Vickers Hardness Change Research Articles

Swift-ion-induced hardening and reduction of dislocation mobility in LiF crystals

Ion-induced change in Vickers hardness and arm length of dislocation rosettes created by indentation on the (1 0 0) face of LiF crystals was studied. The irradiations were performed using swift U, Bi and Ni ions with a specific energy of 11 MeV per nucleon at fluences between 106 and 1013 ions cm−2. Remarkable effects of the ion-induced hardening and reduction of dislocation arm length were observed above the threshold fluences of about 109–1010 ions cm−2 and 106–107 ions cm−2, respectively. The products of track core damage and aggregates of single defects in the halo of overlapping tracks are responsible for the effects. The results are analysed using the Orowan's model of dislocation impeding by strong obstacles. The advantages of the dislocation mobility method for the diagnostics of track damage at low-fluence irradiations are demonstrated.

Change in Vickers Hardness and Substructure during Creep of a Mod.9Cr-1Mo Steel

In order to investigate the structural degradation during creep, interrupted creep tests were conducted of a Mod.9Cr–1Mo steel in the range of stress and temperature from 71 to 167 MPa and 873 to 923 K. The change of hardness and tempered martensitic lath width were measured in grip and gauge parts of interrupted specimens. The lath structure was thermally stable in static conditions, however, it was not stable during creep and the structural change was enhanced by creep strain. The relation between the change in lath width and strain was described quantitatively. The change in Vickers hardness was expressed by a single valued function of creep life consumption ratio. Based on the empirical relation between strain and lath width, a model was proposed to describe the relation between change in hardness and creep life consumption ratio. The comparison of the model with the empirical relation suggests that about 65% of hardness loss is due to the decrease of dislocation density accompanied by the movement of lath boundaries. The role of precipitates on subboundaries was discussed in connection with the abnormal subgrain growth appearing in low stress regime.

Use of high energy ions for the mechanistic study of irradiation embrittlement in pressure vessel steels using Fe–Cu model alloys

To study the mechanism of irradiation embrittlement in pressure vessel steels, it is necessary to sort out the irradiation parameter dependence, which is particularly complex in the neutron irradiation case. Irradiation with high energy heavy ions allows us to carry out single parameter experiments, thereby providing basic data for the modelling of irradiation embrittlement. In this study using Fe–Cu model alloys, three important parameters; ion fluence, irradiation temperature and copper concentration are selected and irradiation induced Vickers hardness change is measured. The hardness change shows a steep increase with fluence after a certain incubation dose. The irradiation temperature dependence of hardness change at fixed fluence shows a peak at around 250–300 °C. Shift of irradiation temperature dependence from neutron irradiation case may be ascribed to the difference in dose rate. Copper concentration dependence shows that the change in hardness seems to depend on the square root of copper concentration. This supports the dispersed barrier hardening model.

Change in Vickers hardness at the glass transition region for fragile and strong glasses

The temperature dependence of Vickers hardness between room temperature and around the glass transition temperature T g in a vacuum for some glasses with different fragile characters was measured. The hardness at T/ T g<0.9 decreases gradually with increasing temperature, but the glasses show unique temperature dependences in the range 0.9< T/ T g<1.1 depending on their fragile character. A sharp decrease in hardness is observed at around T/ T g=0.9–1.0 for fragile Bi 2O 3- and TeO 2-based glasses, but 50CuO x ·50P 2O 5 and soda-lime silicate glasses with strong viscosity characteristics still have relatively large Vickers hardness even at T g and the hardness drops to almost zero around T/ T g=1.05–1.1. It is suggested that for fragile glasses the β-relaxation has an important effect on the Vickers hardness change near the glass transition region, but for strong glasses it is the α-relaxation that governs the hardness near T g.

