stir processed composites have emerged to be more promising because of their better properties such as strength, hardness, ductility. To note that traditional methods have proved to interfere with the bulk properties of the material and have failed to align with the modern green globe standards and hence, Friction stir processing (FSP) has emerged in recent years for producing ex-situ and in-situ surface composites. With the increasing attention towards FSP, surface composites of alloys generated with titanium and steel are also being fabricated, which earlier was limited only to Aluminum and Magnesium alloys. Considering the growth of FSP in recent years, it appears as the appropriate time to review and enhance the quality for references and academia with the main impetus on lesser known and emerging technologies in the field. FSP is a relatively new production technique yet a lot of scholars have reported its use in the fabrication of the composites and on the optimization of its process parameters. On the contrary, the impact of FSP on various mechanical and micro-structural surface properties, highlighting the effect various process variables and the importance of tool wear are few other key points in the field which still need to be revisited. This review article attempts to fill those gaps and provide a comprehensive understanding of the technique with correlations leading to successful modeling and process optimization for defect-free and cost-effective composites.