Was there any way that Titanic's collision with the iceberg could have been avoided after the iceberg had been spotted? Could the ship have been saved from sinking by the pilot or captain after the iceberg was sighted? Was it possible for more passengers to have been saved?
The Titantic tragedy was at least PARTLY avoidable, whether or not the collision was.
First, there were only enough lifeboats for half of the ship's passengers, meaning that at least half of the passengers "had to" drown. Nowadays, ships carry enough lifeboats for all passengers, following changes in maritime law.
Second, the lifeboats were mostly not filled to full capacity, could have taken on more passengers, but empty seats were saved for "women and children" first, to the condition listed above.
Third, nearby ships such as the Californian failed to hurry to the rescue of the Titantic, even though this ship, at least, had been notified.
The Titanic was sunk because the iceberg hit the ship along the side, opening the first 6 compartments to the sea. If the ship had made no attempt to avoid the iceberg, but instead simply hit it head-on, it would have suffered extensive damage to its forward compartments, but would most likely have avoided opening more than a few compartments to the sea. Since the ship was designed to remain afloat with 4 compartments flooded, the direct-impact might have caused the ship to remain intact for much longer, potentially long enough to avoid most of the loss of life, even if the ship eventually wound up sinking later.
As a former naval officer (US) I'll say that in my opinion the Titanic sinking was 100% avoidable. The immediate cause of Titanic's loss was the collision with the iceberg, but the cause of the collision was the callous and negligent disregard by her commanding officer of the dangers involved in transiting an iceberg hazard area at high speed. Getting to her destination in near-record time was considered to be more important by her captain and the on-board representatives of the White Star Line than was safe and prudent navigation, and this prioritization of speed over safety led directly to the collision and loss of the vessel. Everything else, from the metallurgical issues with the ships plates to the design issues regarding her watertight integrity to the lack of sufficient lifeboats is secondary; had the vessel not been hazarded in this manner by her commanding officer the collision would most likely not have occurred; and had a collision with an iceberg occurred at lower speed it would very likely have done less damage to the ship, with consequently greater chance of preventing her loss.
Mark Kozak-Holland argues that it was quite avoidable. Although popular history has it that the ship was designed to remain afloat with 4 compartments flooded (hat tip to @GWLlosa), the truth is somewhat more discouraging - cost cutting measures by the company during construction actually transformed those resiliency features into one of the causes for the disaster. Obligatory disclaimer; I'm not trying to promote Mr. Kozak Holland, and I have no financial interest in his book.
Devsolar asks for more details - I recommend Mr. Kozak-Holland's book as the best place to get those answers. My recollection of the talk (several years ago) is that the original plan for the Titanic involved a double hull all the way up. Cost and schedule constraints reduced the height of the double hull to half the plan. When the exterior hull was pierced, water flooded in between the hulls. What had been planned as a saftey feature to preserve boyancy flooded with water and reduced boyancy. (the actual mechanism was more complicated, but quite frankly I'm not qualified to explain. I'd have to refer to Mr. Kozak Holland's book.
Best alternate source:
When the hull of the Titanic was torn open in the collision with the iceberg, water began to flood the damaged compartments in the bow. As the ship pitched forward under the weight of the water in the bow compartments, water began to spill over the tops of the bulkheads into adjacent, undamaged compartments. Although called watertight, the watertight compartments were actually only watertight horizontally; their tops were open and the walls extended only a few feet above the waterline. By raising the ends of the transverse bulkheads, if a ship were taking in water through the bow compartments and the ship began to pitch forward, the water in the compartments could not flow over the tops of the bulkheads into the next compartments. As a result, flooding of the damaged compartments could be controlled and isolated to only the damaged sections 1 PSU.EDU
1 The citation is to : Gannon, Robert, "What Really Sank the Titanic," Popular Science, vol. 246, no. 2 (February 1995), pp. 49-55.
The exact sentence used in an article about the Titanic was, "The Captain, may, by simply moving an electric switch, instantly close the doors throughout and make the vessel practically unsinkable". This was in the context of the ship having a double bottom (one layer of steel inside another) and 16 watertight compartments. Even if four of these were flooded, the ship would still float. However, the compartments were watertight only on five sides - they were open at the top.
A previous ship, the Great Eastern, had compartments that were watertight on all six sides - but this was very expensive to build. The Great Eastern also had a full double hull all the way to the waterline - safe, but again very expensive to build. But the Titanic had the extra hull layer only on the bottom, not on the sides as well. The full double hull enabled the Great Eastern to survive an 1862 encounter with a rock that opened up a hole 83 feet long and 9 feet wide on her side. ABC.net.au
An alterate source:
The Titanic was another matter. Transatlantic service was now lucrative business. Bit by bit, safety standards yielded to commercial pressures. The Titanic's hull boasted a double bottom, but it had only a single wall on the sides. It had fifteen sections that could be sealed off at the throw of a switch, but the bulkheads between those sections were riddled with access doors to improve luxury service. UH.edu
There are many things that made the Titanic more vulnerable. During the construction, in the boiler room, a welding torch caused a small fire. this happened to be where the iceberg supposedly struck. The fire may have weakened the steel.
Another is that the Titanic's bolts may not have been properly welded which therefore caused a breach as the iceberg hit the side. I know this where my fish tank had a bad seal between the glass so the bad silicone burst and that was the end of our tank. My point is that their may have been a bad mixture of metal that made this happen.