A Review on Friction Stir Welding of Steels

Friction Stir Welding (FSW) is the most promising solid-state metals joining method introduced in this era. Compared to the conventional fusion welding methods, this FSW can produce joints with higher mechanical and metallurgical properties. Formerly, FSW was adopted for low melting metals like aluminum alloys. In recent years it has made significant progress in friction stir welding of steels since unfavourable phase transformations occurred in welds due to the melting of the parent and filler metals in fusion welding can be eliminated. The main advantage of FSW over traditional fusion welding is the reduction in the heat-affected zone (HAZ), and the joints exhibit excellent mechanical and corrosion resistance properties. This article reviews the progress in the relevant issues such as the FSW tool materials and tool profiles for joining steels, microstructure and mechanical properties of steels joints, special problems in joining dissimilar steels. Moreover, in-situ heating sources was used to overcome the main limitations in FSW of hard metals and their alloys, i.e., tool damages and insufficient heat generation. Different in-situ heating sources like laser, induction heat, gas tungsten arc welding assisted FSW for various types of steels are introduced in this review. On the basis of the up-to-date status, some problems that need further investigation are put forward.

GC and Repeats Profiling along Chromosomes—The Future of Fish Compositional Cytogenomics

The study of fish cytogenetics has been impeded by the inability to produce G-bands that could assign chromosomes to their homologous pairs. Thus, the majority of karyotypes published have been estimated based on morphological similarities of chromosomes. The reason why chromosome G-banding does not work in fish remains elusive. However, the recent increase in the number of fish genomes assembled to the chromosome level provides a way to analyse this issue. We have developed a Python tool to visualize and quantify GC percentage (GC%) of both repeats and unique DNA along chromosomes using a non-overlapping sliding window approach. Our tool profiles GC% and simultaneously plots the proportion of repeats (rep%) in a color scale (or vice versa). Hence, it is possible to assess the contribution of repeats to the total GC%. The main differences are the GC% of repeats homogenizing the overall GC% along fish chromosomes and a greater range of GC% scattered along fish chromosomes. This may explain the inability to produce G-banding in fish. We also show an occasional banding pattern along the chromosomes in some fish that probably cannot be detected with traditional qualitative cytogenetic methods.

Fabrication of Magnesium–NiTip Composites via Friction Stir Processing: Effect of Tool Profile

In this study, a solid-state fabrication route via friction stir processing (FSP) was used to fabricate Nitinol particulate (NiTip)-reinforced magnesium-based composites to avoid the diffusion reaction and the formation of brittle interfacial compounds. The effect of four tool profiles on the homogeneity in the dispersion of NiTip particles in the magnesium matrix and microhardness was examined and analyzed. A counter-clockwise scrolled shoulder with a plain cylindrical pin and three tools with a flat shoulder having plain cylindrical pin, left-hand, and right-hand threaded pins were used and compared. The tool profiles were observed to exhibit a significant influence on the microstructure of the fabricated Mg/NiTip composites. A wider and more uniform distribution of NiTip particles along with superior bonding with magnesium matrix was achieved with a left-hand threaded cylindrical pin tool. The incorporation of NiTip gave rise to a significant increase in the microhardness of the fabricated composites due to a variety of strengthening mechanisms.

Effect of Tool Pin Profile and Friction Stir Welding Speed on Tensile & Hardness Properties of Friction Stir Welded Joints of AA6082 & A319 Aluminium Alloy

Fusion welding of aluminium alloys results in solidification cracking, porosity etc. which affects the properties of the weldment. FSW which is broadly used in welding of aluminium alloys. It overcomes the defects of fusion welding process in improving the properties of the joints. The current paper focus on studying the tensile properties of the disparate FSW of aluminium alloys AA6082 and A319 .Three dissimilar tool profiles (square, hexagonal and cylindrical) with three welding speeds (25, 30, 35 mm/min) and three tool rotational speeds (800, 1000 and 1300 rpm) have been used in studying the joint properties of the weld. Higher tensile strength was obtained for the parameters of square tool profile, 30 mm/min and 1300 rpm.

Grey Relational Analysis and Anova to Determine the Optimum Process Parameters for Friction Stir Welding of Ti and Mg Alloys

The welding of Magnesium and Titanium and its alloys has continuously depicted a good challenge for designers and technologists. Ti and Mg alloys, particularly heat-treatable alloys, are difficult to join by fusion fastening techniques. The welding of dissimilar alloy such as Ti (Grade 2) and Mg (AZ91D) Alloy is an important problem during Friction Stir Welding (FSW). In this paper, the influence of Rotation speed (Rpm), Travel Speed (mm/min), Bottom Diameter Tool Pins (mm) and Tool Profiles of Ti and Mg alloy during FSW was investigated by Grey Relational Analysis and Anova was used to work out the foremost important Travel speed and feed rate affecting the Response. The primary and cooperation impact of the information factors on the normal reactions are examined. The expected values and measured values are genuinely close.