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Solute segregation on a macroscopic scale in a weld between two dissimilar metals or alloys has long been recognized, but fundamental understanding of macrosegregation in dissimilar-metal welding is still lacking. Two mechanisms for macrosegregation were proposed based on the liquidus temperature of the bulk weld metal, T LW , relative to the liquidus temperature of metal 1, T L1 , and the liquidus temperature of metal 2, T L2. According to the mechanisms, two distinctly different macrosegregation features can form. A "peninsula" of an unmixed metal 1 can form if T LW < T L1. On the other hand, a "beach" of unmixed metal 2 irregular in shape can form if T LW > T L2. To verify the mechanisms, a pure Cu sheet was butt welded to a low carbon steel sheet by gas-tungsten arc welding without a filler metal. Composition measurements were conducted inside and across the weld metal. A peninsula of unmixed steel and an irregular-shaped beach of unmixed Cu were observed, which verified the mechanisms. In addition, the bulk weld metal exhibited a layered structure caused by undercooling of the bulk weld pool into a metastable miscibility gap in the Cu-Fe phase diagram. Macrosegregation in previous studies on laser-and electron-beam welding of Cu to steel or stainless steel was discussed in light of the findings in the present study.

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Room temperature tensile properties and microhardness of a laser welded Ti-6Al-2Sn-4Zr-2Mo (Ti6242) titanium alloy sheet were examined and correlated to the microstructure evolution across the weld. Tensile testing integrated with the optical image correlation Instron® system indicated that the average yield strength (YS), ultimate tensile strength (UTS), and total elongation of the weldment were respectively 88 %, 87 %, and 69 % of the corresponding base material (BM) values. Electron probe microanalysis (EPMA) demonstrated a uniform distribution of the main alloying elements across the weld. The hardness raised increasingly from the BM toward the heat affected zone (HAZ) and the fusion zone (FZ) due to mainly a higher  volume fraction in HAZ and acicular ' martensite formation in the FZ. Because of the higher hardness of the HAZ and FZ, a higher YS for the weldment relative to the BM would be expected. However, the lower YS as well as the lower UTS of the weldment can be explained by 2 presence of some porosity and underfill in the FZ. The lower total elongation of the weldment compared to the BM can be related to the higher hardness of the HAZ and FZ.

Understanding how tool deterioration affects total force (F) during milling of Ni-based superalloys is important for the improvement of machinability of the alloys and serves to clarify whether and how an F-based method for monitoring tool deterioration is possible. In this study, a series of milling experiments have been conducted on 718Plus Ni-based alloy using cemented tungsten carbide tool inserts. F was monitored, and the conventional flank wear (VB max ) to represent insert deterioration was measured. As would be expected, the general trend of how F increased as the number of milling pass (N pass ) increased agreed with the general trend of increasing VB max as N pass increased. But the F-VB max plot has shown a rather poor F-VB max relationship. This was the results of the different modes of tool deterioration affecting VB max differently, but VB max did not represent fully the true cutting edge of the deteriorating tool insert. Chipping and breakage of the inserts confined in the cutting edge area, resulting in the significant blunting of the edge, caused a high rate of F increase as VB max increased. Fracturing along the flank face of thin pieces effectively increased VB max without increasing the cutting edge area and without further blunting the edge, thus no increase in F was required. That the high rate, meaning high ΔF/ ΔVB max , results from the effect of edge deterioration/ blunting on reducing the effective rake angle and thus increasing F is suggested and discussed.

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