Analysis of the cause of crack in cold rolling of QSn6.5-0.1 strip

In order to know the cause of cracks in cold rolling of QSn6.5 0.1 copper alloy strip, a lot of experiments and analysis were done. The microstructure changes of QSn6.5 0.1 were investigated by means of metallurgical microscope. The morphology of cracks and surface defects were examined using scanning electron microscope. Macroscopic residual stresses produced in every process during manufacturing in the QSn6.5 0.1 strip were measured by X ray diffraction method and hole drilling method. The results show that the cracks in the QSn6.5 0.1 cold rolling strip were caused due to the derivation of metallurgical defects, such as SnO 2, S, fine looses,the inverse segregation unable to clear up when milling, and the accumulation of all kinds of resi dual stresses. When the accumulation of the residual stress reaches the material′s breaking strength, the cracks will be generated. Several measures to avoid the development of these kinds of cracks were put forward, such as: controlling the casting technology, improving homogenization annealing procedure (680 ℃/7 h) and milling quality(using the second milling when necessary), working out a more reasonable rolling technology to ensure intermediate annealing in time.

Experience in the Production of Horizontal Ingots of Platinum Metals and Alloys

The quality of semi-products of platinum metals and alloys, produced by way of plastic working, essentially depends on or, in many cases, is completely determined by the quality of ingots. Plastic working does not make it possible to eliminate or localize metallurgical defects. In many cases it promotes the occurence thereof. Low-rate casting with directional crystallization can ensure the production of dense ingots free of non-metallic inclusions, shrinkage and gas weakness, with observance of certain temperature/rate modes. After comparative tests of vertical and horizontal molds, preference has been given to horizontal water-cooled molds, allowing to cast all alloys in the conditions of directional crystallization.

Theoretical Modelling of Metallurgical Defect Closing-Up Processes During Forming a Forging

Computer modelling using an FEM-based program, i.e. Forge 2008, was carried out. Laboratory model-ling of the process of free hot forging in shaped anvils was conducted to close up metallurgical defects. Results ob- tained from the simulation modelling were processed by using a commercial statistical package, i.e. Statistica 6.0 PL. The influence of the anvil shape and main parameters of the forging process on closing up metallurgical defects were determined. On the basis of the investigation carried out, the optimal values of main forging technologieal parameters and suitable groups of anvils to be used in particular forging tages are proposed for the elimination of metallurgical defects.

Anisotropy study of the microstructure and properties of AlCoCrFeNi2.1 eutectic high entropy alloy additively manufactured by selective laser melting

The AlCoCrFeNi2.1 eutectic high-entropy alloy(EHEA) was prepared by selective laser melting(SLM), focusing on the anisotropy of microstructure and mechanical performance. The AlCoCrFeNi2.1 EHEA printed by SLM has face-centered cubic(FCC) and body-centered cubic(BCC)/B2 phases, and the FCC phase accumulates at the boundary of the molten pool. With the increase in volumetric energy density(VED), the content of the FCC phase parallel to the surface in the direction of the building increases from 30.9% to 41%. The X–Z plane mainly produces columnar crystals along the temperature gradient, while a large number of equiaxed crystals are produced in the X–Y direction. When the volume energy density is 157 k J/mol(VED 157), the average grain size is 1.33 μm for BCC and 1.14 μm for FCC, which is significantly smaller than other preparation methods. Due to defect distribution and size, the microhardness of the X–Y plane is generally higher than that of the X–Z plane, with maximum hardnesses of 660 HV and 655 HV, respectively, which is much higher than those of traditionally manufactured counterparts.The compression performance of SLM process AlCoCrFeNi2.1 EHEAs shows maximum yield strength of 1567 MPa, and the ultimate compressive strength can reach 3276 MPa.

Effect of Hot Isostatic Pressing on Fatigue Properties of Laser Melting Deposited AerMet100 Steel

The ultra-high strength steel AerMetl00 was fabricated .by laser melting deposition （LMD） process. The effect of hot isostatic pressing （HIP） on high-cycle fatigue properties of the LMD AerMet100 steel was investigated, and the influence of defects on fatigue behavior was discussed. Results showed that the LMD AerMetl00 steel had fine directionally solidified cellular dendrite structure and coarse columnar prior austenite grains. Metallurgical de fects such as gas pore and lack-of-fusion porosity were produced during the laser deposition process. After HIP treat- ment, the number and size of metallurgical defects had remarkably decreased. Moreover, high-cycle fatigue proper ties of the alloys after HIP treatment were superior to the as-deposited alloys.