The present study is aimed at understanding the effect of different prior heat treatments on the microstructure and mechanical properties of 0.33% carbon dual-phase (DP) steel. For this purpose, different dual-phase steels were produced by subjecting the as-received steel to ÔhardeningÕ (DP-H), Ôhard-ening + temperingÕ (DP-HT), and ÔaustemperingÕ (DP-AT) treatments prior to the intercritical annealing treatment. The study reveals that the prior hardening treatment in DP-H steel results in significant refinement of ferrite grains and formation of fine elongated martensite plates having an aspect ratio = 6.1 ± 3. These fine elongated martensites are responsible for poor ductility in DP-H steel. Although DP steel without any prior treatment (DP-AR) and DP-AT steel exhibit high strength and hardness, their ductility is limited by the presence of very hard martensite islands which act as the failure initiation sites in these steels. On the other hand, prior Ôhardening + temperingÕ treatment in DP-HT steel results in the formation of nearly spherical-shaped martensite (aspect ratio = 1.24 ± 0.13) along with coarse martensite laths. In addition, the presence of fine carbides is also found along the lath boundaries. These fine spherical martensites and fine carbides provide higher strain hardening to DP-HT steel. Accordingly, DP-HT steel exhibits adequate ductility as well as strength. Therefore, prior Ôhardening + temperingÕ treatment was found to the best prior treatment in the present study.
In the present research work, an aluminum-based metal matrix composite with in situ Al 4 SiC 4 particles has been developed by the incorporation of TiC particles in commercial aluminum melt through a stir-casting method. Microstructure evaluation in correlation to developed hardness and mechanical properties was performed. Furthermore, the dry sliding wear behavior of commercial aluminum and commercial aluminum-5 vol% Al 4 SiC 4 composite was investigated at low sliding speed (1 ms ¡1 ) against a hardened EN 31 disk at different loads. The wear mechanism involved adhesion and microcutting-abrasion at lower loads. On the other hand, at higher loads, abrasive wear involving microcutting along with adherent oxide formation was observed. The overall wear rate increased with load in the alloy as well as in the composite. Moreover, the overall wear rate of the composite was lower than that of the commercial aluminum at all applied loads.' The severe wear region at 39.2 N load in the case of the commercial aluminum-5 vol% Al 4 SiC 4 composite was found to be delayed up to a longer sliding distance compared to commercial aluminum. The in situ Al 4 SiC 4 particles offered resistance to adhesive wear. Accordingly, the commercial aluminum-5 vol% Al 4 SiC 4 composite exhibited superior wear resistance compared to the commercial aluminum.
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