アモルファス・ナノ結晶制御と高機能材料 連続電子ビーム蒸着法により作製したＡｌ‐Ｎｉ合金の組織と機械的性質

Nano-structured Al-based alloys with additions of Ni have been prepared by electron beam evaporation. The composition dependence of the resulting microstructures and mechanical properties has been studied. The Al-Ni deposits consist of Al and A13Ni with a grain size below 100nm. Vickers hardness increases with the Ni-content and reaches values as high as 320Hv at a Ni content of around 20at.%. At higher Ni contents Vickers hardness remains almost constant at this high level. Upon annealing the Al and Al3Ni grain grow and Vickers hardness decreases. The change of Vickers hardness follows the Hall-Petch relationship. The dispersion strengthening by the intermetallic phase of AI-Ni deposits would be estimated from the Orowan-mechanism. It is therefore concluded that the effects of both grain size refinement and dispersion strengthening contribute to the achievement of high Vickers hardness. The continuous electron beam evaporation technique is an effective method to produce nano crystalline high strength bulk material.

Modulated microstructure in Ti-22Al-11 Nb-4Mo alloy

In the previous two decades, considerable effort has been made to develop the Ti{sub 3}Al({alpha}{sub 2})-based and TiAl({gamma})-based titanium aluminides for the elevated temperature applications. However, the application is limited by the low ductility of these alloys at low temperature. During the systematic investigation in the effect of the compositional modification on the physical and mechanical properties of Ti-22Al-27Nb alloy, the authors found that a modulated microstructure was formed in a Ti-22Al-11Nb-4Mo alloy when this alloy was subjected to the water-quenching from above the {beta} transus temperature and subsequent aging in the temperature range up to around 950 C. In this paper, the evolution of modulated microstructure and associated change in Vickers hardness with various heat treatment conditions are presented.

整合歪モデルによるＡｌ‐Ｚｎ‐Ｍｇ‐Ｃｕ系合金における機械的性質の定量的解析

High strength aluminum alloys were aged at 383 K. Their aluminum alloys were made clear to consist of two major substructures with different scale; metastable phase with a few nm size precipitated in the matrix and the quaternary rod-like intermediate phase with a few micrometer length containing Mn. The remarkable strengthening is dominantly attributed to the precipitation hardening due to fine metastable phase. In order to get further high strength, we have carried out systematic investigation using the various Al–Zn–Mg–Cu based alloys with different compositions of Zn and Mg. By a synchrotron radiation small angle scattering technique, the structure change of the alloys during isothermal aging was examined. The change of Vickers hardness during isothermal aging, could be well expressed as a function of the square root of particle size multiplied by volume fraction of metastable precipitates, suggesting the coherency strain model for the interaction of precipitate with dislocation. The coherency strain for each alloy was experimentally estimated.

生体用新Ti合金の組織と力学特性に及ぼす熱処理の効果

Ti-15 mass%Zr-4%Nb-4%Ta-0.2%Pd and Ti-15%Sn-4%Nb-2%Ta-0.2%Pd alloys not containing harmful V and Al for surgical implantation in response to recent concerns about the long term safety of Ti-6%Al-4%V ELI (Extra low interstitial, ASTM specified for surgical implantation) were cast by plasma electron beam melting. The effect of heat treating on room temperature strength was investigated by aging treatment after solution treatment. The alloys were forged in their α and α+β regions, and then solution-treated at 953∼1173 K for 3.6 ks. Vickers hardness in the range below β transition temperature increases with increasing solution treating temperature and change of Vickers hardness in the range over its temperature is small. Optimized solution treatment conditions are 1038 K-3.6 ks for Ti-Zr alloy and 1098 K-3.6 ks for Ti-Sn alloy containing 15∼20 vol% primary α phase. After solution treatment under the optimized condition aging treatment was done at 623∼873 K for 600 s∼36 ks. Vickers hardness in aging below 723 K increases with increasing aging temperature and aging time. Optimized aging conditions for Ti-Zr and Ti-Sn alloys were at 673 K for 36 ks and at 723 K for 36 ks, respectively. The room temperature strengths of those alloys are superior to those of Ti-6%Al-4%V ELI for medical implants. It is revealed by transmission electron macroscopic observation that fine α phase precipitates in the α′ martensitic matrix are responsible for the age hardening.

Characterization of the microstructure of a commercial Al-Cu alloy (2 0 1 1) by differential scanning calorimetry (DSC)

In this work the microstructure of a commercial Al-Cu alloy (2 0 1 1) in several metallurgical states has been studied by means of differential scanning calorimetry (DSC). The metallurgical states were chosen in such a way that the alloy contained predominantly one of the four possible phases in these alloys (i.e. GP zones andθ″,θ′ andθ phases). The commercial tempers T3 and T6 have also been considered. The interpretation of the DSC curves was aided by measuring the changes in Vickers hardness and conductivity during a linear heating similar to that provided by the DSC apparatus; these studies allow, for instance, a clearer distinction between the GP (Guinier-Preston) zone dissolution peak and theθ″ phase dissolution peak. The results are compared with those obtained by other authors.

