Papers by Keyword: Work-Hardening

Abstract: High manganese steel is a wear-resisting steel. With the rapidly development of industry, it is very important to improve the wear resistance of high manganese steel. We do some experiments with cold asynchronous rolling technique on austenitic high manganese steel.The results show that hardness and impact abrasion resistance are enhanced greatly with the increase of deformation, and the toughness not decrease to very low.

Abstract: This study presents experimental results of machined surface integrity of die material (AISI D2 hardened steel) when hot machining (induction heating) assisted end milling using coated carbide is applied. The aim of this work was to study the influence of induction heating temperature, cutting speed, and feed on the effects induced by hard milling on surface integrity (microhardness and work-hardening). Microhardness was measured to observe the distribution of the hardness beneath the surface and to determine the effect of induction heating on the micro-hardness distribution and work-hardening phenomena. The behaviour of microhardness induced in the subsurface region when end milling under room and induction heating cutting conditions using coated carbide inserts was also investigated. The surface integrity and subsurface alteration have been investigated by employing scanning electron microscope (SEM) and Vickers microhardness tester.

Abstract: The work hardening behavior was investigated in ferritic steels containing hard particles or soft Cu particles with various volume fractions and particle diameters, and then the effect of plastically deformable soft particles on the work hardening was evaluated in terms of the accumulation of GN dislocations. The amount of work hardening and dislocation density increased with an increase of volume fraction of dispersion particles and a decrease of particle diameter in hard particle dispersion steel. On the other hand, in soft Cu particle dispersion steel, the effect of volume fraction and particle diameter on work hardening behavior was relatively small. TEM observation suggested that stress relaxation around particle takes place by plastic deformation of Cu particle itself. In order to consider the effect of plastic deformation of Cu particles on accumulation of GN dislocations, "particle plastic accommodation parameter" was proposed to modify the Ashby's work hardening theory. As a result, the amount of work hardening was successfully predicted for both the hard and soft particle dispersion steels

Abstract: The present contribution is aimed at investigating the microstructure evolution of commercially pure silver under severe plastic deformation conditions. ECAP billets have been produced by using a die with channels intersecting at 90° and straining the samples at room temperature. The evolution of the microstructure as a function of imparted strain was evaluated by scanning electron microscopy as well as X-ray diffractometry. Furthermore, tensile properties were measured from ECAP billets in order to evaluate the strengthening and work hardening behaviour of silver as a function of structure evolution. Comparison in terms of grain structure and corresponding properties are also drawn by considering published data about Al-Mg-Si alloy samples ECAP-processed by identical routes and parameters.

Abstract: Effects of the elastic anisotropy on deformation behavior are examined in a Ti-23%Nb-0.7%Ta-2%Zr-1.2%O (in at %) alloy, Gum Metal, and in an Fe-19%Ni-34%Co-8%Ti alloy with body centered cubic (bcc) crystal structure, and microstructural development in the iron based alloy during severe plastic deformation (SPD) process is discussed. Strong elastic anisotropy with reduced shear modulus, C₁₁- C₁₂, results in low ideal shear strength, which implies dislocation mediated plasticity easily occurs at lower stress. On the other hand, high pressure torsion (HPT), a typical SPD method, realizes very high shear stress during processing, which seems to reach the ideal shear strength in these alloys. Significant refinement of the grain size to 20 - 50 nm in the Fe-Ni-Co-Ti alloy is discussed in relation to the unique deformation mechanism which might be activated at ideal shear strength.

Abstract: Railway networks are subjected to more and more severe loading conditions requiring the use of steels with a high resistance to wear and good fatigue behaviour. The surveys carried out on out of use equipment, such as rails or switches, show that these equipments fail by wear after quite a long period of use, but they can fail by fatigue in a substantially shorter time. In service, crossings are submitted to rolling, impact and sliding stresses. The impact-sliding is the result of the wheel transition from rail wing to crossing nose. Very high contact forces act on the crossing nose while such wheels are passing over it. These large contact forces between wheel and crossing can cause severe damage at crossing nose and wing rail. The influence of contact parameters on the damage of the crossing alloy (Hadfield steel GX120Mn13) in comparison with rail steel (R260) was investigated by impact and impact-sliding tests. The results are described and discussed using weight loss and microhardness measurements, optical and scanning electron microscopy observations of the contact surface. Examination of the results shows large plastic deformation in surface and subsurface of samples. In comparison with impact tests, sliding produces a change in size and shape of the contact area, a higher weight loss and lower hardening. A better impact–sliding wear resistance of Hadfield steel has been confirmed.

Abstract: The effects of modified SiC nano-powders on the microstructures and the work-hardening properties of shot peening treatment on high manganese steel have been carried out by means of microstructure observation, x-ray diffraction analysis and hardness testing. The results are showed that compared with the samples without modified SiC nano-powders, the microstructure of ZGMn13 are finer and markedly improved rate of work hardening. The micro-hardness of surface is enhanced significantly after the shot peening. Its strengthening mechanism is mainly twinning and dislocation, but no Martensite strengthening.

Abstract: Based on analyzing the stress-strain characters of material in nosing deformation zone, and considering two influencing factors, i.e. material thickness variation and material work-hardening, according to ignoring and considering the influence of additional bending stress at the entrance of die, and the different forms of work-hardening of metal materials, a new set of mathematical models of deformation force calculated for tube nosing with conical die are set up by utilizing slab method that belongs to one of the theoretic methods solving the problems of metal plastic forming. Furthermore, the scope of the application of every mathematical model of deformation force calculated for tube nosing with conical die is classified from conical die semi-angle and work-hardening of metal material point of view in theory.

Abstract: Mechanical property anisotropy in terms of in-plane anisotropy (A_IP) of yield strength, and work hardening behavior of a heat treated 7010 aluminum alloy sheet has been investigated. The specimens were given two different types of heat treatments that result in a unique single rotated Brass-{110}á556ñ component with different texture intensity and volume fraction of recrystallization. It has been observed that the A_IP increases with increase in texture intensity and volume fraction of recrystallization. The results are discussed on the basis of Schmid factor analyses in conjunction with microstructural features namely, grain morphology and precipitation. On the other hand, work hardening behavior appears to be significantly affected by the microstructural features rather than type of texture present in the samples.

Abstract: The hardening layer of blanking boundary could enhance structure intensity and wear resistance of blanking work piece evidently. Therefore it could enhance fatigue strength and the working life of work piece greatly. This paper carried through fine-blanking with negative clearance processing experiment for the sheet with different hardening index and measured the blanking force and the punch stroke relations curves. The micro hardness of the blanking work pieces sheared surface were measured by Vickers Hardness instrument(MH-6), which obtained the relations curves of punch stroke and the micro hardness of the blanking work pieces. The level of working hardening were compared with different hardening index materials by fine-blanking with negative clearance, and the blanking work pieces working hardening were enhanced evidently by fine-blanking with negative clearance.