Change of Vickers Hardness after Heat-Treatment of Clasp Wires

Change of Vickers Hardness after Heat-Treatment of Clasp Wires

The inquiry into the reliability of the specific volume analysis by means of hardness testing

As the survey on the change of spesific volume makes it possible to analyse the change which takes place inside the material, this method was tried to examine the aging phenomenon of aluminium alloys, as a method in industrial operation. As the resultof this study, it was found that this method can be successfully used for this purpose.10 sorts of specimens such as 1S, 2S, 3S, 17S etc., on which the change in specific volume had already been known by previous study, were applied for this experiment, where in the tempered aging was made for them under the increasing temperature from 20°C to 400°C. The change in vickers hardness and knoop hardness under different temperature were measured and the relation between change in hardness and specific volume analysis was studied.As the result of the experiment, the specific volume analysis was quit reliable as a method for examining the aging in aluminium alloys. The result was also carefully studied from the viewpoint of the knoop ratio.

熱処理によるビッカース圧こんの変化について

The authors previously noticed on the depression in case of measuring hardness, that the Vickers depression had some piling-up even in diagonal direction, which is believed to have little piling-up. The Vickers hardness is measured by the surface area of depression caloulated from the diagonal length of square depression, so if the degree of piling-up differs, the influence of measuring error in the hardness number will be different.In this paper, the change of the piling-up caused by the heat-treatment of materials are examined as a help for obtaining the inquiring data of the measuring error of Vickers hardness.Five sorts of the carbon steel and two sorts of the brass are heat-treated and depressed by Vickers indentator, and the surface of depression are traced by the Ogoshi Surface Roughness Tester (contact needle type). Some of the results are summarized as follows: (1) The degree of piling-up is much affected by the heat-treatment in both materials. (2) The change of the degree agrees with the change of Vickers hardness in case of carbon steels, but does not always agrees with the hardness in that of brass. (3) The degree of piling-up varies by 200%, in case of carbon steel, and by 100%, in that of brass according to the rise of tempering temperature, if the quenching value is taken as standard. These degrees have a great influence on the hardness number. (4) As the ratio of the major diagonal of Knoop depression to the minor diagonal is in the lever relation to the degree of piling-up. One rising, the other falling, so we may easily obtain the general trend of the piling-up.

AGE HARDENING IN HYDRONALIUM SHEETS

Fundamental studies on the age hardening in hydronalium alloys 52S and 56S has been carried out to obtain some basic informations to consider the problem of intercrystalline corrosion. The ageing process at 40°C and 200°C has been observed by measuring the changes in Vickers hardness and the results thus obtained has been compared with that of binary Al-Mg alloys and 3S alloy. A small found in the ageing curves; at about ten minutes from the beginning of ageing at 200°C has been discussed and an explanations has been proposed that the slight hardening is caused by the homogenization of strain which has been heterogenously distributed after quenching.Precipitation occurs locally first, followed by general precipitation and after all over-ageing can be observed when excess coalescence of the precipitates occurs. Hardening occurs in 52S if quenched from 500°C, but the hardening was found to occur chiefly at the grain boundary region. This seem to have an intimate relation with the intercrystalline corrosion problem whether the hardening is caused by local precipitation at the grain boundaries or by the enrichment of Mg atoms at the boundary region.The slight hardening called peak as mentioned above has been discussed, paying attention to the analogy to the first in the low-temperature anneal hardening in brass which has been studied by the author and others in details. This hardening, however, seems to have no practical importance since it is completed within a month at room temperature after the cold working.

18-8不銹鋼熔接棒によるα系鋼材熔接の基礎研究(第1報)

There are many practical applications in which austenitic stainless steel electrodes are utilized in welding of various plain carbon and alloy steels (low and high). Since the above joining is also considered as a so-called disimilar-metal welding from the standpoint of chemical composition, it is naturally expected that penetration ratio of base metal to the austenitic stainless steel weld metal, in other words, the degree of dilution of austenitic stainless steel weld metal by base metal may depend upon several welding conditions, and the mechanical and chemical properties may accordingly he different, too. The present researches were conducted in order to disclose, systematically and fundamentally, the relation between the above properties of austenitic stainless steel weld metal and several welding conditions.In this report, relations between polarity and welding current, amount of penetration and penetration ratio of base metal to the austenitic stainless steel weld metal, hardness of austenitic weld metal and microstructure, etc., in each single bead which was deposited on four kinds of carbon steel plates with plain 18-8 austenitic stainless steel electrode consisting of commercial 18-8 austenitic stainless steel core wire of 4mm. in diameter and suitable coating, were studied. D. C. (straight and reverse polarity) and a. c. were used. Welding speed and thickness of base metal were constant, 203mm/min and 10 mm respectively. The results obtained are as follows :(1) In either d. c. (straight and reverse polarity) or a. c., the amount of penetration and penetration ratio, . etc., have a tendency to increase linearly as welding current increases. And also in this case, the above penetration ratio increases from about 20 to 60 percent as welding current increases from 95 to 175 amperes.(2) Penetration ratio has a little, tendency to increase, as carbon content of base metal increases.(3) Penetration ratio with a. c. is smaller than with d. c., in the same welding current value. (4) There is only a little difference between penetration ratio in d. c. straight polarity and that' in d. c. reverse polarity. In this experiment, however, penetration ratio in d. c. straight polarity is larger than that in d. c. reverse polarity for the range of lower welding current value. On the contrary, penetration ratio in d. c. reverse polarity is larger than in d. c. straight polarity for the range ot higher welding current value.(5) Vickers hardness of austenitic stainless steel weld metal is comparatively high. And Vickers hardness of austenitic weld metal containing high carbon base metal is lower for the range of smaller penetration ratio, but higher for the iange of larger penetration ratio, than that of the metal containing low carbon base metal.(6) Micro-hardness at the side of austenitic stainless steel weld metal of the vicinity of weld fusion line increases linearly as welding current increases, and is higher in the weld metal containing high carbon base metal than in the one containing, low carbon base metal. Consequently, the tendency of the above micro-hardness change is clearly different from that of Vickers hardness change.(7) Both maximum Vickers hardness of heat-affected zone and micro-harness of the vicinity of weld fusion line of that same zone in base metal, tend to decrease as welding current increases.

18-8不透鋼熔接棒によるα係鋼材熔接の基礎研究(第2報)

In the present report, relations between welding current, amount of penetration or penetration ratio of base metal to the austenitic stainless steel weld metal and hardness of austenitic weld metal and microstructure, etc., in each single bead which was deposited on four kinds of carbon steel plates with commercial 18-8 austenitic stainless steel electrode containing about 5 percent of manganese in core wire of 4 mm in diameter, were studied. D. C. reverse polarity was used. And welding speed and thickness of base metal were constant, 200 mm/min and 10. mm respectively. The results obtained are as follows:(1) Penetration variables such as the amount of penetration and penetration ratio, etc. tend to increase linearly as welding current increases. And in this case, the obtained penetration ratio increases from about 20 to 50 percent as welding current increases from 95 to 180 amperes.(2) Penetration ratio has a little tendency to increase, as carbon content of base metal increases.(3) Vickers hardness of austenitic stainless steel weld metal is comparatively lower (Hv is appro ximately from 200 to 220) for the range of smaller penetration ratio, but becomes higher (Hv is max. 400) as penetration ratio becomes larger. But in the case when penetration ratio is the same for the range of larger one, Vickers hardness of austenitic weld metal containing high carbon base metal is lower than that of the metal containing low carbon base metal. This result obtained in the present experiment is different from that of the Ist. report.(4) Micro-hardness at the side of austenitic stainless steel weld metal of the vicinity of weld fusion line increases, for the most part, linearly as welding current increases. Consequently, the above tendency of micro-hardness change is somewhat different from that of Vickers hardness change.(5) Both maximum Vickers hardness of the heat-affected zone in base metal and micro-hardness of the vicinity of weld fusion line of that same zone have a tendency to decrease as welding current increases.